National Library of Energy BETA

Sample records for helium induced cracking

  1. Technique to eliminate helium induced weld cracking in stainless steels

    SciTech Connect (OSTI)

    Chin-An Wang; Chin, B.A.; Grossbeck, M.L.

    1992-12-31

    Experiments have shown that Type 316 stainless steel is susceptible to heat-affected-zone (HAZ) cracking upon cooling when welded using the gas tungsten arc (GTA) process under lateral constraint. The cracking has been hypothesized to be caused by stress-assisted helium bubble growth and rupture at grain boundaries. This study utilized an experimental welding setup which enabled different compressive stresses to be applied to the plates during welding. Autogenous GTA welds were produced in Type 316 stainless steel doped with 256 appm helium. The application of a compressive stress, 55 Mpa, during welding suppressed the previously observed catastrophic cracking. Detailed examinations conducted after welding showed a dramatic change in helium bubble morphology. Grain boundary bubble growth along directions parallel to the weld was suppressed. Results suggest that stress-modified welding techniques may be used to suppress or eliminate helium-induced cracking during joining of irradiated materials.

  2. Remote reactor repair: GTA (gas tungsten Arc) weld cracking caused by entrapped helium

    SciTech Connect (OSTI)

    Kanne, W.R. Jr.

    1988-01-01

    A repair patch was welded to the wall of a nuclear reactor tank using remotely controlled thirty-foot long robot arms. Further repair was halted when gas tungsten arc (GTA) welds joining type 304L stainless steel patches to the 304 stainless steel wall developed toe cracks in the heat-affected zone (HAZ). The role of helium in cracking was investigated using material with entrapped helium from tritium decay. As a result of this investigation, and of an extensive array of diagnostic tests performed on reactor tank wall material, helium embrittlement was shown to be the cause of the toe cracks.

  3. Hydrogen-induced cracking in pure iron

    SciTech Connect (OSTI)

    Armstrong, J.H.; Carpenter, S.H.

    1985-01-01

    The modulus and internal friction of Armco iron were continuously measured during cathodic charging with hydrogen to investigate crack initiation and growth. The observed modulus decrease was attributed to crack initiation and growth. The internal friction increase during cathodic charging was attributed to plastic deformation accompanying the crack formation. Both the modulus and internal friction behavior were found to be a sum of two parallel exponential processes. The two exponential processes were consistent with different sources of carbon for the crack-producing hydrogen bubble nucleation.

  4. Hydrogen-Induced Cracking of the Drip Shield

    SciTech Connect (OSTI)

    F. Hua

    2004-09-07

    Hydrogen-induced cracking is characterized by the decreased ductility and fracture toughness of a material due to the absorption of atomic hydrogen in the metal crystal lattice. Corrosion is the source of hydrogen generation. For the current design of the engineered barrier without backfill, hydrogen-induced cracking may be a concern because the titanium drip shield can be galvanically coupled to rock bolts (or wire mesh), which may fall onto the drip shield, thereby creating conditions for hydrogen production by electrochemical reaction. The purpose of this report is to analyze whether the drip shield will fail by hydrogen-induced cracking under repository conditions within 10,000 years after emplacement. Hydrogen-induced cracking is a scenario of premature failure of the drip shield. This report develops a realistic model to assess the form of hydrogen-induced cracking degradation of the drip shield under the hydrogen-induced cracking. The scope of this work covers the evaluation of hydrogen absorbed due to general corrosion and galvanic coupling to less noble metals (e.g., Stainless Steel Type 316 and carbon steels) under the repository conditions during the 10,000-year regulatory period after emplacement and whether the absorbed hydrogen content will exceed the critical hydrogen concentration value, above which the hydrogen-induced cracking is assumed to occur. This report also provides the basis for excluding the features, events, and processes (FEPs) related to hydrogen-induced cracking of the drip shield with particular emphasis on FEP 2.1.03.04.OB, hydride cracking of drip shields (DTN: M00407SEPFEPLA.000 [DIRS 170760]). This report is prepared according to ''Technical Work Plan (TWP) for: Regulatory Integration Modeling and Analysis of the Waste Form and Waste Package'' (BSC 2004 [DIRS 169944]).

  5. Study of hydrogen induced cracking in iron

    SciTech Connect (OSTI)

    Armstrong, J.H.

    1985-01-01

    The hydrogen assisted crack growth of Armco iron from cathodic charging was studied using continuous measurements of the modulus and internal friction. A Marx composite piezoelectric oscillator was used to measure resonant frequency and internal friction during the cathodic charging. Internal friction measured before and after cathodic charging was separated into dislocation and magnetic effects. The effects of charging time, vibratory strain amplitude and charging current density were studied. In all cases the modulus decreased continuously during cathodic charging. The internal friction increased rapidly during the early portion of cathodic charging and leveled off during the latter portion. Using a composite sample model (a cracked thin outer layer with a solid core), the change in modulus was found to be proportional to the quantity na/sup 3/..delta..d, where n is the crack density, a is the average crack radius and d is the depth of cracking. The kinetic behavior of both the internal friction and modulus change were found to be a two-part parallel exponential process. The rapid process was quite rapid and was found to be consistent with the initiation and growth of cracks due to the combination of hydrogen and carbon found at grain boundaries. The rapid increase in internal friction during the first process was attributed to the rapid plastic deformation from the initiation of the cracks.

  6. Friction-Induced Fluid Heating in Nanoscale Helium Flows

    SciTech Connect (OSTI)

    Li Zhigang [Department of Mechanical Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)

    2010-05-21

    We investigate the mechanism of friction-induced fluid heating in nanoconfinements. Molecular dynamics simulations are used to study the temperature variations of liquid helium in nanoscale Poiseuille flows. It is found that the fluid heating is dominated by different sources of friction as the external driving force is changed. For small external force, the fluid heating is mainly caused by the internal viscous friction in the fluid. When the external force is large and causes fluid slip at the surfaces of channel walls, the friction at the fluid-solid interface dominates over the internal friction in the fluid and is the major contribution to fluid heating. An asymmetric temperature gradient in the fluid is developed in the case of nonidentical walls and the general temperature gradient may change sign as the dominant heating factor changes from internal to interfacial friction with increasing external force.

  7. Laser induced fluorescence spectroscopy of the Ca dimer deposited on helium and mixed helium/xenon clusters

    SciTech Connect (OSTI)

    Gaveau, Marc-André; Pothier, Christophe; Briant, Marc; Mestdagh, Jean-Michel

    2014-12-09

    We study how the laser induced fluorescence spectroscopy of the calcium dimer deposited on pure helium clusters is modified by the addition of xenon atoms. In the wavelength range between 365 and 385 nm, the Ca dimer is excited from its ground state up to two excited electronic states leading to its photodissociation in Ca({sup 1}P)+Ca({sup 1}S): this process is monitored by recording the Ca({sup 1}P) fluorescence at 422.7nm. One of these electronic states of Ca{sub 2} is a diexcited one correlating to the Ca(4s4p{sup 3}P(+Ca(4s3d{sup 3}D), the other one is a repulsive state correlating to the Ca(4s4p1P)+Ca(4s21S) asymptote, accounting for the dissociation of Ca{sub 2} and the observation of the subsequent Ca({sup 1}P) emission. On pure helium clusters, the fluorescence exhibits the calcium atomic resonance line Ca({sup 1}S←{sup 1}P) at 422.7 nm (23652 cm{sup −1}) assigned to ejected calcium, and a narrow red sided band corresponding to calcium that remains solvated on the helium cluster. When adding xenon atoms to the helium clusters, the intensity of these two features decreases and a new spectral band appears on the red side of calcium resonance line; the intensity and the red shift of this component increase along with the xenon quantity deposited on the helium cluster: it is assigned to the emission of Ca({sup 1}P) associated with the small xenon aggregate embedded inside the helium cluster.

  8. Grain boundary chemistry effects on environment-induced crack growth of iron-based alloys

    SciTech Connect (OSTI)

    Jones, R.H.

    1992-11-01

    Relation between grain boundary chemistry and environment-induced crack growth of Fe-based alloys is reviewed. The importance of the cleanliness of steels is clearly demonstrated by direct relations between grain boundary chemistry and crack growth behavior for both H and anodic dissolution-induced crack growth. Relationships between strain to failure, work of fracture, K[sub ISCC], crack velocity and fracture mode and grain boundary chemistry are presented. Only results in which the grain boundary chemistry has been measured directly by Auger electron spectroscopy (AES) on intergranular surfaces exposed by in situ fracture have been considered in this review.

  9. Grain boundary chemistry effects on environment-induced crack growth of iron-based alloys

    SciTech Connect (OSTI)

    Jones, R.H.

    1992-11-01

    Relation between grain boundary chemistry and environment-induced crack growth of Fe-based alloys is reviewed. The importance of the cleanliness of steels is clearly demonstrated by direct relations between grain boundary chemistry and crack growth behavior for both H and anodic dissolution-induced crack growth. Relationships between strain to failure, work of fracture, K{sub ISCC}, crack velocity and fracture mode and grain boundary chemistry are presented. Only results in which the grain boundary chemistry has been measured directly by Auger electron spectroscopy (AES) on intergranular surfaces exposed by in situ fracture have been considered in this review.

  10. Lead induced stress corrosion cracking of Alloy 690 in high temperature water

    SciTech Connect (OSTI)

    Chung, K.K.; Lim, J.K.; Moriya, Shinichi; Watanabe, Yutaka; Shoji, Tetsuo

    1995-12-31

    Recent investigations of cracked steam generator tubes at nuclear power plants concluded that lead significantly contributed to cracking the Alloy 600 materials. In order to investigate the stress corrosion cracking (SCC) behavior of Alloy 690, slow strain rate tests (SSRT) and anodic polarization measurements were performed. The SSRTs were conducted in a lead-chloride solution (PbCl{sub 2}) and in a chloride but lead free solution (NaCl) at pH of 3 and 4.5 at 288 C. The anodic polarization measurements were carried out at 30 C using the same solutions as in SSRT. The SSRT results showed that Alloy 690 was susceptible to SCC in both solutions. In the lead chloride solution, cracking had slight dependence on lead concentration and pH. Cracking tend to increase with a higher lead concentration and a lower pH and was mainly intergranular and was to be a few tens to hundreds micrometers in length. In the chloride only solution, cracking was similar to the lead induced SCC. The results of anodic polarization measurement and electron probe micro analysis (EPMA) helped to understand lead induced SCC. Lead was a stronger active corrosive element but had a minor affect on cracking susceptibility of the alloy. While, chloride was quite different from lead effect to SCC. A possible mechanism of lead induced SCC of Alloy 690 was also discussed based on the test results.

  11. An Assessment of Remote Visual Testing System Capabilities for the Detection of Service Induced Cracking

    SciTech Connect (OSTI)

    Anderson, Michael T.; Cumblidge, Stephen E.; Doctor, Steven R.

    2005-09-01

    Remote visual testing is typically employed to ascertain the condition of materials in components that are inaccessible for direct examination. In the power and petrochemical industries, remote visual testing is used to assess whether service-related degradation is being manifested that, if left unchecked, may eventually impair the structural reliability of a component. Several codes and standards require that visual examinations be periodically conducted. Many of these inspections must be performed remotely due to harsh environments or design geometries of the subject components. This paper describes the attributes and limitations of remote visual testing, performance demonstration standards for camera systems, typical dimensions for service-induced cracking phenomena, and an assessment of the reliability of remote video camera systems at finding cracks. Because many forms of service-induced cracks have very small crack opening dimensions, the reliability of remote visual testing may not be adequate to ensure component integrity, given the capabilities of current camera systems and application practices.

  12. Solvation of molecules in superfluid helium enhances the interaction induced localization effect

    SciTech Connect (OSTI)

    Walewski, ?ukasz Forbert, Harald; Marx, Dominik

    2014-04-14

    Atomic nuclei become delocalized at low temperatures as a result of quantum effects, whereas they are point-like in the high temperature (classical) limit. For non-interacting nuclei, the delocalization upon lowering the temperature is quantitatively described in terms of the thermal de Broglie wavelength of free particles. Clearly, light non-interacting nuclei the proton being a prominent one are much more delocalized at low temperatures compared to heavy nuclei, such as non-interacting oxygen having water in mind. However, strong interactions due to chemical bonding in conjunction with ultra-low temperatures characteristic to superfluid helium nanodroplets change this common picture substantially for nuclei in molecules or clusters. It turns out that protons shared in hydrogen bonds undergo an extreme interaction induced localization at temperatures on the order of 1 K, which compresses the protonic spatial distributions to the size of the much heavier donor or acceptor atoms, such as O or Cl nuclei, corresponding to about 0.1% of the volume occupied by a non-interacting proton at the same temperature. Moreover, applying our recently developed hybrid ab initio path integral molecular dynamics/bosonic path integral Monte Carlo quantum simulation technique to a HCl/water cluster, HCl(H{sub 2}O){sub 4}, we find that helium solvation has a significant additional localizing effect of up to about 30% in volume. In particular, the solvent-induced excess localization is the stronger the lesser the given nucleus is already localized in the gas phase reference situation.

  13. Investigating the dynamics of laser induced sparks in atmospheric helium using Rayleigh and Thomson scattering

    SciTech Connect (OSTI)

    Nedanovska, E.; Nersisyan, G.; Lewis, C. L. S.; Riley, D.; Graham, W. G.; Morgan, T. J.; Hüwel, L.; Murakami, T.

    2015-01-07

    We have used optical Rayleigh and Thomson scattering to investigate the expansion dynamics of laser induced plasma in atmospheric helium and to map its electron parameters both in time and space. The plasma is created using 9 ns duration, 140 mJ pulses from a Nd:YAG laser operating at 1064 nm, focused with a 10 cm focal length lens, and probed with 7 ns, 80 mJ, and 532 nm Nd:YAG laser pulses. Between 0.4 μs and 22.5 μs after breakdown, the electron density decreases from 3.3 × 10{sup 17 }cm{sup −3} to 9 × 10{sup 13 }cm{sup −3}, while the temperature drops from 3.2 eV to 0.1 eV. Spatially resolved Thomson scattering data recorded up to 17.5 μs reveal that during this time the laser induced plasma expands at a rate given by R ∼ t{sup 0.4} consistent with a non-radiative spherical blast wave. This data also indicate the development of a toroidal structure in the lateral profile of both electron temperature and density. Rayleigh scattering data show that the gas density decreases in the center of the expanding plasma with a central scattering peak reemerging after about 12 μs. We have utilized a zero dimensional kinetic global model to identify the dominant particle species versus delay time and this indicates that metastable helium and the He{sub 2}{sup +} molecular ion play an important role.

  14. Probabilistic evaluation of initiation time in RC bridge beams with load-induced cracks exposed to de-icing salts

    SciTech Connect (OSTI)

    Lu Zhaohui; Zhao Yangang; Yu Zhiwu; Ding Faxing

    2011-03-15

    In this study, a reliability-based method for predicting the initiation time of reinforced concrete bridge beams with load-induced cracks exposed to de-icing salts is presented. A practical model for predicting the diffusion coefficient of chloride ingress into load-induced cracked concrete is proposed. Probabilistic information about uncertainties related to the surface chloride content and the threshold chloride concentration has been estimated from a wide review of previous experimental or statistical studies. Probabilistic analysis to estimate the time to corrosion initiation with/without considering the effect of the load-induced cracks on the chloride ingress into concrete has been carried out. Results of the analysis demonstrate the importance of considering the effect of the load-induced cracks for correct prediction of corrosion initiation in RC bridge beams exposed to chlorides.

  15. Simulation of streamers propagating along helium jets in ambient air: Polarity-induced effects

    SciTech Connect (OSTI)

    Naidis, G. V.

    2011-04-04

    Results of modeling of streamer propagation along helium jets for both positive and negative polarities of applied voltage are presented. Obtained patterns of streamer dynamics and structure in these two cases are similar to those observed in experiments with plasma jets.

  16. Identifying and Understanding Environment-Induced Crack propagation Behavior in Ni-based Superalloy INCONEL 617

    SciTech Connect (OSTI)

    Ma, Longzhou

    2012-11-30

    The nickel-based superalloy INCONEL 617 is a candidate material for heat exchanger applications in the next-generation nuclear plant (NGNP) system. This project will study the crack propagation process of alloy 617 at temperatures of 650°C-950°C in air under static/cyclic loading conditions. The goal is to identify the environmental and mechanical damage components and to understand in-depth the failure mechanism. Researchers will measure the fatigue crack propagation (FCP) rate (da/dn) under cyclic and hold-time fatigue conditions, and sustained crack growth rates (da/dt) at elevated temperatures. The independent FCP process will be identified and the rate-controlled sustained loading crack process will be correlated with the thermal activation equation to estimate the oxygen thermal activation energy. The FCP-dependent model indicates that if the sustained loading crack growth rate, da/dt, can be correlated with the FCP rate, da/dn, at the full time dependent stage, researchers can confirm stress-accelerated grain-boundary oxygen embrittlement (SAGBOE) as a predominate effect. Following the crack propagation tests, the research team will examine the fracture surface of materials in various cracking stages using a scanning electron microscope (SEM) and an optical microscope. In particular, the microstructure of the crack tip region will be analyzed in depth using high resolution transmission electron microscopy (TEM) and electron energy loss spectrum (EELS) mapping techniques to identify oxygen penetration along the grain boundary and to examine the diffused oxygen distribution profile around the crack tip. The cracked sample will be prepared by focused ion beam nanofabrication technology, allowing researchers to accurately fabricate the TEM samples from the crack tip while minimizing artifacts. Researchers will use these microscopic and spectroscopic results to interpret the crack propagation process, as well as distinguish and understand the environment or

  17. Prediction of reinforcement corrosion using corrosion induced cracks width in corroded reinforced concrete beams

    SciTech Connect (OSTI)

    Khan, Inamullah; François, Raoul; Castel, Arnaud

    2014-02-15

    This paper studies the evolution of reinforcement corrosion in comparison to corrosion crack width in a highly corroded reinforced concrete beam. Cracking and corrosion maps of the beam were drawn and steel reinforcement was recovered from the beam to observe the corrosion pattern and to measure the loss of mass of steel reinforcement. Maximum steel cross-section loss of the main reinforcement and average steel cross-section loss between stirrups were plotted against the crack width. The experimental results were compared with existing models proposed by Rodriguez et al., Vidal et al. and Zhang et al. Time prediction models for a given opening threshold are also compared to experimental results. Steel cross-section loss for stirrups was also measured and was plotted against the crack width. It was observed that steel cross-section loss in the stirrups had no relationship with the crack width of longitudinal corrosion cracks. -- Highlights: •Relationship between crack and corrosion of reinforcement was investigated. •Corrosion results of natural process and then corresponds to in-situ conditions. •Comparison with time predicting model is provided. •Prediction of load-bearing capacity from crack pattern was studied.

  18. Develop baseline computational model for proactive welding stress management to suppress helium induced cracking during weld repair

    Broader source: Energy.gov [DOE]

    There are over 100 nuclear power plants operating in the U.S., which generate approximately 20% of the nation’s electricity. These plants range from 15 to 40 years old. Extending the service lives...

  19. Temperature dependence of helium-implantation-induced lattice swelling in polycrystalline tungsten: X-ray micro-diffraction and Eigenstrain modelling

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    de Broglie, I.; Beck, C. E.; Liu, W.; Hofmann, Felix

    2015-05-30

    Using synchrotron X-ray micro-diffraction and Eigenstrain analysis the distribution of lattice swelling near grain boundaries in helium-implanted polycrystalline tungsten is quantified. Samples heat-treated at up to 1473 K after implantation show less uniform lattice swelling that varies significantly from grain to grain compared to as-implanted samples. An increase in lattice swelling is found in the vicinity of some grain boundaries, even at depths beyond the implanted layer. As a result, these findings are discussed in terms of the evolution of helium-ion-implantation-induced defects.

  20. Model boiler testing to evaluate inhibitors for caustic induced stress corrosion cracking of Alloy 600 tubes

    SciTech Connect (OSTI)

    Daret, J.; Paine, J.P.N.; Partridge, M.J.

    1995-12-31

    A series of model boiler tests, using a mixture of precracked and non-precracked (virgin) tube-to-tube support plate intersections was performed. The testing supported the qualification of inhibitors for mitigating the secondary side corrosion of alloy 600 steam generator tubes. Many utilities suspect that the caustic impurities come from the feedwater. Candidate inhibitors included boric acid (as a reference), cerous acetate, and two forms of titanium dioxide: a laboratory produced titania-silica sol-gel, and manometer sized anatase The latter was combined with a 150 C pre-soaking with a titanium lactate, and was tested with and without a zeta potential treatment by sodium aluminate. Effectiveness of boric acid to prevent and retard caustic induced intergranular corrosion was confirmed in all crevice configurations (open and packed). The cerous acetate treatment multiplied by two to four the time necessary to detect a primary-to-secondary leak on virgin tubes, and reduced the propagation rate on precracked tubes. Cerium was found intimately mixed, as cerianite, with the free span and crevice deposits, when the crevices were sufficiently accessible. Due to its very low solubility and large particle size, the titania-silica sol-gel was unable to penetrate the crevices and had no effect on the degradation process. The nanometric particle size titania treatment and/or the preceding soaking with soluble titanium lactate drastically increased the titanium concentration in free span and open crevice deposit (with no added sodium aluminate, titania reacted with magnetite to form ilmenite) and showed undeniable capacity to prevent tubing degradation. Its effectiveness, in the case of packed crevices and for arresting cracks, was not so conclusive.

  1. Mechanisms of hydrogen-induced intergranular stress corrosion cracking of Alloy 600 in high-temperature water/steam

    SciTech Connect (OSTI)

    Shen, C.H.

    1989-01-01

    Intergranular stress-corrosion cracking (IGSCC) of Alloy 600 in high-temperature deaerated water or steam has been termed Hydrogen Induced IGSCC. It is suggested here that these cracks are initiated by the nucleation of a high density of bubbles on the grain boundary under the combined action of the applied stress and high-pressure methane formed from carbon in solution reacting with hydrogen injected by corrosion. The bubbles then grow together by grain-boundary diffusion to give local failure. This agrees with the observations made using the electron microscope and two-stage replicas, namely the subsurface formation of closely spaced (0.2 {mu}m) bubbles along boundaries, and the growth of these into fine cracks before they open up to communicate with the corroding atmosphere. The kinetics of this process are examined and shown to be in quantitative agreement with several experimental observations. This mechanism involves no dissolution of the metal, the only role of corrosion being the injection of hydrogen at a high fugacity. It also predicts an activation energy essentially equal to that for grain-boundary diffusion of nickel in the Alloy 600 grain boundary. The activation energy for grain-boundary self-diffusion in nickel is 115 kJ/mol.

  2. Helium damage in austenitic stainless steels

    SciTech Connect (OSTI)

    Caskey, G.R. Jr.; Mezzanotte, D.A. Jr.; Rawl, D.E. Jr.

    1983-01-01

    Helium produced by tritium decay was first shown to embrittle austenitic stainless steel at ambient temperature in tensile specimens of Nitronic-40 steel (Armco, Inc.). A long-term study was initiated to study this form of helium damage in five austenitic alloys. Results from this study have been analyzed by the J-integral technique and show a decrease in ductile fracture toughness with increasing He-3 concentration. Sustained-load cracking tests indicate that the stress intensity required to initiate and propagate a crack also decreases with increasing He-3 concentration. 9 figures, 3 tables.

  3. AN EVALUATION OF HYDROGEN INDUCED CRACKING SUSCEPTIBILITY OF TITANIUM ALLOYS IN US HIGH-LEVEL NUCLEAR WASTE REPOSITORY ENVIRONMENTS

    SciTech Connect (OSTI)

    G. De; K. Mon; G. Gordon; D. Shoesmith; F. Hua

    2006-02-21

    This paper evaluates hydrogen-induced cracking (HIC) susceptibility of titanium alloys in environments anticipated in the Yucca Mountain nuclear waste repository with particular emphasis on the. effect of the oxide passive film on the hydrogen absorption process of titanium alloys being evaluated. The titanium alloys considered in this review include Ti 2, 5 , 7, 9, 11, 12, 16, 17, 18, 24 and 29. In general, the concentration of hydrogen in a titanium alloy can increase due to absorption of atomic hydrogen produced from passive general corrosion of that alloy or galvanic coupling of it to a less noble metal. It is concluded that under the exposure conditions anticipated in the Yucca Mountain repository, the HIC of titanium drip shield will not occur because there will not be sufficient hydrogen in the metal even after 10,000 years of emplacement. Due to the conservatisms adopted in the current evaluation, this assessment is considered very conservative.

  4. Helium bubble distributions in reactor tank repair specimens. Part 1

    SciTech Connect (OSTI)

    Tosten, M.H.; Kestin, P.A.

    1992-03-01

    This report discusses the Reactor Tank Repair (RTR) program was initiated to develop an in-tank repair process capable of repairing stress corrosion cracks within the SRS reactor tank walls, in the event that such a repair is needed. Previous attempts to repair C-reactor tank with a gas tungsten arc (GTA) welding process were unsuccessful due to significant cracking that occurred in the heat-affected-zones adjacent to the repair welds. It was determined that this additional cracking was a result of helium embrittlement caused by the combined effects of helium (existing within the tank walls), the high heat input associated with the GTA process, and weld shrinkage stresses. Based on the results of earlier studies it was suggested that the effects of helium embrittlement could be minimized by using a low heat input GMA process. Metallographic analysis played an important role throughout the investigation of alternative welding methods for the repair of helium-containing materials.

  5. Helium bubble distributions in reactor tank repair specimens

    SciTech Connect (OSTI)

    Tosten, M.H.; Kestin, P.A.

    1992-03-01

    This report discusses the Reactor Tank Repair (RTR) program was initiated to develop an in-tank repair process capable of repairing stress corrosion cracks within the SRS reactor tank walls, in the event that such a repair is needed. Previous attempts to repair C-reactor tank with a gas tungsten arc (GTA) welding process were unsuccessful due to significant cracking that occurred in the heat-affected-zones adjacent to the repair welds. It was determined that this additional cracking was a result of helium embrittlement caused by the combined effects of helium (existing within the tank walls), the high heat input associated with the GTA process, and weld shrinkage stresses. Based on the results of earlier studies it was suggested that the effects of helium embrittlement could be minimized by using a low heat input GMA process. Metallographic analysis played an important role throughout the investigation of alternative welding methods for the repair of helium-containing materials.

  6. Radiation-induced instability of MnS precipitates and its possible consequences on irradiation-induced stress corrosion cracking of austenitic stainless steels

    SciTech Connect (OSTI)

    Chung, H.M.; Sanecki, J.E.; Garner, F.A.

    1996-12-01

    Irradiation-assisted stress corrosion cracking (IASCC) is a significant materials issue for the light water reactor (LWR) industry and may also pose a problem for fusion power reactors that will use water as coolant. A new metallurgical process is proposed that involves the radiation-induced release into solution of minor impurity elements not usually thought to participate in IASCC. MnS-type precipitates, which contain most of the sulfur in stainless steels, are thought to be unstable under irradiation. First, Mn transmutes strongly to Fe in thermalized neutron spectra. Second, cascade-induced disordering and the inverse Kirkendall effect operating at the incoherent interfaces of MnS precipitates are thought to act as a pump to export Mn from the precipitate into the alloy matrix. Both of these processes will most likely allow sulfur, which is known to exert a deleterious influence on intergranular cracking, to re-enter the matrix. To test this hypothesis, compositions of MnS-type precipitates contained in several unirradiated and irradiated heats of Type 304, 316, and 348 stainless steels (SSs) were analyzed by Auger electron spectroscopy. Evidence is presented that shows a progressive compositional modification of MnS precipitates as exposure to neutrons increases in boiling water reactors. As the fluence increases, the Mn level in MnS decreases, whereas the Fe level increases. The S level also decreases relative to the combined level of Mn and Fe. MnS precipitates were also found to be a reservoir of other deleterious impurities such as F and O which could be also released due to radiation-induced instability of the precipitates.

  7. Lead-induced stress corrosion cracking of Alloy 600 and 690 in high temperature water

    SciTech Connect (OSTI)

    Sakai, T.; Senjuh, T.; Aoki, K.; Shigemitsu, T.; Kishi, Y.

    1992-12-31

    Lead is one of the potential contributing impurities to the degradation of PWR steam generator tubing. Recent laboratory testing has shown that lead is a corrosive material for Alloy 600 steam generator tubing. However, it is still unknown how lead influences the corrosion of steam generator tubing, including the effect of lead concentration, solution pH, stress level and material characteristics. In this study, two kinds of experiments were performed. One was to investigate the thin film characteristic and selectively dissolved base metal elements of Alloy 600MA in high temperature solutions of different lead concentrations and pH. The other investigated the dependency of degradation of Alloy 600MA and Alloy 690TT on lead concentration and stress level in mild acidic environment, at 340{degrees}C for 2500 hrs. It was firstly demonstrated that lead-enhanced selective dissolution of nickel from alloy base metal, as a result of electrochemical reaction between lead and nickel, might cause the initiation and propagation of corrosion. Secondly, we showed that Alloy 690TT, generally very corrosion resistant material, also suffered from Pb-induced corrosion. The difference of the lead-induced stress corrosion morphology of Alloy 600MA and Alloy 690TT was also clarified.

  8. An investigation of penetrant techniques for detection of machining-induced surface-breaking cracks on monolithic ceramics

    SciTech Connect (OSTI)

    Forster, G.A.; Ellingson, W.A.

    1996-02-01

    The purpose of this effort was to evaluate penetrant methods for their ability to detect surface-breaking cracks in monolithic ceramic materials with an emphasis on detection of cracks generated by machining. There are two basic penetrant types, visible and fluorescent. The visible penetrant method is usually augmented by powder developers and cracks detected can be seen in visible light. Cracks detected by fluorescent penetrant are visible only under ultraviolet light used with or without a developer. The developer is basically a powder that wicks up penetrant from a crack to make it more observable. Although fluorescent penetrants were recommended in the literature survey conducted early in this effort, visible penetrants and two non-standard techniques, a capillary gaseous diffusion method under development at the institute of Chemical Physics in Moscow, and the {open_quotes}statiflux{close_quotes} method which involves use of electrically charged particles, were also investigated. SiAlON ring specimens (1 in. diameter, 3/4 in. wide) which had been subjected to different thermal-shock cycles were used for these tests. The capillary gaseous diffusion method is based on ammonia; the detector is a specially impregnated paper much like litmus paper. As expected, visible dye penetrants offered no detection sensitivity for tight, surface-breaking cracks in ceramics. Although the non-standard statiflux method showed promise on high-crack-density specimens, it was ineffective on limited-crack-density specimens. The fluorescent penetrant method was superior for surface-breaking crack detection, but successful application of this procedure depends greatly on the skill of the user. Two presently available high-sensitivity fluorescent penetrants were then evaluated for detection of microcracks on Si{sub 3}N{sub 4} and SiC from different suppliers. Although 50X optical magnification may be sufficient for many applications, 200X magnification provides excellent delectability.

  9. Metal tritides helium emission

    SciTech Connect (OSTI)

    Beavis, L.C.

    1980-02-01

    Over the past several years, we have been measuring the release of helium from metal tritides (primarily erbium tritide). We find that qualitatively all tritides of interest to us behave the same. When they are first formed, the helium is released at a low rate that appears to be related to the amount of surface area which has access to the outside of the material (either film or bulk). For example, erbium tritide films initially release about 0.3% of the helium generated. Most tritide films emit helium at about this rate initially. At some later time, which depends upon the amount of helium generated, the parent occluding element and the degree of tritium saturation of the dihydride phase the helium emission changes to a new mode in which it is released at approximately the rate at which it is generated (for example, we measure this value to be approx. = .31 He/Er for ErT/sub 1/./sub 9/ films). If erbium ditritide is saturated beyond 1.9 T/Er, the critical helium/metal ratio decreases. For example, in bulk powders ErT/sub 2/./sub 15/ reaches critical release concentration at approx. = 0.03. Moderate elevation of temperature above room temperature has little impact on the helium release rate. It appears that the process may have approx. = 2 kcal/mol activation energy. The first helium formed is well bound. As the tritide ages, the helium is found in higher energy sites. Similar but less extensive measurements on scandium, titanium, and zirconium tritides are also described. Finally, the thermal desorption of erbium tritides of various ages from 50 days to 3154 days is discussed. Significant helium is desorbed along with the tritium in all but the youngest samples during thermodesorption.

  10. Fatigue and Creep Crack Propagation behaviour of Alloy 617 in the Annealed and Aged Conditions

    SciTech Connect (OSTI)

    Julian K. Benz; Richard N. Wright

    2013-10-01

    The crack propagation behaviour of Alloy 617 was studied under various conditions. Elevated temperature fatigue and creep-fatigue crack growth experiments were conducted at 650 and 800 degrees C under constant stress intensity (triangle K) conditions and triangular or trapezoidal waveforms at various frequencies on as-received, aged, and carburized material. Environmental conditions included both laboratory air and characteristic VHTR impure helium. As-received Alloy 617 displayed an increase in the crack growth rate (da/dN) as the frequency was decreased in air which indicated a time-dependent contribution component in fatigue crack propagation. Material aged at 650°C did not display any influence on the fatigue crack growth rates nor the increasing trend of crack growth rate with decreasing frequency even though significant microstructural evolution, including y’ (Ni3Al) after short times, occurred during aging. In contrast, carburized Alloy 617 showed an increase in crack growth rates at all frequencies tested compared to the material in the standard annealed condition. Crack growth studies under quasi-constant K (i.e. creep) conditions were also completed at 650 degrees C and a stress intensity of K = 40 MPa9 (square root)m. The results indicate that crack growth is primarily intergranular and increased creep crack growth rates exist in the impure helium environment when compared to the results in laboratory air. Furthermore, the propagation rates (da/dt) continually increased for the duration of the creep crack growth either due to material aging or evolution of a crack tip creep zone. Finally, fatigue crack propagation tests at 800 degrees C on annealed Alloy 617 indicated that crack propagation rates were higher in air than impure helium at the largest frequencies and lowest stress intensities. The rates in helium, however, eventually surpass the rates in air as the frequency is reduced and the stress intensity is decreased which was not observed at 650

  11. Helium Energy | Open Energy Information

    Open Energy Info (EERE)

    Energy Jump to: navigation, search Name: Helium Energy Place: Spain Sector: Renewable Energy Product: Spain-based renewable energy development company. References: Helium Energy1...

  12. Assessment of Embrittlement of VHTR Structural Alloys in Impure Helium Environments

    SciTech Connect (OSTI)

    Crone, Wendy; Cao, Guoping; Sridhara, Kumar

    2013-05-31

    The helium coolant in high-temperature reactors inevitably contains low levels of impurities during steady-state operation, primarily consisting of small amounts of H{sub 2}, H{sub 2}O, CH{sub 4}, CO, CO{sub 2}, and N{sub 2} from a variety of sources in the reactor circuit. These impurities are problematic because they can cause significant long-term corrosion in the structural alloys used in the heat exchangers at elevated temperatures. Currently, the primary candidate materials for intermediate heat exchangers are Alloy 617, Haynes 230, Alloy 800H, and Hastelloy X. This project will evaluate the role of impurities in helium coolant on the stress-assisted grain boundary oxidation and creep crack growth in candidate alloys at elevated temperatures. The project team will: • Evaluate stress-assisted grain boundary oxidation and creep crack initiation and crack growth in the temperature range of 500-850°C in a prototypical helium environment. • Evaluate the effects of oxygen partial pressure on stress-assisted grain boundary oxidation and creep crack growth in impure helium at 500°C, 700°C, and 850°C respectively. • Characterize the microstructure of candidate alloys after long-term exposure to an impure helium environment in order to understand the correlation between stress-assisted grain boundary oxidation, creep crack growth, material composition, and impurities in the helium coolant. • Evaluate grain boundary engineering as a method to mitigate stress-assisted grain boundary oxidation and creep crack growth of candidate alloys in impure helium. The maximum primary helium coolant temperature in the high-temperature reactor is expected to be 850-1,000°C.Corrosion may involve oxidation, carburization, or decarburization mechanisms depending on the temperature, oxygen partial pressure, carbon activity, and alloy composition. These corrosion reactions can substantially affect long-term mechanical properties such as crack- growth rate and fracture

  13. The Capabilities and Limitation of Remote Visual Methods to Detect Service-Induced Cracks in Reactor Components

    SciTech Connect (OSTI)

    Cumblidge, Stephen E.; Doctor, Steven R.; Anderson, Michael T.

    2006-11-01

    Since 1977, the U.S. Nuclear Regulatory Commission (NRC) Office of Nuclear Regulatory Research has funded a multiyear program at the Pacific Northwest National Laboratory (PNNL) to evaluate the reliability and accuracy of nondestructive evaluation (NDE) techniques employed for inservice inspection (ISI). Recently, the U.S. nuclear industry proposed replacing current volumetric and/or surface examinations of certain components in commercial nuclear power plants, as required by ASME Boiler and Pressure Vessel Code Section XI, with a simpler visual testing (VT) method. The advantages of VT are that these tests generally involve much less radiation exposure and examination times than do volumetric examinations such as ultrasonic testing (UT). However, for industry to justify supplamenting volumetric metods with VT, and analysis of pertinent issues is needed to support the reliability of VT in determining the structural intefrity of reactor components. As piping and pressure vessel compoents in a nuclear power station are generally underwater and in high radiation field, they need to be examined by VT from a distance with radiation-hardened video systems. Remote visual testing has been used by nuclear utilities to find cracks in pressure vessel cladding in pressurized water reactors, for shrouds in boiling water reactors, and to investigate leaks in piping and reactor components. These visual tests are performed using a wide variety of procedures and equipment. The techniques for remote visual testing use submersible closed-circuit video cameras to examine reactor components and welds. PNNL has conducted a parametric study that examines the important variables that affect the effectiveness of a remote visual test. Tested variables include lighting techniques, camera resolution, camera movement, and magnification. PNNL has also conductrd a laboratory test using a commercial visual testing camera system to experimentally determine the ability of the camera system to

  14. Mechanism of lead-induced stress corrosion cracking of nickel-based alloys in high-temperature water

    SciTech Connect (OSTI)

    Sakai, T.; Nakagomi, N.; Kikuchi, T.; Aoki, K.; Nakayasu, F.; Yamakawa, K.

    1998-07-01

    A study was undertaken to better understand the lead-induced corrosion mechanism of nickel-based alloys used for steam generator tubing materials (alloys 600 and 690 [UNS N06600 and N06690]) in pressurized-water reactor (PWR) plants. Electrochemical measurements (corrosion potential and polarization measurements) and constant extension rate tests (CERT) of tubing materials were performed in lead-contaminated environments. Results of electrochemical measurements showed lead did not raise the corrosion potential but did increase the anodic polarization current in the passivity region, which indicated degradation of the passive oxide film. CERT results showed alloy 690 had better corrosion resistance than alloy 600, which was in good agreement with the lower intensity of the anodic current. The mechanism of lead-induced corrosion was proposed as disruption of the oxide film of the alloys as a result of the incorporation of lead.

  15. Is solid helium a supersolid?

    SciTech Connect (OSTI)

    Hallock, Robert

    2015-05-15

    Recent experiments suggest that helium-4 atoms can flow through an experimental cell filled with solid helium. But that incompletely understood flow is quite different from the reported superfluid-like motion that so excited physicists a decade ago.

  16. How to make Raman-inactive helium visible in Raman spectra of tritium-helium gas mixtures

    SciTech Connect (OSTI)

    Schloesser, M.; Pakari, O.; Rupp, S.; Mirz, S.; Fischer, S.

    2015-03-15

    Raman spectroscopy, a powerful method for the quantitative compositional analysis of molecular gases, e.g. mixtures of hydrogen isotopologues, is not able to detect monoatomic species like helium. This deficit can be overcome by using radioluminescence emission from helium atoms induced by β-electrons from tritium decay. We present theoretical considerations and combined Raman/radioluminescence spectra. Furthermore, we discuss the linearity of the method together with validation measurements for determining the pressure dependence. Finally, we conclude how this technique can be used for samples of helium with traces of tritium, and vice versa. (authors)

  17. Electron Bubbles in Liquid Helium

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Electron Bubbles in Liquid Helium and Quantum Mechanics Humphrey J. Maris Brown University September 16, 2015 4:00 p.m. An electron entering liquid helium forces open a cavity referred to as an electron bubble. These objects have been studied in many past experiments and appear to be well understood. However, experiments have revealed that in addition to these normal electron bubbles there are other negatively charged objects in liquid helium. Despite much effort the structure of these so-called

  18. Determination of crack morphology parameters from service failures for leak-rate analyses

    SciTech Connect (OSTI)

    Wilkowski, G.; Ghadiali, N.; Paul, D.

    1997-04-01

    In leak-rate analyses described in the literature, the crack morphology parameters are typically not well agreed upon by different investigators. This paper presents results on a review of crack morphology parameters determined from examination of service induced cracks. Service induced cracks were found to have a much more tortuous flow path than laboratory induced cracks due to crack branching associated with the service induced cracks. Several new parameters such as local and global surface roughnesses, as well as local and global number of turns were identified. The effect of each of these parameters are dependent on the crack-opening displacement. Additionally, the crack path is typically assumed to be straight through the pipe thickness, but the service data show that the flow path can be longer due to the crack following a fusion line, and/or the number of turns, where the number of turns in the past were included as a pressure drop term due to the turns, but not the longer flow path length. These parameters were statistically evaluated for fatigue cracks in air, corrosion-fatigue, IGSCC, and thermal fatigue cracks. A refined version of the SQUIRT leak-rate code was developed to account for these variables. Sample calculations are provided in this paper that show how the crack size can vary for a given leak rate and the statistical variation of the crack morphology parameters.

  19. Helium dilution refrigeration system

    DOE Patents [OSTI]

    Roach, P.R.; Gray, K.E.

    1988-09-13

    A helium dilution refrigeration system operable over a limited time period, and recyclable for a next period of operation is disclosed. The refrigeration system is compact with a self-contained pumping system and heaters for operation of the system. A mixing chamber contains [sup 3]He and [sup 4]He liquids which are precooled by a coupled container containing [sup 3]He liquid, enabling the phase separation of a [sup 3]He rich liquid phase from a dilute [sup 3]He-[sup 4]He liquid phase which leads to the final stage of a dilution cooling process for obtaining low temperatures. The mixing chamber and a still are coupled by a fluid line and are maintained at substantially the same level with the still cross sectional area being smaller than that of the mixing chamber. This configuration provides maximum cooling power and efficiency by the cooling period ending when the [sup 3]He liquid is depleted from the mixing chamber with the mixing chamber nearly empty of liquid helium, thus avoiding unnecessary and inefficient cooling of a large amount of the dilute [sup 3]He-[sup 4]He liquid phase. 2 figs.

  20. Helium dilution refrigeration system

    DOE Patents [OSTI]

    Roach, Patrick R.; Gray, Kenneth E.

    1988-01-01

    A helium dilution refrigeration system operable over a limited time period, and recyclable for a next period of operation. The refrigeration system is compact with a self-contained pumping system and heaters for operation of the system. A mixing chamber contains .sup.3 He and .sup.4 He liquids which are precooled by a coupled container containing .sup.3 He liquid, enabling the phase separation of a .sup.3 He rich liquid phase from a dilute .sup.3 He-.sup.4 He liquid phase which leads to the final stage of a dilution cooling process for obtaining low temperatures. The mixing chamber and a still are coupled by a fluid line and are maintained at substantially the same level with the still cross sectional area being smaller than that of the mixing chamber. This configuration provides maximum cooling power and efficiency by the cooling period ending when the .sup.3 He liquid is depleted from the mixing chamber with the mixing chamber nearly empty of liquid helium, thus avoiding unnecessary and inefficient cooling of a large amount of the dilute .sup.3 He-.sup.4 He liquid phase.

  1. The relationship between crack-tip strain and subcritical cracking...

    Office of Scientific and Technical Information (OSTI)

    crack-tip strain and subcritical cracking thresholds for steels in high-pressure hydrogen gas. Citation Details In-Document Search Title: The relationship between crack-tip...

  2. Effect of Helium Accumulation on the Spent Fuel Microstructure

    SciTech Connect (OSTI)

    Ferry, Cecile; Piron, Jean-Paul; Stout, Ray

    2007-07-01

    In a nuclear spent fuel repository, the aqueous rapid release of radio-activity from exposed spent fuel surfaces will depend on the pellet microstructure at the arrival time of water into the disposal container. Research performed on spent fuel evolution in a closed system has shown that the evolution of microstructure under disposal conditions should be governed by the cumulated {alpha}-decay damage and the subsequent helium behavior. The evolution of fission gas bubble characteristics under repository conditions has to be assessed. In UO{sub 2} fuels with a burnup of 47.5 GWd/t, the pressure in fission gas bubbles, including the pressure increase from {alpha}-decay helium atoms, is not expected to reach the critical bubble pressure that will cause failure, thus micro-cracking in UO{sub 2} spent fuel grains is not expected. (authors)

  3. Cavity morphology in a Ni based superalloy under heavy ion irradiation with hot pre-injected helium. II

    SciTech Connect (OSTI)

    Zhang, He; Yao, Zhongwen, E-mail: yaoz@me.queensu.ca; Daymond, Mark R. [Department of Mechanical and Materials Engineering, Queen's University Kingston, Ontario K7L 3N6 (Canada); Kirk, Marquis A. [Material Science Division, Argonne National Laboratory Argonne, Illinois 60439 (United States)

    2014-03-14

    In the current investigation, TEM in-situ heavy ion (1?MeV Kr{sup 2+}) irradiation with helium pre-injected at elevated temperature (400?C) was conducted to simulate in-reactor neutron irradiation induced damage in CANDU spacer material Inconel X-750, in an effort to understand the effects of helium on irradiation induced cavity microstructures. Three different quantities of helium, 400 appm, 1000 appm, and 5000 appm, were pre-injected directly into TEM foils at 400?C. The samples containing helium were then irradiated in-situ with 1?MeV Kr{sup 2+} at 400?C to a final dose of 5.4 dpa (displacement per atom). Cavities were formed from the helium injection solely and the cavity density and size increased with increasing helium dosage. In contrast to previous heavy ion irradiations with cold pre-injected helium, heterogeneous nucleation of cavities was observed. During the ensuing heavy ion irradiation, dynamical observation showed noticeable size increase in cavities which nucleated close to the grain boundaries. A bubble-void transformation was observed after Kr{sup 2+} irradiation to high dose (5.4?dpa) in samples containing 1000 appm and 5000 appm helium. Cavity distribution was found to be consistent with in-reactor neutron irradiation induced cavity microstructures. This implies that the distribution of helium is greatly dependent on the injection temperature, and helium pre-injection at high temperature is preferred for simulating the migration of the transmutation produced helium.

  4. Helium segregation on surfaces of plasma-exposed tungsten

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Maroudas, Dimitrios; Blondel, Sophie; Hu, Lin; Hammond, Karl D.; Wirth, Brian D.

    2016-01-21

    Here we report a hierarchical multi-scale modeling study of implanted helium segregation on surfaces of tungsten, considered as a plasma facing component in nuclear fusion reactors. We employ a hierarchy of atomic-scale simulations based on a reliable interatomic interaction potential, including molecular-statics simulations to understand the origin of helium surface segregation, targeted molecular-dynamics (MD) simulations of near-surface cluster reactions, and large-scale MD simulations of implanted helium evolution in plasma-exposed tungsten. We find that small, mobile He-n (1 <= n <= 7) clusters in the near-surface region are attracted to the surface due to an elastic interaction force that provides themore » thermodynamic driving force for surface segregation. Elastic interaction force induces drift fluxes of these mobile Hen clusters, which increase substantially as the migrating clusters approach the surface, facilitating helium segregation on the surface. Moreover, the clusters' drift toward the surface enables cluster reactions, most importantly trap mutation, in the near-surface region at rates much higher than in the bulk material. Moreover, these near-surface cluster dynamics have significant effects on the surface morphology, near-surface defect structures, and the amount of helium retained in the material upon plasma exposure. We integrate the findings of such atomic-scale simulations into a properly parameterized and validated spatially dependent, continuum-scale reaction-diffusion cluster dynamics model, capable of predicting implanted helium evolution, surface segregation, and its near-surface effects in tungsten. This cluster-dynamics model sets the stage for development of fully atomistically informed coarse-grained models for computationally efficient simulation predictions of helium surface segregation, as well as helium retention and surface morphological evolution, toward optimal design of plasma facing components.« less

  5. LPG storage vessel cracking experience

    SciTech Connect (OSTI)

    Cantwell, J.E. )

    1988-10-01

    In order to evaluate liquefied petroleum gas (LPG) handling and storage hazards, Caltex Petroleum Corp. (Dallas) surveyed several installations for storage vessel cracking problems. Cracking was found in approximately one-third of the storage vessels. In most cases, the cracking appeared to be due to original fabrication problems and could be removed without compromising the pressure containment. Several in-service cracking problems found were due to exposure to wet hydrogen sulfide. Various procedures were tried in order to minimize the in-service cracking potential. One sphere was condemned because of extensive subsurface cracking. This article's recommendations concern minimizing cracking on new and existing LPG storage vessels.

  6. LPG storage vessel cracking experience

    SciTech Connect (OSTI)

    Cantwell, J.E.

    1988-01-01

    As part of an overall company program to evaluate LPG handling and storage hazards the authors surveyed several installations for storage vessel cracking problems. Cracking was found in approximately one third of the storage vessels. In most cases the cracking appeared due to original fabrication problems and could be removed without compromising the pressure containment. Several in-service cracking problems due to exposure to wet hydrogen sulfide were found. Various procedures were tried in order to minimize the in-service cracking potential. One sphere was condemned because of extensive subsurface cracking. Recommendations are made to minimize cracking on new and existing LPG storage vessels.

  7. ITER helium ash accumulation

    SciTech Connect (OSTI)

    Hogan, J.T.; Hillis, D.L.; Galambos, J.; Uckan, N.A. ); Dippel, K.H.; Finken, K.H. . Inst. fuer Plasmaphysik); Hulse, R.A.; Budny, R.V. . Plasma Physics Lab.)

    1990-01-01

    Many studies have shown the importance of the ratio {upsilon}{sub He}/{upsilon}{sub E} in determining the level of He ash accumulation in future reactor systems. Results of the first tokamak He removal experiments have been analysed, and a first estimate of the ratio {upsilon}{sub He}/{upsilon}{sub E} to be expected for future reactor systems has been made. The experiments were carried out for neutral beam heated plasmas in the TEXTOR tokamak, at KFA/Julich. Helium was injected both as a short puff and continuously, and subsequently extracted with the Advanced Limiter Test-II pump limiter. The rate at which the He density decays has been determined with absolutely calibrated charge exchange spectroscopy, and compared with theoretical models, using the Multiple Impurity Species Transport (MIST) code. An analysis of energy confinement has been made with PPPL TRANSP code, to distinguish beam from thermal confinement, especially for low density cases. The ALT-II pump limiter system is found to exhaust the He with maximum exhaust efficiency (8 pumps) of {approximately}8%. We find 1<{upsilon}{sub He}/{upsilon}{sub E}<3.3 for the database of cases analysed to date. Analysis with the ITER TETRA systems code shows that these values would be adequate to achieve the required He concentration with the present ITER divertor He extraction system.

  8. Pulsed helium ionization detection system

    DOE Patents [OSTI]

    Ramsey, Roswitha S. (Knoxville, TN); Todd, Richard A. (Knoxville, TN)

    1987-01-01

    A helium ionization detection system is provided which produces stable operation of a conventional helium ionization detector while providing improved sensitivity and linearity. Stability is improved by applying pulsed dc supply voltage across the ionization detector, thereby modifying the sampling of the detectors output current. A unique pulse generator is used to supply pulsed dc to the detector which has variable width and interval adjust features that allows up to 500 V to be applied in pulse widths ranging from about 150 nsec to about dc conditions.

  9. Pulsed helium ionization detection system

    DOE Patents [OSTI]

    Ramsey, R.S.; Todd, R.A.

    1985-04-09

    A helium ionization detection system is provided which produces stable operation of a conventional helium ionization detector while providing improved sensitivity and linearity. Stability is improved by applying pulsed dc supply voltage across the ionization detector, thereby modifying the sampling of the detectors output current. A unique pulse generator is used to supply pulsed dc to the detector which has variable width and interval adjust features that allows up to 500 V to be applied in pulse widths ranging from about 150 nsec to about dc conditions.

  10. Catalytic cracking process

    DOE Patents [OSTI]

    Lokhandwala, Kaaeid A.; Baker, Richard W.

    2001-01-01

    Processes and apparatus for providing improved catalytic cracking, specifically improved recovery of olefins, LPG or hydrogen from catalytic crackers. The improvement is achieved by passing part of the wet gas stream across membranes selective in favor of light hydrocarbons over hydrogen.

  11. CIRCUMFERENTIAL MFL IN-LINE INSPECTION FOR CRACKS IN PIPELINES

    SciTech Connect (OSTI)

    J.B. Nestleroth

    2003-06-01

    Circumferential MFL is a new implementation of a widely used technology that has potential to provide improved detection and quantification of axially oriented defects such as cracks, seam weld defects, mechanical damage, and groove corrosion. This implementation works by orienting the magnetic field around the pipe rather that along the axis. By orienting the magnetic field around the pipe (the circumferential direction), the axial defects that were magnetically transparent can disrupt more of the magnetic field and can be more easily detected. Initial implementations of circumferential MFL have found that flux leakage from cracks at the interior of the pipe is small, and the signals from cracks are difficult to detect. The objective of this project is to improve detection of cracks by changing the implementation along with using data from overlapping and complementary inspection techniques. Two technology enhancements were investigated: Combining high- and low-magnetization technology for stress detection; and Combining axial and circumferential MFL methods. Although a method combining high- and low-magnetization technology showed promise for characterizing gouges cause by third party excavation equipment, its commercial development was not successful for two reasons. First, the stress diminishes the crack signal, while the opening of the crack increases the signal. The stress-induced changes in flux leakage around cracks were small and any critical information on the severity of cracks and crack-like defects is difficult to distinguish from changes caused by the crack opening and other inspection variables. Second, it is difficult to magnetize pipe material in the circumferential direction. A relatively low, non-uniform magnetization level produced by the circumferential magnetizer makes detection of changes due to stress extremely difficult. This project also examined combining axial and circumferential MFL to improve crack detection and distinguish cracks for

  12. Insights into Stress Corrosion Cracking Mechanisms from High-Resolution Measurements of Crack-Tip Structures and Compositions

    SciTech Connect (OSTI)

    Bruemmer, Stephen M.; Thomas, Larry E.

    2010-04-05

    The fundamental basis for mechanistic understanding and modeling of SCC remains in question for many systems. Specific mechanisms controlling SCC can vary with changes in alloy characteristics, applied/residual stress or environmental conditions. The local crack electrochemistry, crack-tip mechanics and material metallurgy are the main factors controlling crack growth. These localized properties are difficult or impossible to measure in active cracks. Nevertheless, it is essential to quantitatively interrogate these crack-tip conditions if mechanistic understanding is to be obtained. A major recent advance has been the ability to investigate SCC cracks and crack tips using high-resolution ATEM techniques. ATEM enables the characterization of SCC cracks including trapped tip solution chemistries, corrosion product/film compositions and structures, and elemental composition gradients and defect microstructures along the crack walls and at the crack tip. A wide variety of methods for imaging and analyses at resolutions down to the atomic level can be used to examine the crack and corrosion film characteristics. Surface films and reaction layers have been examined by cross-sectional TEM techniques, but little work had been conducted on environmentally induced internal cracks until that of Lewis and co-workers [1-3] and the current authors [4-17]. This capability combined with modern ATEM techniques has enabled exciting new insights into corrosion processes occurring at buried interfaces and is being used to identify mechanisms controlling IGSCC in boiling water reactor (BWR) and pressurized water reactor (PWR) components. The objective of this paper is to summarize certain results focused on IGSCC of Fe- base and Ni-base stainless alloys in high-temperature water environments. Representative crack-tip examples will be shown to illustrate specific aspects that are characteristic of SCC in the material/environment combinations. Differences and similarities in crack

  13. Energy, helium, and the future: II

    SciTech Connect (OSTI)

    Krupka, M.C.; Hammel, E.F.

    1980-01-01

    The importance of helium as a critical resource material has been recognized specifically by the scientific community and more generally by the 1960 Congressional mandate to institute a long-range conservation program. A major study mandated by the Energy Reorganization Act of 1974 resulted in the publication in 1975 of the document, The Energy-Related Applications of Helium, ERDA-13. This document contained a comprehensive review and analysis relating to helium resources and present and future supply/demand relationships with particular emphasis upon those helium-dependent energy-related technologies projected to be implemented in the post-2000 year time period, e.g., fusion. An updated overview of the helium situation as it exists today is presented. Since publication of ERDA-13, important changes in the data base underlying that document have occurred. The data have since been reexamined, revised, and new information included. Potential supplies of helium from both conventional and unconventional natural gas resources, projected supply/demand relationships to the year 2030 based upon a given power-generation scenario, projected helium demand for specific energy-related technologies, and the supply options (national and international) available to meet that demand are discussed. An updated review will be given of the energy requirements for the extraction of helium from natural gas as they relate to the concentration of helium. A discussion is given concerning the technical and economic feasibility of several methods available both now and conceptually possible, to extract helium from helium-lean natural gas, the atmosphere, and outer space. Finally, a brief review is given of the 1980 Congressional activities with respect to the introduction and possible passage of new helium conservation legislation.

  14. Heat-affected zone liquation crack on resistance spot welded TWIP steels

    SciTech Connect (OSTI)

    Saha, Dulal Chandra [Department of Advanced Materials Engineering, Dong-Eui University, 995 Eomgwangno, Busanjin-gu, Busan 614-714 (Korea, Republic of); Chang, InSung [Automotive Production Development Division, Hyundai Motor Company (Korea, Republic of); Park, Yeong-Do, E-mail: ypark@deu.ac.kr [Department of Advanced Materials Engineering, Dong-Eui University, 995 Eomgwangno, Busanjin-gu, Busan 614-714 (Korea, Republic of)

    2014-07-01

    In this study, the heat affected zone (HAZ) liquation crack and segregation behavior of the resistance spot welded twinning induced plasticity (TWIP) steel have been reported. Cracks appeared in the post-welded joints that originated at the partially melted zone (PMZ) and propagated from the PMZ through the heat affected zone (HAZ) to the base metal (BM). The crack length and crack opening widths were observed increasing with heat input; and the welding current was identified to be the most influencing parameter for crack formation. Cracks appeared at the PMZ when nugget diameter reached at 4.50 mm or above; and the liquation cracks were found to occur along two sides of the notch tip in the sheet direction rather than in the electrode direction. Cracks were backfilled with the liquid films which has lamellar structure and supposed to be the eutectic constituent. Co-segregation of alloy elements such as, C and Mn were detected on the liquid films by electron-probe microanalysis (EPMA) line scanning and element map which suggests that the liquid film was enrich of Mn and C. The eutectic constituent was identified by analyzing the calculated phase diagram along with thermal temperature history of finite element simulation. Preliminary experimental results showed that cracks have less/no significant effect on the static cross-tensile strength (CTS) and the tensile-shear strength (TSS). In addition, possible ways to avoid cracking were discussed. - Highlights: The HAZ liquation crack during resistance spot welding of TWIP steel was examined. Cracks were completely backfilled and healed with divorced eutectic secondary phase. Co-segregation of C and Mn was detected in the cracked zone. Heat input was the most influencing factor to initiate liquation crack. Cracks have less/no significant effect on static tensile properties.

  15. LANL researchers simulate helium bubble behavior in fusion reactors

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Researchers simulate helium bubble behavior LANL researchers simulate helium bubble behavior in fusion reactors A team performed simulations to understand more fully how tungsten behaves in such harsh conditions, particularly in the presence of implanted helium that forms bubbles in the material. August 4, 2015 Simulation snapshots of the helium bubble just before bursting. Colors indicate tungsten atoms (red) and helium atoms (blue). Simulation snapshots of the helium bubble just before

  16. Double, Double Toil and Trouble: Tungsten Burns and Helium Bubbles...

    Office of Science (SC) Website

    Helium bubbles are detrimental to plasma-facing materials such as tungsten in fusion reactors, which could serve as a possible new power source. Thus, understanding how helium ...

  17. Surprisingly Large Generation and Retention of Helium and Hydrogen...

    Office of Scientific and Technical Information (OSTI)

    Journal Article: Surprisingly Large Generation and Retention of Helium and Hydrogen in ... Title: Surprisingly Large Generation and Retention of Helium and Hydrogen in Pure Nickel ...

  18. Helium Migration Mechanisms in Polycrystalline Uranium Dioxide

    SciTech Connect (OSTI)

    Martin, Guillaume; Desgardin, Pierre; Sauvage, Thierry; Barthe, Marie-France; Garcia, Philippe; Carlot, Gaelle

    2007-07-01

    This study aims at identifying the release mechanisms of helium in uranium dioxide. Two sets of polycrystalline UO{sub 2} sintered samples presenting different microstructures were implanted with {sup 3}He ions at concentrations in the region of 0.1 at.%. Changes in helium concentrations were monitored using two Nuclear Reaction Analysis (NRA) techniques based on the {sup 3}He(d,{alpha}){sup 1}H reaction. {sup 3}He release is measured in-situ during sample annealing at temperatures ranging between 700 deg. C and 1000 deg. C. Accurate helium depth profiles are generated after each annealing stage. Results that provide data for further understanding helium release mechanisms are discussed. It is found that helium diffusion appears to be enhanced above 900 deg. C in the vicinity of grain boundaries possibly as a result of the presence of defects. (authors)

  19. Influence of Composition, Helium Generation Rate and Dpa Rate on Neutron-Induced Swelling of Fe-15Cr-16Ni-0.25Ti Alloys in FFTF at {approx} 400 Degrees C

    SciTech Connect (OSTI)

    Okita, T; Wolfer, W G; Sato, T; Sekimura, N; Garner, F A

    2003-08-05

    Contrary to the behavior of swelling of f.c.c. Fe-15Cr-16Ni and Fe-15Cr-16Ni-0.25Ti alloys irradiated together in the same FFTF-MOTA experiment, Fe-15Cr-16Ti-0.25Ti-0.05C does not exhibit a dependence of swelling on dpa rate at {approx}400 C. The transient regime of swelling is prolonged by carbon addition, however. Addition of boron to the carbon-doped alloy decreases the swelling somewhat but does not restore the sensitivity to dpa rate. It appears that the primary influence of boron is chemical in nature, probably associated with boron's impact on the behavior of carbon. Boron's role as a source of helium is thought to be secondary.

  20. Peridynamic model for fatigue cracking.

    SciTech Connect (OSTI)

    Silling, Stewart A.; Abe Askari

    2014-10-01

    The peridynamic theory is an extension of traditional solid mechanics in which the field equations can be applied on discontinuities, such as growing cracks. This paper proposes a bond damage model within peridynamics to treat the nucleation and growth of cracks due to cyclic loading. Bond damage occurs according to the evolution of a variable called the %22remaining life%22 of each bond that changes over time according to the cyclic strain in the bond. It is shown that the model reproduces the main features of S-N data for typical materials and also reproduces the Paris law for fatigue crack growth. Extensions of the model account for the effects of loading spectrum, fatigue limit, and variable load ratio. A three-dimensional example illustrates the nucleation and growth of a helical fatigue crack in the torsion of an aluminum alloy rod.

  1. Helium refrigeration considerations for cryomodule design

    SciTech Connect (OSTI)

    Ganni, V.; Knudsen, P.

    2014-01-29

    Many of the present day accelerators are based on superconducting radio frequency (SRF) cavities, packaged in cryo-modules (CM), which depend on helium refrigeration at sub-atmospheric pressures, nominally 2 K. These specialized helium refrigeration systems are quite cost intensive to produce and operate. Particularly as there is typically no work extraction below the 4.5-K supply, it is important that the exergy loss between this temperature level and the CM load temperature(s) be minimized by the process configuration choices. This paper will present, compare and discuss several possible helium distribution process arrangements to support the CM loads.

  2. Cracking behavior of cored structures

    SciTech Connect (OSTI)

    Wahid, A.; Olson, D.L.; Matlock, D.K.; Kelly, T.J.

    1991-12-31

    The effects of compositional gradients, are considered based on a thermodynamic analysis, referred to as the Cahn-Hillard analysis, which describes the degree to which a local surface energy is modified by the presence of a composition gradient. The analysis predicts that both ductile and brittle fracture mechanisms are enhanced by the presence of a composition gradient. Data on stress corrosion cracking and fatigue crack growth in selected FCC alloys are used to illustrate the significance of microsegregation on mechanical properties.

  3. Cracking behavior of cored structures

    SciTech Connect (OSTI)

    Wahid, A.; Olson, D.L.; Matlock, D.K. . Center for Welding and Joining Research); Kelly, T.J. )

    1991-01-01

    The effects of compositional gradients, are considered based on a thermodynamic analysis, referred to as the Cahn-Hillard analysis, which describes the degree to which a local surface energy is modified by the presence of a composition gradient. The analysis predicts that both ductile and brittle fracture mechanisms are enhanced by the presence of a composition gradient. Data on stress corrosion cracking and fatigue crack growth in selected FCC alloys are used to illustrate the significance of microsegregation on mechanical properties.

  4. Tritium-helium effects in metals

    SciTech Connect (OSTI)

    Caskey, G.R.

    1985-09-01

    Investigations of helium effects in metals at the Savannah River Laboratory have been carried out by introducing helium by radioactive decay of tritium. This process does not create concurrent radiation damage, such as accompanies ion implantation and (n,..cap alpha..) reactions. The process has its own peculiarities, however, which partially mask and interact with the helium effect of interest. The distribution and local concentration of helium and tritium, which are responsible for changes in mechanical properties and fracture mode, are controlled by the large difference in solubility and diffusivity between the two atoms and by their differing interaction energies with lattice defects, impurities, and internal boundaries. Furthermore, in all investigations with helium generated from tritium decay, some tritium and deuterium are always present. Consequently, property changes include tritium-helium interaction effects to some extent. Results of investigations with several austenitic stainless steels, Armco iron, and niobium single crystals illustrate the variety of phenomena and some of the complex interactions that can be encountered.

  5. Tritium-helium effects in metals

    SciTech Connect (OSTI)

    Caskey, G.R. Jr.

    1985-01-01

    Investigations of helium effects in metals at the Savannah River Laboratory have been carried out by introducing helium by radioactive decay of tritium. This process does not create concurrent radiation damage, such as accompanies ion implantation and (n,..cap alpha..) reactions. The process has its own peculiarities, however, which partially mask and interact with the helium effect of interest. The distribution and local concentration of helium and tritium, which are responsible for changes in mechanical properties and fracture mode, are controlled by the large difference in solubility and diffusivity between the two atoms and by their differing interaction energies with lattice defects, impurities, and internal boundaries. Furthermore, in all investigations with helium generated from tritium decay, some tritium and deuterium are always present. Consequently, property changes include tritium-helium interaction effects to some extent. Results of investigations with several austenitic stainless steels, Armco iron, and niobium single crystals illustrate the variety of phenomena and some of the complex interactions that can be encountered.

  6. Innovative Approach to Establish Root Causes for Cracking in Aggressive Reactor Environments

    SciTech Connect (OSTI)

    Bruemmer, Stephen M.; Thomas, Larry E.; Vetrano, John S.; Simonen, Edward P.

    2003-10-31

    The research focuses on the high-resolution characterization of degradation microstructures and microchemistries in specimens tested under controlled conditions for the environment and for the material where in-service complexities can be minimized. Thermodynamic and kinetic modeling of crack-tip processes is employed to analyze corrosion-induced structures and gain insights into degradation mechanisms. Novel mechanistic ''fingerprinting'' of crack-tip structures is used to isolate causes of environmental cracking in tandem with quantitative measurements of crack growth. Sample preparation methods and advanced analytical techniques are used to characterize corrosion/oxidation reactions and crack-tip structures at near atomic dimensions in order to gain insight into fundamental environmental cracking mechanisms. Reactions at buried interfaces, not accessible by conventional approaches, are being systematically interrogated. Crack-growth experiments in high-temperature water environments are evaluating and isolating the effects of material condition (matrix strength, grain boundary composition and precipitation) on stress corrosion cracking (SCC). The fundamental understanding of crack advance mechanisms will establish the basis to design new corrosion-resistant alloys for current light-water reactors and advanced reactor systems.

  7. Getter materials for cracking ammonia

    DOE Patents [OSTI]

    Boffito, Claudio; Baker, John D.

    1999-11-02

    A method is provided for cracking ammonia to produce hydrogen. The method includes the steps of passing ammonia over an ammonia-cracking catalyst which is an alloy including (1) alloys having the general formula Zr.sub.1-x Ti.sub.x M.sub.1 M.sub.2, wherein M.sub.1 and M.sub.2 are selected independently from the group consisting of Cr, Mn, Fe, Co, and Ni, and x is between about 0.0 and about 1.0 inclusive; and between about 20% and about 50% Al by weight. In another aspect, the method of the invention is used to provide methods for operating hydrogen-fueled internal combustion engines and hydrogen fuel cells. In still another aspect, the present invention provides a hydrogen-fueled internal combustion engine and a hydrogen fuel cell including the above-described ammonia-cracking catalyst.

  8. Environmentally assisted cracking in light water reactors. Semiannual report, July 1998-December 1998.

    SciTech Connect (OSTI)

    Chopra, O. K.; Chung, H. M.; Gruber, E. E.; Kassner, T. F.; Ruther, W. E.; Shack, W. J.; Smith, J. L.; Soppet, W. K.; Strain; R. V.

    1999-10-01

    This report summarizes work performed by Argonne National Laboratory on fatigue and environmentally assisted cracking (EAC) in light water reactors from July 1998 to December 1998. Topics that have been investigated include (a) environmental effects on fatigue S-N behavior of primary pressure boundary materials, (b) irradiation-assisted stress corrosion cracking of austenitic stainless steels (SSs), and (c) EAC of Alloys 600 and 690. Fatigue tests have been conducted to determine the crack initiation and crack growth characteristics of austenitic SSs in LWR environments. Procedures are presented for incorporating the effects of reactor coolant environments on the fatigue life of pressure vessel and piping steels. Slow-strain-rate tensile tests and posttest fractographic analyses were conducted on several model SS alloys irradiated to {approx}0.3 and 0.9 x 10{sup 21} n {center_dot} cm{sup -2} (E > 1 MeV) in helium at 289 C in the Halden reactor. The results have been used to determine the influence of alloying and impurity elements on the susceptibility of these steels to irradiation-assisted stress corrosion cracking. Fracture toughness J-R curve tests were also conducted on two heats of Type 304 SS that were irradiated to {approx}0.3 x 10{sup 21} n {center_dot} cm{sup -2} in the Halden reactor. Crack-growth-rate tests have been conducted on compact-tension specimens of Alloys 600 and 690 under constant load to evaluate the resistance of these alloys to stress corrosion cracking in LWR environments.

  9. Nonlinear structural crack growth monitoring

    DOE Patents [OSTI]

    Welch, Donald E.; Hively, Lee M.; Holdaway, Ray F.

    2002-01-01

    A method and apparatus are provided for the detection, through nonlinear manipulation of data, of an indicator of imminent failure due to crack growth in structural elements. The method is a process of determining energy consumption due to crack growth and correlating the energy consumption with physical phenomena indicative of a failure event. The apparatus includes sensors for sensing physical data factors, processors or the like for computing a relationship between the physical data factors and phenomena indicative of the failure event, and apparatus for providing notification of the characteristics and extent of such phenomena.

  10. TRANSPARENT HELIUM IN STRIPPED ENVELOPE SUPERNOVAE

    SciTech Connect (OSTI)

    Piro, Anthony L.; Morozova, Viktoriya S., E-mail: piro@caltech.edu [Theoretical Astrophysics, California Institute of Technology, 1200 E. California Blvd., M/C 350-17, Pasadena, CA 91125 (United States)

    2014-09-01

    Using simple arguments based on photometric light curves and velocity evolution, we propose that some stripped envelope supernovae (SNe) show signs that a significant fraction of their helium is effectively transparent. The main pieces of evidence are the relatively low velocities with little velocity evolution, as are expected deep inside an exploding star, along with temperatures that are too low to ionize helium. This means that the helium should not contribute to the shaping of the main SN light curve, and thus the total helium mass may be difficult to measure from simple light curve modeling. Conversely, such modeling may be more useful for constraining the mass of the carbon/oxygen core of the SN progenitor. Other stripped envelope SNe show higher velocities and larger velocity gradients, which require an additional opacity source (perhaps the mixing of heavier elements or radioactive nickel) to prevent the helium from being transparent. We discuss ways in which similar analysis can provide insights into the differences and similarities between SNe Ib and Ic, which will lead to a better understanding of their respective formation mechanisms.

  11. Prevention of crack initiation in valve bodies under thermal shock

    SciTech Connect (OSTI)

    Delmas, J.; Coppolani, P.

    1996-12-01

    On site and testing experience has shown that cracking in valves affects mainly the stellite hardfacing on seats and discs but may also be a concern for valve bodies. Metallurgical investigations conducted by EDF laboratories on many damaged valves have shown that most of the damage had either a chemical, manufacturing, or operating origin with a strong correlation between the origins and the type of damage. The chemical defects were either excess ferritic dilution of stellite or excess carburizing. Excess carburizing leads to a too brittle hardfacing which cracks under excessive stresses induced on the seating surfaces, via the stem, by too high operating thrusts. The same conditions can also induce cracks of the seats in the presence, in the hardfacing, of hidden defects generated during the welding process. Reduction of the number of defects results first from controls during manufacturing, mainly in the thickness of stellite. On the other hand, maintenance must be fitted to the type of defect. In-situ lapping may lead to release of cobalt, resulting in contamination of the circuit. Furthermore, it is ineffectual in the case of a crack through the seating surface, as is often found on globe valves. The use of new technologies of valves with removable seats and cobalt-free alloys solves permanently this kind of problem.

  12. J-controlled crack growth as an indicator of hydrogen-stainless steel compatibility

    SciTech Connect (OSTI)

    Dietrich, M.R.; Caskey, G.R. Jr.; Donovan, J.A.

    1980-01-01

    The J-integral was evaluated as a parameter to characterize fracture of stainless steels and as a measure of hydrogen damage. C-shaped specimens of type 304L, 316, and 21-6-9 stainless steels were tested in high pressure helium and hydrogen. The critical force for crack initiation (Jm), and tearing resistance (dJ/da) were decreased by hydrogen in all three alloys. The J-integral appears useful as a measure of hydrogen compatibility because it is sensitive to both test environment and microstructure.

  13. SCREW COMPRESSOR CHARACTERISTICS FOR HELIUM REFRIGERATION SYSTEMS

    SciTech Connect (OSTI)

    Ganni, Venkatarao; Knudsen, Peter; Creel, Jonathan; Arenius, Dana; Casagrande, Fabio; Howell, Matt

    2008-03-01

    The oil injected screw compressors have practically replaced all other types of compressors in modern helium refrigeration systems due to their large displacement capacity, minimal vibration, reliability and capability of handling helium's high heat of compression.At the present state of compressor system designs for helium systems, typically two-thirds of the lost input power is due to the compression system. Therefore it is important to understand the isothermal and volumetric efficiencies of these machines to help properly design these compression systems to match the refrigeration process. This presentation summarizes separate tests that have been conducted on Sullair compressors at the Superconducting Super-Collider Laboratory (SSCL) in 1993, Howden compressors at Jefferson Lab (JLab) in 2006 and Howden compressors at the Spallation Neutron Source (SNS) in 2006. This work is part of an ongoing study at JLab to understand the theoretical basis for these efficiencies and their loss

  14. Continuum-scale Modeling of Hydrogen and Helium Bubble Growth...

    Office of Environmental Management (EM)

    Continuum-scale Modeling of Hydrogen and Helium Bubble Growth in Metals Continuum-scale Modeling of Hydrogen and Helium Bubble Growth in Metals Presentation from the 34th Tritium ...

  15. Fatigue cracking of a bare steel first wall in an inertial confinement fusion chamber

    SciTech Connect (OSTI)

    Hunt, R. M.; Abbott, R. P.; Havstad, M. A.; Dunne, A. M.

    2013-06-01

    Inertial confinement fusion power plants will deposit high energy X-rays onto the outer surfaces of the first wall many times a second for the lifetime of the plant. These X-rays create brief temperature spikes in the first few microns of the wall, which cause an associated highly compressive stress response on the surface of the material. The periodicity of this stress pulse is a concern due to the possibility of fatigue cracking of the wall. We have used finite element analyses to simulate the conditions present on the first wall in order to evaluate the driving force of crack propagation on fusion-facing surface cracks. Analysis results indicate that the X-ray induced plastic compressive stress creates a region of residual tension on the surface between pulses. This tension film will likely result in surface cracking upon repeated cycling. Additionally, the compressive pulse may induce plasticity ahead of the crack tip, leaving residual tension in its wake. However, the stress amplitude decreases dramatically for depths greater than 80100 ?m into the fusion-facing surface. Crack propagation models as well as stress-life estimates agree that even though small cracks may form on the surface of the wall, they are unlikely to propagate further than 100 ?m without assistance from creep or grain erosion phenomena.

  16. Creep crack growth in ductile alloys

    SciTech Connect (OSTI)

    Argon, A.S.; Lau, C.W.; Ozmat, B.; Parks, D.M.

    1984-01-01

    Creep crack growth in ductile alloys involves considerable fragmentation of the crack tip region in its early phases of growth. This is a result of the defocusing action of crack tip blunting by both distortional and cavitational strains on the distribution of intergranular creep damage and is affected significantly by the initial sharpness of the crack. Specific models of intergranular damage combining non-steady creep flow, evolution and growth of grain boundary facet cracks in the inelastic deformation field leading to final fracture have been developed. When used in conjunction with finite element programs for crack tips, these damage models can explain such crack extension modes. The combination of mechanistic three dimensional damage models and large strain finite element codes, promise to be of wide-spread utility in predicting the development of creep damage under complex loading histories.

  17. A comparison of hydrogen vs. helium glow discharge effects on fusion device first-wall conditioning

    SciTech Connect (OSTI)

    Dylla, H.F.

    1989-09-01

    Hydrogen- and deuterium-fueled glow discharges are used for the initial conditioning of magnetic fusion device vacuum vessels following evacuation from atmospheric pressure. Hydrogenic glow discharge conditioning (GDC) significantly reduces the near-surface concentration of simple adsorbates, such as H/sub 2/O, CO, and CH/sub 4/, and lowers ion-induced desorption coefficients by typically three orders of magnitude. The time evolution of the residual gas production observed during hydrogen-glow discharge conditioning of the carbon first-wall structure of the TFTR device is similar to the time evolution observed during hydrogen GDC of the initial first-wall configuration in TFTR, which was primarily stainless steel. Recently, helium GDC has been investigated for several wall-conditioning tasks on a number of tokamaks including TFTR. Helium GDC shows negligible impurity removal with stainless steel walls. For impurity conditioning with carbon walls, helium GDC shows significant desorption of H/sub 2/O, CO, and CO/sub 2/; however, the total desorption yield is limited to the monolayer range. In addition, helium GDC can be used to displace hydrogen isotopes from the near-surface region of carbon first-walls in order to lower hydrogenic retention and recycling. 38 refs., 6 figs.

  18. Helium bubble formation in ultrafine and nanocrystalline tungsten under different extreme conditions

    SciTech Connect (OSTI)

    El-atwani, O.; Hattar, Khalid Mikhiel; Hinks, J. A.; Greaves, G.; Harilal, S. S.; Hassanein, A.

    2014-12-25

    We investigated the effects of helium ion irradiation energy and sample temperature on the performance of grain boundaries as helium sinks in ultrafine grained and nanocrystalline tungsten. Irradiations were performed at displacement and non-displacement energies and at temperatures above and below that required for vacancy migration. Microstructural investigations were performed using Transmission Electron Microscopy (TEM) combined with either in-situ or ex-situ ion irradiation. Under helium irradiation at an energy which does not cause atomic displacements in tungsten (70 eV), regardless of temperature and thus vacancy migration conditions, bubbles were uniformly distributed with no preferential bubble formation on grain boundaries. Moreover, at energies that can cause displacements, bubbles were observed to be preferentially formed on the grain boundaries only at high temperatures where vacancy migration occurs. Under these conditions, the decoration of grain boundaries with large facetted bubbles occurred on nanocrystalline grains with dimensions less than 60 nm. Finally, we discuss the importance of vacancy supply and the formation and migration of radiation-induced defects on the performance of grain boundaries as helium sinks and the resulting irradiation tolerance of ultrafine grained and nanocrystalline tungsten to bubble formation.

  19. Helium bubble formation in ultrafine and nanocrystalline tungsten under different extreme conditions

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    El-atwani, O.; Hattar, Khalid Mikhiel; Hinks, J. A.; Greaves, G.; Harilal, S. S.; Hassanein, A.

    2014-12-25

    We investigated the effects of helium ion irradiation energy and sample temperature on the performance of grain boundaries as helium sinks in ultrafine grained and nanocrystalline tungsten. Irradiations were performed at displacement and non-displacement energies and at temperatures above and below that required for vacancy migration. Microstructural investigations were performed using Transmission Electron Microscopy (TEM) combined with either in-situ or ex-situ ion irradiation. Under helium irradiation at an energy which does not cause atomic displacements in tungsten (70 eV), regardless of temperature and thus vacancy migration conditions, bubbles were uniformly distributed with no preferential bubble formation on grain boundaries. Moreover,more » at energies that can cause displacements, bubbles were observed to be preferentially formed on the grain boundaries only at high temperatures where vacancy migration occurs. Under these conditions, the decoration of grain boundaries with large facetted bubbles occurred on nanocrystalline grains with dimensions less than 60 nm. Finally, we discuss the importance of vacancy supply and the formation and migration of radiation-induced defects on the performance of grain boundaries as helium sinks and the resulting irradiation tolerance of ultrafine grained and nanocrystalline tungsten to bubble formation.« less

  20. Crack growth and propagation in metallic alloys

    SciTech Connect (OSTI)

    Morrey, W.C.; Wille, L.T.

    1996-12-01

    Using large-scale molecular dynamics simulation on a massively parallel computer, the authors have studied the initiation of cracking in a Monel-like alloy of Cu-Ni. In a low temperature 2D sample, fracture from a notch starts at a little beyond 2.5% critical strain when the propagation direction is perpendicular to a cleavage plane. The authors discuss a method of characterizing crack tip position using a measure of area around the crack tip.

  1. THERMAL OSCILLATIONS IN LIQUID HELIUM TARGETS.

    SciTech Connect (OSTI)

    WANG,L.; JIA,L.X.

    2001-07-16

    A liquid helium target for the high-energy physics was built and installed in the proton beam line at the Alternate Gradient Synchrotron of Brookhaven National Laboratory in 2001. The target flask has a liquid volume of 8.25 liters and is made of thin Mylar film. A G-M/J-T cryocooler of five-watts at 4.2K was used to produce liquid helium and refrigerate the target. A thermosyphon circuit for the target was connected to the J-T circuit by a liquid/gas separator. Because of the large heat load to the target and its long transfer lines, thermal oscillations were observed during the system tests. To eliminate the oscillation, a series of tests and analyses were carried out. This paper describes the phenomena and provides the understanding of the thermal oscillations in the target system.

  2. Closed-loop pulsed helium ionization detector

    DOE Patents [OSTI]

    Ramsey, Roswitha S.; Todd, Richard A.

    1987-01-01

    A helium ionization detector for gas chromatography is operated in a constant current, pulse-modulated mode by configuring the detector, electrometer and a high voltage pulser in a closed-loop control system. The detector current is maintained at a fixed level by varying the frequency of fixed-width, high-voltage bias pulses applied to the detector. An output signal proportional to the pulse frequency is produced which is indicative of the charge collected for a detected species.

  3. Combined cold compressor/ejector helium refrigerator

    DOE Patents [OSTI]

    Brown, Donald P.

    1985-01-01

    A refrigeration apparatus having an ejector operatively connected with a cold compressor to form a two-stage pumping system. This pumping system is used to lower the pressure, and thereby the temperature of a bath of boiling refrigerant (helium). The apparatus as thus arranged and operated has substantially improved operating efficiency when compared to other processes or arrangements for achieving a similar low pressure.

  4. Combined cold compressor/ejector helium refrigerator

    DOE Patents [OSTI]

    Brown, D.P.

    1984-06-05

    A refrigeration apparatus having an ejector operatively connected with a cold compressor to form a two-stage pumping system. This pumping system is used to lower the pressure, and thereby the temperature of a bath of boiling refrigerant (helium). The apparatus as thus arranged and operated has substantially improved operating efficiency when compared to other processes or arrangements for achieving a similar low pressure.

  5. Investigations of Low Temperature Time Dependent Cracking

    SciTech Connect (OSTI)

    Van der Sluys, W A; Robitz, E S; Young, B A; Bloom, J

    2002-09-30

    The objective of this project was to investigate metallurgical and mechanical phenomena associated with time dependent cracking of cold bent carbon steel piping at temperatures between 327 C and 360 C. Boiler piping failures have demonstrated that understanding the fundamental metallurgical and mechanical parameters controlling these failures is insufficient to eliminate it from the field. The results of the project consisted of the development of a testing methodology to reproduce low temperature time dependent cracking in laboratory specimens. This methodology was used to evaluate the cracking resistance of candidate heats in order to identify the factors that enhance cracking sensitivity. The resultant data was integrated into current available life prediction tools.

  6. Helium bubble linkage and the transition to rapid He release in aging Pd tritide.

    SciTech Connect (OSTI)

    Cowgill, Donald F.

    2006-02-01

    A model is presented for the linking of helium bubbles growing in aging metal tritides. Stresses created by neighboring bubbles are found to produce bubble growth toward coalescence. This process is interrupted by the fracture of ligaments between bubble arrays. The condition for ligament fracture percolates through the material to reach external surfaces, leading to material micro-cracking and the release of helium within the linked-bubble cluster. A comparison of pure coalescence and pure fracture mechanisms shows the critical HeM concentration for bubble linkage is not strongly dependent on details of the linkage process. The combined stress-directed growth and fracture process produces predictions for the onset of rapid He release and the He emission rate. Transition to this rapid release state is determined from the physical size of the linked-bubble clusters, which is calculated from dimensional invariants in classical percolation theory. The result is a transition that depends on material dimensions. The onset of bubble linkage and rapid He release are found to be quite sensitive to the bubble spacing distribution, which is log-normal for bubbles nucleated by self-trapping.

  7. In situ controlled modification of the helium density in single helium-filled nanobubbles

    SciTech Connect (OSTI)

    David, M.-L. Pailloux, F.; Alix, K.; Mauchamp, V.; Pizzagalli, L.; Couillard, M.; Botton, G. A.

    2014-03-28

    We demonstrate that the helium density and corresponding pressure can be modified in single nano-scale bubbles embedded in semiconductors by using the electron beam of a scanning transmission electron microscope as a multifunctional probe: the measurement probe for imaging and chemical analysis and the irradiation source to modify concomitantly the pressure in a controllable way by fine tuning of the electron beam parameters. The control of the detrapping rate is achieved by varying the experimental conditions. The underlying physical mechanisms are discussed; our experimental observations suggest that the helium detrapping from bubbles could be interpreted in terms of direct ballistic collisions, leading to the ejection of the helium atoms from the bubble.

  8. Development of crack shape: LBB methodology for cracked pipes

    SciTech Connect (OSTI)

    Moulin, D.; Chapuliot, S.; Drubay, B.

    1997-04-01

    For structures like vessels or pipes containing a fluid, the Leak-Before-Break (LBB) assessment requires to demonstrate that it is possible, during the lifetime of the component, to detect a rate of leakage due to a possible defect, the growth of which would result in a leak before-break of the component. This LBB assessment could be an important contribution to the overall structural integrity argument for many components. The aim of this paper is to review some practices used for LBB assessment and to describe how some new R & D results have been used to provide a simplified approach of fracture mechanics analysis and especially the evaluation of crack shape and size during the lifetime of the component.

  9. Research questions reality of 'supersolid' in helium-4

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Research questions reality of 'supersolid' in helium-4 Research questions reality of 'supersolid' in helium-4 When cooled to temperatures below minus 452 degrees below zero Fahrenheit, helium-4 becomes a liquid-and an extraordinary liquid at that. May 17, 2011 Los Alamos National Laboratory sits on top of a once-remote mesa in northern New Mexico with the Jemez mountains as a backdrop to research and innovation covering multi-disciplines from bioscience, sustainable energy sources, to plasma

  10. Crack initiation under generalized plane strain conditions

    SciTech Connect (OSTI)

    Shum, D.K.M.; Merkle, J.G.

    1991-01-01

    A method for estimating the decrease in crack-initiation toughness, from a reference plane strain value, due to positive straining along the crack front of a circumferential flaw in a reactor pressure vessel is presented in this study. This method relates crack initiation under generalized plane strain conditions with material failure at points within a distance of a few crack-tip-opening displacements ahead of a crack front, and involves the formulation of a micromechanical crack-initiation model. While this study is intended to address concerns regarding the effects of positive out-of- plane straining on ductile crack initiation, the approach adopted in this work can be extended in a straightforward fashion to examine conditions of macroscopic cleavage crack initiation. Provided single- parameter dominance of near-tip fields exists in the flawed structure, results from this study could be used to examine the appropriateness of applying plane strain fracture toughness to the evaluation of circumferential flaws, in particular to those in ring-forged vessels which have no longitudinal welds. In addition, results from this study could also be applied toward the analysis of the effects of thermal streaming on the fracture resistance of circumferentially oriented flaws in a pressure vessel. 37 refs., 8 figs., 1 tab.

  11. Investigation of Cracked Lithium Hydride Reactor Vessels

    SciTech Connect (OSTI)

    bird, e.l.; mustaleski, t.m.

    1999-06-01

    Visual examination of lithium hydride reactor vessels revealed cracks that were adjacent to welds, most of which were circumferentially located in the bottom portion of the vessels. Sections were cut from the vessels containing these cracks and examined by use of the metallograph, scanning electron microscope, and microprobe to determine the cause of cracking. Most of the cracks originated on the outer surface just outside the weld fusion line in the base material and propagated along grain boundaries. Crack depths of those examined sections ranged from {approximately}300 to 500 {micro}m. Other cracks were reported to have reached a maximum depth of 1/8 in. The primary cause of cracking was the creation of high tensile stresses associated with the differences in the coefficients of thermal expansion between the filler metal and the base metal during operation of the vessel in a thermally cyclic environment. This failure mechanism could be described as creep-type fatigue, whereby crack propagation may have been aided by the presence of brittle chromium carbides along the grain boundaries, which indicates a slightly sensitized microstructure.

  12. Crack length determination by ultrasonic methods

    SciTech Connect (OSTI)

    Rehbein, D.K.; Thompson, R.B.; Buck, O.

    1992-01-01

    Under the restriction of being able to operate in through transmission with focussed transducers, it has been shown that the location of the tip of a fatigue crack can be determined to within 0.5 mm in those cases where curvature of the crack front is significant with correspondingly better accuracy as the curvature decreases. Location of the crack tip is accomplished through use of the distributed spring model and also yields information on the residual stresses due to closure. The technique used is able to determine the crack length to within [plus minus] 0.5 mm in the unloaded condition in contrast to most of the work done previously, removing the necessity for application of a load sufficient to fully open the crack.

  13. Crack length determination by ultrasonic methods

    SciTech Connect (OSTI)

    Rehbein, D.K.; Thompson, R.B.; Buck, O.

    1992-12-31

    Under the restriction of being able to operate in through transmission with focussed transducers, it has been shown that the location of the tip of a fatigue crack can be determined to within 0.5 mm in those cases where curvature of the crack front is significant with correspondingly better accuracy as the curvature decreases. Location of the crack tip is accomplished through use of the distributed spring model and also yields information on the residual stresses due to closure. The technique used is able to determine the crack length to within {plus_minus} 0.5 mm in the unloaded condition in contrast to most of the work done previously, removing the necessity for application of a load sufficient to fully open the crack.

  14. Simplified Helium Refrigerator Cycle Analysis Using the `Carnot Step'

    SciTech Connect (OSTI)

    P. Knudsen; V. Ganni

    2006-05-01

    An analysis of the Claude form of an idealized helium liquefier for the minimum input work reveals the ''Carnot Step'' for helium refrigerator cycles. As the ''Carnot Step'' for a multi-stage polytropic compression process consists of equal pressure ratio stages; similarly for an idealized helium liquefier the ''Carnot Step'' consists of equal temperature ratio stages for a given number of expansion stages. This paper presents the analytical basis and some useful equations for the preliminary examination of existing and new Claude helium refrigeration cycles.

  15. Boron-10 Neutron Detectors for Helium-3 Replacement

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    efficiencies comparable to Helium-3 detectors, with demonstrated gamma neutron discrimination. Available for thumbnail of Feynman Center (505) 665-9090 Email Boron-10 Neutron...

  16. Helium isotopes in geothermal systems- Iceland, The Geysers,...

    Open Energy Info (EERE)

    isotopes in geothermal systems- Iceland, The Geysers, Raft River and Steamboat Springs Jump to: navigation, search OpenEI Reference LibraryAdd to library Journal Article: Helium...

  17. Crack shape developments and leak rates for circumferential complex-cracked pipes

    SciTech Connect (OSTI)

    Brickstad, B.; Bergman, M.

    1997-04-01

    A computerized procedure has been developed that predicts the growth of an initial circumferential surface crack through a pipe and further on to failure. The crack growth mechanism can either be fatigue or stress corrosion. Consideration is taken to complex crack shapes and for the through-wall cracks, crack opening areas and leak rates are also calculated. The procedure is based on a large number of three-dimensional finite element calculations of cracked pipes. The results from these calculations are stored in a database from which the PC-program, denoted LBBPIPE, reads all necessary information. In this paper, a sensitivity analysis is presented for cracked pipes subjected to both stress corrosion and vibration fatigue.

  18. Constraint effects observed in crack initiation stretch

    SciTech Connect (OSTI)

    Lambert, D.M.; Ernst, H.A.

    1995-12-31

    The current paper characterizes constraint in fracture: J-modified resistance (Jr) curves were developed for two tough structural materials, 6061-T651 (aluminum) and IN718-STA1 (nickel-base superalloy). A wide variety of configurations was tested to consider load configurations from bending to tension including three specimen types (compact tension, center-crack tension, and single-edge notched tension), and a range of ligament lengths and thicknesses, as well as side-grooved and smooth-sided ligaments. The Jr curves exhibited an inflection point after some crack extension, and the data were excluded beyond the inflection. Qualified Jr curves for the two materials showed similar behavior, but R-curves were identical for equal ligament length-to-thickness ratio (RL), for the aluminum alloy, with increasing slope for increasing RL, while for the nickel, the resistance curves aligned for equal ligament thickness, B, and the slope increased for decreasing B. Displacements at the original crack tip (CToD) were recorded throughout the test for several specimens. CToD-versus-crack extension curves were developed, and data were excluded beyond the inflection point (as with the Jr curves). The data collapsed into two distinct curves, thought to represent the surface, plane stress effect and the central, plane strain effect. This was observed for both materials. A technique called profiling is presented for the aluminum alloy only, where the crack face displacements are recorded at the final point of the test as a function of the position throughout the crack cavity, along with an effort to extract the observations in a usable form. Displacements were consistent throughout the cross-section at and behind the original crack tip. In the region where the crack grew, this displacement was developed by a combination of stretch and crack growth. The stretch required to initiate crack extension was a function of the depth beneath the surface into the cross-section.

  19. Dose dependence of helium bubble formation in nano-engineered SiC at 700 °C

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Chen, Chien -Hung; Zhang, Yanwen; Wang, Yongqiang; Crespillo, Miguel L.; Fontana, Cristiano L.; Graham, Joseph T.; Duscher, Gerd; Shannon, Steven C.; Weber, William J.

    2016-02-03

    Knowledge of radiation-induced helium bubble nucleation and growth in SiC is essential for applications in fusion and fission environments. Here we report the evolution of microstructure in nano-engineered (NE) 3C SiC, pre-implanted with helium, under heavy ion irradiation at 700 °C up to doses of 30 displacements per atom (dpa). Elastic recoil detection analysis confirms that the as-implanted helium depth profile does not change under irradiation to 30 dpa at 700 °C. While the helium bubble size distribution becomes narrower with increasing dose, the average size of bubbles remains unchanged and the density of bubbles increases somewhat with dose. Thesemore » results are consistent with a long helium bubble incubation process under continued irradiation at 700 °C up to 30 dpa, similar to that reported under dual and triple beam irradiation at much higher temperatures. The formation of bubbles at this low temperature is enhanced by the nano-layered stacking fault structure in the NE SiC, which enhances point defect mobility parallel to the stacking faults. Here, this stacking fault structure is stable at 700 °C up to 30 dpa and suppresses the formation of dislocation loops normally observed under these irradiation conditions.« less

  20. Heavy oil catalytic cracking process and apparatus (Patent) ...

    Office of Scientific and Technical Information (OSTI)

    Heavy oil catalytic cracking process and apparatus Citation Details In-Document Search Title: Heavy oil catalytic cracking process and apparatus This paper describes a fluidized ...

  1. Intergranular Strain Evolution near Fatigue Crack Tips in Polycrystall...

    Office of Scientific and Technical Information (OSTI)

    and history of the residual strain along the crack path depend on the stress multiaxiality, material properties, and history of stress intensity factor and crack growth rate. ...

  2. Uncommon Deformation Mechanisms during Fatigue-Crack Propagation...

    Office of Scientific and Technical Information (OSTI)

    Uncommon Deformation Mechanisms during Fatigue-Crack Propagation in Nanocrystalline Alloys Prev Next Title: Uncommon Deformation Mechanisms during Fatigue-Crack Propagation ...

  3. Resid cracking process and apparatus (Patent) | SciTech Connect

    Office of Scientific and Technical Information (OSTI)

    and the cracking catalyst is coked, catalyst is separated from cracked products in a separation means, coked catalyst is stripped of strippable hydrocarbons with a stripping gas, ...

  4. Alternatives for Helium-3 in Multiplicity Counters

    SciTech Connect (OSTI)

    Ely, James H.; Siciliano, Edward R.; Lintereur, Azaree T.; Swinhoe, Martyn T.

    2013-04-01

    Alternatives to helium-3 are being actively pursued due to the shortage and rising costs of helium-3. For safeguards applications, there are a number of ongoing investigations to find alternatives that provide the same capability in a cost-effective manner. One of the greatest challenges is to find a comparable alternative for multiplicity counters, since they require high efficiency and short collection or die-away times. Work has been progressing on investigating three commercially available alternatives for high efficiency multiplicity counters: boron trifluoride (BF3) filled proportional tubes, boron-lined proportional tubes, and lithium fluoride with zinc sulfide coated light guides. The baseline multiplicity counter used for the investigation is the Epithermal Neutron Multiplicity Counter with 121 helium-3 filled tubes at 10 atmosphere pressure, which is a significant capability to match. The primary tool for the investigation has been modeling and simulation using the Monte Carlo N-Particle eXtended (MCNPX) radiation transport program, with experiments to validate the models. To directly calculate the coincidence rates in boron-lined (and possibly other) detectors, the MCNPX code has been enhanced to allow the existing coincidence tally to be used with energy deposition rather than neutron capture reactions. This allows boron-lined detectors to be modeled more accurately. Variations of tube number and diameter along with variations in the amount of inter-tube moderator have been conducted for the BF3 and boron-lined cases. Tube pressure was investigated for BF3, up to two atmospheres, as well as optimal boron thickness in the boron-lined tubes. The lithium fluoride was modeled as sheets of material with light guides in between, and the number and thickness of the sheets investigated. The amount of light guide, which in this case doubles as a moderator, was also optimized. The results of these modeling and simulation optimization investigations are described

  5. Helium transport and ash control studies

    SciTech Connect (OSTI)

    Miley, G.H.

    1992-01-01

    The Primary goal of this research is to develop a helium (ash) transport scaling law based on experimental data from devices such as TFTR and JET. To illustrate the importance of this, we have studied ash accumulation effects on ignition requirements using a O-D transport model. Ash accumulation is characterized in the model by the ratio of the helium particle confinement time to the energy confinement time t{sub {alpha}}/t{sub E}. Results show that the ignition window'' shrinks rapidly as t{sub {alpha}}/t{sub E} increases, closing for high t{sub {alpha}}/t{sub E} increases, closing for high t{sub {alpha}}/t{sub E}. A best'' value for t{sub {alpha}}/t{sub E} will ultimately be determined from our scaling law studies. A helium transport scaling law is being sought that expresses the transport coefficients (D{sub {alpha}}, V{sub {alpha}}) as a function of the local plasma parameters. This is necessary for use in transport code calculations, e.g. for BALDUR. Based on experimental data from L-mode plasma operation in TFTR, a scaling law to a power law expression has been obtained using a least-square fit method. It is found that the transport coefficients are strongly affected by the local magnetic field and safety factor q. A preliminary conclusion from this work is that active control of ash buildup must be developed. To study control, we have developed a O-D plasma model which employs a simple pole-placement control model. Some preliminary calculations with this model are presented.

  6. Helium-3 and Helium-4 acceleration by high power laser pulses for hadron therapy

    SciTech Connect (OSTI)

    Bulanov, S. S.; Esarey, E.; Schroeder, C. B.; Leemans, W. P.; Bulanov, S. V.; Margarone, D.; Korn, G.; Haberer, T.

    2015-06-24

    The laser driven acceleration of ions is considered a promising candidate for an ion source for hadron therapy of oncological diseases. Though proton and carbon ion sources are conventionally used for therapy, other light ions can also be utilized. Whereas carbon ions require 400 MeV per nucleon to reach the same penetration depth as 250 MeV protons, helium ions require only 250 MeV per nucleon, which is the lowest energy per nucleon among the light ions. This fact along with the larger biological damage to cancer cells achieved by helium ions, than that by protons, makes this species an interesting candidate for the laser driven ion source. Two mechanisms (Magnetic Vortex Acceleration and hole-boring Radiation Pressure Acceleration) of PW-class laser driven ion acceleration from liquid and gaseous helium targets are studied with the goal of producing 250 MeV per nucleon helium ion beams that meet the hadron therapy requirements. We show that He3 ions, having almost the same penetration depth as He4 with the same energy per nucleon, require less laser power to be accelerated to the required energy for the hadron therapy.

  7. Production of thorium-229 using helium nuclei

    DOE Patents [OSTI]

    Mirzadeh, Saed (Knoxville, TN) [Knoxville, TN; Garland, Marc Alan (Knoxville, TN) [Knoxville, TN

    2010-12-14

    A method for producing .sup.229Th includes the steps of providing .sup.226Ra as a target material, and bombarding the target material with alpha particles, helium-3, or neutrons to form .sup.229Th. When neutrons are used, the neutrons preferably include an epithermal neutron flux of at least 1.times.10.sup.13 n s.sup.-1cm.sup.-2. .sup.228Ra can also be bombarded with thermal and/or energetic neutrons to result in a neutron capture reaction to form .sup.229Th. Using .sup.230Th as a target material, .sup.229Th can be formed using neutron, gamma ray, proton or deuteron bombardment.

  8. Liquid uranium alloy-helium fission reactor

    DOE Patents [OSTI]

    Minkov, V.

    1984-06-13

    This invention describes a nuclear fission reactor which has a core vessel and at least one tandem heat exchanger vessel coupled therewith across upper and lower passages to define a closed flow loop. Nuclear fuel such as a uranium alloy in its liquid phase fills these vessels and flow passages. Solid control elements in the reactor core vessel are adapted to be adjusted relative to one another to control fission reaction of the liquid fuel therein. Moderator elements in the other vessel and flow passages preclude fission reaction therein. An inert gas such as helium is bubbled upwardly through the heat exchanger vessel operable to move the liquid fuel upwardly therein and unidirectionally around the closed loop and downwardly through the core vessel. This helium gas is further directed to heat conversion means outside of the reactor vessels to utilize the heat from the fission reaction to generate useful output. The nuclear fuel operates in the 1200 to 1800/sup 0/C range, and even higher to 2500/sup 0/C.

  9. Liquid uranium alloy-helium fission reactor

    DOE Patents [OSTI]

    Minkov, Vladimir (Skokie, IL)

    1986-01-01

    This invention teaches a nuclear fission reactor having a core vessel and at least one tandem heat exchanger vessel coupled therewith across upper and lower passages to define a closed flow loop. Nuclear fuel such as a uranium alloy in its liquid phase fills these vessels and flow passages. Solid control elements in the reactor core vessel are adapted to be adjusted relative to one another to control fission reaction of the liquid fuel therein. Moderator elements in the other vessel and flow passages preclude fission reaction therein. An inert gas such as helium is bubbled upwardly through the heat exchanger vessel operable to move the liquid fuel upwardly therein and unidirectionally around the closed loop and downwardly through the core vessel. This helium gas is further directed to heat conversion means outside of the reactor vessels to utilize the heat from the fission reaction to generate useful output. The nuclear fuel operates in the 1200.degree.-1800.degree. C. range, and even higher to 2500.degree. C., limited only by the thermal effectiveness of the structural materials, increasing the efficiency of power generation from the normal 30-35% with 300.degree.-500.degree. C. upper limit temperature to 50-65%. Irradiation of the circulating liquid fuel, as contrasted to only localized irradiation of a solid fuel, provides improved fuel utilization.

  10. The primordial helium abundance from updated emissivities

    SciTech Connect (OSTI)

    Aver, Erik; Olive, Keith A.; Skillman, Evan D.; Porter, R.L. E-mail: olive@umn.edu E-mail: skillman@astro.umn.edu

    2013-11-01

    Observations of metal-poor extragalactic H II regions allow the determination of the primordial helium abundance, Y{sub p}. The He I emissivities are the foundation of the model of the H II region's emission. Porter, Ferland, Storey, and Detisch (2012) have recently published updated He I emissivities based on improved photoionization cross-sections. We incorporate these new atomic data and update our recent Markov Chain Monte Carlo analysis of the dataset published by Izotov, Thuan, and Stasi'nska (2007). As before, cuts are made to promote quality and reliability, and only solutions which fit the data within 95% confidence level are used to determine the primordial He abundance. The previously qualifying dataset is almost entirely retained and with strong concordance between the physical parameters. Overall, an upward bias from the new emissivities leads to a decrease in Y{sub p}. In addition, we find a general trend to larger uncertainties in individual objects (due to changes in the emissivities) and an increased variance (due to additional objects included). From a regression to zero metallicity, we determine Y{sub p} = 0.2465 ± 0.0097, in good agreement with the BBN result, Y{sub p} = 0.2485 ± 0.0002, based on the Planck determination of the baryon density. In the future, a better understanding of why a large fraction of spectra are not well fit by the model will be crucial to achieving an increase in the precision of the primordial helium abundance determination.

  11. MECHANICS OF CRACK BRIDGING UNDER DYNAMIC LOADS

    SciTech Connect (OSTI)

    N. SRIDHAR; ET AL

    2001-02-01

    A bridging law for fiber reinforced composites under dynamic crack propagation conditions has been derived. Inertial effects in the mechanism of fiber pullout during dynamic propagation of a bridged crack are critically examined for the first time. By reposing simple shear lag models of pullout as problems of dynamic wave propagation, the effect of the frictional coupling between the fibers and the matrix is accounted for in a fairly straightforward way. The solutions yield the time-dependent relationship between the crack opening displacement and the bridging traction. Engineering criteria and the role of material and geometrical parameters for significant inertial effects are identified.

  12. Cracked-fuel mechanics. [PWR; BWR

    SciTech Connect (OSTI)

    Williford, R.E.; Lanning, D.D.

    1982-01-01

    This paper presents a modelling concept and a set of measurable parameters that have been shown to improve the prediction of the mechanical behavior of cracked fuel/cladding systems without added computational expense. The transition from classical annular gap/cylindrical pellet models to modified bulk properties and further to local behavior for cracked fuel systems is discussed. The results of laboratory experiments to verify these modelling parameters are shown. Data are also presented from laboratory experiments on unirradiated and irradiated rods which show that fuel rod mechanical response depends on fuel fragment size. The impact of these data on cracked fuel behavior and failure modelling is also discussed.

  13. Helium irradiation induced micro-swelling and phase separation...

    Office of Scientific and Technical Information (OSTI)

    Type: Publisher's Accepted Manuscript Journal Name: Nuclear Instruments and Methods in Physics Research. Section B, Beam Interactions with Materials and Atoms Additional Journal ...

  14. Stress Corrosion Cracking Model for High Level Radioactive-Waste Packages

    SciTech Connect (OSTI)

    P. Andresen; G. Gordon; S. Lu

    2004-10-05

    A stress corrosion cracking (SCC) model has been adapted for performance prediction of high level radioactive-waste packages to be emplaced in the proposed Yucca Mountain repository. For waste packages of the proposed Yucca Mountain repository, the outer barrier material is the highly corrosion-resistant Alloy UNS-N06022 (Alloy 22), the environment is represented by aqueous brine films present on the surface of the waste package from dripping or deliquescence of soluble salts present in any surface deposits, and the tensile stress is principally from weld induced residual stress. SCC has historically been separated into ''initiation'' and ''propagation'' phases. Initiation of SCC will not occur on a smooth surface if the surface stress is below a threshold value defined as the threshold stress. Cracks can also initiate at and propagate from flaws (or defects) resulting from manufacturing processes (such as welding); or that develop from corrosion processes such as pitting or dissolution of inclusions. To account for crack propagation, the slip dissolution/film rupture (SDFR) model is adopted to provide mathematical formulae for prediction of the crack growth rate. Once the crack growth rate at an initiated SCC is determined, it can be used by the performance assessment to determine the time to through-wall penetration for the waste package. This paper presents the development of the SDFR crack growth rate model based on technical information in the literature as well as experimentally determined crack growth rates developed specifically for Alloy UNS-N06022 in environments relevant to high level radioactive-waste packages of the proposed Yucca Mountain radioactive-waste repository. In addition, a seismic damage related SCC crack opening area density model is briefly described.

  15. Double photoionization of helium with synchrotron x-rays: Proceedings

    SciTech Connect (OSTI)

    Not Available

    1994-01-01

    This report contains papers on the following topics: Overview and comparison of photoionization with charged particle impact; The ratio of double to single ionization of helium: the relationship of photon and bare charged particle impact ionization; Double photoionization of helium at high energies; Compton scattering of photons from electrons bound in light elements; Electron ionization and the Compton effect in double ionization of helium; Elimination of two atomic electrons by a single energy photon; Double photoionization of helium at intermediate energies; Double Photoionization: Gauge Dependence, Coulomb Explosion; Single and Double Ionization by high energy photon impact; The effect of Compton Scattering on the double to single ionization ratio in helium; and Double ionization of He by photoionization and Compton scattering. These papers have been cataloged separately for the database.

  16. Detailed and simplified nonequilibrium helium ionization in the solar atmosphere

    SciTech Connect (OSTI)

    Golding, Thomas Peter; Carlsson, Mats; Leenaarts, Jorrit E-mail: mats.carlsson@astro.uio.no

    2014-03-20

    Helium ionization plays an important role in the energy balance of the upper chromosphere and transition region. Helium spectral lines are also often used as diagnostics of these regions. We carry out one-dimensional radiation-hydrodynamics simulations of the solar atmosphere and find that the helium ionization is set mostly by photoionization and direct collisional ionization, counteracted by radiative recombination cascades. By introducing an additional recombination rate mimicking the recombination cascades, we construct a simplified three-level helium model atom consisting of only the ground states. This model atom is suitable for modeling nonequilibrium helium ionization in three-dimensional numerical models. We perform a brief investigation of the formation of the He I 10830 and He II 304 spectral lines. Both lines show nonequilibrium features that are not recovered with statistical equilibrium models, and caution should therefore be exercised when such models are used as a basis for interpretating observations.

  17. 3:2:1 Crack Spread

    Annual Energy Outlook [U.S. Energy Information Administration (EIA)]

    To calculate the 3:2:1 crack spread for a Gulf Coast refinery that processes Louisiana Light Sweet (LLS) crude oil, add the spot price for two barrels of Gulf Coast conventional ...

  18. Cavity morphology in a Ni based superalloy under heavy ion irradiation with cold pre-injected helium. I

    SciTech Connect (OSTI)

    Zhang, He; Yao, Zhongwen Daymond, Mark R.; Kirk, Marquis A.

    2014-03-14

    In order to understand radiation damage in the nickel based superalloy Inconel X-750 in thermal reactors, where (n, ?) transmutation reaction also occurred in addition to fast neutron induced atomic displacement, heavy ion (1?MeV Kr{sup 2+}) irradiation with pre-injected helium was performed under in-situ observations of an intermediate voltage electron microscope at Argonne National Laboratory. By comparing to our previous studies using 1?MeV Kr{sup 2+} irradiation solely, the pre-injected helium was found to be essential in cavity nucleation. Cavities started to be visible after Kr{sup 2+} irradiation to 2.7 dpa at ?200?C in samples containing 200 appm, 1000 appm, and 5000 appm helium, respectively, but not at lower temperatures. The cavity growth was observed during the continuous irradiation. Cavity formation appeared along with a reduced number density of stacking fault tetrahedra, vacancy type defects. With higher pre-injected helium amount, a higher density of smaller cavities was observed. This is considered to be the result of local trapping effect of helium which disperses vacancies. The average cavity size increases with increasing irradiation temperatures; the density reduced; and the distribution of cavities became heterogeneous at elevated temperatures. In contrast to previous characterization of in-reactor neutron irradiated Inconel X-750, no obvious cavity sink to grain boundaries and phase boundaries was found even at high doses and elevated temperatures. MC-type carbides were observed as strong sources for agglomeration of cavities due to their enhanced trapping strength of helium and vacancies.

  19. Superconducting cable cooling system by helium gas and a mixture of gas and liquid helium

    DOE Patents [OSTI]

    Dean, John W.

    1977-01-01

    Thermally contacting, oppositely streaming cryogenic fluid streams in the same enclosure in a closed cycle that changes from a cool high pressure helium gas to a cooler reduced pressure helium fluid comprised of a mixture of gas and boiling liquid so as to be near the same temperature but at different pressures respectively in go and return legs that are in thermal contact with each other and in thermal contact with a longitudinally extending superconducting transmission line enclosed in the same cable enclosure that insulates the line from the ambient at a temperature T.sub.1. By first circulating the fluid in a go leg from a refrigerator at one end of the line as a high pressure helium gas near the normal boiling temperature of helium; then circulating the gas through an expander at the other end of the line where the gas becomes a mixture of reduced pressure gas and boiling liquid at its boiling temperature; then by circulating the mixture in a return leg that is separated from but in thermal contact with the gas in the go leg and in the same enclosure therewith; and finally returning the resulting low pressure gas to the refrigerator for compression into a high pressure gas at T.sub.2 is a closed cycle, where T.sub.1 >T.sub.2, the temperature distribution is such that the line temperature is nearly constant along its length from the refrigerator to the expander due to the boiling of the liquid in the mixture. A heat exchanger between the go and return lines removes the gas from the liquid in the return leg while cooling the go leg.

  20. Compact hydrogen/helium isotope mass spectrometer

    DOE Patents [OSTI]

    Funsten, Herbert O.; McComas, David J.; Scime, Earl E.

    1996-01-01

    The compact hydrogen and helium isotope mass spectrometer of the present invention combines low mass-resolution ion mass spectrometry and beam-foil interaction technology to unambiguously detect and quantify deuterium (D), tritium (T), hydrogen molecule (H.sub.2, HD, D.sub.2, HT, DT, and T.sub.2), .sup.3 He, and .sup.4 He concentrations and concentration variations. The spectrometer provides real-time, high sensitivity, and high accuracy measurements. Currently, no fieldable D or molecular speciation detectors exist. Furthermore, the present spectrometer has a significant advantage over traditional T detectors: no confusion of the measurements by other beta-emitters, and complete separation of atomic and molecular species of equivalent atomic mass (e.g., HD and .sup.3 He).

  1. Helium isotopes and tectonics in southern Italy

    SciTech Connect (OSTI)

    Sano, Yuji; Wakita, Hiroshi ); Nuccio, M.P. ); Italiano, F.

    1989-06-01

    Geodynamic evolution of southern Italy can be understood within the framework of the Mediterranean-Alpine System. Subduction of a plate along the Sicily-Calabrian forearc under the Tyrrhenian Sea has been suggested by many geophysicists, although it is not yet confirmed and remains somewhat controversial. Helium isotope ratios provide useful information on the geotectonic structure of the region. The authors report here the {sup 3}H/{sup 4}He ratios of terrestrial gas samples from southern Italy. The observed {sup 3}He/{sup 4}He ratios are relatively high in the Eolian volcanic arc region and low in the other areas. Dichotomous explanations are presented. Firstly, volcanic arc-forearc hypothesis suggests the subduction along the Sicily-Calabrian forearc. Secondly, horizontal transport hypothesis is described based on the relationship between the ratios and radial distance from the recent spreading basin in Southern Tyrrhenian Sea.

  2. Stress corrosion cracking of alloys 600 and 690 in all-volatile-treated water at elevated temperatures: Final report

    SciTech Connect (OSTI)

    Miglin, B.P.; Theus, G.J.

    1988-05-01

    This report describes stress corrosion (SCC) tests of Inconnel alloys 600 and 690 in all-volatile treated (AVT) water. Specimens of alloys 600 and 690 were exposed to AVT water at 288/degree/, 332/degree/, 343/degree/, and 360/degree/C. Alloy 660 generally resists SCC in high-purity water at normal sevice temperatures, but is susceptible to SCC at higher temperatures. In general, mill-annealed alloy 600 is more susceptible than high-treated material with fine lacy grain boundary carbides. Very high stresses (near or above yield) are required to induce cracking of alloy 600 in AVT or other high-purity waters. For alloy 600, 78 of 520 alloy 600 specimens eventually cracked. Although exposed for less total time than alloy 600 specimens, no alloy 690 specimens cracked. Three alloy 600 specimens cracked in the same autoclave tests in less time than those accumulated by the alloy 690 specimens. Longitudinally-oriented ID cracks became evident on alloy 690 split-tube U-bend specimens after autoclave exposures. These cracks on the 690 specimens were from three to ten times longer after exposure than similar defects found on unexposed alloy 690 specimens. The longitudinal crack lengthening on the alloy 690 split-tube U-bend specimens may have been a stress relaxation process or possibly a crack opening process of pre-existing, partially closed, longitudinal defects. Similar cracks were present in alloy 600 specimens, but in at least one case SCC did initiate from these shallow, blunt cracks.

  3. Directory

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    122410 4:52 AM Send Document Link Develpo Baseline Computational Model for Proactive Welding Stress Management to Suppress Helium-Induced Cracking During Weld Repair Develpo...

  4. Document Library | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    September 30, 2011 Develop baseline computational model for proactive welding stress management to suppress helium induced cracking during weld repair There are over 100 nuclear...

  5. TRANSPORT THROUGH CRACKED CONCRETE: LITERATURE REVIEW

    SciTech Connect (OSTI)

    Langton, C.

    2012-05-11

    Concrete containment structures and cement-based fills and waste forms are used at the Savannah River Site to enhance the performance of shallow land disposal systems designed for containment of low-level radioactive waste. Understanding and measuring transport through cracked concrete is important for describing the initial condition of radioactive waste containment structures at the Savannah River Site (SRS) and for predicting performance of these structures over time. This report transmits the results of a literature review on transport through cracked concrete which was performed by Professor Jason Weiss, Purdue University per SRR0000678 (RFP-RQ00001029-WY). This review complements the NRC-sponsored literature review and assessment of factors relevant to performance of grouted systems for radioactive waste disposal. This review was performed by The Center for Nuclear Waste Regulatory Analyses, San Antonio, TX, and The University of Aberdeen, Aberdeen Scotland and was focused on tank closure. The objective of the literature review on transport through cracked concrete was to identify information in the open literature which can be applied to SRS transport models for cementitious containment structures, fills, and waste forms. In addition, the literature review was intended to: (1) Provide a framework for describing and classifying cracks in containment structures and cementitious materials used in radioactive waste disposal, (2) Document the state of knowledge and research related to transport through cracks in concrete for various exposure conditions, (3) Provide information or methodology for answering several specific questions related to cracking and transport in concrete, and (4) Provide information that can be used to design experiments on transport through cracked samples and actual structures.

  6. Recent evaluations of crack-opening-area in circumferentially cracked pipes

    SciTech Connect (OSTI)

    Rahman, S.; Brust, F.; Ghadiali, N.; Wilkowski, G.; Miura, N.

    1997-04-01

    Leak-before-break (LBB) analyses for circumferentially cracked pipes are currently being conducted in the nuclear industry to justify elimination of pipe whip restraints and jet shields which are present because of the expected dynamic effects from pipe rupture. The application of the LBB methodology frequently requires calculation of leak rates. The leak rates depend on the crack-opening area of the through-wall crack in the pipe. In addition to LBB analyses which assume a hypothetical flaw size, there is also interest in the integrity of actual leaking cracks corresponding to current leakage detection requirements in NRC Regulatory Guide 1.45, or for assessing temporary repair of Class 2 and 3 pipes that have leaks as are being evaluated in ASME Section XI. The objectives of this study were to review, evaluate, and refine current predictive models for performing crack-opening-area analyses of circumferentially cracked pipes. The results from twenty-five full-scale pipe fracture experiments, conducted in the Degraded Piping Program, the International Piping Integrity Research Group Program, and the Short Cracks in Piping and Piping Welds Program, were used to verify the analytical models. Standard statistical analyses were performed to assess used to verify the analytical models. Standard statistical analyses were performed to assess quantitatively the accuracy of the predictive models. The evaluation also involved finite element analyses for determining the crack-opening profile often needed to perform leak-rate calculations.

  7. Unified continuum damage model for matrix cracking in composite rotor blades

    SciTech Connect (OSTI)

    Pollayi, Hemaraju; Harursampath, Dineshkumar

    2015-03-10

    This paper deals with modeling of the first damage mode, matrix micro-cracking, in helicopter rotor/wind turbine blades and how this effects the overall cross-sectional stiffness. The helicopter/wind turbine rotor system operates in a highly dynamic and unsteady environment leading to severe vibratory loads present in the system. Repeated exposure to this loading condition can induce damage in the composite rotor blades. These rotor/turbine blades are generally made of fiber-reinforced laminated composites and exhibit various competing modes of damage such as matrix micro-cracking, delamination, and fiber breakage. There is a need to study the behavior of the composite rotor system under various key damage modes in composite materials for developing Structural Health Monitoring (SHM) system. Each blade is modeled as a beam based on geometrically non-linear 3-D elasticity theory. Each blade thus splits into 2-D analyzes of cross-sections and non-linear 1-D analyzes along the beam reference curves. Two different tools are used here for complete 3-D analysis: VABS for 2-D cross-sectional analysis and GEBT for 1-D beam analysis. The physically-based failure models for matrix in compression and tension loading are used in the present work. Matrix cracking is detected using two failure criterion: Matrix Failure in Compression and Matrix Failure in Tension which are based on the recovered field. A strain variable is set which drives the damage variable for matrix cracking and this damage variable is used to estimate the reduced cross-sectional stiffness. The matrix micro-cracking is performed in two different approaches: (i) Element-wise, and (ii) Node-wise. The procedure presented in this paper is implemented in VABS as matrix micro-cracking modeling module. Three examples are presented to investigate the matrix failure model which illustrate the effect of matrix cracking on cross-sectional stiffness by varying the applied cyclic load.

  8. Probing Electron Correlation via Attosecond xuv Pulses in the Two-Photon Double Ionization of Helium

    SciTech Connect (OSTI)

    Feist, J.; Nagele, S.; Pazourek, R.; Persson, E.; Burgdoerfer, J.; Schneider, B. I.; Collins, L. A.

    2009-08-07

    Recent experimental developments of high-intensity, short-pulse extreme ultraviolet light sources are enhancing our ability to study electron-electron correlations. We perform time-dependent calculations to investigate the so-called 'sequential' regime ((Planck constant/2pi)omega>54.4 eV) in the two-photon double ionization of helium. We show that attosecond pulses allow us not only to probe but also to induce angular and energy correlations of the emitted electrons. The final momentum distribution reveals regions dominated by the Wannier ridge breakup scenario and by postcollision interaction.

  9. STRESS CORROSION CRACKING IN TEAR DROP SPECIMENS

    SciTech Connect (OSTI)

    Lam, P; Philip Zapp, P; Jonathan Duffey, J; Kerry Dunn, K

    2009-05-01

    Laboratory tests were conducted to investigate the stress corrosion cracking (SCC) of 304L stainless steel used to construct the containment vessels for the storage of plutonium-bearing materials. The tear drop corrosion specimens each with an autogenous weld in the center were placed in contact with moist plutonium oxide and chloride salt mixtures. Cracking was found in two of the specimens in the heat affected zone (HAZ) at the apex area. Finite element analysis was performed to simulate the specimen fabrication for determining the internal stress which caused SCC to occur. It was found that the tensile stress at the crack initiation site was about 30% lower than the highest stress which had been shifted to the shoulders of the specimen due to the specimen fabrication process. This finding appears to indicate that the SCC initiation took place in favor of the possibly weaker weld/base metal interface at a sufficiently high level of background stress. The base material, even subject to a higher tensile stress, was not cracked. The relieving of tensile stress due to SCC initiation and growth in the HAZ and the weld might have foreclosed the potential for cracking at the specimen shoulders where higher stress was found.

  10. Flaw Tolerance for Multiple Fatique Cracks

    SciTech Connect (OSTI)

    Gosselin, Stephen R.; Simonen, Fredric A.; Carter, R. G.

    2005-07-01

    This paper documents important details of the technical bases for changes to Appendix L. Calculations identified aspect ratios for equivalent single cracks (ESC) between the extremes of a 6:1 ratio and a full circumferential crack that can be used in Appendix L flaw tolerance assessments to account for the initiation, growth, and linking of multiple fatigue cracks. Probabilistic fracture mechanics (PFM) calculations determined ESC aspect ratios that result in the same through-wall crack probability as multiple small cracks (0.02 inch depth) that initiate and coalesce. The computations considered two materials (stainless and low alloy steels), three pipe diameters, five cyclic membrane-to-gradient stress ratios and a wide range of primary loads. Subsequent deterministic calculations identified the ESC aspect ratio for the hypothetical reference flaw depth assumptions in Appendix L. This paper also describes computations that compare the Appendix L flaw tolerance allowable operating period for the ESC models with results obtained when the a single default 6:1 aspect ratio reference flaw.

  11. Ab initio study of helium behavior in titanium tritides

    SciTech Connect (OSTI)

    Liang, J. H.; Dai, Yunya; Yang, Li; Peng, SM; Fan, K. M.; Long, XG; Zhou, X. S.; Zu, Xiaotao; Gao, Fei

    2013-03-01

    Ab initio calculations based on density functional theory have been performed to investigate the relative stability of titanium tritides and the helium behavior in stable titanium tritides. The results show that the β-phase TiT1.5 without two tritium along the [100] direction (TiT1.5[100]) is more stable than other possible structures. The stability of titanium tritides decrease with the increased generation of helium in TiT1.5[100]. In addition, helium generated by tritium decay prefers locating at a tetrahedral site, and favorably migrates between two neighbor vacant tetrahedral sites through an intermediate octahedral site in titanium tritides, with a migration energy of 0.23 eV. Furthermore, helium is easily accumulated on a (100) plane in β-phase TiT1.5[100].

  12. Demonstrating Strong Electric Fields in Liquid Helium for Tests...

    Office of Science (SC) Website

    Image courtesy of Los Alamos National Laboratory The Medium Scale High Voltage Test apparatus in TA-53 Building 10 allowed scientists to test electric fields in liquid helium, a ...

  13. Underground helium travels to the Earth's surface via aquifers...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Tweet EmailPrint Before it can put the party in party balloons, helium is carried from deep within the Earth's crust to the surface via aquifers, according to new research...

  14. The Hall D solenoid helium refrigeration system at JLab

    SciTech Connect (OSTI)

    Laverdure, Nathaniel A.; Creel, Jonathan D.; Dixon, Kelly d.; Ganni, Venkatarao; Martin, Floyd D.; Norton, Robert O.; Radovic, Sasa

    2014-01-01

    Hall D, the new Jefferson Lab experimental facility built for the 12GeV upgrade, features a LASS 1.85 m bore solenoid magnet supported by a 4.5 K helium refrigerator system. This system consists of a CTI 2800 4.5 K refrigerator cold box, three 150 hp screw compressors, helium gas management and storage, and liquid helium and nitrogen storage for stand-alone operation. The magnet interfaces with the cryo refrigeration system through an LN2-shielded distribution box and transfer line system, both designed and fabricated by JLab. The distribution box uses a thermo siphon design to respectively cool four magnet coils and shields with liquid helium and nitrogen. We describe the salient design features of the cryo system and discuss our recent commissioning experience.

  15. Helium Pumping Wall for a Liquid Lithium Tokamak Richard Majeski |

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Princeton Plasma Physics Lab Helium Pumping Wall for a Liquid Lithium Tokamak Richard Majeski This invention is designed to be a subsystem of a device, a tokamak with walls or plasma facing components of liquid lithium. This approach to constructing the lithium-bearing walls of the tokamak allows the wall to fulfill a necessary function -- helium pumping - for which a complex structure was formerly required. The primary novel feature of the invention is that a permeable wall is used to

  16. Recovery of purified helium or hydrogen from gas mixtures

    DOE Patents [OSTI]

    Merriman, J.R.; Pashley, J.H.; Stephenson, M.J.; Dunthorn, D.I.

    1974-01-15

    A process is described for the removal of helium or hydrogen from gaseous mixtures also containing contaminants. The gaseous mixture is contacted with a liquid fluorocarbon in an absorption zone maintained at superatomspheric pressure to preferentially absorb the contaminants in the fluorocarbon. Unabsorbed gas enriched in hydrogen or helium is withdrawn from the absorption zone as product. Liquid fluorocarbon enriched in contaminants is withdrawn separately from the absorption zone. (10 claims)

  17. Process Options for Nominal 2-K Helium Refrigeration System Designs

    SciTech Connect (OSTI)

    Peter Knudsen, Venkatarao Ganni

    2012-07-01

    Nominal 2-K helium refrigeration systems are frequently used for superconducting radio frequency and magnet string technologies used in accelerators. This paper examines the trade-offs and approximate performance of four basic types of processes used for the refrigeration of these technologies; direct vacuum pumping on a helium bath, direct vacuum pumping using full or partial refrigeration recovery, cold compression, and hybrid compression (i.e., a blend of cold and warm sub-atmospheric compression).

  18. Stress corrosion cracking of Alloy 600. [PWR

    SciTech Connect (OSTI)

    Serra, E.

    1981-11-01

    The stress corrosion cracking of Alloy 600 tubing has affected the performance of several pressurized water reactor steam generators. The purpose of this report is to summarize the research which has followed that reviewed by D. van Rooyen in 1975. Although several papers and reports have been published there still is not a general model that can explain the stress corrosion cracking behavior of Alloy 600 in deaerated or aerated high-temperature pure water or in the environments that might exist in the primary and secondary coolant of a steam generator. Such a model, if it exists, must cover the complex interaction of the environmental, metallurgical, and mechanical variables which control the susceptibility of Alloy 600 to stress corrosion cracking. Each of these classes of variables is discussed in the text.

  19. Fracture of surface cracks loaded in bending

    SciTech Connect (OSTI)

    Chao, Y.J.; Reuter, W.G.

    1997-12-31

    Theoretical background of the constraint effect in brittle fracture of solids is reviewed. Fracture test data from D6-aC, a high strength steel, using three-point-bend (SE(B)) specimens and surface cracked plate (SC(B)) specimens under bending are presented. It is shown that the SE(B) data has an elevated fracture toughness for increasing a/W, i.e., a crack geometry with a larger T/K corresponds to a higher K{sub c} which is consistent with the theoretical prediction. The fundamental fracture properties, i.e., the critical strain and the critical distance, determined from the SE(B) test data are then applied to the interpretation and prediction of the SC(B) test data. Reasonable agreement is achieved for the crack growth initiation site and the load.

  20. Crack detection using resonant ultrasound spectroscopy

    DOE Patents [OSTI]

    Migliori, A.; Bell, T.M.; Rhodes, G.W.

    1994-10-04

    Method and apparatus are provided for detecting crack-like flaws in components. A plurality of exciting frequencies are generated and applied to a component in a dry condition to obtain a first ultrasonic spectrum of the component. The component is then wet with a selected liquid to penetrate any crack-like flaws in the component. The plurality of exciting frequencies are again applied to the component and a second ultrasonic spectrum of the component is obtained. The wet and dry ultrasonic spectra are then analyzed to determine the second harmonic components in each of the ultrasonic resonance spectra and the second harmonic components are compared to ascertain the presence of crack-like flaws in the component. 5 figs.

  1. Crack detection using resonant ultrasound spectroscopy

    DOE Patents [OSTI]

    Migliori, Albert; Bell, Thomas M.; Rhodes, George W.

    1994-01-01

    Method and apparatus are provided for detecting crack-like flaws in components. A plurality of exciting frequencies are generated and applied to a component in a dry condition to obtain a first ultrasonic spectrum of the component. The component is then wet with a selected liquid to penetrate any crack-like flaws in the component. The plurality of exciting frequencies are again applied to the component and a second ultrasonic spectrum of the component is obtained. The wet and dry ultrasonic spectra are then analyzed to determine the second harmonic components in each of the ultrasonic resonance spectra and the second harmonic components are compared to ascertain the presence of crack-like flaws in the component.

  2. Crack detection using resonant ultrasound spectroscopy

    SciTech Connect (OSTI)

    Migliori, A.; Bell, T.M.

    1992-12-31

    This invention is comprised of a method and apparatus for detecting crack-like flaws in components. A plurality of exciting frequencies are generated and applied to a component in a dry condition to obtain a first ultrasonic spectrum of the component. The component is then wet with a selected liquid to penetrate any crack-like flaws in the component. The plurality of exciting frequencies are again applied to the component and a second ultrasonic spectrum of the component is obtained. The wet and dry ultrasonic spectra are then analyzed to determine the second harmonic components in each of the ultrasonic resonance spectra and the second harmonic components are compared to ascertain the presence of crack-like flaws in the component.

  3. Environmentally assisted cracking of LWR materials.

    SciTech Connect (OSTI)

    Chopra, O. K.; Chung, H. M.; Kassner, T. F.; Park, J. H.; Shack, W. J.; Zhang, J.; Brust, F. W.; Dong, P.

    1997-12-05

    The effect of dissolved oxygen level on fatigue life of austenitic stainless steels is discussed and the results of a detailed study of the effect of the environment on the growth of cracks during fatigue initiation are presented. Initial test results are given for specimens irradiated in the Halden reactor. Impurities introduced by shielded metal arc welding that may affect susceptibility to stress corrosion cracking are described. Results of calculations of residual stresses in core shroud weldments are summarized. Crack growth rates of high-nickel alloys under cyclic loading with R ratios from 0.2-0.95 in water that contains a wide range of dissolved oxygen and hydrogen concentrations at 289 and 320 C are summarized.

  4. Stress corrosion cracking of Alloy 600 and Alloy 690 in all volatile treated water at elevated temperatures. Final report. [PWR

    SciTech Connect (OSTI)

    Theus, G.J.; Emanuelson, R.H.

    1983-05-01

    This report describes a continuing study of stress corrosion cracking (SCC) of Inconel alloys 600 and 690 in all-volatile treated (AVT) water. Specimens of alloys 600 and 690 are being exposed to AVT water at 288/sup 0/, 332/sup 0/, 343/sup 0/, and 360/sup 0/C. Alloy 600 generally resists SCC in high-purity water under normal service conditions but is susceptible under other specific conditions. In general, mill-annealed alloy 600 is more susceptible than stress-relieved material. Susceptibility to SCC increases rapidly with increasing exposure temperature. Very high stresses (near or above yield) are required to induce cracking in AVT or other high-purity waters. Most of the data presented in this report are for alloy 600; alloy 690 has not yet cracked. However, the program is being continued and will subsequently characterize the high-purity water cracking behavior, if any, of alloy 690.

  5. Helium Loop Cooling Channel Hydraulic Characterization

    SciTech Connect (OSTI)

    Olivas, Eric Richard; Morgan, Robert Vaughn; Woloshun, Keith Albert

    2015-07-02

    New methods for generating ⁹⁹Mo are being explored in an effort to eliminate proliferation issues and provide a domestic supply of ⁹⁹mTc for medical imaging. Electron accelerating technology is used by sending an electron beam through a series of ¹⁰⁰Mo targets. During this process a large amount of heat is created, which directly affects the operating temperature set for the system. In order to maintain the required temperature range, helium gas is used to serve as a cooling agent that flows through narrow channels between the target disks. Currently we are tailoring the cooling channel entrance and exits to decrease the pressure drop through the targets. Currently all hardware has be procured and manufactured to conduct flow measurements and visualization via solid particle seeder. Pressure drop will be studied as a function of mass flow and diffuser angle. The results from these experiments will help in determining target cooling geometry and validate CFD code results.

  6. Investigation of Countercurrent Helium-Air Flows in Air-ingress Accidents for VHTRs

    SciTech Connect (OSTI)

    Sun, Xiaodong; Christensen, Richard; Oh, Chang

    2013-10-03

    The primary objective of this research is to develop an extensive experimental database for the air- ingress phenomenon for the validation of computational fluid dynamics (CFD) analyses. This research is intended to be a separate-effects experimental study. However, the project team will perform a careful scaling analysis prior to designing a scaled-down test facility in order to closely tie this research with the real application. As a reference design in this study, the team will use the 600 MWth gas turbine modular helium reactor (GT-MHR) developed by General Atomic. In the test matrix of the experiments, researchers will vary the temperature and pressure of the helium— along with break size, location, shape, and orientation—to simulate deferent scenarios and to identify potential mitigation strategies. Under support of the Department of Energy, a high-temperature helium test facility has been designed and is currently being constructed at Ohio State University, primarily for high- temperature compact heat exchanger testing for the VHTR program. Once the facility is in operation (expected April 2009), this study will utilize high-temperature helium up to 900°C and 3 MPa for loss-of-coolant accident (LOCA) depressurization and air-ingress experiments. The project team will first conduct a scaling study and then design an air-ingress test facility. The major parameter to be measured in the experiments is oxygen (or nitrogen) concentration history at various locations following a LOCA scenario. The team will use two measurement techniques: 1) oxygen (or similar type) sensors employed in the flow field, which will introduce some undesirable intrusiveness, disturbing the flow, and 2) a planar laser-induced fluorescence (PLIF) imaging technique, which has no physical intrusiveness to the flow but requires a transparent window or test section that the laser beam can penetrate. The team will construct two test facilities, one for high-temperature helium tests with

  7. Residual stresses and stress corrosion cracking in pipe fittings

    SciTech Connect (OSTI)

    Parrington, R.J.; Scott, J.J.; Torres, F.

    1994-06-01

    Residual stresses can play a key role in the SCC performance of susceptible materials in PWR primary water applications. Residual stresses are stresses stored within the metal that develop during deformation and persist in the absence of external forces or temperature gradients. Sources of residual stresses in pipe fittings include fabrication processes, installation and welding. There are a number of methods to characterize the magnitude and orientation of residual stresses. These include numerical analysis, chemical cracking tests, and measurement (e.g., X-ray diffraction, neutron diffraction, strain gage/hole drilling, strain gage/trepanning, strain gage/section and layer removal, and acoustics). This paper presents 400 C steam SCC test results demonstrating that residual stresses in as-fabricated Alloy 600 pipe fittings are sufficient to induce SCC. Residual stresses present in as-fabricated pipe fittings are characterized by chemical cracking tests (stainless steel fittings tested in boiling magnesium chloride solution) and by the sectioning and layer removal (SLR) technique.

  8. Strip edge cracking simulation in cold rolling

    SciTech Connect (OSTI)

    Hubert, C.; Dubar, L.; Dubar, M.; Dubois, A.

    2011-01-17

    This research work focuses on a specific defect which occurs during cold rolling of steel strips: edge-serration. Investigations on the industrial processes have led to the conclusion that this defect is the result of the edge-trimming and cold rolling sequences. The aim of this research work is to analyze the effect of the cutting process and the cold rolling on cracks occurrence, especially on strip edges.This study is performed using an experimental testing stand called Upsetting Rolling Test (URT). It allows to reproduce cold rolling contact parameters such as forward slip, reduction ratio and friction coefficients. Specimens sampled near trimmed industrial strip edges are deformed using the URT stand. Two sets of specimens with different stress states, obtained by annealing, are submitted to two reduction passes with extreme forward slips.Scanning electron microscopy observations added to 3D optical surface profiler topographies show that on one hand, forward slip has a major effect on cracks opening. On the other hand, cracks opening decreases according to high roll strip speed gradient. Concerning the heat-treated specimens, no crack appeared after all reduction passes, showing a large influence of the cutting process and consequently of the local stress state in the vicinity of the burnish and fracture regions.

  9. Sulfide stress cracking resistance of nitrogen-strengthened stainless steel

    SciTech Connect (OSTI)

    Gaugh, R.R.

    1981-01-01

    The paper describes sulfide stress cracking tests performed on a number of these alloys. Most were found to be somewhat susceptible to cracking, depending on the stress level. It was determined that this was due to their high manganese content. The mechanism responsible for cracking was not firmly established. One commercial nitrogen-strengthened stainless steel, XM19, was highly resistant to sulfide stress cracking despite a manganese content of 5%. This difference is attributed to the superior corrosion resistance of the alloy.

  10. Heavy oil catalytic cracking apparatus (Patent) | SciTech Connect

    Office of Scientific and Technical Information (OSTI)

    It comprises a catalytic cracking reactor means; a separation means connective with the ... PETROLEUM REFINERIES; CATALYSTS; SEPARATION PROCESSES; CHEMICAL REACTIONS; ...

  11. Application of the cracked pipe element to creep crack growth prediction

    SciTech Connect (OSTI)

    Brochard, J.; Charras, T.

    1997-04-01

    The modification of a computer code for leak before break analysis is very briefly described. The CASTEM2000 code was developed for ductile fracture assessment of piping systems with postulated circumferential through-wall cracks under static or dynamic loading. The modification extends the capabilities of the cracked pipe element to the determination of fracture parameters under creep conditions (C*, {phi}c and {Delta}c). The model has the advantage of evaluating significant secondary effects, such as those from thermal loading.

  12. US NRC-Sponsored Research on Stress Corrosion Cracking Susceptibility of Dry Storage Canister Materials in Marine Environments - 13344

    SciTech Connect (OSTI)

    Oberson, Greg; Dunn, Darrell; Mintz, Todd; He, Xihua; Pabalan, Roberto; Miller, Larry

    2013-07-01

    At a number of locations in the U.S., spent nuclear fuel (SNF) is maintained at independent spent fuel storage installations (ISFSIs). These ISFSIs, which include operating and decommissioned reactor sites, Department of Energy facilities in Idaho, and others, are licensed by the U.S. Nuclear Regulatory Commission (NRC) under Title 10 of the Code of Federal Regulations, Part 72. The SNF is stored in dry cask storage systems, which most commonly consist of a welded austenitic stainless steel canister within a larger concrete vault or overpack vented to the external atmosphere to allow airflow for cooling. Some ISFSIs are located in marine environments where there may be high concentrations of airborne chloride salts. If salts were to deposit on the canisters via the external vents, a chloride-rich brine could form by deliquescence. Austenitic stainless steels are susceptible to chloride-induced stress corrosion cracking (SCC), particularly in the presence of residual tensile stresses from welding or other fabrication processes. SCC could allow helium to leak out of a canister if the wall is breached or otherwise compromise its structural integrity. There is currently limited understanding of the conditions that will affect the SCC susceptibility of austenitic stainless steel exposed to marine salts. NRC previously conducted a scoping study of this phenomenon, reported in NUREG/CR-7030 in 2010. Given apparent conservatisms and limitations in this study, NRC has sponsored a follow-on research program to more systematically investigate various factors that may affect SCC including temperature, humidity, salt concentration, and stress level. The activities within this research program include: (1) measurement of relative humidity (RH) for deliquescence of sea salt, (2) SCC testing within the range of natural absolute humidity, (3) SCC testing at elevated temperatures, (4) SCC testing at high humidity conditions, and (5) SCC testing with various applied stresses. Results

  13. The study of stress application and corrosion cracking on Ni-16 Cr-9 Fe (Alloy 600) C-ring samples by polychromatic X-ray microdiffraction

    SciTech Connect (OSTI)

    Chao, Jing; Fuller, Marina L Suominen; McIntyre, N Stewart; Carcea, Anatolie G; Newman, Roger C; Kunz, Martin; Tamura, Nobumichi

    2012-03-27

    Microscopic strains associated with stress corrosion cracks have been investigated in stressed C-rings of Ni-16 Cr-9 Fe (Alloy 600) boiler tubing. Polychromatic X-ray microdiffraction was used to measure deviatoric strain tensors and the distribution of dislocations near cracks that had been propagated in electrochemically accelerated corrosion tests. An associated investigation of the C-ring-induced strains prior to corrosion showed significant tensile strain in the stress axis direction by the torsional closure of the alloy tube section in the C-ring test. Significant grain lattice rotation and pronounced plastic strain at some grain boundaries were noted. Stress-corrosion-cracking-generated intergranular cracks were produced in two Alloy 600 specimens after 6 h and 18 h tests. The diffraction patterns and resultant strain tensors were mapped around the cracked area to a 1 μm spatial resolution. The strain tensor transverse to the crack growth direction showed tensile strain at the intergranular region just ahead of the crack tip for both specimens. Both cracks were found to follow grain boundary pathways that had the lowest angle of misorientation. Dislocation distributions within each grain were qualitatively obtained from the shapes of the diffraction spots and the effect of 'hard' and 'soft' grains on the crack pathway was explored for both 6 h and 18 h specimens. The Schmid factor of one of the grains adjacent to the crack at the 6 h and 18 h initiation sites was found to be the lowest, compared to Schmid factors calculated for surface grains away from the initiation site, and also along the crack path into the bulk.

  14. Corrosion fatigue crack growth in clad low-alloy steel. Part 2, Water flow rate effects in high sulfur plate steel

    SciTech Connect (OSTI)

    James, L.A; Lee, H.B.; Wire, G.L.; Novak, S.R.; Cullen, W.H.

    1996-04-01

    Corrosion fatigue crack propagation tests were conducted on a high- sulfur ASTM A302-B plate steel overlaid with weld-deposited Alloy EN82H cladding. The specimens featured semi-elliptical surface cracks penetrating approximately 6.3 mm of cladding into the underlying steel. The initial crack sizes were relatively large with surface lengths of 22.8--27.3 mm, and depths of 10.5--14.1 mm. The experiments were initiated in a quasi-stagnant low-oxygen (O{sub 2} < 10 ppb) aqueous environment at 243{degrees}C, under loading conditions ({Delta}K, R, cyclic frequency) conducive to environmentally-assisted cracking (EAC) under quasi-stagnant conditions. Following fatigue testing under quasi-stagnant conditions where EAC was observed, the specimens were then fatigue tested under conditions where active water flow of either 1.7 m/sec. or 4.7 m/sec. was applied parallel to the crack. Earlier experiments on unclad surface-cracked specimens of the same steel exhibited EAC under quasi- stagnant conditions, but water flow rates at 1.7 m/sec. and 5.0 m/sec. parallel to the crack mitigated EAC. In the present experiments on clad specimens, water flow at approximately the same as the lower of these velocities did not mitigate EAC, and a free stream velocity approximately the same as the higher of these velocities resulted in sluggish mitigation of EAC. The lack of robust EAC mitigation was attributed to the greater crack surface roughness in the cladding interfering with flow induced within the crack cavity. An analysis employing the computational fluid dynamics code, FIDAP, confirmed that frictional forces associated with the cladding crack surface roughness reduced the interaction between the free stream and the crack cavity.

  15. Helium gas bubble trapped in liquid helium in high magnetic field

    SciTech Connect (OSTI)

    Bai, H. Hannahs, S. T.; Markiewicz, W. D.; Weijers, H. W.

    2014-03-31

    High magnetic field magnets are used widely in the area of the condensed matter physics, material science, chemistry, geochemistry, and biology at the National High Magnetic Field Laboratory. New high field magnets of state-of-the-art are being pursued and developed at the lab, such as the current developing 32 T, 32 mm bore fully superconducting magnet. Liquid Helium (LHe) is used as the coolant for superconducting magnets or samples tested in a high magnetic field. When the magnetic field reaches a relatively high value the boil-off helium gas bubble generated by heat losses in the cryostat can be trapped in the LHe bath in the region where BzdBz/dz is less than negative 2100 T{sup 2}/m, instead of floating up to the top of LHe. Then the magnet or sample in the trapped bubble region may lose efficient cooling. In the development of the 32 T magnet, a prototype Yttrium Barium Copper Oxide coil of 6 double pancakes with an inner diameter of 40 mm and an outer diameter of 140 mm was fabricated and tested in a resistive magnet providing a background field of 15 T. The trapped gas bubble was observed in the tests when the prototype coil was ramped up to 7.5 T at a current of 200 A. This letter reports the test results on the trapped gas bubble and the comparison with the analytical results which shows they are in a good agreement.

  16. Controlled Chemistry Helium High Temperature Materials Test Loop

    SciTech Connect (OSTI)

    Richard N. WRight

    2005-08-01

    A system to test aging and environmental effects in flowing helium with impurity content representative of the Next Generation Nuclear Plant (NGNP) has been designed and assembled. The system will be used to expose microstructure analysis coupons and mechanical test specimens for up to 5,000 hours in helium containing potentially oxidizing or carburizing impurities controlled to parts per million levels. Impurity levels in the flowing helium are controlled through a feedback mechanism based on gas chromatography measurements of the gas chemistry at the inlet and exit from a high temperature retort containing the test materials. Initial testing will focus on determining the nature and extent of combined aging and environmental effects on microstructure and elevated temperature mechanical properties of alloys proposed for structural applications in the NGNP, including Inconel 617 and Haynes 230.

  17. Process for magnetic beneficiating petroleum cracking catalyst

    DOE Patents [OSTI]

    Doctor, R.D.

    1993-10-05

    A process is described for beneficiating a particulate zeolite petroleum cracking catalyst having metal values in excess of 1000 ppm nickel equivalents. The particulate catalyst is passed through a magnetic field in the range of from about 2 Tesla to about 5 Tesla generated by a superconducting quadrupole open-gradient magnetic system for a time sufficient to effect separation of said catalyst into a plurality of zones having different nickel equivalent concentrations. A first zone has nickel equivalents of about 6,000 ppm and greater, a second zone has nickel equivalents in the range of from about 2000 ppm to about 6000 ppm, and a third zone has nickel equivalents of about 2000 ppm and less. The zones of catalyst are separated and the second zone material is recycled to a fluidized bed of zeolite petroleum cracking catalyst. The low nickel equivalent zone is treated while the high nickel equivalent zone is discarded. 1 figures.

  18. Process for magnetic beneficiating petroleum cracking catalyst

    DOE Patents [OSTI]

    Doctor, Richard D.

    1993-01-01

    A process for beneficiating a particulate zeolite petroleum cracking catalyst having metal values in excess of 1000 ppm nickel equivalents. The particulate catalyst is passed through a magnetic field in the range of from about 2 Tesla to about 5 Tesla generated by a superconducting quadrupole open-gradient magnetic system for a time sufficient to effect separation of said catalyst into a plurality of zones having different nickel equivalent concentrations. A first zone has nickel equivalents of about 6,000 ppm and greater, a second zone has nickel equivalents in the range of from about 2000 ppm to about 6000 ppm, and a third zone has nickel equivalents of about 2000 ppm and less. The zones of catalyst are separated and the second zone material is recycled to a fluidized bed of zeolite petroleum cracking catalyst. The low nickel equivalent zone is treated while the high nickel equivalent zone is discarded.

  19. Operation of drift chambers with helium based mixtures

    SciTech Connect (OSTI)

    Sharma, A. ); Sauli, F. )

    1994-08-01

    Helium based gas mixtures have been investigated for lowering multiple scattering contributions to the momentum resolution for intermediate energy particles. The relevant transport parameters, namely drift velocity and diffusion have been calculated for several mixtures and compared to standard argon based mixtures. Some fast, low diffusion mixtures have been identified. The small Lorentz angle computed make them promising candidates for drift chamber operation in magnetic fields. Measurements on high accuracy drift chambers in a test beam with a helium-DME (dimethyl ether) (70-30) mixture have resulted in a spatial resolution ranging from 70[mu]m to 100[mu]m.

  20. Isotope Effects and Helium Retention Behavior in Vanadium Tritide

    SciTech Connect (OSTI)

    Bowman, Jr., R. C.; Attalla, A.; Craft, B. D.

    1985-04-01

    The relaxation times of the H, T, and 3He nuclei have been measured in vanadium hydride and tritide samples. Substantial isotope effects in both the phase transition temperatures and diffusion parameters have been found. When compared to hydrides, the tritide samples have lower transition temperatures and faster mobilities. The differences in the occupancies of the interstitial sites are largely responsible for these isotope effects. Most of the helium atoms generated by tritium decay remain trapped in microscopic bubbles formed with the VTx lattice. Evidence is presented for the gradual growth of the helium bubbles over periods of hundreds of days.

  1. Status of the helium afterglow injector for MAMI

    SciTech Connect (OSTI)

    Arianer, J.; Cohen, S.; Essabaa, S.; Frascaria, R.; Zerhouni, O.; Szeremeta, F.; Wurzinger, R.; Aulenbacher, K.

    1998-01-20

    For the parity-violation experiment at the Mami cw electron accelerator facility at the University of Mainz, we need a stable polarized electron source able to deliver a current >150 {mu}A with polarization >60%. We develop the Orsay polarized electron source SELPO as an injector for MAMI. SELPO source based on a flowing helium afterglow is now operating in a high voltage platform. The terminal will be tested completely at Orsay and is foreseen to be installed at MAMI before the end of this year. Recent results obtained with an array of capillaries to generate the helium flow and a longitudinal spin direction are described.

  2. Structures for dense, crack free thin films

    DOE Patents [OSTI]

    Jacobson, Craig P.; Visco, Steven J.; De Jonghe, Lutgard C.

    2011-03-08

    The process described herein provides a simple and cost effective method for making crack free, high density thin ceramic film. The steps involve depositing a layer of a ceramic material on a porous or dense substrate. The deposited layer is compacted and then the resultant laminate is sintered to achieve a higher density than would have been possible without the pre-firing compaction step.

  3. Improvement of microbead cracking catalyst manufacture

    SciTech Connect (OSTI)

    Mirskii, Ya.B.; Kosolapova, A.P.; Meged, N.F.

    1986-11-01

    In order to improve the manufacturing process for KMTsR microbead catalyst for use in new cracking units, the authors consider the method of increasing the content of aluminum oxide in its amorphous part. A microbead catalyst of zeolite, containing rare-earth elements of the KMTsR type was obtained by spray-drying a slurry prepared by mechanical dispersion of hydrogel beads, with the subsequent molding and processing operations the same as in the production of bead catalyst.

  4. Atomistic simulations of brittle crack growth.

    SciTech Connect (OSTI)

    Hoyt, Jeffrey John

    2007-04-01

    Ceramic materials such as lead zirconium titanates (PZT), low temperature co-fired ceramics and silica glasses are used in several of Sandia's mission critical components. Brittle fracture, either during machining and processing or after many years in service, remains a serious reliability and cost issue. Despite its technological importance, brittle fracture remains poorly understand, especially the onset and propagation of sub-critical cracks. However, some insights into the onset of fracture can be gleaned from the atomic scale structure of the amorphous material. In silica for example, it is well known [1] that the Si-O-Si bonds are relatively weak and, in angle distribution functions determined from scattering experiments, the bonds exhibit a wide spread around a peak at 150. By contrast the O-Si-O bonds are strong with a narrow peak in the distribution around the 109 dictated by the SiO{sub 4} tetrahedron. In addition, slow energy release in silica, as deduced from dissolution experiments, depends on the distribution of 3-fold and higher rings in the amorphous structure. The purpose of this four month LDRD project was to investigate the atomic structure of silica in the bulk and in the vicinity of a crack tip using molecular dynamics simulations. Changes in the amorphous structure in the neighborhood of an atomically sharp tip may provide important clues as to the initiation sites and the stress intensity required to propagate a sub-critical crack.

  5. Statistical properties of inter-series mixing in helium: From integrability to chaos

    SciTech Connect (OSTI)

    Puttner, R; Gremaud, B.; Delande, D.; Domke, M.; Martins, M.; Schlachter, A.S.; Kaindl, G.

    2001-04-23

    The photoionization spectrum of helium near the double-ionization threshold shows structure which indicated a transition towards quantum chaos.

  6. Flow instabilities in non-uniformly heated helium jet arrays used for divertor PFCs

    SciTech Connect (OSTI)

    Youchison, Dennis L.

    2015-07-30

    In this study, due to a lack of prototypical experimental data, little is known about the off-normal behavior of recently proposed divertor jet cooling concepts. This article describes a computational fluid dynamics (CFD) study on two jet array designs to investigate their susceptibility to parallel flow instabilities induced by non-uniform heating and large increases in the helium outlet temperature. The study compared a single 25-jet helium-cooled modular divertor (HEMJ) thimble and a micro-jet array with 116 jets. Both have pure tungsten armor and a total mass flow rate of 10 g/s at a 600 C inlet temperature. We investigated flow perturbations caused by a 30 MW/m2 off-normal heat flux applied over a 25 mm2 area in addition to the nominal 5 MW/m2 applied over a 75 mm2 portion of the face. The micro-jet array exhibited lower temperatures and a more uniform surface temperature distribution than the HEMJ thimble. We also investigated the response of a manifolded nine-finger HEMJ assembly using the nominal heat flux and a 274 mm2 heated area.

  7. Deformation fields near a steady fatigue crack with anisotropic plasticity

    SciTech Connect (OSTI)

    Gao, Yanfei

    2015-11-30

    In this work, from finite element simulations based on an irreversible, hysteretic cohesive interface model, a steady fatigue crack can be realized if the crack extension exceeds about twice the plastic zone size, and both the crack increment per loading cycle and the crack bridging zone size are smaller than the plastic zone size. The corresponding deformation fields develop a plastic wake behind the crack tip and a compressive residual stress field ahead of the crack tip. In addition, the Hill’s plasticity model is used to study the role of plastic anisotropy on the retardation of fatigue crack growth and the elastic strain fields. It is found that for Mode-I cyclic loading, an enhanced yield stress in directions that are inclined from the crack plane will lead to slower crack growth rate, but this retardation is insignificant for typical degrees of plastic anisotropy. Furthermore, these results provide key inputs for future comparisons to neutron and synchrotron diffraction measurements that provide full-field lattice strain mapping near fracture and fatigue crack tips, especially in textured materials such as wrought or rolled Mg alloys.

  8. Ultrasonic size determination of cracks with large closure regions

    SciTech Connect (OSTI)

    Rehbein, D.K.; Thompson, R.B.; Buck, O.

    1995-04-01

    A number of investigators have developed acoustic methods for measurement and determination of crack length. These methods have generally fallen into one of three categories, determination of crack area, time of flight to determine crack length, or recognition of the crack tip by changes in the signal response. These methods have been successful in location of the crack tip to within {+-}0.5 mm. In all cases, however, it was necessary for the crack length or the crack-tip position to be determined with the crack in a fully open state in order to remove the effects of crack closure. Recent work has developed acoustic scanning techniques and subsequent analysis to the point where the same accuracy of {+-}0.5 mm is now possible through scanning of the crack in an unloaded condition with closure accounted for. A review of the previous methods will be given together with an explanation of the advances in scanning technique and analysis that have allowed this simplification to occur.

  9. Deformation fields near a steady fatigue crack with anisotropic plasticity

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Gao, Yanfei

    2015-11-30

    In this work, from finite element simulations based on an irreversible, hysteretic cohesive interface model, a steady fatigue crack can be realized if the crack extension exceeds about twice the plastic zone size, and both the crack increment per loading cycle and the crack bridging zone size are smaller than the plastic zone size. The corresponding deformation fields develop a plastic wake behind the crack tip and a compressive residual stress field ahead of the crack tip. In addition, the Hill’s plasticity model is used to study the role of plastic anisotropy on the retardation of fatigue crack growth andmore » the elastic strain fields. It is found that for Mode-I cyclic loading, an enhanced yield stress in directions that are inclined from the crack plane will lead to slower crack growth rate, but this retardation is insignificant for typical degrees of plastic anisotropy. Furthermore, these results provide key inputs for future comparisons to neutron and synchrotron diffraction measurements that provide full-field lattice strain mapping near fracture and fatigue crack tips, especially in textured materials such as wrought or rolled Mg alloys.« less

  10. An investigation of thermally driven acoustical oscillations in helium systems

    SciTech Connect (OSTI)

    Fuerst, J.D.

    1990-08-01

    The phenomenon of thermal-acoustic oscillation is seen to arise spontaneously in gas columns subjected to steep temperature gradients, particularly in tubes connecting liquid helium reservoirs with the ambient environment. This if often the arrangement for installed cryogenic instrumentation and is accompanied by undesirably large heat transfer rates to the cold region. Experimental data are collected and matched to theoretical predictions of oscillatory behavior; these results are in good agreement with the analytical model and with previously collected data. The present experiment places the open ends of oscillating tubes of the various lengths and cross sections in communication with flowing helium in the subcooled, 2-phase, or superheated state while the other ends are maintained at some controlled, elevated temperature. Assorted cold end conditions are achieved through adjustments to the Fermilab Tevatron satellite test refrigerator to which the test cryostat is connected. The warm, closed ends of the tubes are maintained by isothermal baths of liquid nitrogen, ice water, and boiling water. The method is contrasted to previous arrangements whereby tubes are run from room temperature into or adjacent to a stagnant pool of liquid helium. Additionally, the effect of pulsations in the flowing helium stream is explored through operation of the refrigerator's wet and dry expanders during data collection. These data confirm the theory to which try were compared and support its use in the design of cryogenic sensing lines for avoidance of thermoacoustic oscillation.

  11. TRANSMISSION ELECTRON MICROSCOPY STUDY OF HELIUM BEARING FUSION WELDS

    SciTech Connect (OSTI)

    Tosten, M; Michael Morgan, M

    2008-12-12

    A transmission electron microscopy (TEM) study was conducted to characterize the helium bubble distributions in tritium-charged-and-aged 304L and 21Cr-6Ni-9Mn stainless steel fusion welds containing approximately 150 appm helium-3. TEM foils were prepared from C-shaped fracture toughness test specimens containing {delta} ferrite levels ranging from 4 to 33 volume percent. The weld microstructures in the low ferrite welds consisted mostly of austenite and discontinuous, skeletal {delta} ferrite. In welds with higher levels of {delta} ferrite, the ferrite was more continuous and, in some areas of the 33 volume percent sample, was the matrix/majority phase. The helium bubble microstructures observed were similar in all samples. Bubbles were found in the austenite but not in the {delta} ferrite. In the austenite, bubbles had nucleated homogeneously in the grain interiors and heterogeneously on dislocations. Bubbles were not found on any austenite/austenite grain boundaries or at the austenite/{delta} ferrite interphase interfaces. Bubbles were not observed in the {delta} ferrite because of the combined effects of the low solubility and rapid diffusion of tritium through the {delta} ferrite which limited the amount of helium present to form visible bubbles.

  12. Application of the cracked pipe element to creep crack growth prediction

    SciTech Connect (OSTI)

    Brochard, J.; Charras, T.

    1997-04-01

    Modifications to a computer code for ductile fracture assessment of piping systems with postulated circumferential through-wall cracks under static or dynamic loading are very briefly described. The modifications extend the capabilities of the CASTEM2000 code to the determination of fracture parameters under creep conditions. The main advantage of the approach is that thermal loads can be evaluated as secondary stresses. The code is applicable to piping systems for which crack propagation predictions differ significantly depending on whether thermal stresses are considered as primary or secondary stresses.

  13. Cyclic crack resistance of an anticorrosion surfacing steel joint

    SciTech Connect (OSTI)

    Zuezdin, Y.I.; Andrusiv, B.N.; Nikiforchin, G.N.; Timofeev, B.T.; Zima, Y.V.

    1986-03-01

    An investigation was made of the cyclic crack resistance of the austenitic surfacing - 15Kh2MFA steel transition zone taking into consideration the fatigue crack geometry, the fracture mechanism, and the effect of crack closure. Microstructural analysis showed significant heterogeneity of the surfacing-base metal transition zone. An analysis of the base metal showed that in the area of low-fatigue crack growth rates, there is a significant spread in the experimental data obtained in tests of three specimens. Under steady service conditions, an increased loading asymmetry sharply accelerates failure of the alloy as the result of growth only of the subsurfacing crack, which is partically insensitive to the direction of crack development and to structural changes in the transition zone materials.

  14. Stress Corrosion Cracking of the Drip Shield, the Waste Package Outer Barrier, and the Stainless Steel Structural Material

    SciTech Connect (OSTI)

    G. Gordon

    2004-10-13

    Stress corrosion cracking is one of the most common corrosion-related causes for premature breach of metal structural components. Stress corrosion cracking is the initiation and propagation of cracks in structural components due to three factors that must be present simultaneously: metallurgical susceptibility, critical environment, and static (or sustained) tensile stresses. This report was prepared according to ''Technical Work Plan for: Regulatory Integration Modeling and Analysis of the Waste Form and Waste Package'' (BSC 2004 [DIRS 171583]). The purpose of this report is to provide an evaluation of the potential for stress corrosion cracking of the engineered barrier system components (i.e., the drip shield, waste package outer barrier, and waste package stainless steel inner structural cylinder) under exposure conditions consistent with the repository during the regulatory period of 10,000 years after permanent closure. For the drip shield and waste package outer barrier, the critical environment is conservatively taken as any aqueous environment contacting the metal surfaces. Appendix B of this report describes the development of the SCC-relevant seismic crack density model (SCDM). The consequence of a stress corrosion cracking breach of the drip shield, the waste package outer barrier, or the stainless steel inner structural cylinder material is the initiation and propagation of tight, sometimes branching, cracks that might be induced by the combination of an aggressive environment and various tensile stresses that can develop in the drip shields or the waste packages. The Stainless Steel Type 316 inner structural cylinder of the waste package is excluded from the stress corrosion cracking evaluation because the Total System Performance Assessment for License Application (TSPA-LA) does not take credit for the inner cylinder. This document provides a detailed description of the process-level models that can be applied to assess the performance of Alloy 22

  15. Method and apparatus for generating a natural crack

    DOE Patents [OSTI]

    Fulton, Fred J.; Honodel, Charles A.; Holman, William R.; Weingart, Richard C.

    1984-01-01

    A method and apparatus for generating a measurable natural crack includes forming a primary notch in the surface of a solid material. A non-sustained single pressure pulse is then generated in the vicinity of the primary notch, resulting in the formation of a shock wave which travels through the material. The shock wave creates a measurable natural crack within the material which extends from the primary notch. The natural crack formed possesses predictable geometry, location and orientation.

  16. Method and apparatus for generating a natural crack

    DOE Patents [OSTI]

    Fulton, F.J.; Honodel, C.A.; Holman, W.R.; Weingart, R.C.

    1982-05-06

    A method and apparatus for generating a measurable natural crack includes forming a primary notch in the surface of a solid material. A nonsustained single pressure pulse is then generated in the vicinity of the primary notch, reuslting in the formation of a shock wave which travels through the material. The shock wave creates a measurable natural crack within the material which extends from the primary notch. The natural crack formed possesses predictable geometry, location and orientation.

  17. Helium Release Behavior of Aged Titanium Tritides

    SciTech Connect (OSTI)

    SHANAHAN, KIRKL.

    2004-07-27

    One sample of bulk Ti has been loaded with a 50 per cent / 50 per cent deuterium/tritium mixture and statically aged for 6.5 years. Thermal desorption of the sample shows an initial release of hydrogen isotopes followed by 3He release. Subsequent D2 loading/desorption was used to quantify the trapped tritium heel. The sample shows an excess hydrogen capacity as a second thermal desorption peak that partially disappears and shifts with annealing at 923-973K. The main hydrogen desorption peak also shifts to higher temperature, indicating a partial reversal of the tritium-decay induced damage by annealing.

  18. Kinetics of fatigue cracks in iron in electrolytic hydrogen impregnation

    SciTech Connect (OSTI)

    Pokhmurskii, V.I.; Bilyi, L.M.

    1985-05-01

    Fatigue failure of metals is localized in the zone of plastic deformation at the tip of the developing crack. Crack development depends to a large extent upon the parameters of the deformed volume, the loading conditions, and features of the material microstructure. It may be assumed that the medium, especially a hydrogen-impregnating medium, leads to a change in the zone of plastic deformation and thereby influences the rate of fatigue crack growth. This work is devoted to a study of cyclic crack resistance and determination of the zone of plastic deformation of failure specimens of Armco iron under conditions of the action of a hydrogen-impregnating medium.

  19. Heavy oil catalytic cracking process and apparatus (Patent) ...

    Office of Scientific and Technical Information (OSTI)

    Subject: 02 PETROLEUM; 42 ENGINEERING; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CATALYSTS; COOLING; PETROLEUM; CATALYTIC CRACKING; AIR POLLUTION CONTROL; COKE; ...

  20. Hot Rolling Scrap Reduction through Edge Cracking and Surface...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    aluminum alloy plate to microstructure and rolling process parameters. Validate the model by predicting the stress intensity factor at onset of crack branching in hard alloys ...

  1. Evolution of an interfacial crack on the concrete-embankment...

    Office of Scientific and Technical Information (OSTI)

    Title: Evolution of an interfacial crack on the concrete-embankment boundary Authors: Glascoe, L ; Antoun, T ; Kanarska, Y ; Lomove, I ; Hall, R ; Woodson, S ; Smith, J Publication ...

  2. Alloy 400 tube failures by stress corrosion cracking

    SciTech Connect (OSTI)

    Amar, A.S.

    1995-12-01

    A feedwater heater with SB163 Alloy 400 (cold drawn - stress relieved) tubing experienced numerous tube failures and was replaced after of 4.5 years. Failures were attributed to Inter Granular Stress Corrosion Cracking (IGSCC) in the roll transition area. An eddy current test method was developed with EPRI NDE Center technical support to detect the cracks in the tubesheet region. Three tubes were pulled for metallurgical examination. Short axial cracks were found on tube inner surface. Measured crack depths were correlated with the eddy current indications. A large number of tubes were plugged. However, the heater continued to deteriorate rapidly. Potential contributors to IGSCC are discussed.

  3. P wave anisotropy, stress, and crack distribution at Coso geothermal...

    Open Energy Info (EERE)

    scalar. The resulting anisotropy distribution is used to estimate variations in crack density, stress distribution and permeability within the producing geothermal field. A...

  4. The Effect of Crack Orientation on the Nonlinear Interaction of a P-wave with an S-wave

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    TenCate, J. A.; Malcolm, A. E.; Feng, X.; Fehler, M. C.

    2016-06-06

    Cracks, joints, fluids, and other pore-scale structures have long been hypothesized to be the cause of the large elastic nonlinearity observed in rocks. It is difficult to definitively say which pore-scale features are most important, however, because of the difficulty in isolating the source of the nonlinear interaction. In this work, we focus on the influence of cracks on the recorded nonlinear signal and in particular on how the orientation of microcracks changes the strength of the nonlinear interaction. We do this by studying the effect of orientation on the measurements in a rock with anisotropy correlated with the presencemore » and alignment of microcracks. We measure the nonlinear response via the traveltime delay induced in a low-amplitude P wave probe by a high-amplitude S wave pump. We find evidence that crack orientation has a significant effect on the nonlinear signal.« less

  5. Crack opening area estimates in pressurized through-wall cracked elbows under bending

    SciTech Connect (OSTI)

    Franco, C.; Gilles, P.; Pignol, M.

    1997-04-01

    One of the most important aspects in the leak-before-break approach is the estimation of the crack opening area corresponding to potential through-wall cracks at critical locations during plant operation. In order to provide a reasonable lower bound to the leak area under such loading conditions, numerous experimental and numerical programs have been developed in USA, U.K. and FRG and widely discussed in literature. This paper aims to extend these investigations on a class of pipe elbows characteristic of PWR main coolant piping. The paper is divided in three main parts. First, a new simplified estimation scheme for leakage area is described, based on the reference stress method. This approach mainly developed in U.K. and more recently in France provides a convenient way to account for the non-linear behavior of the material. Second, the method is carried out for circumferential through-wall cracks located in PWR elbows subjected to internal pressure. Finite element crack area results are presented and comparisons are made with our predictions. Finally, in the third part, the discussion is extended to elbows under combined pressure and in plane bending moment.

  6. Impurity gettering in silicon using cavities formed by helium implantation and annealing

    DOE Patents [OSTI]

    Myers, S.M. Jr.; Bishop, D.M.; Follstaedt, D.M.

    1998-11-24

    Impurity gettering in silicon wafers is achieved by a new process consisting of helium ion implantation followed by annealing. This treatment creates cavities whose internal surfaces are highly chemically reactive due to the presence of numerous silicon dangling bonds. For two representative transition-metal impurities, copper and nickel, the binding energies at cavities were demonstrated to be larger than the binding energies in precipitates of metal silicide, which constitutes the basis of most current impurity gettering. As a result the residual concentration of such impurities after cavity gettering is smaller by several orders of magnitude than after precipitation gettering. Additionally, cavity gettering is effective regardless of the starting impurity concentration in the wafer, whereas precipitation gettering ceases when the impurity concentration reaches a characteristic solubility determined by the equilibrium phase diagram of the silicon-metal system. The strong cavity gettering was shown to induce dissolution of metal-silicide particles from the opposite side of a wafer. 4 figs.

  7. Impurity gettering in silicon using cavities formed by helium implantation and annealing

    DOE Patents [OSTI]

    Myers, Jr., Samuel M.; Bishop, Dawn M.; Follstaedt, David M.

    1998-01-01

    Impurity gettering in silicon wafers is achieved by a new process consisting of helium ion implantation followed by annealing. This treatment creates cavities whose internal surfaces are highly chemically reactive due to the presence of numerous silicon dangling bonds. For two representative transition-metal impurities, copper and nickel, the binding energies at cavities were demonstrated to be larger than the binding energies in precipitates of metal silicide, which constitutes the basis of most current impurity gettering. As a result the residual concentration of such impurities after cavity gettering is smaller by several orders of magnitude than after precipitation gettering. Additionally, cavity gettering is effective regardless of the starting impurity concentration in the wafer, whereas precipitation gettering ceases when the impurity concentration reaches a characteristic solubility determined by the equilibrium phase diagram of the silicon-metal system. The strong cavity gettering was shown to induce dissolution of metal-silicide particles from the opposite side of a wafer.

  8. Patterned Exfoliation of GaAs Based on Masked Helium Implantation and Subsequent Rapid Thermal Annealing

    SciTech Connect (OSTI)

    Woo, H. J.; Choi, H. W.; Kim, G. D.; Hong, W.; Kim, J. K.

    2009-03-10

    A method of patterning single crystal GaAs based on ion implantation induced selective area exfoliation is suggested. Samples were implanted with 200-500 keV helium ions to a fluence range of 2-4x10{sup 16} He{sup +}/cm{sup 2} at room temperature through masks of Ni mesh (40 {mu}m opening) or stainless steel wire (50 {mu}m in diameter), and subsequent rapid thermal annealing at 350-500{open_square} resulted in expulsion of ion beam exposed material. The influences of ion energy, ion fluence, implantation temperature, subsequent annealing conditions (temperature and ramp rate), and mask pattern and its orientation with GaAs lattice on the patterned exfoliation were examined.

  9. Analysis of Mode III Elastodynamic Cracked Plane using the Fractal Two-Level Finite Element Method

    SciTech Connect (OSTI)

    Fan, J.; Lee, Y. Y.; Leung, A. Y. T.

    2010-05-21

    In this study, the fractal two-level finite element method, which has mainly been used for static cracked plane problems, is applied to the cracked plane problem. Using the transformation process in the proposed method, the infinite dimension of the finite element matrices that are assembled for a singular region is made finite in terms of the dynamics stress intensity factors directly, and thus the computational time can be reduced significantly. The Newmark time integration scheme is then used to obtain the dynamic stress intensity factors. The results from the proposed method are in reasonable agreement with those of classical methods. The main drawback of the time integration scheme is that numerical oscillations are induced in some cases.

  10. Development of reduced crude cracking catalysts

    SciTech Connect (OSTI)

    Hettinger, W.P. Jr. )

    1987-08-01

    In 1974 OPEC imposed an embargo on oil to the United States and caused a rapid rise in the price of a barrel of oil. At the time of the embargo, Ashland imported a considerable portion of its oil from the Middle East, thus raising the question of oil availability. As the problem increased in severity, Messrs. George Meyer, Oliver Zandona and Llyod Busch, began to explore alternative ways of squeezing more product from a given barrel of crude. After considering many alternatives, they arrived at the innovative thought that it might be possible to catalytically crack the 1050{degree}F plus fraction of the barrel directly to gasoline which would in effect, give them an additional volume of crude oil. Also, if vacuum fractionation were eliminated and if the entire 650{degree}F plus (reduced crude) portion of the barrel processed, this would further reduce operating costs. With these objectives and some new process innovations in mind, they began reduced crude cracking experimentation in a small 12,000 B/D FCC operating unit at Louisville. It was from these goals, concepts and a small operating unit, that the RCC process was born.

  11. Insights into Stress Corrosion Cracking Mechanisms from High-Resolution Measurements of Crack-Tip Structures and Compositions

    SciTech Connect (OSTI)

    Bruemmer, Stephen M.; Thomas, Larry E.

    2004-11-25

    Recent results are presented demonstrating the application of cross-sectional analytical transmission electron microscopy (ATEM) to corrosion and cracking in high-temperature, light-water-reactor (LWR) environments. Structural, compositional and crystallographic characterizations of crack-tip oxide films and interfaces at near-atomic resolutions reveal evidence for unexpected local environments, corrosion reactions and local changes in the alloy metallurgy. Information obtained by high-resolution imaging and analysis indicates the corrosion processes that occur during crack advance, and provides insights into the mechanisms controlling environmental degradation. Examples of intergranular stress-corrosion cracking (IGSCC) in Ni- and Fe-base stainless alloys are reviewed to illustrate the value of this approach. Comparisons are made between crack characteristics found in components removed from long-term LWR service and those in materials tested under well-controlled laboratory conditions. Key insights into crack corrosion environments and advance mechanisms are established for Ni-base alloy 600 in steam-generator, secondary-water environments. Solution impurities such as Pb are often found in high concentrations at leading-edge reaction zones within porous, corrosion-product films. The presence of nanometer-wide, deeply attacked grain boundaries off the main SCC cracks (without evidence for plastic deformation) is believed to indicate a major role of active-path IG corrosion in the SCC process. Similar characteristics are identified for alloy 600 cracking in primary water. This suggests that Pb may only accelerate the IG corrosion process and not alter the basic degradation mechanism. Quite different IGSCC crack and crack-tip characteristics have been discovered for Fe-base stainless steels in LWR environments. More classic SCC crack and crack-tip structures have been seen in non-sensitized materials with wall oxide films extending to the tips. Cracked components

  12. Source localization of brain activity using helium-free interferometer

    SciTech Connect (OSTI)

    Dammers, Jürgen Chocholacs, Harald; Eich, Eberhard; Boers, Frank; Faley, Michael; Dunin-Borkowski, Rafal E.; Jon Shah, N.

    2014-05-26

    To detect extremely small magnetic fields generated by the human brain, currently all commercial magnetoencephalography (MEG) systems are equipped with low-temperature (low-T{sub c}) superconducting quantum interference device (SQUID) sensors that use liquid helium for cooling. The limited and increasingly expensive supply of helium, which has seen dramatic price increases recently, has become a real problem for such systems and the situation shows no signs of abating. MEG research in the long run is now endangered. In this study, we report a MEG source localization utilizing a single, highly sensitive SQUID cooled with liquid nitrogen only. Our findings confirm that localization of neuromagnetic activity is indeed possible using high-T{sub c} SQUIDs. We believe that our findings secure the future of this exquisitely sensitive technique and have major implications for brain research and the developments of cost-effective multi-channel, high-T{sub c} SQUID-based MEG systems.

  13. Quantum entanglement for helium atom in the Debye plasmas

    SciTech Connect (OSTI)

    Lin, Yen-Chang; Fang, Te-Kuei; Ho, Yew Kam

    2015-03-15

    In the present work, we present an investigation on quantum entanglement of the two-electron helium atom immersed in weakly coupled Debye plasmas, modeled by the Debye-Hckel, or screened Coulomb, potential to mimic the interaction between two charged particles inside the plasma. Quantum entanglement is related to correlation effects in a multi-particle system. In a bipartite system, a measurement made on one of the two entangled particles affects the outcome of the other particle, even if such two particles are far apart. Employing wave functions constructed with configuration interaction B-spline basis, we have quantified von Neumann entropy and linear entropy for a series of He {sup 1,3}S{sup e} and {sup 1,3}P{sup o} states in plasma-embedded helium atom.

  14. Elastic Electron Scattering from Tritium and Helium-3

    DOE R&D Accomplishments [OSTI]

    Collard, H.; Hofstadter, R.; Hughes, E. B.; Johansson, A.; Yearian, M. R.; Day, R. B.; Wagner, R. T.

    1964-10-01

    The mirror nuclei of tritium and helium-3 have been studied by the method of elastic electron scattering. Absolute cross sections have been measured for incident electron energies in the range 110 - 690 MeV at scattering angles lying between 40 degrees and 135 degrees in this energy range. The data have been interpreted in a straightforward manner and form factors are given for the distributions of charge and magnetic moment in the two nuclei over a range of four-momentum transfer squared 1.0 - 8.0 F{sup -2}. Model-independent radii of the charge and magnetic moment distributions are given and an attempt is made to deduce form factors describing the spatial distribution of the protons in tritium and helium-3.

  15. Investigation of Cellular Interactions of Nanoparticles by Helium Ion Microscopy

    SciTech Connect (OSTI)

    Arey, Bruce W.; Shutthanandan, V.; Xie, Yumei; Tolic, Ana; Williams, Nolann G.; Orr, Galya

    2011-06-01

    The helium ion mircroscope (HIM) probes light elements (e.g. C, N, O, P) with high contrast due to the large variation in secondary electron yield, which minimizes the necessity of specimen staining. A defining characteristic of HIM is its remarkable capability to neutralize charge by the implementation of an electron flood gun, which eliminates the need for coating non-conductive specimens for imaging at high resolution. In addition, the small convergence angle in HeIM offers a large depth of field (~5x FE-SEM), enabling tall structures to be viewed in focus within a single image. Taking advantage of these capabilities, we investigate the interactions of engineered nanoparticles (NPs) at the surface of alveolar type II epithelial cells grown at the air-liquid interface (ALI). The increasing use of nanomaterials in a wide range of commercial applications has the potential to increase human exposure to these materials, but the impact of such exposure on human health is still unclear. One of the main routs of exposure is the respiratory tract, where alveolar epithelial cells present a vulnerable target at the interface with ambient air. Since the cellular interactions of NPs govern the cellular response and ultimately determine the impact on human health, our studies will help delineating relationships between particle properties and cellular interactions and response to better evaluate NP toxicity or biocompatibility. The Rutherford backscattered ion (RBI) is a helium ions imaging mode, which backscatters helium ions from every element except hydrogen, with a backscatter yield that depends on the atomic number of the target. Energy-sensitive backscatter analysis is being developed, which when combined with RBI image information, supports elemental identification at helium ion nanometer resolution. This capability will enable distinguishing NPs from cell surface structures with nanometer resolution.

  16. Electrochemical aspects of stress-corrosion crack growth

    SciTech Connect (OSTI)

    Newman, R.C.; Sieradzki, K.

    1982-06-01

    Some contributions of electrochemical methods to the understanding of stress-corrosion cracking are described, with examples drawn from studies of stainless steels, nickel alloys and brasses. Considerations related to the local alloy composition, solution composition and electrode potential within a crack are classified and illustrated. The relationship between electrochemical and acoustic noise is discussed.

  17. Stress corrosion crack tip microstructure in nickel-based alloys

    SciTech Connect (OSTI)

    Shei, S.A.; Yang, W.J.

    1994-04-01

    Stress corrosion cracking behavior of several nickel-base alloys in high temperature caustic environments has been evaluated. The crack tip and fracture surfaces were examined using Auger/ESCA and Analytical Electron Microscopy (AEM) to determine the near crack tip microstructure and microchemistry. Results showed formation of chromium-rich oxides at or near the crack tip and nickel-rich de-alloying layers away from the crack tip. The stress corrosion resistance of different nickel-base alloys in caustic may be explained by the preferential oxidation and dissolution of different alloying elements at the crack tip. Alloy 600 (UNS N06600) shows good general corrosion and intergranular attack resistance in caustic because of its high nickel content. Thermally treated Alloy 690 (UNS N06690) and Alloy 600 provide good stress corrosion cracking resistance because of high chromium contents along grain boundaries. Alloy 625 (UNS N06625) does not show as good stress corrosion cracking resistance as Alloy 690 or Alloy 600 because of its high molybdenum content.

  18. Ultrasonic Study of Crack Under a Dynamic Thermal Load

    SciTech Connect (OSTI)

    Pitkaenen, J.; Kemppainen, M.; Virkkunen, I.

    2004-02-26

    In piping the defects play a key role for determining the life of component. Also the risk for pipe failure combined to the defects has to be taken into account. In this study thermal dynamic load has been applied to austenitic material (AISI 304) in order to introduce dynamic behaviour into the crack. The studied crack ({approx}20 mm x 7 mm) has been produced by thermal fatigue in advance. Different ultrasonic techniques were used to reveal information from interaction of ultrasonic waves from dynamic behaviour of a crack face in the sonified volume. The ultrasonic probes in the study are typical probes for defect detection and sizing on site inspections This information helps us to understand some effects in nuclear piping such as detection of cracks with special techniques and difficulties in sizing of the cracks in real situations. In this case the material is loaded to exceed the yield strength. The thermal cycles used caused high variations in the temperature scale from 20 deg. C (68 F) to 600 deg. C (1112 F) in the crack volume especially on the crack surface area. These factors cause large stress variations in the vicinity of the crack. Effects which have been detected during analysis from the measurements explain well difficulties in ultrasonic inspections of those materials on site. Experimental work explains reasons why some defects are missed in the real piping. Ultrasonic techniques used are described in details and conclusion for applicability of those techniques has been drawn.

  19. Prediction of pure water stress corrosion cracking (PWSCC) in nickel base alloys using crack growth rate models

    SciTech Connect (OSTI)

    Thompson, C.D.; Krasodomski, H.T.; Lewis, N.; Makar, G.L.

    1995-02-22

    The Ford/Andresen slip dissolution SCC model, originally developed for stainless steel components in BWR environments, has been applied to Alloy 600 and Alloy X-750 tested in deaerated pure water chemistry. A method is described whereby the crack growth rates measured in compact tension specimens can be used to estimate crack growth in a component. Good agreement was found between model prediction and measured SCC in X-750 threaded fasteners over a wide range of temperatures, stresses, and material condition. Most data support the basic assumption of this model that cracks initiate early in life. The evidence supporting a particular SCC mechanism is mixed. Electrochemical repassivation data and estimates of oxide fracture strain indicate that the slip dissolution model can account for the observed crack growth rates, provided primary rather than secondary creep rates are used. However, approximately 100 cross-sectional TEM foils of SCC cracks including crack tips reveal no evidence of enhanced plasticity or unique dislocation patterns at the crack tip or along the crack to support a classic slip dissolution mechanism. No voids, hydrides, or microcracks are found in the vicinity of the crack tips creating doubt about classic hydrogen related mechanisms. The bulk oxide films exhibit a surface oxide which is often different than the oxides found within a crack. Although bulk chromium concentration affects the rate of SCC, analytical data indicates the mechanism does not result from chromium depletion at the grain boundaries. The overall findings support a corrosion/dissolution mechanism but not one necessarily related to slip at the crack tip.

  20. Mathematical modeling of a Fermilab helium liquefier coldbox

    SciTech Connect (OSTI)

    Geynisman, M.G.; Walker, R.J.

    1995-12-01

    Fermilab Central Helium Liquefier (CHL) facility is operated 24 hours-a-day to supply 4.6{degrees}K for the Fermilab Tevatron superconducting proton-antiproton collider Ring and to recover warm return gases. The centerpieces of the CHL are two independent cold boxes rated at 4000 and 5400 liters/hour with LN{sub 2} precool. These coldboxes are Claude cycle and have identical heat exchangers trains, but different turbo-expanders. The Tevatron cryogenics demand for higher helium supply from CHL was the driving force to investigate an installation of an expansion engine in place of the Joule-Thompson valve. A mathematical model was developed to describe the thermo- and gas-dynamic processes for the equipment included in the helium coldbox. The model is based on a finite element approach, opposite to a global variables approach, thus providing for higher accuracy and conversion stability. Though the coefficients used in thermo- and gas-dynamic equations are unique for a given coldbox, the general approach, the equations, the methods of computations, and most of the subroutines written in FORTRAN can be readily applied to different coldboxes. The simulation results are compared against actual operating data to demonstrate applicability of the model.

  1. Multiple reheat helium Brayton cycles for sodium fast reactors

    SciTech Connect (OSTI)

    Haihua Zhao; Per F. Peterson

    2008-07-01

    Sodium fast reactors (SFR) traditionally adopt the steam Rankine cycle for power conversion. The resulting potential for water-sodium reaction remains a continuing concern which at least partly delays the SFR technology commercialization and is a contributor to higher capital cost. Supercritical CO2 provides an alternative, but is also capable of sustaining energetic chemical reactions with sodium. Recent development on advanced inert-gas Brayton cycles could potentially solve this compatibility issue, increase thermal efficiency, and bring down the capital cost close to light water reactors. In this paper, helium Brayton cycles with multiple reheat and intercooling states are presented for SFRs with reactor outlet temperatures in the range of 510°C to 650°C. The resulting thermal efficiencies range from 39% and 47%, which is comparable with supercritical recompression CO2 cycles (SCO2 cycle). A systematic comparison between multiple reheat helium Brayton cycle and the SCO2 cycle is given, considering compatibility issues, plant site cooling temperature effect on plant efficiency, full plant cost optimization, and other important factors. The study indicates that the multiple reheat helium cycle is the preferred choice over SCO2 cycle for sodium fast reactors.

  2. Predicting stress-induced velocity anisotropy in rocks

    SciTech Connect (OSTI)

    Mavko, G.; Mukerji, T.; Godfrey, N.

    1995-07-01

    A simple transformation, using measured isotropic V{sub P} and V{sub S} versus hydrostatic pressure, is presented for predicting stress-induced seismic velocity anisotropy in rocks. The compliant, crack-like portions of the pore space are characterized by generalized compressional and shear compliances that are estimated form the isotropic V{sub P} and V{sub S}. The physical assumption that the compliant porosity is crack-like means that the pressure dependence of the generalized compliances is governed primarily by normal tractions resolved across cracks and defects. This allows the measured pressure dependence to be mapped form the hydrostatic stress state to any applied nonhydrostatic stress. Predicted P- and S-wave velocities agree reasonably well with uniaxial stress data for Barre Granite and Massillon Sandstone. While it is mechanically similar to methods based on idealized ellipsoidal cracks, the approach is relatively independent of any assumed crack geometry and is not limited to small crack densities.

  3. Predicting crack growth in continuous-fiber composite materials

    SciTech Connect (OSTI)

    Cordes, J.A.; Yazici, R.

    1995-12-31

    Pre-notched composite lamina with unidirectional fibers were studied experimentally and using finite element analysis. Experiments were conducted on notched graphite/aluminum and glass/epoxy panels and the results were compared to a finite element method. Under remote tensile loading, cracks in the graphite/aluminum panels propagated perpendicular to the applied load without stable crack growth. In the glass/epoxy panels, crack propagation was initially stable and parallel to the fibers. A nonlinear damage zone method (DZM) was used to predict the crack growth directions, estimate damages, model stable and unstable crack growths, and predict the loads at failure. For both materials, the predicted loads at failure were within 20% of experimental loads.

  4. Experimental study of thermodynamics propagation fatigue crack in metals

    SciTech Connect (OSTI)

    Vshivkov, A. Iziumova, A. Plekhov, O.

    2015-10-27

    This work is devoted to the development of an experimental method for studying the energy balance during cyclic deformation and fracture. The studies were conducted on 304 stainless steel AISE samples. The investigation of the fatigue crack propagation was carried out on flat samples with stress concentrators. The stress concentrator was three central holes. The heat flux sensor was developed based on the Seebeck effect. This sensor was used for measuring the heat dissipation power in the examined samples during the fatigue tests. The measurements showed that the rate of fatigue crack growth depends on the heat flux at the crack tip and there are two propagation mode of fatigue crack with different link between the propagation mode and heat flux from crack tip.

  5. Helium-Based Soundwave Chiller: Trillium: A Helium-Based Sonic Chiller- Tons of Freezing with 0 GWP Refrigerants

    SciTech Connect (OSTI)

    2010-09-01

    BEETIT Project: Penn State is designing a freezer that substitutes the use of sound waves and environmentally benign refrigerant for synthetic refrigerants found in conventional freezers. Called a thermoacoustic chiller, the technology is based on the fact that the pressure oscillations in a sound wave result in temperature changes. Areas of higher pressure raise temperatures and areas of low pressure decrease temperatures. By carefully arranging a series of heat exchangers in a sound field, the chiller is able to isolate the hot and cold regions of the sound waves. Penn State’s chiller uses helium gas to replace synthetic refrigerants. Because helium does not burn, explode or combine with other chemicals, it is an environmentally-friendly alternative to other polluting refrigerants. Penn State is working to apply this technology on a large scale.

  6. Action Plan Submissions

    Office of Environmental Management (EM)

    Helium 600 appm helium Decay Helium Reduces Threshold For Cracking Tritium Causes Slow Crack Growth 10 Failure Assessment Approach for Pressure Vessels Requires Fracture...

  7. Cracking in liquid petroleum gas Horton spheres

    SciTech Connect (OSTI)

    Trivedi, D.K. Gupta, S.C.

    1997-07-01

    A gas processing plant on the western coast of India produces sweet gas after processing sour natural gas. Liquid petroleum gas (LPG) is recovered from the sweet gas. The LPG, containing a H{sub 2}S concentration of 10 ppm to 20 ppm, is stored in Horton spheres, each 17 m in diameter with a capacity of {minus}27 C to 55 C. Horton spheres for containing liquid petroleum gas (LPG) were fabricated on-site using prestressed plates of high-strength carbon steel (CS) SA 537 Class-1 with post-weld heat treatment. High-residual tensile stresses and hydrogen absorption from H{sub 2}S present in LPG could be the cause of cracking at weld and heat-affected zone interfaces at high hardness locations. Recommendations are given for inspection and use of lower-strength CS and improved welding procedures.

  8. Saber's heavy oil cracking refinery project

    SciTech Connect (OSTI)

    Benefield, C.S.; Glasscock, W.L.

    1983-03-01

    Perhaps more than any other industry, petroleum refining has been subjected to the radical swings in business and political climates of the past several decades. Because of the huge investments and long lead times to construct refining facilities, stable government policies, predictable petroleum prices, secure feedstock supplies and markets, and reliable cost estimates are necessary ingredients to effectively plan new refinery projects. However, over the past ten years the political and economic climates have provided anything but these conditions. Yet, refiners have demonstrated a willingness to undertake risks by continuing to expand and modernize their refineries. The refining business -- just as most businesses -- responds to economic incentives. These incentives, when present, result in new technology and capacity additions. In the 1940's, significant technology advances were commercialized to refine higher-octane motor gasolines. Such processes as continuous catalytic cracking (Houdry Process Corporation), fluid catalytic cracking (Standard Oil Development Company), HF alkylation (UOP and Phillips Petroleum Company), and catalytic reforming (UOP) began to supply a growing gasoline market, generated from the war effort and the ever increasing numbers of automobiles on the road. The post-war economy of the 1950's and 1960's further escalated demand for refined products, products which had to meet higher performance specifications and be produced from a wider range of raw materials. The refining industry met the challenge by introducing hydro-processing technology, such as hydrocracking developed in 1960. But, the era must be characterized by the large crude processing capacity additions, required to meet demand from the rapidly expanding U.S. economy. In 1950, refining capacity was 6.2 million BPD. By 1970, capacity had grown to 11.9 million BPD, an increase of 91%.

  9. Flow instabilities in non-uniformly heated helium jet arrays used for divertor PFCs

    SciTech Connect (OSTI)

    Youchison, Dennis L.

    2015-07-30

    In this study, due to a lack of prototypical experimental data, little is known about the off-normal behavior of recently proposed divertor jet cooling concepts. This article describes a computational fluid dynamics (CFD) study on two jet array designs to investigate their susceptibility to parallel flow instabilities induced by non-uniform heating and large increases in the helium outlet temperature. The study compared a single 25-jet helium-cooled modular divertor (HEMJ) thimble and a micro-jet array with 116 jets. Both have pure tungsten armor and a total mass flow rate of 10 g/s at a 600 °C inlet temperature. We investigated flow perturbations caused by a 30 MW/m2 off-normal heat flux applied over a 25 mm2 area in addition to the nominal 5 MW/m2 applied over a 75 mm2 portion of the face. The micro-jet array exhibited lower temperatures and a more uniform surface temperature distribution than the HEMJ thimble. We also investigated the response of a manifolded nine-finger HEMJ assembly using the nominal heat flux and a 274 mm2 heated area. For the 30 MW/m2 case, the micro-jet array absorbed 750 W in the helium with a maximum armor surface temperature of 1280 °C and a fluid/solid interface temperature of 801 °C. The HEMJ absorbed 750 W with a maximum armor surface temperature of 1411 °C and a fluid/solid interface temperature of 844 °C. For comparison, both the single HEMJ finger and the micro-jet array used 5-mm-thick tungsten armor. The ratio of maximum to average temperature and variations in the local heat transfer coefficient were lower for the micro-jet array compared to the HEMJ device. Although high heat flux testing is required to validate the results obtained in these simulations, the results provide important guidance in jet design and manifolding to increase heat removal while providing more even temperature distribution and minimizing non-uniformity in the gas flow and thermal stresses at the

  10. Flow instabilities in non-uniformly heated helium jet arrays used for divertor PFCs

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Youchison, Dennis L.

    2015-07-30

    In this study, due to a lack of prototypical experimental data, little is known about the off-normal behavior of recently proposed divertor jet cooling concepts. This article describes a computational fluid dynamics (CFD) study on two jet array designs to investigate their susceptibility to parallel flow instabilities induced by non-uniform heating and large increases in the helium outlet temperature. The study compared a single 25-jet helium-cooled modular divertor (HEMJ) thimble and a micro-jet array with 116 jets. Both have pure tungsten armor and a total mass flow rate of 10 g/s at a 600 °C inlet temperature. We investigated flowmore » perturbations caused by a 30 MW/m2 off-normal heat flux applied over a 25 mm2 area in addition to the nominal 5 MW/m2 applied over a 75 mm2 portion of the face. The micro-jet array exhibited lower temperatures and a more uniform surface temperature distribution than the HEMJ thimble. We also investigated the response of a manifolded nine-finger HEMJ assembly using the nominal heat flux and a 274 mm2 heated area. For the 30 MW/m2 case, the micro-jet array absorbed 750 W in the helium with a maximum armor surface temperature of 1280 °C and a fluid/solid interface temperature of 801 °C. The HEMJ absorbed 750 W with a maximum armor surface temperature of 1411 °C and a fluid/solid interface temperature of 844 °C. For comparison, both the single HEMJ finger and the micro-jet array used 5-mm-thick tungsten armor. The ratio of maximum to average temperature and variations in the local heat transfer coefficient were lower for the micro-jet array compared to the HEMJ device. Although high heat flux testing is required to validate the results obtained in these simulations, the results provide important guidance in jet design and manifolding to increase heat removal while providing more even temperature distribution and minimizing non-uniformity in the gas flow and thermal stresses at the armor joint.« less

  11. Helium-cooled solid breeder blanket design for a tokamak fusion reactor

    SciTech Connect (OSTI)

    Huggenberger, M.; Schultz, K.R.

    1983-11-01

    A preliminary design for a helium-cooled solid breeder blanket for a tokamak fusion reactor has been developed, and its performance looks quite good. The design is capable of bearing a 4 MW/m/sup 2/ neutron wall load, and the ideal pumping power required for the whole primary helium loop including the steam generators is only 2.5% of the total thermal power. The maximum blanket thickness including the helium duct work is only 860 mm, the minimum thickness is only 730 mm. The design work was focused on the thermalhydraulic aspects, which represent the key problems associated with using helium as a coolant. The present work demonstrates that the potential disadvantages helium has, due to its limited heat transfer capabilities, can be avoided or minimized by an appropriate thermal-hydraulic design. As a result, helium with its many advantages remains a promising fusion blanket coolant.

  12. Asteroseismic estimate of helium abundance of a solar analog binary system

    SciTech Connect (OSTI)

    Verma, Kuldeep; Antia, H. M.; Faria, Joo P.; Monteiro, Mrio J. P. F. G.; Basu, Sarbani; Mazumdar, Anwesh; Appourchaux, Thierry; Chaplin, William J.; Garca, Rafael A.

    2014-08-01

    16 Cyg A and B are among the brightest stars observed by Kepler. What makes these stars more interesting is that they are solar analogs. 16 Cyg A and B exhibit solar-like oscillations. In this work we use oscillation frequencies obtained using 2.5 yr of Kepler data to determine the current helium abundance of these stars. For this we use the fact that the helium ionization zone leaves a signature on the oscillation frequencies and that this signature can be calibrated to determine the helium abundance of that layer. By calibrating the signature of the helium ionization zone against models of known helium abundance, the helium abundance in the envelope of 16 Cyg A is found to lie in the range of 0.231 to 0.251 and that of 16 Cyg B lies in the range of 0.218 to 0.266.

  13. Production of carbon monoxide-free hydrogen and helium from a high-purity source

    DOE Patents [OSTI]

    Golden, Timothy Christopher; Farris, Thomas Stephen

    2008-11-18

    The invention provides vacuum swing adsorption processes that produce an essentially carbon monoxide-free hydrogen or helium gas stream from, respectively, a high-purity (e.g., pipeline grade) hydrogen or helium gas stream using one or two adsorber beds. By using physical adsorbents with high heats of nitrogen adsorption, intermediate heats of carbon monoxide adsorption, and low heats of hydrogen and helium adsorption, and by using vacuum purging and high feed stream pressures (e.g., pressures of as high as around 1,000 bar), pipeline grade hydrogen or helium can purified to produce essentially carbon monoxide -free hydrogen and helium, or carbon monoxide, nitrogen, and methane-free hydrogen and helium.

  14. Analysis of Alloy 600 and X-750 stress corrosion cracks

    SciTech Connect (OSTI)

    Thompson, C.D.; Lewis, N.; Krasodomski, H.

    1993-06-01

    A few months ago, KAPL evidence supported the view that Primary or Pure Water Stress Corrosion Cracking (PWSCC) of Alloy 600 results from a hydrogen mechanism. Figure 1 shows an Analytical Electron Microscope (AEM) analysis of a stress corrosion crack (SCC) crack in an A600 split tube U-bend specimen exposed to primary water at 338{degree}C (640{degrees}F) for 462 days. The features which appear to confirm a hydrogen mechanism are: (1) A very narrow (< 200 {angstrom}) crack with a sharp tip, nearly free of deposits. (2) No evidence of severe plastic deformation in the region immediately ahead of the crack tip. (3) A line of small voids preceding the main crack tip, of which the largest is about 5 x 10{sup {minus}6} cm in length. Shen and Shewmon proposed that PWSCC of Alloy 600 occurs due to small microvoids ahead of a main crack tip. The hypothesis is that such voids result from pockets of methane gas formed by the reaction of atomic hydrogen with carbon in the base metal. The voids are about 10 x 10{sup {minus}6} cm diameter, approximately a factor of 2 larger than the largest voids.

  15. Stress corrosion cracking of Alloy 600 in high temperature water

    SciTech Connect (OSTI)

    Congleton, J.; Parkins, R.N.; Hemsworth, B.

    1987-01-01

    Slow strain rate stress corrosion tests have been performed on specimens cut from four separate heats of alloy 600 steam generator tubing. Material was tested in the mill annealed and thermally stabilized conditions and after various low temperature aging treatments. Only limited cracking was observed, even for tests at 340/sup 0/C, but the initiation of intergranular cracking was easier on the inner than on the outer surfaces of the tubing. Polarization data has been obtained in high temperature water and in saturated boric acid and saturated lithium hydroxide at the atmospheric boiling points, and slow strain tests were performed at controlled potentials in these environments. Again, only very short cracks formed during the slow strain rate tests which were performed at a strain rate of about 10/sup -6/ s/sup -1/. The data is discussed in terms of the probable crack tip strain rates that would exist in these tests and at other strain rates. It is argued that if cracking occurs, the main role of very low strain rate tests is to provide time for initiation and crack growth, so that cyclic loading or intermittent loading long tests are likely to be more successful in sustaining crack growth in this alloy.

  16. Three-dimensional crack growth assessment by microtopographic examination

    SciTech Connect (OSTI)

    Lloyd, W.R.; Piascik, R.S.

    1995-12-31

    The initial stage of the stable tearing process in two 2.3 mm sheet 2024-T3 aluminum alloy M(T) specimens are analyzed using fracture surface microtopography reconstruction techniques. The local crack tip opening angles (CTOA) in the interior of the specimens are determined relative to both crack extension and through-thickness position. The microtopographic analysis of cracks grown in the L-T and T-L orientations reveal that interior CTOA is comparable to those measured on the surface using standard optical analysis methods. Similar to surface CTOA results, interior (mid-thickness) CTOA exhibit a transient behavior; CTOA transitions from high angles, at near crack initiation, to a lower steady-state value of 5 deg. and 4.2 deg. for L-T and T-L, respectively, at crack lengths greater than 1.5mm. Fracture surface topographic projection maps are used to study the evolution of crack front tunneling during the initial stage of the fracture process. Stable tearing initiates at mid-thickness followed by a crack front tunneling process to a depth of approximately 2mm. A brief discussion of the basis of the fracture process reconstruction method is provided and comments on the general utility of microtopographic fracture surface examination for general assessment of elastic-plastic and fully-plastic fracture processes are made.

  17. Fatigue crack growth behavior of Ti-1100 at elevated temperature

    SciTech Connect (OSTI)

    Maxwell, D.C.; Nicholas, T.

    1995-12-31

    Effects of temperature, frequency, and cycles with superimposed hold times are evaluated in Ti-1100 in order to study the complex creep-fatigue-environment interactions in this material. Crack growth rate tests conducted at cyclic loading frequency of 1.0 Hz show that raising the temperature from 593 to 650 C has only a slightly detrimental effect on crack growth rate, although these temperatures produce growth rates significantly higher than at room temperature. From constant {Delta}K tests, the effects of temperature at constant frequency show a minimum crack growth rate at 250 C. From the minimum crack growth rate at 250 C, the crack growth rate increases linearly with temperature. Increases in frequency at constant temperatures of 593 and 650 C produce a continuous decrease in growth rate in going from 0.001 to 1.0 Hz, although the behavior is primarily cycle dependent in this region. Tests at 1.0 Hz with superimposed hold times from 1 to 1,000 s are used to evaluate creep-fatigue-environment interactions. Hold times at maximum load are found to initially decrease and then increase the cyclic crack growth rate with increasing duration. This is attributed to crack-tip blunting during short hold times and environmental degradation at long hold times. Hold times at minimum load show no change in growth rates, indicating that there is no net environmental degradation to the bulk material beyond that experienced during the baseline 1 Hz cycling.

  18. Interim Report on the Optimization and Feasibility Studies for the Neutron Detection without Helium-3 Project

    SciTech Connect (OSTI)

    Ely, James H.

    2012-03-19

    This report provides the status and results of the first year's effort in modeling and simulation to investigate alternatives to helium-3 for neutron detection in safeguards applications.

  19. Ultra high vacuum pumping system and high sensitivity helium leak detector

    DOE Patents [OSTI]

    Myneni, G.R.

    1997-12-30

    An improved helium leak detection method and apparatus are disclosed which increase the leak detection sensitivity to 10{sup {minus}13} atm cc/s. The leak detection sensitivity is improved over conventional leak detectors by completely eliminating the use of o-rings, equipping the system with oil-free pumping systems, and by introducing measured flows of nitrogen at the entrances of both the turbo pump and backing pump to keep the system free of helium background. The addition of dry nitrogen flows to the system reduces back streaming of atmospheric helium through the pumping system as a result of the limited compression ratios of the pumps for helium. 2 figs.

  20. Energy-related applications of helium: a revision of the ERDA-13 data base

    SciTech Connect (OSTI)

    Hammel, E.F.; Krupka, M.C.

    1980-08-01

    A re-examination, revision, and re-evaluation of the data base contained within the 1975 document, ERDA-13, The Energy-Related Applications of Helium, were completed and results are presented in this report. New technical and resource data, current legislative proposals, updated supply-and-demand relationships, latest legal developments, programmatic changes affectng the future demand for helium, socio-economic aspects, and the effects of the latest energy-consumption projections were considered and are discussed. In contrast to ERDA-13, however, explicit recommendations with respect to the formulation of Federal helium policy, as it pertains to the energy-related applications of helium, are not given.

  1. Ultra high vacuum pumping system and high sensitivity helium leak detector

    DOE Patents [OSTI]

    Myneni, Ganapati Rao

    1997-01-01

    An improved helium leak detection method and apparatus are disclosed which increase the leak detection sensitivity to 10.sup.-13 atm cc s.sup.-1. The leak detection sensitivity is improved over conventional leak detectors by completely eliminating the use of o-rings, equipping the system with oil-free pumping systems, and by introducing measured flows of nitrogen at the entrances of both the turbo pump and backing pump to keep the system free of helium background. The addition of dry nitrogen flows to the system reduces backstreaming of atmospheric helium through the pumping system as a result of the limited compression ratios of the pumps for helium.

  2. The Other Helium Shortage Smart Telescopes Go Stargazing No-bang...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    ... Less well known, however, is a more severe shortage of the much rarer isotope helium-3. Essential for key scientific, medical, and national security applications, no one would ...

  3. Theory of Positron Annihilation in Helium-Filled Bubbles in Plutonium...

    Office of Scientific and Technical Information (OSTI)

    Theory of Positron Annihilation in Helium-Filled Bubbles in Plutonium Citation Details ... This method is capable of treating system cell sizes of several thousand atoms, allowing ...

  4. Photoelectrochemical protection of stainless alloys from the stress-corrosion cracking in BWR primary coolant environment

    SciTech Connect (OSTI)

    Akashi, Masatsune; Iso-o, Hiroyuki; Kubota, Nobuhiko; Fukuda, Takanori; Ayabe, Muneo; Hirano, Kenji

    1995-12-31

    The feasibility of counteracting or preventing the stress-corrosion cracking in the BWR core internals by the photoelectrochemical method has been examined. For the purpose TiO{sub 2} semiconductor is noted for its capability of photo electrochemically inducing the water-oxidizing anodic reaction in low enough potential domain if supplied with a light of a wavelength shorter than 410 nm. This paper offers an empirical proof by showing that Type 304 stainless steel and Alloy 600 stainless alloy that have been plasma-spray coated with TiO{sub 2} film will do quite well in environments of BWR primary coolant.

  5. Stress-corrosion cracking of copper single crystals

    SciTech Connect (OSTI)

    Sieradzki, K.; Newman, R.C.; Sabatini, R.L.

    1984-10-01

    Constant extension rate tests have been carried out in a sodium nitrite solution. Crack velocities up to 30 nm per second were obtained at 30/sup 0/C. If dynamic straining is stopped, the cracks apparently stop growing within about 20 ..mu..m. The steps between adjacent flat facets are more energy-absorbing than in ..cap alpha..-brass, providing a possible explanation for the importance of dynamic strain. Simultaneous acoustic emission and electrochemical current transients suggest that cracking proceeds by discontinuous cleavage.

  6. Helium measurements of pore-fluids obtained from SAFOD drillcore

    SciTech Connect (OSTI)

    Ali, S.; Stute, M.; Torgersen, T.; Winckler, G.; Kennedy, B.M.

    2010-04-15

    {sup 4}He accumulated in fluids is a well established geochemical tracer used to study crustal fluid dynamics. Direct fluid samples are not always collectable; therefore, a method to extract rare gases from matrix fluids of whole rocks by diffusion has been adapted. Helium was measured on matrix fluids extracted from sandstones and mudstones recovered during the San Andreas Fault Observatory at Depth (SAFOD) drilling in California, USA. Samples were typically collected as subcores or from drillcore fragments. Helium concentration and isotope ratios were measured 4-6 times on each sample, and indicate a bulk {sup 4}He diffusion coefficient of 3.5 {+-} 1.3 x 10{sup -8} cm{sup 2}s{sup -1} at 21 C, compared to previously published diffusion coefficients of 1.2 x 10{sup -18} cm{sup 2}s{sup -1} (21 C) to 3.0 x 10{sup -15} cm{sup 2}s{sup -1} (150 C) in the sands and clays. Correcting the diffusion coefficient of {sup 4}He{sub water} for matrix porosity ({approx}3%) and tortuosity ({approx}6-13) produces effective diffusion coefficients of 1 x 10{sup -8} cm{sup 2}s{sup -1} (21 C) and 1 x 10{sup -7} (120 C), effectively isolating pore fluid {sup 4}He from the {sup 4}He contained in the rock matrix. Model calculations indicate that <6% of helium initially dissolved in pore fluids was lost during the sampling process. Complete and quantitative extraction of the pore fluids provide minimum in situ porosity values for sandstones 2.8 {+-} 0.4% (SD, n=4) and mudstones 3.1 {+-} 0.8% (SD, n=4).

  7. Active helium target: Neutron scalar polarizability extraction via Compton scattering

    SciTech Connect (OSTI)

    Morris, Meg Hornidge, David; Annand, John; Strandberg, Bruno

    2015-12-31

    Precise measurement of the neutron scalar polarizabilities has been a lasting challenge because of the lack of a free-neutron target. Led by the University of Glasgow and the Mount Allison University groups of the A2 collaboration in Mainz, Germany, preparations have begun to test a recent theoretical model with an active helium target with the hope of determining these elusive quantities with small statistical, systematic, and model-dependent errors. Apparatus testing and background-event simulations have been carried out, with the full experiment projected to run in 2015. Once determined, these values can be applied to help understand quantum chromodynamics in the nonperturbative region.

  8. Dual-frequency glow discharges in atmospheric helium

    SciTech Connect (OSTI)

    Huang, Xiaojiang; Guo, Ying; Dai, Lu; Zhang, Jing; Shi, J. J.

    2015-10-15

    In this paper, the dual-frequency (DF) glow discharges in atmospheric helium were experimented by electrical and optical measurements in terms of current voltage characteristics and optical emission intensity. It is shown that the waveforms of applied voltages or discharge currents are the results of low frequency (LF) waveforms added to high frequency (HF) waveforms. The HF mainly influences discharge currents, and the LF mainly influences applied voltages. The gas temperatures of DF discharges are mainly affected by HF power rather than LF power.

  9. Helium nano-bubble evolution in aging metal tritides.

    SciTech Connect (OSTI)

    Cowgill, Donald F.

    2004-05-01

    A continuum-scale, evolutionary model of helium (He) nano-bubble nucleation, growth and He release for aging bulk metal tritides is presented which accounts for major features of the experimental database. Bubble nucleation, modeled as self-trapping of interstitially diffusing He atoms, is found to occur during the first few days following tritium introduction into the metal and is sensitive to the He diffusivity and pairing energy. An effective helium diffusivity of 0.3 x 10{sup -16} cm{sup 2}/s at 300 K is required to generate the average bubble density of 5x 1017 bubbles/cm3 observed by transmission electron microscopy (TEM). Early bubble growth by dislocation loop punching with a l/radius bubble pressure dependence produces good agreement with He atomic volumes and bubble pressures determined from swelling data, nuclear magnetic resonance (NMR) measurements, and hydride pressure-composition-temperature (PCT) shifts. The model predicts that later in life neighboring bubble interactions may first lower the loop punching pressure through cooperative stress effects, then raise the pressure by partial blocking of loops. It also accounts for the shape of the bubble spacing distribution obtained from NMR data. This distribution is found to remain fixed with age, justifying the separation of nucleation and growth phases, providing a sensitive test of the growth formulation, and indicating that further significant bubble nucleation does not occur throughout life. Helium generated within the escape depth of surfaces and surface-connected porosity produces the low-level early helium release. Accelerated or rapid release is modeled as inter-bubble fracture using an average ligament stress criterion. Good agreement is found between the predicted onset of fracture and the observed He-metal ratio (HeM) for rapid He release from bulk palladium tritide. An examination of how inter-bubble fracture varies over the bubble spacing distribution shows that the critical Hem will be

  10. Process to minimize cracking of pyrolytic carbon coatings

    DOE Patents [OSTI]

    Lackey, Jr., Walter J.; Sease, John D.

    1978-01-01

    Carbon-coated microspheroids useful as fuels in nuclear reactors are produced with a low percentage of cracked coatings and are imparted increased strength and mechanical stability characteristics by annealing immediately after the carbon coating processes.

  11. Primary Water Stress Corrosion Crack Morphology and Nondestructive Evaluation Reliability

    SciTech Connect (OSTI)

    Doctor, Steven R.; Schuster, George J.; Anderson, Michael T.

    2004-12-01

    A research program on primary stress corrosion crack (PWSCC) is being conducted by Pacific Northwest National Laboratory (PNNL). In this program, the material degradation problem in Alloys 600, 182, and 82 is being investigated with objectives that include compling a knowledge base on all cracking in nickel based materials at all degradation sites in nuclear power plants, assessing NDE methods using mockups to quantify the detection, sizing, and using mockups to quantify the detection sizing and characterization of tight cracks, and determining the role of welding processes in degradation. In this paper, the resuts of the initial literature searchs are presented. The relevant data on crack properties such as shape and orientation are presented and their impace on nondestructive evaluation (NDE) reliability is discussed.

  12. Stress corrosion cracking of zirconium used in the reprocessing plant

    SciTech Connect (OSTI)

    Kato, Chiaki; Motooka, Takafumi; Yamamoto, Masahiro

    2007-07-01

    We investigated stress corrosion cracking (SCC) of zirconium by constant load test and the small-scale mock-up test simulated the fuel dissolve. These tests operated in the simulated solution, which substituted non-radioactive elements, i.e. V with radioactive elements such as Pu and Np. From the results of constant load test, the cracks were not observed on 150 MPa after 908 hours in approximately 3 % strain. However a lot of cracks caused by SCC were observed over 20 % strain under high tensile stress in the simulated solution and the heat-transfer condition having more corrosive circumstance and noble potential accelerated the susceptibility of SCC. The cracking behavior would be caused by the creep phenomena. The small-scale mock-up test had been operated for about 50000 hours during 7 year. From the results, zirconium showed excellent corrosion resistance and no SCC was observed during these long-term operations. (authors)

  13. Modeling Crack Propagation in Polycrystalline Microstructure Using Variational Multiscale Method

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Sun, S.; Sundararaghavan, V.

    2016-01-01

    Crack propagation in a polycrystalline microstructure is analyzed using a novel multiscale model. The model includes an explicit microstructural representation at critical regions (stress concentrators such as notches and cracks) and a reduced order model that statistically captures the microstructure at regions far away from stress concentrations. Crack propagation is modeled in these critical regions using the variational multiscale method. In this approach, a discontinuous displacement field is added to elements that exceed the critical values of normal or tangential tractions during loading. Compared to traditional cohesive zone modeling approaches, the method does not require the use of any specialmore » interface elements in the microstructure and thus can model arbitrary crack paths. The capability of the method in predicting both intergranular and transgranular failure modes in an elastoplastic polycrystal is demonstrated under tensile and three-point bending loads.« less

  14. Hot Rolling Scrap Reduction through Edge Cracking and Surface Defects

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Control | Department of Energy Hot Rolling Scrap Reduction through Edge Cracking and Surface Defects Control Hot Rolling Scrap Reduction through Edge Cracking and Surface Defects Control hot_rolling.pdf (541.63 KB) More Documents & Publications ITP Aluminum: Aluminum Industry Roadmap for the Automotive Market (May 1999) Vehicle Technologies Office: 2012 Lightweight Materials R&D Annual Progress Report ITP Aluminum: Aluminum Industry Technology Roadmap

  15. Process for the detection of micro-cracks

    DOE Patents [OSTI]

    Lapinski, Norman; Sather, Allen

    1979-01-01

    A process for the nondestructive testing of ceramic objects to detect the presence of defects and micro-cracks in the surface in which a solution of silver nitrate is applied to the surface of the object which penetrates into the surface defects, drying the object so that the silver nitrate remains in the defects, and preparing an X-ray radiograph whereby any defects and micro-cracks will appear in the radiograph.

  16. Effects of microstructure banding on hydrogen assisted fatigue crack growth in X65 pipeline steels

    SciTech Connect (OSTI)

    Ronevich, Joseph A.; Somerday, Brian P.; San Marchi, Chris W.

    2015-09-10

    Banded ferrite-pearlite X65 pipeline steel was tested in high pressure hydrogen gas to evaluate the effects of oriented pearlite on hydrogen assisted fatigue crack growth. Test specimens were oriented in the steel pipe such that cracks propagated either parallel or perpendicular to the banded pearlite. The ferrite-pearlite microstructure exhibited orientation dependent behavior in which fatigue crack growth rates were significantly lower for cracks oriented perpendicular to the banded pearlite compared to cracks oriented parallel to the bands. Thus the reduction of hydrogen assisted fatigue crack growth across the banded pearlite is attributed to a combination of crack-tip branching and impeded hydrogen diffusion across the banded pearlite.

  17. Effects of microstructure banding on hydrogen assisted fatigue crack growth in X65 pipeline steels

    SciTech Connect (OSTI)

    Ronevich, Joseph A.; Somerday, Brian P.; San Marchi, Chris W.

    2015-09-10

    Banded ferritepearlite X65 pipeline steel was tested in high pressure hydrogen gas to evaluate the effects of oriented pearlite on hydrogen assisted fatigue crack growth. Test specimens were oriented in the steel pipe such that cracks propagated either parallel or perpendicular to the banded pearlite. The ferritepearlite microstructure exhibited orientation dependent behavior in which fatigue crack growth rates were significantly lower for cracks oriented perpendicular to the banded pearlite compared to cracks oriented parallel to the bands. Thus the reduction of hydrogen assisted fatigue crack growth across the banded pearlite is attributed to a combination of crack-tip branching and impeded hydrogen diffusion across the banded pearlite.

  18. Ignition and extinction phenomena in helium micro hollow cathode discharges

    SciTech Connect (OSTI)

    Kulsreshath, M. K.; Schwaederle, L.; Dufour, T.; Lefaucheux, P.; Dussart, R.; Overzet, L. J.

    2013-12-28

    Micro hollow cathode discharges (MHCD) were produced using 250??m thick dielectric layer of alumina sandwiched between two nickel electrodes of 8??m thickness. A through cavity at the center of the chip was formed by laser drilling technique. MHCD with a diameter of few hundreds of micrometers allowed us to generate direct current discharges in helium at up to atmospheric pressure. A slowly varying ramped voltage generator was used to study the ignition and the extinction periods of the microdischarges. The analysis was performed by using electrical characterisation of the V-I behaviour and the measurement of He*({sup 3}S{sub 1}) metastable atoms density by tunable diode laser spectroscopy. At the ignition of the microdischarges, 2??s long current peak as high as 24?mA was observed, sometimes followed by low amplitude damped oscillations. At helium pressure above 400?Torr, an oscillatory behaviour of the discharge current was observed just before the extinction of the microdischarges. The same type of instability in the extinction period at high pressure also appeared on the density of He*({sup 3}S{sub 1}) metastable atoms, but delayed by a few ?s relative to the current oscillations. Metastable atoms thus cannot be at the origin of the generation of the observed instabilities.

  19. Gettering of Hydrogen and Methane from a Helium Gas Mixture

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Cardenas, Rosa E.; Stewart, Kenneth D.; Cowgill, Donald F.

    2014-10-21

    In our study, the authors developed an approach for accurately quantifying the helium content in a gas mixture also containing hydrogen and methane using commercially available getters. The authors performed a systematic study to examine how both H2 and CH4 can be removed simultaneously from the mixture using two SAES St 172® getters operating at different temperatures. The remaining He within the gas mixture can then be measured directly using a capacitance manometer. Moreover, the optimum combination involved operating one getter at 650°C to decompose the methane, and the second at 110°C to remove the hydrogen. Finally, this approach eliminatedmore » the need to reactivate the getters between measurements, thereby enabling multiple measurements to be made within a short time interval, with accuracy better than 1%. The authors anticipate that such an approach will be particularly useful for quantifying the He-3 in mixtures that include tritium, tritiated methane, and helium-3. The presence of tritiated methane, generated by tritium activity, often complicates such measurements.« less

  20. Gettering of Hydrogen and Methane from a Helium Gas Mixture

    SciTech Connect (OSTI)

    Cardenas, Rosa E.; Stewart, Kenneth D.; Cowgill, Donald F.

    2014-10-21

    In our study, the authors developed an approach for accurately quantifying the helium content in a gas mixture also containing hydrogen and methane using commercially available getters. The authors performed a systematic study to examine how both H2 and CH4 can be removed simultaneously from the mixture using two SAES St 172® getters operating at different temperatures. The remaining He within the gas mixture can then be measured directly using a capacitance manometer. Moreover, the optimum combination involved operating one getter at 650°C to decompose the methane, and the second at 110°C to remove the hydrogen. Finally, this approach eliminated the need to reactivate the getters between measurements, thereby enabling multiple measurements to be made within a short time interval, with accuracy better than 1%. The authors anticipate that such an approach will be particularly useful for quantifying the He-3 in mixtures that include tritium, tritiated methane, and helium-3. The presence of tritiated methane, generated by tritium activity, often complicates such measurements.

  1. Gettering of hydrogen and methane from a helium gas mixture

    SciTech Connect (OSTI)

    Crdenas, Rosa Elia; Stewart, Kenneth D.; Cowgill, Donald F.

    2014-11-01

    In this study, the authors developed an approach for accurately quantifying the helium content in a gas mixture also containing hydrogen and methane using commercially available getters. The authors performed a systematic study to examine how both H{sub 2} and CH{sub 4} can be removed simultaneously from the mixture using two SAES St 172{sup } getters operating at different temperatures. The remaining He within the gas mixture can then be measured directly using a capacitance manometer. The optimum combination involved operating one getter at 650?C to decompose the methane, and the second at 110?C to remove the hydrogen. This approach eliminated the need to reactivate the getters between measurements, thereby enabling multiple measurements to be made within a short time interval, with accuracy better than 1%. The authors anticipate that such an approach will be particularly useful for quantifying the He-3 in mixtures that include tritium, tritiated methane, and helium-3. The presence of tritiated methane, generated by tritium activity, often complicates such measurements.

  2. Helium Nano-Bubble Evolution in Aging Metal Tritides

    SciTech Connect (OSTI)

    Cowgill, Donald F.

    2005-07-15

    A continuum-scale, evolutionary model of bubble nucleation, growth and He release for aging metal tritides is described which accounts for major features of the tritide database. Bubble nucleation, modeled as self-trapping of interstitially diffusing He atoms, occurs during the first few days following tritium introduction into the metal. Bubble growth by dislocation loop punching yields good agreement between He atomic volumes and bubble pressures determined from bulk swelling and {sup 3}He NMR data. The bubble spacing distribution determined from NMR is shown to remain fixed with age, justifying the separation of nucleation and growth phases and providing a sensitive test of the growth formulation. Late in life, bubble interactions are proposed to produce cooperative stress effects, which lower the bubble pressure. Helium generated near surfaces and surface-connected porosity accounts for the low-level early helium release. Use of an average ligament stress criterion predicts an onset of inter-bubble fracture in good agreement with the He/Metal ratio observed for rapid He release. From the model, it is concluded that He retention can be controlled through control of bubble nucleation.

  3. Partial cross sections of helium satellites at medium photon energies

    SciTech Connect (OSTI)

    Wehlitz, R.; Sellin, I.A.; Hemmers, O.

    1997-04-01

    Still of current interest is the important role of single ionization with excitation compared to single ionization alone. The coupling between the electrons and the incoming photon is a single-particle operator. Thus, an excitation in addition to an ionization, leading to a so-called satellite line in a photoelectron spectrum, is entirely due to electron-electron interaction and probes the electron correlation in the ground and final state. Therefore the authors have undertaken the study of the intensity of helium satellites He{sup +}nl (n = 2 - 6) relative to the main photoline (n = 1) as a function of photon energy at photon energies well above threshold up to 900 eV. From these results they could calculate the partial cross-sections of the helium satellites. In order to test the consistency of their satellite-to-1s ratios with published double-to-single photoionization ratios, the authors calculated the double-to-single photoionization ratio from their measured ratios using the theoretical energy-distribution curves of Chang and Poe and Le Rouzo and Dal Cappello which proved to be valid for photon energies below 120 eV. These calculated double-to-single ionization ratios agree fairly well with recent ion measurements. In the lower photon energy range the authors ratios agree better with the ratios of Doerner et al. while for higher photon energies the agreement is better with the values of Levin et al.

  4. Analytical determination of critical crack size in solar cells

    SciTech Connect (OSTI)

    Chen, C.P.

    1988-05-01

    Although solar cells usually have chips and cracks, no material specifications concerning the allowable crack size on solar cells are available for quality assurance and engineering design usage. Any material specifications that the cell manufacturers use were developed for cosmetic reasons that have no technical basis. Therefore, the Applied Solar Energy Corporation (ASEC) has sponsored a continuing program for the fracture mechanics evaluation of GaAs. Fracture mechanics concepts were utilized to develop an analytical model that can predict the critical crack size of solar cells. This model indicates that the edge cracks of a solar cell are more critical than its surface cracks. In addition, the model suggests that the material specifications on the allowable crack size used for Si solar cells should not be applied to GaAs solar cells. The analytical model was applied to Si and GaAs solar cells, but it would also be applicable to the semiconductor wafers of other materials, such as a GaAs thin film on a Ge substrate, using appropriate input data.

  5. Assessment of crack opening area for leak rates

    SciTech Connect (OSTI)

    Sharples, J.K.; Bouchard, P.J.

    1997-04-01

    This paper outlines the background to recommended crack opening area solutions given in a proposed revision to leak before break guidance for the R6 procedure. Comparisons with experimental and analytical results are given for some selected cases of circumferential cracks in cylinders. It is shown that elastic models can provide satisfactory estimations of crack opening displacement (and area) but they become increasingly conservative for values of L{sub r} greater than approximately 0.4. The Dugdale small scale yielding model gives conservative estimates of crack opening displacement with increasing enhancement for L{sub r} values greater than 0.4. Further validation of the elastic-plastic reference stress method for up to L{sub r} values of about 1.0 is presented by experimental and analytical comparisons. Although a more detailed method, its application gives a best estimate of crack opening displacement which may be substantially greater than small scale plasticity models. It is also shown that the local boundary conditions in pipework need to be carefully considered when evaluating crack opening area for through-wall bending stresses resulting from welding residual stresses or geometry discontinuities.

  6. Mass spectrometric helium analysis of solid and gas samples from cold-fusion type experiments

    SciTech Connect (OSTI)

    Oliver, B.M.

    1995-12-01

    A custom mass spectrometer system, operating in static mode, has been used to measure helium in both solid and gas samples front cold-fusion type experiments. The mass spectrometer is a 2-in. Radius, 60{degrees}, permanent angle magnet instrument with a single electron-multiplier collecting. Depending on the absolute levels of helium expected, the analysis are conducted by isotope dilution or by measuring absolute collector values. Solid samples are vaporized to ensure complete helium release. Prior to analysis, the fraction of sample gas to be analyzed is exposed to a series of physical and chemical getters, including room temperature Zr-Al alloy (SAES type 101) and liquid-nitrogen cooled activated charcoal. This is done to remove active gases and hydrogen isotopes which could interfere with the helium determinations. Generally, the analysis protocol is to analyze an equal or greater number of {open_quotes}controls{close_quotes} along with the samples to accurately characterize system background and reproducibility. Absolute sensitivity for the system is approximately 1 x 10{sup 9} atoms. Absolute accuracy is 1% or better for helium levels > 10{sup 11} atoms. With few exceptions, helium analysis of solid samples front cold fusion type experiments have yielded no excess helium above usual system background. A few samples have shown helium levels in the low 10{sup 9} atom range, and some gas samples have shown {sup 4}He levels up to several hundred ppm.

  7. Strengthening, Crack Arrest And Multiple Cracking In Brittle Materials Using Residual Stresses.

    DOE Patents [OSTI]

    Green, David J.; Sglavo, Vincenzo M.; Tandon, Rajan

    2003-02-11

    Embodiments include a method for forming a glass which displays visible cracking prior to failure when subjected to predetermined stress level that is greater than a predetermined minimum stress level and less than a failure stress level. The method includes determining a critical flaw size in the glass and introducing a residual stress profile to the glass so that a plurality of visible cracks are formed prior to failure when the glass is subjected to a stress that is greater than the minimum stress level and lower than the critical stress. One method for forming the residual stress profile includes performing a first ion exchange so that a first plurality of ions of a first element in the glass are exchanged with a second plurality of ions of a second element that have a larger volume than the first ions. A second ion exchange is also performed so that a plurality of the second ions in the glass are exchanged back to ions of the first element.

  8. Extensile cracking in porous rock under differential compressive stress

    SciTech Connect (OSTI)

    Myer, L.R.; Kemeny, J.M.; Zheng, Z.

    1992-08-01

    Under differential compressive stress rocks exhibit nonlinear deformation that includes initial compaction, near-linear elastic behavior, and strain-hardening followed by strain-softening and dilation (or compaction in clastic rocks) and localization. This behavior derives largely from changes in the microstructure of the rocks. Much of it has been attributed to the growth of extensile microcracks. The stress-induced microstructural changes brought about by successively more complicated states of stress produced by uniaxial and triaxial compression of circular cylinders, axisymmetric stresses in hollow cylinders, and indentation by hemispheres in Indiana limestone and Berea sandstone have been preserved using Wood`s metal porosimetry. In this technique molten Wood`s metal at about 100{degrees}C is used as a pore fluid at a pressure of about 10 MPa, and the experiments are conducted using the concepts of effective stress. At the deformation state of interest, the temperature is lowered to solidify the metal, thereby preserving the microstructure as it exists under load and facilitating subsequent preparation of the specimen for microscopic study. Mode I microcrack growth is observed to occur by a variety of mechanisms such as bending, point loading and sliding cracks. The effects of this are analyzed using an elastic continuum within which Mode II displacement across microcracks and Mode I microcrack growth results from heterogeneous stress concentrations that produce local tensile stresses. While the continuum model replicates many of the observations, it fails to account for localization by en echelon arrays of extensile microcracks that precede macroscopic shear faulting. Using a {open_quotes}zero order{close_quotes} continuum approximation, the spatially stochastic distribution of grains in clastic rocks is shown to be important in the formation of the en echelon arrays of microcracks that form shear bands. 63 refs., 26 figs., 1 tab.

  9. Fundamental and applied studies of helium ingrowth and aging in plutonium

    SciTech Connect (OSTI)

    Stevens, M.F.; Zocco, T.; Albers, R.; Becker, J.D.; Walter, K.; Cort, B.; Paisley, D.; Nastasi, M.

    1998-12-31

    This is the final report of a two-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The purpose of this project was to develop new capabilities to assess the nucleation and growth of helium-associated defects in aged plutonium metal. This effort involved both fundamental and applied models to assist in predicting the transport and kinetics of helium in the metal lattice as well as ab initio calculations of the disposition of gallium in the fcc plutonium lattice and its resulting effects on phase stability. Experimentally this project aimed to establish experimental capabilities crucial to the prediction of helium effects in metals, such as transmission electron microscopy, thermal helium effusion, and the development of a laser-driven mini-flyer for understanding the role of helium and associated defects on shock response of plutonium surrogates.

  10. Effect of helium on the electronic structure of palladium tritide

    SciTech Connect (OSTI)

    Gupta, R.P.; Gupta, M.

    1998-12-31

    Tritium is usually stored in the form of a metal tritide since it is safe to handle in this form, easily recoverable, and further large quantities of tritium can be stored. However, since tritium is radioactive it decays into {sup 3}He and an electron. Helium recoil energy in this reaction is very small, and not enough to create defects. The authors have performed ab-initio electronic structure calculations that show that in PdT, a considerable amount of {sup 3}He can be accommodated at the octahedral interstitial sites where it is produced. Their calculations also show that the presence of {sup 3}He results in an overall enhancement in the strength of the metal-tritium bonding that leads to the lowering of the plateau pressure. They also find that there is a weakening of the metal-metal bonds due to the repulsive interaction with {sup 3}He.

  11. Options for Cryogenic Load Cooling with Forced Flow Helium Circulation

    SciTech Connect (OSTI)

    Peter Knudsen, Venkatarao Ganni, Roberto Than

    2012-06-01

    Cryogenic pumps designed to circulate super-critical helium are commonly deemed necessary in many super-conducting magnet and other cooling applications. Acknowledging that these pumps are often located at the coldest temperature levels, their use introduces risks associated with the reliability of additional rotating machinery and an additional load on the refrigeration system. However, as it has been successfully demonstrated, this objective can be accomplished without using these pumps by the refrigeration system, resulting in lower system input power and improved reliability to the overall cryogenic system operations. In this paper we examine some trade-offs between using these pumps vs. using the refrigeration system directly with examples of processes that have used these concepts successfully and eliminated using such pumps

  12. Symmetric And Non-Symmetric Muonic Helium Atoms Studies

    SciTech Connect (OSTI)

    Mohammadi, S.

    2011-10-28

    The ground state hyperfine structure and other properties are calculated for muonic helium atoms ({sup 3}He{sup +2}{mu}{sup -}e{sup -} or {sup 4}He{sup +2}{mu}{sup -}e{sup -}) with the use of some local properties of the wave functions in the domains where two particles are close to each other or far away. Simple wave functions incorporating these properties with one variational parameter is developed. The calculated values for hyperfine structure, energy and average interparticle distances in ground state are compared with the correlation function hyper-spherical harmonic method and multibox variational approach. The obtained results are very close to the values calculated by mentioned methods, giving strong indications that the proposed wave functions provide relatively accurate values.

  13. Fatigue crack growth behavior of Al-Li alloy 1441

    SciTech Connect (OSTI)

    Prakash, R.V.; Parida, B.K.

    1995-12-31

    Fatigue crack growth behavior of Al-Li alloy 1441 having a marginally lower lithium content, compared to 80xx and 20xx series Al-Li alloys is presented in this paper. This investigation was conducted on single edge tension--SE(T)--specimens, under constant amplitude as well as under MiniLCA flight spectrum loading with the specific objective of determining the effects of stress ratio, orientation, thickness and cladding. Three thicknesses were considered: 1.2 mm(clad and unclad), 2.0 mm(clad and unclad) and 8.0 mm unclad. Constant amplitude fatigue tests were conducted at stress ratios of {minus}0.3, 0.1 and 0.7. Testing was performed under ambient conditions and along three orientations, namely L-T, T-L and L+45 degrees. Crack growth characteristics of this alloy are compared with that of BS:L73 (2014-T4 equivalent) for assessing the possibility of replacing BS:L73. Significant effect of stress ratio on crack growth rate was observed in all thicknesses. However, in case of 1.2 and 2.0 mm thick sheets, the effect was minimal at intermediate-crack growth regime. The orientation of the specimen does not adversely affect the fatigue crack growth behavior of 8.0 mm and 2.0 mm thick specimens. However, for 1.2 mm unclad sheet crack growth resistance in L-T direction was found to be superior to that along T-L direction. In majority of test cases considered, no significant effect was observed on crack growth rate due to thickness or cladding. Crack growth characteristics of Al-Li alloy 1441 and Al-Cu alloy BS:L73 under constant amplitude as well as MiniLCA spectrum loading are similar in the low and intermediate-crack growth rate regime. Based on these observations, it is felt that this Al-Li alloy has the potential for future aerospace applications.

  14. Evaluation of the Gas Turbine Modular Helium Reactor

    SciTech Connect (OSTI)

    Not Available

    1994-02-01

    Recent advances in gas-turbine and heat exchanger technology have enhanced the potential for a Modular Helium Reactor (MHR) incorporating a direct gas turbine (Brayton) cycle for power conversion. The resulting Gas Turbine Modular Helium Reactor (GT-MHR) power plant combines the high temperature capabilities of the MHR with the efficiency and reliability of modern gas turbines. While the passive safety features of the steam cycle MHR (SC-MHR) are retained, generation efficiencies are projected to be in the range of 48% and steam power conversion systems, with their attendant complexities, are eliminated. Power costs are projected to be reduced by about 20%, relative to the SC-MHR or coal. This report documents the second, and final, phase of a two-part evaluation that concluded with a unanimous recommendation that the direct cycle (DC) variant of the GT-MHR be established as the commercial objective of the US Gas-Cooled Reactor Program. This recommendation has been endorsed by industrial and utility participants and accepted by the US Department of Energy (DOE). The Phase II effort, documented herein, concluded that the DC GT-MHR offers substantial technical and economic advantages over both the IDC and SC systems. Both the DC and IDC were found to offer safety advantages, relative to the SC, due to elimination of the potential for water ingress during power operations. This is the dominant consequence event for the SC. The IDC was judged to require somewhat less development than the direct cycle, while the SC, which has the greatest technology base, incurs the least development cost and risk. While the technical and licensing requirements for the DC were more demanding, they were judged to be incremental and feasible. Moreover, the DC offers significant performance and cost improvements over the other two concepts. Overall, the latter were found to justify the additional development needs.

  15. Superconducting cable cooling system by helium gas at two pressures

    DOE Patents [OSTI]

    Dean, John W.

    1977-01-01

    Thermally contacting, oppositely streaming, cryogenic fluid streams in the same enclosure in a closed cycle that changes the fluid from a cool high pressure helium gas to a cooler reduced pressure helium gas in an expander so as to be at different temperature ranges and pressures respectively in go and return legs that are in thermal contact with each other and in thermal contact with a longitudinally extending superconducting transmission line enclosed in the same cable enclosure that insulates the line from the ambient at a temperature T.sub.1. By first circulating the fluid from a refrigerator at one end of the line as a cool gas at a temperature range T.sub.2 to T.sub.3 in the go leg, then circulating the gas through an expander at the other end of the line where the gas becomes a cooler gas at a reduced pressure and at a reduced temperature T.sub.4 and finally by circulating the cooler gas back again to the refrigerator in a return leg at a temperature range T.sub.4 to T.sub.5, while in thermal contact with the gas in the go leg, and in the same enclosure therewith for compression into a higher pressure gas at T.sub.2 in a closed cycle, where T.sub.2 >T.sub.3 and T.sub.5 >T.sub.4, the fluid leaves the enclosure in the go leg as a gas at its coldest point in the go leg, and the temperature distribution is such that the line temperature decreases along its length from the refrigerator due to the cooling from the gas in the return leg.

  16. Process for catalytic cracking of heavy hydrocarbon feed to lighter products

    SciTech Connect (OSTI)

    Herbst, J.A.; Owen, H.; Schipper, P.H.

    1990-05-29

    This patent describes a process for catalytic cracking of a feed of hydrocarbons boiling in the gas oil and heavier boiling range to lighter products by contacting the feed at catalytic cracking conditions and catalytically cracking the feed to lighter products with a cracking catalyst. It comprises: a mixture of separate particles of: a bulk conversion cracking catalyst containing at least one component with an equivalent pore size of at least about 7 angstroms in a matrix, the bulk conversion cracking catalyst having fluidization properties which permit use in a fluidized or moving bed catalytic cracking reactor; a light paraffin upgrading catalyst comprising at least one zeolite having a constraint index of 1--12 and paraffin cracking/isomerization activity; and, a light paraffin upgrading catalyst comprising at least one zeolite having a constraint index of 1--12 and paraffin aromatization activity; and wherein the upgrading catalysts have substantially the same fluidization properties as the bulk conversion cracking catalyst.

  17. Modeling fatigue crack growth in cross ply titanium matrix composites

    SciTech Connect (OSTI)

    Bakuckas, J.G. Jr.; Johnson, W.S.

    1993-05-01

    In this study, the fatigue crack growth behavior of fiber bridging matrix cracks in cross-ply SCS-6/Ti-15-3 and SCS-6/Timetal-21S laminates containing center holes was investigated. Experimental observations revealed that matrix cracking was far more extensive and wide spread in the SCS-6/Ti-15-3 laminates compared to that in the SCS-6/Timetal-21S laminates. In addition, the fatigue life of the SCS-6/Ti-15-3 laminates was significantly longer than that of the SCS-6/Timetal-21S laminates. The matrix cracking observed in both material systems was analyzed using a fiber bridging (FB) model which was formulated using the boundary correction factors and weight functions for center hole specimen configurations. A frictional shear stress is assumed in the FB model and was used as a curve fitting parameter to model matrix crack growth data. The higher frictional shear stresses calculated in the SCS-6/Timetal-21S laminates resulted in lower stress intensity factors in the matrix and higher axial stresses in the fibers compared to those in the SCS-6/Ti-15-3 laminates at the same applied stress levels.

  18. Facile time-of-flight methods for characterizing pulsed superfluid helium droplet beams

    SciTech Connect (OSTI)

    He, Yunteng; Zhang, Jie; Li, Yang; Freund, William M.; Kong, Wei

    2015-08-15

    We present two facile time-of-flight (TOF) methods of detecting superfluid helium droplets and droplets with neutral dopants. Without an electron gun and with only a heated filament and pulsed electrodes, the electron impact ionization TOF mass spectrometer can resolve ionized helium clusters such as He{sub 2}{sup +} and He{sub 4}{sup +}, which are signatures of superfluid helium droplets. Without ionizing any helium atoms, multiphoton non-resonant laser ionization of CCl{sub 4} doped in superfluid helium droplets at 266 nm generates complex cluster ions of dopant fragments with helium atoms, including (He){sub n}C{sup +}, (He){sub n}Cl{sup +}, and (He){sub n}CCl{sup +}. Using both methods, we have characterized our cryogenic pulsed valve—the Even-Lavie valve. We have observed a primary pulse with larger helium droplets traveling at a slower speed and a rebound pulse with smaller droplets at a faster speed. In addition, the pickup efficiency of dopant is higher for the primary pulse when the nozzle temperature is higher than 13 K, and the total time duration of the doped droplet pulse is only on the order of 20 μs. These results stress the importance of fast and easy characterization of the droplet beam for sensitive measurements such as electron diffraction of doped droplets.

  19. Preparation and thermal desorption properties of dc sputtered zirconium-hydrogen-helium thin films

    SciTech Connect (OSTI)

    Wei, Y. C.; Shi, L. Q.; Zhang, L.; He, Z. J.; Zhang, B.; Wang, L. B.

    2008-11-15

    We developed a new approach for preparing hydrogen and helium co-containing zirconium films (Zr-H-He) to simulate aging metal tritides. We also studied the effect of hydrogen on helium behavior, in which we applied direct current magnetron sputtering in a mixture of working gases (helium, argon, and hydrogen). The amount and depth profile of helium and hydrogen trapped in the films were determined using the elastic recoil detection analysis. The microstructure and surface morphology of the Zr-H-He films were studied by x-ray diffraction, transmission electron microscopy, and atomic force microscopy. To investigate the effect of hydrogen on the thermal release behavior of helium in the Zr film, thermal desorption spectrometry (TDS) was used, which revealed a similar desorption behavior to aged tritides. TDS experiments showed that the spectra were constituted by low-temperature peaks around 300 deg. C and high temperature peaks above 750 deg. C. Furthermore, the solid-phase {alpha} to {delta} transformation changed the shapes of the high-temperature peaks related to microstates of helium bubbles and caused the peak with a massive helium release shift toward lower temperature obviously.

  20. Method for fabrication of crack-free ceramic dielectric films

    DOE Patents [OSTI]

    Ma, Beihai; Narayanan, Manoj; Balachandran, Uthamalingam; Chao, Sheng; Liu, Shanshan

    2016-05-31

    The invention provides a process for forming crack-free dielectric films on a substrate. The process comprises the application of a dielectric precursor layer of a thickness from about 0.3 .mu.m to about 1.0 .mu.m to a substrate. The deposition is followed by low temperature heat pretreatment, prepyrolysis, pyrolysis and crystallization step for each layer. The deposition, heat pretreatment, prepyrolysis, pyrolysis and crystallization are repeated until the dielectric film forms an overall thickness of from about 1.5 .mu.m to about 20.0 .mu.m and providing a final crystallization treatment to form a thick dielectric film. The process provides a thick crack-free dielectric film on a substrate, the dielectric forming a dense thick crack-free dielectric having an overall dielectric thickness of from about 1.5 .mu.m to about 20.0 .mu.m.

  1. Method for fabrication of crack-free ceramic dielectric films

    DOE Patents [OSTI]

    Ma, Beihai; Balachandran, Uthamalingam; Chao, Sheng; Liu, Shanshan; Narayanan, Manoj

    2014-02-11

    The invention provides a process for forming crack-free dielectric films on a substrate. The process comprise the application of a dielectric precursor layer of a thickness from about 0.3 .mu.m to about 1.0 .mu.m to a substrate. The deposition is followed by low temperature heat pretreatment, prepyrolysis, pyrolysis and crystallization step for each layer. The deposition, heat pretreatment, prepyrolysis, pyrolysis and crystallization are repeated until the dielectric film forms an overall thickness of from about 1.5 .mu.m to about 20.0 .mu.m and providing a final crystallization treatment to form a thick dielectric film. Also provided was a thick crack-free dielectric film on a substrate, the dielectric forming a dense thick crack-free dielectric having an overall dielectric thickness of from about 1.5 .mu.m to about 20.0 .mu.m.

  2. Relationships between stress corrosion cracking tests and utility operating experience

    SciTech Connect (OSTI)

    Baum, Allen

    1999-10-22

    Several utility steam generator and stress corrosion cracking databases are synthesized with the view of identifying the crevice chemistry that is most consistent with the plant cracking data. Superheated steam and neutral solution environments are found to be inconsistent with the large variations in the observed SCC between different plants, different support plates within a plant, and different crevice locations. While the eddy current response of laboratory tests performed with caustic chemistries approximates the response of the most extensively affected steam generator tubes, the crack propagation kinetics in these tests differ horn plant experience. The observations suggest that there is a gradual conversion of the environment responsible for most steam generator ODSCC from a concentrated, alkaline-forming solution to a progressively more steam-enriched environment.

  3. Effects of helium content of microstructural development in Type 316 stainless steel under neutron irradiation

    SciTech Connect (OSTI)

    Maziasz, P.J.

    1985-11-01

    This work investigated the sensitivity of microstructural evolution, particularly precipitate development, to increased helium content during thermal aging and during neutron irradiation. Helium (110 at. ppM) was cold preinjected into solution annealed (SA) DO-heat type 316 stainess steel (316) via cyclotron irradiation. These specimens were then exposed side by side with uninjected samples. Continuous helium generation was increased considerably relative to EBR-II irradiation by irradiation in HFIR. Data were obtained from quantitative analytical electron microscopy (AEM) in thin foils and on extraction replicas. 480 refs., 86 figs., 19 tabs.

  4. DEUTERIUM, TRITIUM, AND HELIUM DESORPTION FROM AGED TITANIUM TRITIDES. PART I.

    SciTech Connect (OSTI)

    Shanahan, K; Jeffrey Holder, J

    2006-07-10

    Six new samples of tritium-aged bulk titanium have been examined by thermal desorption and isotope exchange chemistry. The discovery of a lower temperature hydrogen desorption state in these materials, previously reported, has been confirmed in one of the new samples. The helium release of the samples shows the more severe effects obtained from longer aging periods, i.e. higher initial He/M ratios. Several of the more aged samples were spontaneously releasing helium. Part I will discuss the new results on the new lower temperature hydrogen desorption state found in one more extensively studied sample. Part II will discuss the hydrogen/helium release behavior of the remaining samples.

  5. DEUTERIUM, TRITIUM, AND HELIUM DESORPTION FROM AGED TITANIUM TRITIDES. PART II.

    SciTech Connect (OSTI)

    Shanahan, K; Jeffrey Holder, J

    2006-08-17

    Six new samples of tritium-aged bulk titanium have been examined by thermal desorption and isotope exchange chemistry. The discovery of a lower temperature hydrogen desorption state in these materials, previously reported, has been confirmed in one of the new samples. The helium release of the samples shows the more severe effects obtained from longer aging periods, i.e. higher initial He/M ratios. Several of the more aged samples were spontaneously releasing helium. Part I discussed the new results on the new lower temperature hydrogen desorption state found in one more extensively studied sample. Part II will discuss the hydrogen/helium release behavior of the remaining samples.

  6. Weld solidification cracking in 304 to 304L stainless steel

    SciTech Connect (OSTI)

    Hochanadel, Patrick W; Lienert, Thomas J; Martinez, Jesse N; Martinez, Raymond J; Johnson, Matthew Q

    2010-01-01

    A series of annulus welds were made between 304 and 304L stainless steel coaxial tubes using both pulsed laser beam welding (LBW) and pulsed gas tungsten arc welding (GTAW). In this application, a change in process from pulsed LBW to pulsed gas tungsten arc welding was proposed to limit the possibility of weld solidification cracking since weldability diagrams developed for GTAW display a greater range of compositions that are not crack susceptible relative to those developed for pulsed LBW. Contrary to the predictions of the GTAW weldability diagram, cracking was found. This result was rationalized in terms of the more rapid solidification rate of the pulsed gas tungsten arc welds. In addition, for the pulsed LBW conditions, the material compositions were predicted to be, by themselves, 'weldable' according to the pulsed LBW weldability diagram. However, the composition range along the tie line connecting the two compositions passed through the crack susceptible range. Microstructurally, the primary solidification mode (PSM) of the material processed with higher power LBW was determined to be austenite (A), while solidification mode of the materials processed with lower power LBW apparently exhibited a dual PSM of both austenite (A) and ferrite-austenite (FA) within the same weld. The materials processed by pulsed GT A W showed mostly primary austenite solidification, with some regions of either primary austenite-second phase ferrite (AF) solidification or primary ferrite-second phase austenite (FA) solidification. This work demonstrates that variations in crack susceptibility may be realized when welding different heats of 'weldable' materials together, and that slight variations in processing can also contribute to crack susceptibility.

  7. Weld solidification cracking in 304 to 204L stainless steel

    SciTech Connect (OSTI)

    Hochanadel, Patrick W; Lienert, Thomas J; Martinez, Jesse N; Johnson, Matthew Q

    2010-09-15

    A series of annulus welds were made between 304 and 304L stainless steel coaxial tubes using both pulsed laser beam welding (LBW) and pulsed gas tungsten arc welding (GTAW). In this application, a change in process from pulsed LBW to pulsed gas tungsten arc welding was proposed to limit the possibility of weld solidification cracking since weldability diagrams developed for GTAW display a greater range of compositions that are not crack susceptible relative to those developed for pulsed LBW. Contrary to the predictions of the GTAW weldability diagram, cracking was found.This result was rationalized in terms of the more rapid solidification rate of the pulsed gas tungsten arc welds. In addition, for the pulsed LBW conditions, the material compositions were predicted to be, by themselves, 'weldable' according to the pulsed LBW weldability diagram. However, the composition range along the tie line connecting the two compositions passed through the crack susceptible range. Microstructurally, the primary solidification mode (PSM) of the material processed with higher power LBW was determined to be austenite (A), while solidification mode of the materials processed with lower power LBW apparently exhibited a dual PSM of both austenite (A) and ferrite-austenite (FA) within the same weld. The materials processed by pulsed GTAW showed mostly primary austenite solidification, with some regions of either primary austenite-second phase ferrite (AF) solidification or primary ferrite-second phase austenite (FA) solidification. This work demonstrates that variations in crack susceptibility may be realized when welding different heats of 'weldable' materials together, and that slight variations in processing can also contribute to crack susceptibility.

  8. Dynamic crack initiation toughness : experiments and peridynamic modeling.

    SciTech Connect (OSTI)

    Foster, John T.

    2009-10-01

    This is a dissertation on research conducted studying the dynamic crack initiation toughness of a 4340 steel. Researchers have been conducting experimental testing of dynamic crack initiation toughness, K{sub Ic}, for many years, using many experimental techniques with vastly different trends in the results when reporting K{sub Ic} as a function of loading rate. The dissertation describes a novel experimental technique for measuring K{sub Ic} in metals using the Kolsky bar. The method borrows from improvements made in recent years in traditional Kolsky bar testing by using pulse shaping techniques to ensure a constant loading rate applied to the sample before crack initiation. Dynamic crack initiation measurements were reported on a 4340 steel at two different loading rates. The steel was shown to exhibit a rate dependence, with the recorded values of K{sub Ic} being much higher at the higher loading rate. Using the knowledge of this rate dependence as a motivation in attempting to model the fracture events, a viscoplastic constitutive model was implemented into a peridynamic computational mechanics code. Peridynamics is a newly developed theory in solid mechanics that replaces the classical partial differential equations of motion with integral-differential equations which do not require the existence of spatial derivatives in the displacement field. This allows for the straightforward modeling of unguided crack initiation and growth. To date, peridynamic implementations have used severely restricted constitutive models. This research represents the first implementation of a complex material model and its validation. After showing results comparing deformations to experimental Taylor anvil impact for the viscoplastic material model, a novel failure criterion is introduced to model the dynamic crack initiation toughness experiments. The failure model is based on an energy criterion and uses the K{sub Ic} values recorded experimentally as an input. The failure model

  9. Helium bubble evolution in a Zr–Sn–Nb–Fe–Cr alloy during post-annealing: An in-situ investigation

    SciTech Connect (OSTI)

    Shen, H.H.; Peng, S.M.; Chen, B.; Naab, F.N.; Sun, G.A.; Zhou, W.; Xiang, X.; Sun, K.; Zu, X.T.

    2015-09-15

    The formation of helium bubbles is considered to be detrimental to the mechanical performance of the nuclear materials. The growth behaviors of helium bubbles in a helium ion implanted Zr–Sn–Nb–Fe–Cr alloy with respect to the helium fluence and subsequently annealing procedure were investigated by in-situ transmission electron microscopy. In the as-implanted sample, the measured size distributions of the helium bubbles are consistent with the simulated helium concentrations. Moreover, the mean size of the helium bubbles increases with the increase of the irradiation temperatures and the helium fluence. The in-situ heating study performed in a transmission electron microscope indicates that the mean size of the helium bubbles increase slowly below 923 K and dramatically above 923 K. The coarsening mechanism of the helium bubbles in the alloy is suggested based on the study. - Highlights: • Helium bubble growth in zirconium with annealing was in-situ investigated in TEM. • The mean helium bubble size increase with helium fluence and annealing temperature. • Helium bubble size distribution is same as that of helium concentration by SRIM. • Mean bubble size increases slowly and quickly with temperature below and above 923 K. • The growth mechanism of the helium bubbles in Zr alloy has been discussed.

  10. Relative Humidity and the Susceptibility of Austenitic Stainless Steel to Stress Corrosion Cracking in an impure Plutonium Oxide Environment

    SciTech Connect (OSTI)

    Zapp, P.; Duffey, J.; Lam, P.; Dunn, K.

    2010-05-05

    Laboratory tests to investigate the corrosivity of moist plutonium oxide/chloride salt mixtures on 304L and 316L stainless steel coupons showed that corrosion occurred in selected samples. The tests exposed flat coupons for pitting evaluation and 'teardrop' stressed coupons for stress corrosion cracking (SCC) evaluation at room temperature to various mixtures of PuO{sub 2} and chloride-bearing salts for periods up to 500 days. The exposures were conducted in sealed containers in which the oxide-salt mixtures were loaded with about 0.6 wt % water from a humidified helium atmosphere. Observations of corrosion ranged from superficial staining to pitting and SCC. The extent of corrosion depended on the total salt concentration, the composition of the salt and the moisture present in the test environment. The most significant corrosion was found in coupons that were exposed to 98 wt % PuO{sub 2}, 2 wt % chloride salt mixtures that contained calcium chloride and 0.6 wt% water. SCC was observed in two 304L stainless steel teardrop coupons exposed in solid contact to a mixture of 98 wt % PuO{sub 2}, 0.9 wt % NaCl, 0.9 wt % KCl, and 0.2 wt % CaCl{sub 2}. The cracking was associated with the heat-affected zone of an autogenous weld that ran across the center of the coupon. Cracking was not observed in coupons exposed to the headspace gas above the solid mixture, or in coupons exposed to other mixtures with either no CaCl{sub 2} or 0.92 wt% CaCl{sub 2}. SCC was present where the 0.6 wt % water content exceeded the value needed to fully hydrate the available CaCl{sub 2}, but was absent where the water content was insufficient. These results reveal the significance of the relative humidity in the austenitic stainless steels environment to their susceptibility to corrosion. The relative humidity in the test environment was controlled by the water loading and the concentration of the hydrating salts such as CaCl{sub 2}. For each salt or salt mixture there is a threshold relative

  11. The relationship between observed stress corrosion cracking fracture morphology and microstructure in Alloy 600

    SciTech Connect (OSTI)

    Symons, D.M.; Burke, M.G.; Foster, J.P.

    1997-12-31

    Microstructure is known to influence the stress corrosion cracking (SCC) behavior of Alloy 600 in both hydrogenated water and steam environments. This study evaluated the relative SCC response of a single heat of Alloy 600 as a function of microstructure in a hydrogenated doped-steam environment. The 400 C doped-steam environment was selected for the SCC tests to accelerate cracking. The material was evaluated in three conditions: (1) as-received (2) as-annealed, and (3) as-annealed + 26% deformation. Microstructural characterization was performed using analytical electron microscopy (AEM) techniques for the evaluation of carbide type and morphology, and general structure. Constant displacement (bolt-loaded) compact tension specimens were used to induce SCC. The as-annealed and as-annealed plus cold worked samples had two fracture morphologies: a rough intergranular SCC fracture morphology and a smooth intergranular fracture morphology. The SCC fracture in the as-received specimens was characterized by a classic intergranular morphology at low magnification, consistent with the microstructural evaluation of cross-sectional metallographic samples. More detailed examination revealed a pseudo-intergranular fracture morphology. This pseudo-intergranular morphology appears to be comprised of very fine cleavage-like microfacets. These observations may assist in understanding the difference in SCC fracture morphologies as reported in the open literature.

  12. Technical Letter Report on the Cracking of Irradiated Cast Stainless Steels with Low Ferrite Content

    SciTech Connect (OSTI)

    Chen, Y.; Alexandreanu, B.; Natesan, K.

    2014-11-01

    Crack growth rate and fracture toughness J-R curve tests were performed on CF-3 and CF-8 cast austenite stainless steels (CASS) with 13-14% of ferrite. The tests were conducted at ~320°C in either high-purity water with low dissolved oxygen or in simulated PWR water. The cyclic crack growth rates of CF-8 were higher than that of CF-3, and the differences between the aged and unaged specimens were small. No elevated SCC susceptibility was observed among these samples, and the SCC CGRs of these materials were comparable to those of CASS alloys with >23% ferrite. The fracture toughness values of unirradiated CF-3 were similar between unaged and aged specimens, and neutron irradiation decreased the fracture toughness significantly. The fracture toughness of CF-8 was reduced after thermal aging, and declined further after irradiation. It appears that while lowering ferrite content may help reduce the tendency of thermal aging embrittlement, it is not very effective to mitigate irradiation-induced embrittlement. Under a combined condition of thermal aging and irradiation, neutron irradiation plays a dominant role in causing embrittlement in CASS alloys.

  13. Transient Eddy Current Response Due to a Subsurface Crack in a Conductive Plate

    SciTech Connect (OSTI)

    Fangwei Fu

    2006-08-09

    Eddy current nondestructive evaluation (NDE) is usually carried out by exciting a time harmonic field using an inductive probe. However, a viable alternative is to use transient eddy current NDE in which a current pulse in a driver coil produces a transient .eld in a conductor that decays at a rate dependent on the conductivity and the permeability of the material and the coil configuration. By using transient eddy current, it is possible to estimate the properties of the conductive medium and to locate and size potential .aws from the measured probe response. The fundamental study described in this dissertation seeks to establish a theoretical understanding of the transient eddy current NDE. Compared with the Fourier transform method, the derived analytical formulations are more convenient when the transient eddy current response within a narrow time range is evaluated. The theoretical analysis provides a valuable tool to study the effect of layer thickness, location of defect, crack opening as well as the optimization of probe design. Analytical expressions have been developed to evaluate the transient response due to eddy currents in a conductive plate based on two asymptotic series. One series converges rapidly for a short time regime and the other for a long time regime and both of them agree with the results calculated by fast Fourier transform over all the times considered. The idea of asymptotic expansion is further applied to determine the induced electromotive force (EMF) in a pick-up coil due to eddy currents in a cylindrical rod. Starting from frequency domain representation, a quasi-static time domain dyadic Green's function for an electric source in a conductive plate has been derived. The resulting expression has three parts; a free space term, multiple image terms and partial reflection terms. The dyadic Green's function serves as the kernel of an electric field integral equation which defines the interaction of an ideal crack with the transient

  14. Note: Control of liquid helium supply to cryopanels of Kolkata superconducting cyclotron

    SciTech Connect (OSTI)

    Bhattacharyya, T. K. Pal, G.

    2015-02-15

    The Kolkata superconducting cyclotron utilises liquid helium to cool the main magnet niobium-titanium (NbTi) coil and the cryopanels. Three liquid helium cooled cryopanels, placed inside the dees of the radio-frequency system, maintain the high vacuum in the acceleration region of the superconducting cyclotron. The small cryostat placed inside the cryogenic distribution manifold located at the basement of the superconducting cyclotron building supplies liquid helium in parallel branches to three cold heads, used for cooling their associated cryopanels. The level in the cryostat has to be maintained at an optimum value to ensure uninterrupted flow of liquid helium to these three cold heads. This paper describes the transfer function of the overall system, its tuning parameters, and discusses the actual control of cryostat level by using these parameters.

  15. Research and development of a helium-4 based solar neutrino detector

    SciTech Connect (OSTI)

    Lanou, R.E.; Maris, H.J.; Seidel, G.M.

    1990-12-01

    We report on work accomplished in the first 30 months of a research and development program to investigate the feasibility of a new technique to detect solar neutrinos in superfluid helium. Accomplishments include the successful completion of design, construction and operation of the entire cryogenic, mechanical and electronic apparatus. During the last several months we have begun a series of experiments in superfluid helium to test the method. Experimental results include the first observation of the combined physical processes essential to the detection technique: ballistic roton generation by energetic charged particles, quantum evaporation of helium at a free surface and bolometric detection of the evaporated helium by physisorption on a cold silicon wafer. Additional results are also presented.

  16. Helium release rates and ODH calculations from RHIC magnet cooling line failure

    SciTech Connect (OSTI)

    Liaw, C.J.; Than, Y.; Tuozzolo, J.

    2011-03-28

    A catastrophic failure of the magnet cooling lines, similar to the LHC superconducting bus failure incident, could discharge cold helium into the RHIC tunnel and cause an Oxygen Deficiency Hazard (ODH) problem. A SINDA/FLUINT{reg_sign} model, which simulated the 4.5K/4 atm helium flowing through the magnet cooling system distribution lines, then through a line break into the insulating vacuum volumes and discharging via the reliefs into the RHIC tunnel, had been developed. Arc flash energy deposition and heat load from the ambient temperature cryostat surfaces are included in the simulations. Three typical areas: the sextant arc, the Triplet/DX/D0 magnets, and the injection area, had been analyzed. Results, including helium discharge rates, helium inventory loss, and the resulting oxygen concentration in the RHIC tunnel area, are reported. Good agreement had been achieved when comparing the simulation results, a RHIC sector depressurization test measurement, and some simple analytical calculations.

  17. Evaluation of helium impurity impacts on Spent Nuclear Fuel project processes (OCRWM)

    SciTech Connect (OSTI)

    SHERRELL, D.L.

    1999-09-21

    This document identifies the types and quantities of impurities that may be present within helium that is introduced into multi-canister overpacks (MCO)s by various SNF Project facilities, including, but not limited to the Cold Vacuum Drying (CVD) Facility (CVDF). It then evaluates possible impacts of worst case impurity inventories on MCO drying, transportation, and storage processes. Based on the evaluation results, this document: (1) concludes that the SNF Project helium procurement specification can be a factor-of-ten less restrictive than a typical vendor's standard offering (99.96% pure versus the vendor's 99.997% pure standard offering); (2) concludes that the CVDF's current 99.5% purity requirement is adequate to control the quality of the helium that is delivered to the MCO by the plant's helium distribution system; and (3) recommends specific impurity limits for both of the above cases.

  18. The application of a logic framework for fatigue crack growth analyses to microstructural effects

    SciTech Connect (OSTI)

    Xu, J.G.; Liu, H.W.

    1995-12-31

    {Delta}K has been widely used to correlate da/dN data. The relation between da/dN and {Delta}K is usually found empirically. However, fatigue crack growth relations can also be derived theoretically. Three fatigue crack growth theories are derived for the state of small scale yielding and plane strain. These three theories constitute a logic framework useful for fatigue crack growth analyses. The application of the logic framework to the analyses of microstructural effects on fatigue crack growth is illustrated. The fatigue crack growth curve of 7075-T651 aluminum alloy has five distinct regions. A fatigue crack grows by crack-tip shear decohesion forming striations and by brittle fractures of particles followed by localized shear decohesion at these microcracks forming dimples. The logic framework helps to relate the fatigue crack growth behaviors in these five regions to the fractures of inclusions and to the resistance of grain boundaries and dispersoids to shear decohesion.

  19. Exploring the isopycnal mixing and helium-heat paradoxes in a suite of Earth System Models

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Gnanadesikan, A.; Abernathey, R.; Pradal, M.-A.

    2014-11-20

    This paper uses a suite of Earth System models which simulate the distribution of He isotopes and radiocarbon to examine two paradoxes in Earth science. The helium-heat paradox refers to the fact that helium emissions to the deep ocean are far lower than would be expected given the rate of geothermal heating, since both are thought to be the result of radioactive decay in the earth's interior. The isopycnal mixing paradox comes from the fact that many theoretical parameterizations of the isopycnal mixing coefficient ARedi that link it to baroclinic instability project it to be small (of order a fewmore » hundred m2 s−1) in the ocean interior away from boundary currents. However, direct observations using tracers and floats (largely in the upper ocean) suggest that values of this coefficient are an order of magnitude higher. Because helium isotopes equilibrate rapidly with the atmosphere, but radiocarbon equilibrates slowly, it might be thought that resolving the isopycnal mixing paradox in favor of the higher observational estimates of ARedi might also solve the helium paradox. In this paper we show that this is not the case. In a suite of models with different spatially constant and spatially varying values of ARedi the distribution of radiocarbon and helium isotopes is sensitive to the value of ARedi. However, away from strong helium sources in the Southeast Pacific, the relationship between the two is not sensitive, indicating that large-scale advection is the limiting process for removing helium and radiocarbon from the deep ocean. The helium isotopes, in turn, suggest a higher value of ARedi in the deep ocean than is seen in theoretical parameterizations based on baroclinic growth rates. We argue that a key part of resolving the isopycnal mixing paradox is to abandon the idea that ARedi has a direct relationship to local baroclinic instability and to the so called "thickness" mixing coefficient AGM.« less

  20. Radon and helium in soil gases in the Phlegraean Fields, central Italy

    SciTech Connect (OSTI)

    Lombardi, S. ); Reimer, G.M. )

    1990-05-01

    The distribution and migration of radon and helium soil-gas concentrations in the Phlegraean Fields, Italy, are controlled by the tectonic features of the area. Radon is supplied from surficial sources and helium has both surficial and deep origins. There is no direct correlation between the two noble gases on a point-to-point basis but the areal distribution of both gases is similar, suggesting that the distribution is controlled primarily by fractures and movement of geothermal fluids.

  1. Method of making crack-free zirconium hydride

    DOE Patents [OSTI]

    Sullivan, Richard W.

    1980-01-01

    Crack-free hydrides of zirconium and zirconium-uranium alloys are produced by alloying the zirconium or zirconium-uranium alloy with beryllium, or nickel, or beryllium and scandium, or nickel and scandium, or beryllium and nickel, or beryllium, nickel and scandium and thereafter hydriding.

  2. Crack-resistant siloxane molding compounds. [Patent application

    DOE Patents [OSTI]

    McFarland, J.W.; Swearngin, C.B.

    1980-11-03

    The crack resistance of phenyl silicone molding resins containing siliceous fillers is improved by incorporating therein about 0.5 to 5.5% by weight of ..beta..-eucryptite, a lithium aluminum silicate having a negative thermal expansion coefficient. These molding resins are particularly suitable for encapsulating electronic devices such as diodes, coils, resistors, and the like.

  3. Incipient Crack Detection in Composite Wind Turbine Blades

    SciTech Connect (OSTI)

    Taylor, Stuart G.; Choi, Mijin; Jeong, Hyomi; Jang, Jae Kyeong; Park, Gyuhae; Farinholt, Kevin; Farrar, Charles R.; Ammerman, Curtt N.; Todd, Michael D.; Lee, Jung-Ryul

    2012-08-28

    This paper presents some analysis results for incipient crack detection in a 9-meter CX-100 wind turbine blade that underwent fatigue loading to failure. The blade was manufactured to standard specifications, and it underwent harmonic excitation at its first resonance using a hydraulically-actuated excitation system until reaching catastrophic failure. This work investigates the ability of an ultrasonic guided wave approach to detect incipient damage prior to the surfacing of a visible, catastrophic crack. The blade was instrumented with piezoelectric transducers, which were used in an active, pitchcatch mode with guided waves over a range of excitation frequencies. The performance results in detecting incipient crack formation in the fiberglass skin of the blade is assessed over the range of frequencies in order to determine the point at which the incipient crack became detectable. Higher excitation frequencies provide consistent results for paths along the rotor blade's carbon fiber spar cap, but performance falls off with increasing excitation frequencies for paths off of the spar cap. Lower excitation frequencies provide more consistent performance across all sensor paths.

  4. Sulfide stress cracking resistance of low-alloy nickel steels

    SciTech Connect (OSTI)

    Yoshino, Y.; Minozaki, Y.

    1986-04-01

    The sulfide stress cracking (SSC) resistance of Ni-containing low-alloy steels was studied using laboratory and commercial heats over the range of 600 to 800 MPa yield strength (700 to 900 MPa tensile strength). The results were interpreted with regard to observations by metallurgical and electrochemical analyses. In steel containing 1% Cr and 0.5% Mo, the SSC resistance is not affected by up to 2% Ni. A commercial steel with 3.7% Ni-1.8% Cr-0.4% Mo exhibits the same K/sub ISSC/ and Ni-free steels. The cracking resistance begins to deteriorate when fresh martensite exceeds 5 vol%. The lattice diffusion of hydrogen is decreased by the additional Ni, whereas the subsurface hydrogen concentration remains constant in 5% NaCl solution and decreases in NACE TM-01-77 solution up to 5% Ni. Thus, nickel has no harmful effect in terms of hydrogen absorption and diffusion. However, nickel enhances the formation of surface trenches in acidified solutions. This is intensified in the anodically polarized slow extension rate test, which results in loss in elongation. Consequently, nickel per se has no effect on the propagation of SSC unless its addition results in the formation of fresh martensite. However, it may or may not enhance crack initiation, depending on a specific combination of solution and steel, by forming surface trenches that subsequently trigger hydrogen cracking from their bottom.

  5. Stress corrosion cracking of welded Alloy 600 penetration mockups

    SciTech Connect (OSTI)

    Sarver, J.M.; Pathania, R.S.; Stuckey, K.; Fyfitch, S.; Gelpi, A.; Foucault, M.; Hunt, E.S.

    1995-12-31

    The primary water stress corrosion cracking (PWSCC) of Alloy 600 in components other than steam generators is a problem of increasing concern for nuclear power plants. Of greatest concern at the present time is the PWSCC of Alloy 600 vessel head penetrations. The common elements of these components are threefold: (1) the Alloy 600 material has a susceptible microstructure, (2) the Alloy 600 material is either a thick-walled tube or a bar which has been machined into a thick-walled tube, and (3) the Alloy 600 material has been welded into a structure such that high residual welding stresses exist in the postwelded Alloy 600 material. The objectives of the present program were to evaluate the PWSCC behavior of various configurations of welded Alloy 600 penetrations, and possible remedial measures which would prevent or retard PWSCC in these components. Mockups were instrumented to permit instantaneous remote sensing of through-wall cracking and were autoclave tested along with control C-rings in a doped steam environment. Following the test exposures, the mockups were split and examined to characterize the cracking morphology and the material microstructure. A Weibull distribution was used to analyze the time-to-failure results, and the observed cracking locations were compared to residual stress levels predicted by an elastic-plastic finite element analysis of the mockups.

  6. An environmental cracking evaluation of fastener materials for seawater applications

    SciTech Connect (OSTI)

    Aylor, D.M.

    1994-12-31

    Slow strain rate tests (SSRT) were conducted on various nickel-base, titanium base, and copper-nickel (Cu-Ni) alloys in order to identify a replacement material for Alloy K-500 in seawater fastener applications. SSRT data and fracture surface analysis of the test specimens identified a susceptibility to environmental cracking in cathodically polarized environments for Alloy K-500, Alloy 625 Plus, and Alloy 625PH. Alloy 625 Plus exhibited slightly increased environmental cracking resistance-at {minus}850 mV vs. SCE over Alloy K-500 and Alloy 625PH. Ti-6Al-4V ELI, Beta C, and Beta 21S titanium displayed no susceptibility to environmental cracking in freely corroding 3.5% NaCl or cathodically polarized conditions. Precharging these titanium alloys for 8 weeks at {minus}1,250 mV vs. SCE did not adversely affect their environmental cracking resistance. The Cu-3Ni and Cu-15Ni-7Sn spray formed alloys exhibited extensive scatter and low measured maximum loads, presumably due to macroporosity present in the as-fabricated material.

  7. Thin film with oriented cracks on a flexible substrate

    DOE Patents [OSTI]

    Feng, Bao; McGilvray, Andrew; Shi, Bo

    2010-07-27

    A thermoelectric film is disclosed. The thermoelectric film includes a substrate that is substantially electrically non-conductive and flexible and a thermoelectric material that is deposited on at least one surface of the substrate. The thermoelectric film also includes multiple cracks oriented in a predetermined direction.

  8. Performance Testing of Jefferson Lab 12 GeV Helium Screw Compressors

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Knudsen, P.; Ganni, V.; Dixon, K.; Norton, R.; Creel, J.

    2015-08-10

    Oil injected screw compressors have essentially superseded all other types of compressors in modern helium refrigeration systems due to their large displacement capacity, reliability, minimal vibration, and capability of handling helium's high heat of compression. At the present state of compressor system designs for helium refrigeration systems, typically two-thirds of the lost input power is due to the compression system. It is important to understand the isothermal and volumetric efficiencies of these machines to help properly design the compression system to match the refrigeration process. It is also important to identify those primary compressor skid exergetic loss mechanisms which maymore » be reduced, thereby offering the possibility of significantly reducing the input power to helium refrigeration processes which are extremely energy intensive. This paper summarizes the results collected during the commissioning of the new compressor system for Jefferson Lab's (JLab's) 12 GeV upgrade. The compressor skid packages were designed by JLab and built to print by industry. They incorporate a number of modifications not typical of helium screw compressor packages and most importantly allow a very wide range of operation so that JLab's patented Floating Pressure Process can be fully utilized. This paper also summarizes key features of the skid design that allow this process and facilitate the maintenance and reliability of these helium compressor systems.« less

  9. The initiation and propagation of helium detonations in white dwarf envelopes

    SciTech Connect (OSTI)

    Shen, Ken J. [Department of Astronomy and Theoretical Astrophysics Center, University of California, Berkeley, CA 94720 (United States); Moore, Kevin, E-mail: kenshen@astro.berkeley.edu [Department of Applied Mathematics and Statistics, University of California, Santa Cruz, CA 95064 (United States)

    2014-12-10

    Detonations in helium-rich envelopes surrounding white dwarfs have garnered attention as triggers of faint thermonuclear '.Ia' supernovae and double detonation Type Ia supernovae. However, recent studies have found that the minimum size of a hotspot that can lead to a helium detonation is comparable to, or even larger than, the white dwarf's pressure scale height, casting doubt on the successful ignition of helium detonations in these systems. In this paper, we examine the previously neglected effects of C/O pollution and a full nuclear reaction network, and we consider hotspots with spatially constant pressure in addition to constant density hotspots. We find that the inclusion of these effects significantly decreases the minimum hotspot size for helium-rich detonation ignition, making detonations far more plausible during turbulent shell convection or during double white dwarf mergers. The increase in burning rate also decreases the minimum shell mass in which a helium detonation can successfully propagate and alters the composition of the shell's burning products. The ashes of these low-mass shells consist primarily of silicon, calcium, and unburned helium and metals and may explain the high-velocity spectral features observed in most Type Ia supernovae.

  10. Performance Testing of Jefferson Lab 12 GeV Helium Screw Compressors

    SciTech Connect (OSTI)

    Knudsen, P.; Ganni, V.; Dixon, K.; Norton, R.; Creel, J.

    2015-08-10

    Oil injected screw compressors have essentially superseded all other types of compressors in modern helium refrigeration systems due to their large displacement capacity, reliability, minimal vibration, and capability of handling helium's high heat of compression. At the present state of compressor system designs for helium refrigeration systems, typically two-thirds of the lost input power is due to the compression system. It is important to understand the isothermal and volumetric efficiencies of these machines to help properly design the compression system to match the refrigeration process. It is also important to identify those primary compressor skid exergetic loss mechanisms which may be reduced, thereby offering the possibility of significantly reducing the input power to helium refrigeration processes which are extremely energy intensive. This paper summarizes the results collected during the commissioning of the new compressor system for Jefferson Lab's (JLab's) 12 GeV upgrade. The compressor skid packages were designed by JLab and built to print by industry. They incorporate a number of modifications not typical of helium screw compressor packages and most importantly allow a very wide range of operation so that JLab's patented Floating Pressure Process can be fully utilized. This paper also summarizes key features of the skid design that allow this process and facilitate the maintenance and reliability of these helium compressor systems.

  11. Dependence of dynamic fracture resistance on crack velocity in tungsten: Pt. II. Bicrystals and polycrystals

    SciTech Connect (OSTI)

    Liv, J.M.; Shen, B.W.

    1986-06-01

    The experimental techniques for crack velocity measurements have been applied to bicrystals of tungsten with twist orientations about (100) and polycrystals. The hesitation of the propagating cleavage crack in the vicinity of the grain boundary is examined. The contributions to energy dissipation from deformation and fracture processes in the grain boundary region as well as the in direct effects of crack deceleration are discussed. These findings have been applied to explain th dynamic fracture resistance and crack arrest in polycrystals.

  12. Device build at ODU to crack nature's code takes ride to JLab (Device build

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    at ODU to crack nature's code takes ride to JLab | Jefferson Lab Device build at ODU to crack nature's code takes ride to JLab (Device build at ODU to crack nature's code takes ride to JLab External Link: http://hamptonroads.com/2012/02/device-built-odu-crack-natures-code-takes-ride By jlab_admin on Tue, 2012-02-14

  13. Agglutination of single catalyst particles during fluid catalytic cracking as observed by X-ray nanotomography

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Meirer, F.; Kalirai, S.; Weker, J. Nelson; Liu, Y.; Andrews, J. C.; Weckhuysen, B. M.

    2015-04-14

    Metal accumulation at the catalyst particle surface plays a role in particle agglutination during fluid catalytic cracking.

  14. Atomic-scale mechanisms of helium bubble hardening in iron

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Osetskiy, Yury N.; Stoller, Roger E.

    2015-06-03

    Generation of helium due to (n,α) transmutation reactions changes the response of structural materials to neutron irradiation. The whole process of radiation damage evolution is affected by He accumulation and leads to significant changes in the material s properties. A population of nanometric He-filled bubbles affects mechanical properties and the impact can be quite significant because of their high density. Understanding how these basic mechanisms affect mechanical properties is necessary for predicting radiation effects. In this paper we present an extensive study of the interactions between a moving edge dislocation and bubbles using atomic-scale modeling. We focus on the effectmore » of He bubble size and He concentration inside bubbles. Thus, we found that ability of bubbles to act as an obstacle to dislocation motion is close to that of voids when the He-to-vacancy ratio is in the range from 0 to 1. A few simulations made at higher He contents demonstrated that the interaction mechanism is changed for over-pressurized bubbles and they become weaker obstacles. The results are discussed in light of post-irradiation materials testing.« less

  15. Atomic-scale mechanisms of helium bubble hardening in iron

    SciTech Connect (OSTI)

    Osetskiy, Yury N.; Stoller, Roger E.

    2015-06-03

    Generation of helium due to (n,α) transmutation reactions changes the response of structural materials to neutron irradiation. The whole process of radiation damage evolution is affected by He accumulation and leads to significant changes in the material s properties. A population of nanometric He-filled bubbles affects mechanical properties and the impact can be quite significant because of their high density. Understanding how these basic mechanisms affect mechanical properties is necessary for predicting radiation effects. In this paper we present an extensive study of the interactions between a moving edge dislocation and bubbles using atomic-scale modeling. We focus on the effect of He bubble size and He concentration inside bubbles. Thus, we found that ability of bubbles to act as an obstacle to dislocation motion is close to that of voids when the He-to-vacancy ratio is in the range from 0 to 1. A few simulations made at higher He contents demonstrated that the interaction mechanism is changed for over-pressurized bubbles and they become weaker obstacles. The results are discussed in light of post-irradiation materials testing.

  16. Performance Characterization of the Production Facility Prototype Helium Flow System

    SciTech Connect (OSTI)

    Woloshun, Keith Albert; Dale, Gregory E.; Dalmas, Dale Allen; Romero, Frank Patrick

    2015-12-16

    The roots blower in use at ANL for in-beam experiments and also at LANL for flow tests was sized for 12 mm diameter disks and significantly less beam heating. Currently, the disks are 29 mm in diameter, with a 12 mm FWHM Gaussian beam spot at 42 MeV and 2.86 μA on each side of the target, 5.72 μA total. The target design itself is reported elsewhere. With the increased beam heating, the helium flow requirement increased so that a larger blower was need for a mass flow rate of 400 g/s at 2.76 MPa (400 psig). An Aerzen GM 12.4 blower was selected, and is currently being installed at the LANL facility for target and component flow testing. This report describes this blower/motor/pressure vessel package and the status of the facility preparations. Blower performance (mass flow rate as a function of loop pressure drop) was measured at 4 blower speeds. Results are reported below.

  17. Surface cracking in resistance seam welding of coated steels

    SciTech Connect (OSTI)

    Adonyi, Y.; Kimchi, M.

    1994-12-31

    In this experimental work, the focus was on the understanding the electrode-wheel/coated steel surface phenomena by building operational lobes and by correlating the weld quality with static-and dynamic-contact-resistance variation during welding. Conventional AC, DC, and electrode-wire resistance-seam weldability of printed zinc-coated and hot-dipped tin-coated steel was performed in this work, as compared with traditional lead-tin (terne) coating used as reference material. Variables included steel substrate type, welding equipment type, electrode-wheel cleaning practice, and electrode-wire geometry. Optic and electron microscopy were used for the evaluation of specimens extracted from longitudinal cross-sections of representative welds. The size and morphology of surface cracks was characterized and correlated with variations in the above-mentioned parameters. It was found that the tin-coated (unpainted) steel sheet had a superior all-together performance to the zinc-coated steel and terne-coated steel, both in terms of wider weldability lobes and lesser surface cracking. The extent of surface cracking was greatly reduced by using the electrode-wire seam welding process using a longitudinally grooved wire profile, which also widened the corresponding weldability lobes. It was also found that the extent of cracking depended on the electrode knurl geometry, substrate type, and the presence of conductive paint applied on top of the metallic coating. An attempt was made to characterize the specific mechanisms governing the LME phenomenon for the lead-, zinc and tin-based coating systems and to assess the potential for crack propagation in the welds. The dynamic contact resistance was found to be a good measure of the welding process stability and an indicator of defect formation. It was found that the ratio between the static and dynamic contact resistances of the tin-coated sheet was considerably lower than similar ratios for bare and zinc-coated sheet.

  18. Development of a novel technique to assess the vulnerability of micro-mechanical system components to environmentally assisted cracking.

    SciTech Connect (OSTI)

    Enos, David George; Goods, Steven Howard

    2006-11-01

    Microelectromechanical systems (MEMS) will play an important functional role in future DOE weapon and Homeland Security applications. If these emerging technologies are to be applied successfully, it is imperative that the long-term degradation of the materials of construction be understood. Unlike electrical devices, MEMS devices have a mechanical aspect to their function. Some components (e.g., springs) will be subjected to stresses beyond whatever residual stresses exist from fabrication. These stresses, combined with possible abnormal exposure environments (e.g., humidity, contamination), introduce a vulnerability to environmentally assisted cracking (EAC). EAC is manifested as the nucleation and propagation of a stable crack at mechanical loads/stresses far below what would be expected based solely upon the materials mechanical properties. If not addressed, EAC can lead to sudden, catastrophic failure. Considering the materials of construction and the very small feature size, EAC represents a high-risk environmentally induced degradation mode for MEMS devices. Currently, the lack of applicable characterization techniques is preventing the needed vulnerability assessment. The objective of this work is to address this deficiency by developing techniques to detect and quantify EAC in MEMS materials and structures. Such techniques will allow real-time detection of crack initiation and propagation. The information gained will establish the appropriate combinations of environment (defining packaging requirements), local stress levels, and metallurgical factors (composition, grain size and orientation) that must be achieved to prevent EAC.

  19. EFFECTS OF CHEMISTRY AND OTHER VARIABLES ON CORROSION AND STRESS CORROSION CRACKING IN HANFORD DOUBLE SHELL TANKS

    SciTech Connect (OSTI)

    BROWN MH

    2008-11-13

    Laboratory testing was performed to develop a comprehensive understanding of the corrosivity of the tank wastes stored in Double-Shell Tanks using simulants primarily from Tanks 241-AP-105, 241-SY-103 and 241-AW-105. Additional tests were conducted using simulants of the waste stored in 241-AZ-102, 241-SY-101, 241-AN-107, and 241-AY-101. This test program placed particular emphasis on defining the range of tank waste chemistries that do not induce the onset of localized forms of corrosion, particularly pitting and stress corrosion cracking. This document summarizes the key findings of the research program.

  20. Characteristics of acoustic emission during stress corrosion cracking of Inconel 600 alloy

    SciTech Connect (OSTI)

    Sung, K.Y.; Kim, I.S.; Yoon, Y.K.

    1997-10-15

    It is possible to detect by use of the acoustic emission (AE) technique the dynamic processes in stressed materials. In this study, the AE technique is applied to SCC of Inconel 600 due to depletion of chromium at grain boundaries to investigate the AE capability of detecting crack growth and to obtain the relation between AE characteristics and crack mechanisms such as fracture mode and crack growth rate during SCC. In addition, the generation of initial cracks was detected, and minimum crack size detectable with AE was determined to assess the potential of AE as a non-destructive method.

  1. ALTERNATIVES TO HELIUM-3 FOR NEUTRON MULTIPLICITY DETECTORS

    SciTech Connect (OSTI)

    Ely, James H.; Siciliano, Edward R.; Swinhoe, Martyn T.

    2012-02-07

    Collaboration between the Pacific Northwest National Laboratory (PNNL) and the Los Alamos National Laboratory (LANL) is underway to evaluate neutron detection technologies that might replace the high-pressure helium (3He) tubes currently used in neutron multiplicity counter for safeguards applications. The current stockpile of 3He is diminishing and alternatives are needed for a variety of neutron detection applications including multiplicity counters. The first phase of this investigation uses a series of Monte Carlo calculations to simulate the performance of an existing neutron multiplicity counter configuration by replacing the 3He tubes in a model for that counter with candidate alternative technologies. These alternative technologies are initially placed in approximately the same configuration as the 3He tubes to establish a reference level of performance against the 3He-based system. After these reference-level results are established, the configurations of the alternative models will be further modified for performance optimization. The 3He model for these simulations is the one used by LANL to develop and benchmark the Epithermal Neutron Multiplicity Counter (ENMC) detector, as documented by H.O. Menlove, et al. in the 2004 LANL report LA-14088. The alternative technologies being evaluated are the boron-tri-fluoride-filled proportional tubes, boron-lined tubes, and lithium coated materials previously tested as possible replacements in portal monitor screening applications, as documented by R.T. Kouzes, et al. in the 2010 PNNL report PNNL-72544 and NIM A 623 (2010) 1035–1045. The models and methods used for these comparative calculations will be described and preliminary results shown

  2. Blunt-crack band propagation in finite-element analysis for concrete structures. [LMFBR

    SciTech Connect (OSTI)

    Pfeiffer, P.A.; Bazant, Z.P.; Marchertas, A.H.

    1983-01-01

    The knowledge of concrete fracture is needed in nuclear reactor safety. The question of safety arises from the potential of concrete to crack under thermal loading. It has been postulated that structural concrete could be exposed to very high temperature, which may result from hot reactor coolant or even core debris coming in direct contact with the concrete. The utilization of the blunt crack approach for simulating concrete cracking in a general-purpose code is explored. The difficulties encountered in establishing the proper direction of crack propagation in an arbitrary discretization are described. Crack propagation is considered within the context of two types of solution techniques: (1) implicit solution of the static crack advance, and (2) explicit time integration using a dynamic relaxation technique to simulate the static crack advance. Also, in both solution techniques an elastic model is used to characterize the concrete.

  3. Effects of microstructure banding on hydrogen assisted fatigue crack growth in X65 pipeline steels

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Ronevich, Joseph A.; Somerday, Brian P.; San Marchi, Chris W.

    2015-09-10

    Banded ferrite-pearlite X65 pipeline steel was tested in high pressure hydrogen gas to evaluate the effects of oriented pearlite on hydrogen assisted fatigue crack growth. Test specimens were oriented in the steel pipe such that cracks propagated either parallel or perpendicular to the banded pearlite. The ferrite-pearlite microstructure exhibited orientation dependent behavior in which fatigue crack growth rates were significantly lower for cracks oriented perpendicular to the banded pearlite compared to cracks oriented parallel to the bands. Thus the reduction of hydrogen assisted fatigue crack growth across the banded pearlite is attributed to a combination of crack-tip branching and impededmore » hydrogen diffusion across the banded pearlite.« less

  4. Optimization of ultrasonic array inspections using an efficient hybrid model and real crack shapes

    SciTech Connect (OSTI)

    Felice, Maria V.; Velichko, Alexander Wilcox, Paul D.; Barden, Tim; Dunhill, Tony

    2015-03-31

    Models which simulate the interaction of ultrasound with cracks can be used to optimize ultrasonic array inspections, but this approach can be time-consuming. To overcome this issue an efficient hybrid model is implemented which includes a finite element method that requires only a single layer of elements around the crack shape. Scattering Matrices are used to capture the scattering behavior of the individual cracks and a discussion on the angular degrees of freedom of elastodynamic scatterers is included. Real crack shapes are obtained from X-ray Computed Tomography images of cracked parts and these shapes are inputted into the hybrid model. The effect of using real crack shapes instead of straight notch shapes is demonstrated. An array optimization methodology which incorporates the hybrid model, an approximate single-scattering relative noise model and the real crack shapes is then described.

  5. Primary water stress corrosion crack growth rates in Alloy 600 steam generator tubing

    SciTech Connect (OSTI)

    Lott, R.G.; Jacko, R.J.; Gold, R.E.

    1992-12-31

    Direct measurements of SCC crack growth rates have been used to determine the effects of changes in PWR primary water chemistry on the stress corrosion cracking behavior of Alloy 600 steam generator tubing. Reversing current DC potential measurement techniques have been adapted for use on thin walled tubing containing through-wall circumferential cracks. These techniques have been used to monitor crack rates in Alloy 600 tubing exposed to typical PWR primary water chemistries at 330{degrees}C. Crack growth rate studies, conducted under well defined stress intensity conditions, provide a sensitivity in the assessment of stress corrosion cracking susceptibility that is not possible using more traditional techniques. Preliminary studies have been conducted to determine the effects of B and Li concentrations on the stress corrosion crack growth rate of Alloy 600 tubing.

  6. Design, fabrication, and testing of a getter-based atmosphere purification and waste treatment system for a nitrogen-hydrogen-helium glovebox

    SciTech Connect (OSTI)

    Bibeault, M. L.; Paglieri, S. N.; Tuggle, D. G.; Wermer, J. R.; Nobile Jr, A.

    2008-07-15

    A system containing a combination of getters (Zr-Mn-Fe, SAES St909; and Zr{sub 2}Fe, SAES St198) was used to process the nitrogen-hydrogen-helium atmosphere in a glovebox used for handling metal tritide samples. During routine operations, the glovebox atmosphere is recirculated and hydrogenous impurities (i.e. CQ{sub 4}, Q{sub 2}O, and NQ{sub 3}, where Q =H, D, T) are decomposed (cracked) and removed by Zr-Mn-Fe without absorbing elemental hydrogen isotopes. If the tritium content of the glovebox atmosphere becomes unacceptably high, the getter system can rapidly strip the glovebox atmosphere of all hydrogen isotopes by absorption on the Zr{sub 2}Fe, thus lessening the burden on the facility waste gas treatment system. The getter system was designed for high flowrate ( > 100 1/min), which is achieved by using a honeycomb support for the getter pellets and 1.27-cm diameter tubing throughout the system for reduced pressure drop. The novel getter bed design also includes an integral preheater and copper liner to accommodate swelling of the getter pellets, which occurs during loading with oxygen and carbon impurities. Non-tritium functional tests were conducted to determine the gettering efficiencies at different getter bed temperatures and flowrates by recirculating gas through the system from, a 6-m{sup 3} glovebox containing known concentrations of impurities. (authors)

  7. Cyclic corrosion crack resistance curves of certain vessel steels

    SciTech Connect (OSTI)

    Panasyuk, V.V.; Fedorova, V.A.; Pusyak, S.A.; Ratych, L.V.; Timofeev, L.V.; Zuezdin, Y.I.

    1985-11-01

    Results are presented of investigations of 15Kh2MFA and 15Kh2NMFA steels. In the first stage of the investigations, the cyclic corrosion crack resistance characteristics were determined with limiting values of the various factors: loading frequency, loading cycle stress ratio, temperature and length of service. An intense flow of ionizing radiation may markedly change the mechanical properties in 30-40 years; this acts on the reactor vessel. The experimental data for strength categories KP-45 and KP-90 of both vessel steels lies in a quite narrow band of spread, which provides a basis for representing it by a single generalized curve, presented here. The result of cyclic corrosion crack resistance tests of disk specimens of 15Kh2MFA and 15Kh2NMFA vessel steels in boric acid controlled reactor water solution in distilled water with the addition of KOH to pH 8 was established.

  8. Formulation of cracking catalyst based on zeolite and natural clays

    SciTech Connect (OSTI)

    Aliev, R.R.; Lupina, M.I.

    1995-11-01

    Domestically manufactured cracking catalysts are based on a synthetic amorphous aluminosilicate matrix and Y zeolite. A multistage {open_quotes}gel{close_quotes} technology is used in manufacturing the catalysts. The process includes mixing solutions of sodium silicate and acidic aluminum sulfate, forming, syneresis, and activation of the beaded gel. In the manufacture of bead catalysts, the next steps in the process are washing, drying, and calcining; in the manufacture of microbead catalysts, the next steps are dispersion and formation of a hydrogel slurry, spray-drying, and calcining. The Y zeolite is either introduced into the alumina-silica sol in the stage of forming the beads, or introduced in the dispersion stage. With the aim of developing an active and selective cracking catalyst based on Y zeolite and natural clays, with improved physicomechanical properties, the authors carried out a series of studies, obtaining results that are set forth in the present article.

  9. Upgrading of heavy oils by asphaltenic bottom cracking

    SciTech Connect (OSTI)

    Sudoh, j.; Shiroto, Y.; Fukui, Y.; Takeuchi, C.

    1983-03-01

    Results of the pilot plant study of the conversion of heavy petroleum residues (Khafji VR) to lighter feedstocks deasphalted oil (DAO) by a combination process involving asphaltenic bottom cracking (ABC) and solvent deasphalting (SDA) are reported. In addition to correlations between DAO and asphalt yield under various hydrotreating conditions, a mathematical model describing quantitative relationships between recycle rate of SDA asphalt and ABC in extinction and recycle operations are described. Effects of process variations on product (DAO, asphalt) quality are also discussed.

  10. Method for making dense crack free thin films

    DOE Patents [OSTI]

    Jacobson, Craig P.; Visco, Steven J.; De Jonghe, Lutgard C.

    2007-01-16

    The process described herein provides a simple and cost effective method for making crack free, high density thin ceramic film. The steps involve depositing a layer of a ceramic material on a porous or dense substrate. The deposited layer is compacted and then the resultant laminate is sintered to achieve a higher density than would have been possible without the pre-firing compaction step.

  11. Forced Two-Phase Helium Cooling Scheme for the Mu2e Transport Solenoid

    SciTech Connect (OSTI)

    Tatkowski, G.; Cheban, S.; Dhanaraj, N.; Evbota, D.; Lopes, M.; Nicol, T.; Sanders, R.; Schmitt, R.; Voirin, E.

    2015-01-01

    The Mu2e Transport Solenoid (TS) is an S-shaped magnet formed by two separate but similar magnets, TS-u and TS-d. Each magnet is quarter-toroid shaped with a centerline radius of approximately 3 m utilizing a helium cooling loop consisting of 25 to 27 horizontal-axis rings connected in series. This cooling loop configuration has been deemed adequate for cooling via forced single phase liquid helium; however it presents major challenges to forced two-phase flow such as “garden hose” pressure drop, concerns of flow separation from tube walls, difficulty of calculation, etc. Even with these disadvantages, forced two-phase flow has certain inherent advantages which make it a more attractive option than forced single phase flow. It is for this reason that the use of forced two-phase flow was studied for the TS magnets. This paper will describe the analysis using helium-specific pressure drop correlations, conservative engineering approach, helium properties calculated and updated at over fifty points, and how the results compared with those in literature. Based on the findings, the use of forced-two phase helium is determined to be feasible for steady-state cooling of the TS solenoids

  12. Helium embrittlement model and program plan for weldability of ITER materials

    SciTech Connect (OSTI)

    Louthan, M.R. Jr.; Kanne, W.R. Jr.; Tosten, M.H.; Rankin, D.T.; Cross, B.J.

    1997-02-01

    This report presents a refined model of how helium embrittles irradiated stainless steel during welding. The model was developed based on experimental observations drawn from experience at the Savannah River Site and from an extensive literature search. The model shows how helium content, stress, and temperature interact to produce embrittlement. The model takes into account defect structure, time, and gradients in stress, temperature and composition. The report also proposes an experimental program based on the refined helium embrittlement model. A parametric study of the effect of initial defect density on the resulting helium bubble distribution and weldability of tritium aged material is proposed to demonstrate the roll that defects play in embrittlement. This study should include samples charged using vastly different aging times to obtain equivalent helium contents. Additionally, studies to establish the minimal sample thickness and size are needed for extrapolation to real structural materials. The results of these studies should provide a technical basis for the use of tritium aged materials to predict the weldability of irradiated structures. Use of tritium charged and aged material would provide a cost effective approach to developing weld repair techniques for ITER components.

  13. Elucidation of fundamental properties of helium in metals by nuclear magnetic resonance techniques

    SciTech Connect (OSTI)

    Abell, G.C.

    1990-01-01

    The nuclear magnetic resonance (NMR) properties of very high density {sup 3}He in metals are discussed in the context of the corresponding properties in relatively high density bulk {sup 3}He. In particular, the effects of the {sup 3}He diffusion on the contribution of the {sup 3}He-{sup 3}He dipolar interaction to the lineshape and to the spin-lattice relaxation parameter (T{sub 1}) are described. It is shown that the temperature dependence of the lineshape and of T{sub 1} are independent sources of information about helium density and also about helium diffusivity. Moreover, T{sub 1} is shown to be a sensitive indicator of melting transitions in bulk {sup 3}He. Palladium tritide is presented as a model system for NMR studies of {sup 3}He in metals. Experimental NMR studies of this system reveal behavior analogous to what has been observed for bulk helium. Evidence for a {sup 3}He phase transition near 250 K is provided by the temperature dependence of T{sub 1}. Assuming this to be a melting transition, a density is obtained from the bulk helium EOS that is in good agreement with theory and with swelling measurements on related metal tritides. {sup 3}He NMR measurements have also provided information about the density distribution, helium diffusivity, and mean bubble size in palladium tritide. 22 refs., 8 figs.

  14. Helium release and microstructural changes in Er(D,T)2-x3Hex films).

    SciTech Connect (OSTI)

    Gelles, D. S.; Browning, James Frederick; Snow, Clark Sheldon; Banks, James Clifford; Mangan, Michael A.; Rodriguez, Mark Andrew; Brewer, Luke N.; Kotula, Paul Gabriel

    2007-12-01

    Er(D,T){sub 2-x} {sup 3}He{sub x}, erbium di-tritide, films of thicknesses 500 nm, 400 nm, 300 nm, 200 nm, and 100 nm were grown and analyzed by Transmission Electron Microscopy, X-Ray Diffraction, and Ion Beam Analysis to determine variations in film microstructure as a function of film thickness and age, due to the time-dependent build-up of {sup 3}He in the film from the radioactive decay of tritium. Several interesting features were observed: One, the amount of helium released as a function of film thickness is relatively constant. This suggests that the helium is being released only from the near surface region and that the helium is not diffusing to the surface from the bulk of the film. Two, lenticular helium bubbles are observed as a result of the radioactive decay of tritium into {sup 3}He. These bubbles grow along the [111] crystallographic direction. Three, a helium bubble free zone, or 'denuded zone' is observed near the surface. The size of this region is independent of film thickness. Four, an analysis of secondary diffraction spots in the Transmission Electron Microscopy study indicate that small erbium oxide precipitates, 5-10 nm in size, exist throughout the film. Further, all of the films had large erbium oxide inclusions, in many cases these inclusions span the depth of the film.

  15. Crack growth monitoring in harsh environments by electrical potential measurements

    SciTech Connect (OSTI)

    W. R. Lloyd; W. G. Reuter; D. M. Weinberg

    1999-09-19

    Electric potential measurement (EPM) technology offers an attractive alternative to conventional nondestructive evaluation (NDE) for monitoring crack growth in harsh environments. Where conventional NDE methods typically require localized human interaction, the EPM technique developed at the Idaho National Engineering and Environmental Laboratory (INEEL) can be operated remotely and automatically. Once a crack-like defect is discovered via conventional means, EPM can be applied to monitor local crack size changes. This is of particular interest in situations where an identified structural defect is not immediately rejectable from a fitness-for-service viewpoint, but due to operational and environmental conditions may grow to an unsafe size with continuing operation. If the location is in a harsh environment where periodic monitoring by normal means is either too costly or not possible, a very expensive repair may be immediately mandated. However, the proposed EPM methodology may offer a unique monitoring capability that would allow for continuing service. INEEL has developed this methodology, supporting equipment, and calibration information to apply EPM in a field environment for just this purpose. Laboratory and pilot scale tests on full-size engineering structures (pressure vessels and piping) have been successfully performed. The technique is applicable to many severe environments because the sensitive equipment (electronics, operators) can be situated in a remote location, with only current and voltage probe electrical leads entering into the harsh environment. Experimental results showing the utility of the methodology are presented, and unique application concepts that have been examined by multiple experiments are discussed.

  16. Crack stability analysis of low alloy steel primary coolant pipe

    SciTech Connect (OSTI)

    Tanaka, T.; Kameyama, M.; Urabe, Y.

    1997-04-01

    At present, cast duplex stainless steel has been used for the primary coolant piping of PWRs in Japan and joints of dissimilar material have been applied for welding to reactor vessels and steam generators. For the primary coolant piping of the next APWR plants, application of low alloy steel that results in designing main loops with the same material is being studied. It means that there is no need to weld low alloy steel with stainless steel and that makes it possible to reduce the welding length. Attenuation of Ultra Sonic Wave Intensity is lower for low alloy steel than for stainless steel and they have advantageous inspection characteristics. In addition to that, the thermal expansion rate is smaller for low alloy steel than for stainless steel. In consideration of the above features of low alloy steel, the overall reliability of primary coolant piping is expected to be improved. Therefore, for the evaluation of crack stability of low alloy steel piping to be applied for primary loops, elastic-plastic future mechanics analysis was performed by means of a three-dimensioned FEM. The evaluation results for the low alloy steel pipings show that cracks will not grow into unstable fractures under maximum design load conditions, even when such a circumferential crack is assumed to be 6 times the size of the wall thickness.

  17. Crack Growth Monitoring in Harsh Environments by Electric Potential Measurements

    SciTech Connect (OSTI)

    Lloyd, Wilson Randolph; Reuter, Walter Graham; Weinberg, David Michael

    1999-09-01

    Electric potential measurement (EPM) technology offers an attractive alternative to conventional nondestructive evaluation (NDE) for monitoring crack growth in harsh environments. Where conventional NDE methods typically require localized human interaction, the EPM technique developed at the Idaho National Engineering and Environmental Laboratory (INEEL) can be operated remotely and automatically. Once a crack-like defect is discovered via conventional means, EPM can be applied to monitor local crack size changes. This is of particular interest in situations where an identified structural defect is not immediately rejectable from a fitness-for-service viewpoint, but due to operational and environmental conditions may grow to an unsafe size with continuing operation. If the location is in a harsh environment where periodic monitoring by normal means is either too costly or not possible, a very expensive repair may be immediately mandated. However, the proposed EPM methodology may offer a unique monitoring capability that would allow for continuing service. INEEL has developed this methodology, supporting equipment, and calibration information to apply EPM in a field environment for just this purpose. Laboratory and pilot scale tests on full-size engineering structures (pressure vessels and piping) have been successfully performed. The technique applicable is many severe environments because the sensitive equipment (electronics, operators) can be situated in a remote location, with only current and voltage probe electrical leads entering into the harsh environment. Experimental results showing the utility of the methodology are presented, and unique application concepts that have been examined by multiple experiments are discussed.

  18. Influence of stress intensity and loading mode on intergranular stress corrosion cracking of Alloy 600 in primary waters of pressurized water reactors

    SciTech Connect (OSTI)

    Rebak, R.B.; Szklarska-Smialowska, Z. . Fontana Corrosion Center)

    1994-05-01

    The steam generator in a pressurized water reactor (PWR) of a nuclear power plant consists mainly of a shell made of carbon (C) steel and tubes made of alloy 600 (UNS N06600). However, alloy 600 suffers environmentally induced cracking with exposure to high-temperature primary water. The susceptibility of alloy 600 to integranular stress corrosion cracking (IGSCC) was investigated as a function of the level of applied stresses and mode of loading. Constant load tests were conducted with specimens prepared from thin wall tubes, and constant deformation tests were conducted using specimens prepared from plates. With tubes exposed to primary water at 330 C, the crack propagation rate (CPR) was found to increase from 1 [times] 10[sup [minus]11] m/s at a stress intensity (K[sub i]) of 10 MPa[radical]m to 1 [times] 10[sup [minus]9] at K[sub i] = 60 MPa[radical]m. CPR obtained using compact specimens prepared from plates were 1 order of magnitude lower than values measured in tubes at the same temperature and in the same solution at each stress intensity. The corollary was that values of crack propagation and threshold stress intensities obtained using compact specimens could not be extrapolated to the behavior of thin wall tubes.

  19. Commissioning of helium compression system for the 12 GeV refrigerator

    SciTech Connect (OSTI)

    Knudsen, Peter N.; Ganni, Venkatarao; Dixon, Kelly D.; Norton, Robert O.; Creel, Jonathan D.; Arenius, Dana M.

    2014-01-01

    The compressor system used for the Jefferson Lab (JLab) 12 GeV upgrade, also known as the CHL-2 compressor system, incorporates many design changes to the typical compressor skid design to improve the efficiency, reliability and maintainability from previous systems. These include a considerably smaller bulk oil separator design that does not use coalescing elements/media, automated control of cooling oil injection based on the helium discharge temperature, a helium after-cooler design that is designed for and promotes coalescing of residual oil and a variable speed bearing oil pump to reduce oil bypass. The CHL-2 helium compression system has five compressors configured with four pressure levels that supports the three pressure levels in the cold box. This paper will briefly review several of these improvements and discuss some of the recent commissioning results.

  20. Ab initio study of formation, migration and binding properties of helium-vacancy clusters in aluminum

    SciTech Connect (OSTI)

    Yang, Li; Zu, Xiaotao T.; Gao, Fei

    2008-08-01

    Ab initio calculations based on density functional theory have been performed to study the dissolution and migration of helium, and the stability of small helium-vacancy clusters HenVm (n, m=0 to 4) in aluminum. The results indicate that the octahedral configuration is more stable than the tetrahedral. Interstitial helium atoms are predicted to have attractive interactions and jump between two octahedral sites via an intermediate tetrahedral site with low migration energy of 0.10 eV. The binding energies of an interstitial He atom and an isolated vacancy to a HenVm cluster are also obtained from the calculated formation energies of the clusters. We find that the divacancy and tri--vacancy clusters are not stable, but He atoms can increase the stability of vacancy clusters. The interactions of He atoms with a vacancy are found to be in good agreement with the experimental results.

  1. STAC -- a new Swedish code for statistical analysis of cracks in SG-tubes

    SciTech Connect (OSTI)

    Poern, K.

    1997-02-01

    Steam generator (SG) tubes in pressurized water reactor plants are exposed to various types of degradation processes, among which stress corrosion cracking in particular has been observed. To be able to evaluate the safety importance of such cracking of SG-tubes one has to have a good and empirically founded knowledge about the scope and the size of the cracks as well as the rate of their continuous growth. The basis of experience is to a large extent constituted of the annually performed SG-inspections and crack sizing procedures. On the basis of this experience one can estimate the distribution of existing crack lengths, and modify this distribution with regard to maintenance (plugging) and the predicted rate of crack propagation. Finally, one can calculate the rupture probability of SG-tubes as a function of a given critical crack length. On account of the Swedish Nuclear Power Inspectorate an introductory study has been performed in order to get a survey of what has been done elsewhere in this field. The study resulted in a proposal of a computerizable model to be able to estimate the distribution of true cracks, to modify this distribution due to the crack growth and to compute the probability of tube rupture. The model has now been implemented in a compute code, called STAC (STatistical Analysis of Cracks). This paper is aimed to give a brief outline of the model to facilitate the understanding of the possibilities and limitations associated with the model.

  2. Stress Corrosion Cracking and Non-Destructive Examination of Dissimilar Metal Welds and Alloy 600

    SciTech Connect (OSTI)

    Jackson, Deborah A.

    2002-07-01

    The United States Nuclear Regulatory Commission (USNRC) has conducted research since 1977 in the areas of environmentally assisted cracking and assessment and reliability of non-destructive examination (NDE). Recent occurrences of cracking in Alloy 82/182 welds and Alloy 600 base metal at several domestic and overseas plants have raised several issues relating to both of these areas of NRC research. The occurrences of cracking were identified by the discovery of boric acid deposits resulting from through-wall cracking in the primary system pressure boundary. Analyses indicate that the cracking has occurred due to primary water stress corrosion cracking (PWSCC) in Alloy 82/182 welds. This cracking has occurred in two different locations: in hot leg nozzle-to-safe end welds and in control rod drive mechanism (CRDM) nozzle welds. The cracking associated with safe-end welds is important due to the potential for a large loss of reactor coolant inventory, and the cracking of CRDM nozzle base metal and welds, particularly circumferential cracking of CRDM nozzle base metal, is important due to the potential for a control rod to eject resulting in a loss of coolant accident. The industry response in the U.S. to this cracking is being coordinated through the Electric Power Research Institute's Materials Reliability Project (EPRI-MRP) in a comprehensive, multifaceted effort. Although the industry program is addressing many of the issues raised by these cracking occurrences, confirmatory research is necessary for the staff to evaluate the work conducted by industry groups. Several issues requiring additional consideration regarding the generic implications of these isolated events have been identified. This paper will discuss the recent events of significant cracking in domestic and foreign plants, discuss the limitations of NDE in detecting SCC, identify deficiencies in information available in this area, discuss the USNRC approach to address these issues, and discuss the

  3. Molecular-dynamics analysis of mobile helium cluster reactions near surfaces of plasma-exposed tungsten

    SciTech Connect (OSTI)

    Hu, Lin; Maroudas, Dimitrios; Hammond, Karl D.; Wirth, Brian D.

    2015-10-28

    We report the results of a systematic atomic-scale analysis of the reactions of small mobile helium clusters (He{sub n}, 4 ≤ n ≤ 7) near low-Miller-index tungsten (W) surfaces, aiming at a fundamental understanding of the near-surface dynamics of helium-carrying species in plasma-exposed tungsten. These small mobile helium clusters are attracted to the surface and migrate to the surface by Fickian diffusion and drift due to the thermodynamic driving force for surface segregation. As the clusters migrate toward the surface, trap mutation (TM) and cluster dissociation reactions are activated at rates higher than in the bulk. TM produces W adatoms and immobile complexes of helium clusters surrounding W vacancies located within the lattice planes at a short distance from the surface. These reactions are identified and characterized in detail based on the analysis of a large number of molecular-dynamics trajectories for each such mobile cluster near W(100), W(110), and W(111) surfaces. TM is found to be the dominant cluster reaction for all cluster and surface combinations, except for the He{sub 4} and He{sub 5} clusters near W(100) where cluster partial dissociation following TM dominates. We find that there exists a critical cluster size, n = 4 near W(100) and W(111) and n = 5 near W(110), beyond which the formation of multiple W adatoms and vacancies in the TM reactions is observed. The identified cluster reactions are responsible for important structural, morphological, and compositional features in the plasma-exposed tungsten, including surface adatom populations, near-surface immobile helium-vacancy complexes, and retained helium content, which are expected to influence the amount of hydrogen re-cycling and tritium retention in fusion tokamaks.

  4. Ultrasonic Flaw Detection of Cracks and Machined Flaws as Observed Through Austenitic Stainless Steel Piping Welds

    SciTech Connect (OSTI)

    Anderson, Michael T.; Cinson, Anthony D.; Crawford, Susan L.; Cumblidge, Stephen E.; Diaz, Aaron A.

    2009-07-01

    Piping welds in the pressure boundary of light water reactors (LWRs) are subject to a volumetric examination based on Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code. Due to access limitations and high background radiation levels, the technique used is primarily ultrasonic rather than radiographic. Many of the austenitic welds in safety-related piping systems provide limited access to both sides of the weld, so a far-side examination is necessary. Historically, far-side inspections have performed poorly because of the coarse and elongated grains that make up the microstructures of austenitic weldments. The large grains cause the ultrasound to be scattered, attenuated, and redirected. Additionally, grain boundaries or weld geometry may reflect coherent ultrasonic echoes, making flaw detection and discrimination a more challenging endeavor. Previous studies conducted at the Pacific Northwest National Laboratory (PNNL) on ultrasonic far-side examinations in austenitic piping welds involved the application of conventional transducers, use of low-frequency Synthetic Aperture Focusing Techniques (SAFT), and ultrasonic phased-array (PA) methods on specimens containing implanted thermal fatigue cracks and machined reflectors [1-2]. From these studies, PA inspection provided the best results, detecting nearly all of the flaws from the far side. These results were presented at the Fifth International Conference on NDE in Relation to Structural Integrity for Nuclear and Pressurised Components in 2006. This led to an invitation to examine field-removed specimens containing service-induced intergranular stress corrosion cracks (IGSCC) at the Electric Power Research Institute’s (EPRI) Nondestructive Evaluation (NDE) Center, in Charlotte, North Carolina. Results from this activity are presented.

  5. Cryogenic system with GM cryocooler for krypton, xenon separation from hydrogen-helium purge gas

    SciTech Connect (OSTI)

    Chu, X. X.; Zhang, D. X.; Qian, Y.; Liu, W.; Zhang, M. M.; Xu, D.

    2014-01-29

    In the thorium molten salt reactor (TMSR), fission products such as krypton, xenon and tritium will be produced continuously in the process of nuclear fission reaction. A cryogenic system with a two stage GM cryocooler was designed to separate Kr, Xe, and H{sub 2} from helium purge gas. The temperatures of two stage heat exchanger condensation tanks were maintained at about 38 K and 4.5 K, respectively. The main fluid parameters of heat transfer were confirmed, and the structural heat exchanger equipment and cold box were designed. Designed concentrations after cryogenic separation of Kr, Xe and H{sub 2} in helium recycle gas are less than 1 ppb.

  6. Effect of helium growth and carbon impurities on the properties of aged metal tritides

    SciTech Connect (OSTI)

    McConville, G.T.; Menke, D.A.; West, D.; Woods, C.M.

    1995-10-01

    The interaction of tritium with metals is made complex by two phenomena. The beta decay in the metal produces {sup 3}He. The helium moves to form bubbles. We shall show that the growth of the bubbles produces a two stage swelling of the metal coming first from the appearance of the helium and second from the relaxation of the lattice disorder caused by the bubble growth. The second phenomenon is the steady state ion and free radical concentration in the tritium over gas which interacts with impurities on the metal surface. We shall show that the reaction rates are much faster than for normal hydrogen cleaning. 12 refs., 7 figs., 3 tabs.

  7. SPHERICALLY SYMMETRIC NLTE MODEL ATMOSPHERES OF HOT HYDROGEN-HELIUM FIRST STARS

    SciTech Connect (OSTI)

    Kubat, Jiri

    2012-12-15

    We present results of our calculations of NLTE model stellar atmospheres for hot Population III stars composed of hydrogen and helium. We use our own computer code for the calculation of spherically symmetric NLTE model atmospheres in hydrostatic and radiative equilibrium. The model atmospheres are then used for the calculation of emergent fluxes. These fluxes serve to evaluate the flow of high-energy photons for energies higher than ionization energies of hydrogen and helium, the so-called ionizing photon fluxes. We also present the time evolution of the ionizing photon fluxes.

  8. Application of JLab 12GeV helium refrigeration system for the FRIB accelerator at MSU

    SciTech Connect (OSTI)

    Ganni, Venkatarao; Knudsen, Peter N.; Arenius, Dana M.; Casagrande, Fabio

    2014-01-01

    The planned approach to have a turnkey helium refrigeration system for the MSU-FRIB accelerator system, encompassing the design, fabrication, installation and commissioning of the 4.5-K refrigerator cold box(es), cold compression system, warm compression system, gas management, oil removal and utility/ancillary systems, was found to be cost prohibitive. Following JLab’s suggestion, MSU-FRIB accelerator management made a formal request to evaluate the applicability of the recently designed 12GeV JLab cryogenic system for this application. The following paper will outline the findings and the planned approach for the FRIB helium refrigeration system.

  9. Application of JLab 12GeV helium refrigeration system for the FRIB accelerator at MSU

    SciTech Connect (OSTI)

    Ganni, V.; Knudsen, P.; Arenius, D.; Casagrande, F.

    2014-01-29

    The planned approach to have a turnkey helium refrigeration system for the MSU-FRIB accelerator system, encompassing the design, fabrication, installation and commissioning of the 4.5-K refrigerator cold box(es), cold compression system, warm compression system, gas management, oil removal and utility/ancillary systems, was found to be cost prohibitive. Following JLab’s suggestion, MSU-FRIB accelerator management made a formal request to evaluate the applicability of the recently designed 12GeV JLab cryogenic system for this application. The following paper will outline the findings and the planned approach for the FRIB helium refrigeration system.

  10. Mechanism of Irradiation Assisted Cracking of Core Components in Light Water Reactors

    SciTech Connect (OSTI)

    Gary S. Was; Michael Atzmon; Lumin Wang

    2003-04-28

    The overall goal of the project is to determine the mechanism of irradiation assisted stress corrosion cracking (IASCC). IASCC has been linked to hardening, microstructural and microchemical changes during irradiation. Unfortunately, all of these changes occur simultaneously and at similar rates during irradiation, making attribution of IASCC to any one of these features nearly impossible to determine. The strategy set forth in this project is to develop means to separate microstructural from microchemical changes to evaluate each separately for their effect on IASCC. In the first part, post irradiation annealing (PIA) treatments are used to anneal the irradiated microstructure, leaving only radiation induced segregation (RIS) for evaluation for its contribution to IASCC. The second part of the strategy is to use low temperature irradiation to produce a radiation damage dislocation loop microstructure without radiation induced segregation in order to evaluate the effect of the dislocation microstructure alone. A radiation annealing model was developed based on the elimination of dislocation loops by vacancy absorption. Results showed that there were indeed, time-temperature annealing combinations that leave the radiation induced segregation profile largely unaltered while the dislocation microstructure is significantly reduced. Proton irradiation of 304 stainless steel irradiated with 3.2 MeV protons to 1.0 or 2.5 dpa resulted in grain boundary depletion of chromium and enrichment of nickel and a radiation damaged microstructure. Post irradiation annealing at temperatures of 500 ? 600C for times of up to 45 min. removed the dislocation microstructure to a greater degree with increasing temperatures, or times at temperature, while leaving the radiation induced segregation profile relatively unaltered. Constant extension rate tensile (CERT) experiments in 288C water containing 2 ppm O2 and with a conductivity of 0.2 mS/cm and at a strain rate of 3 x 10-7 s-1 showed

  11. Effects of helium implantation on the tensile properties and microstructure of Ni??P?? metallic glass nanostructures

    SciTech Connect (OSTI)

    Liontas, Rachel; Gu, X. Wendy; Fu, Engang; Wang, Yongqiang; Li, Nan; Mara, Nathan; Greer, Julia R.

    2014-09-10

    We report fabrication and nanomechanical tension experiments on as-fabricated and helium-implanted ~130 nm diameter Ni??P?? metallic glass nano-cylinders. The nano-cylinders were fabricated by a templated electroplating process and implanted with He? at energies of 50, 100, 150, and 200 keV to create a uniform helium concentration of ~3 at. % throughout the nano-cylinders. Transmission electron microscopy (TEM) imaging and through-focus analysis reveal that the specimens contained ~2 nm helium bubbles distributed uniformly throughout the nano-cylinder volume. In-situ tensile experiments indicate that helium-implanted specimens exhibit enhanced ductility as evidenced by a 2-fold increase in plastic strain over as-fabricated specimens, with no sacrifice in yield and ultimate tensile strengths. This improvement in mechanical properties suggests that metallic glasses may actually exhibit a favorable response to high levels of helium implantation.

  12. Effects of helium implantation on the tensile properties and microstructure of Ni₇₃P₂₇ metallic glass nanostructures

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Liontas, Rachel; Gu, X. Wendy; Fu, Engang; Wang, Yongqiang; Li, Nan; Mara, Nathan; Greer, Julia R.

    2014-09-10

    We report fabrication and nanomechanical tension experiments on as-fabricated and helium-implanted ~130 nm diameter Ni₇₃P₂₇ metallic glass nano-cylinders. The nano-cylinders were fabricated by a templated electroplating process and implanted with He⁺ at energies of 50, 100, 150, and 200 keV to create a uniform helium concentration of ~3 at. % throughout the nano-cylinders. Transmission electron microscopy (TEM) imaging and through-focus analysis reveal that the specimens contained ~2 nm helium bubbles distributed uniformly throughout the nano-cylinder volume. In-situ tensile experiments indicate that helium-implanted specimens exhibit enhanced ductility as evidenced by a 2-fold increase in plastic strain over as-fabricated specimens, with nomore » sacrifice in yield and ultimate tensile strengths. This improvement in mechanical properties suggests that metallic glasses may actually exhibit a favorable response to high levels of helium implantation.« less

  13. Stress corrosion cracking of Alloys 600 and 182 in BWR environments

    SciTech Connect (OSTI)

    Ljungberg, L.G.; Hofling, C.G.; Sahlberg, A.; Moeller, J. )

    1992-05-01

    Wrought Alloy 600 and weldments of Alloy 182 are being tested for initiation and propagation of intergranular stress corrosion cracking (IGSCC). Crack initiation is tested on compact tension (CT) specimens with U-notches of various radii under enhanced crevice conditions, in a test loop in a Swedish BWR. After one year exposure there was initiation of IGSCC in a large portion of the Alloy 182 specimens, but nearly no initiation in Alloy 600. Crack propagation was measured in a laboratory loop on CT specimens under constant or cyclic load. Low carbon Alloy 600, or Alloy 182 high in titanium and niobium versus carbon, cracked at lower rates than material with high carbon activity. Materials with low concentrations of phosphorus and sulfur cracked slower than those high in these elements in clean environment, but no such effect was found in environment with sulfate. Alloy 182 weld metal generally cracked at higher rates than Alloy 600.

  14. Stress corrosion cracking of Alloys 600 and 182 in BWR environments. Interim report

    SciTech Connect (OSTI)

    Ljungberg, L.G.; Hofling, C.G.; Sahlberg, A.; Moeller, J.

    1992-05-01

    Wrought Alloy 600 and weldments of Alloy 182 are being tested for initiation and propagation of intergranular stress corrosion cracking (IGSCC). Crack initiation is tested on compact tension (CT) specimens with U-notches of various radii under enhanced crevice conditions, in a test loop in a Swedish BWR. After one year exposure there was initiation of IGSCC in a large portion of the Alloy 182 specimens, but nearly no initiation in Alloy 600. Crack propagation was measured in a laboratory loop on CT specimens under constant or cyclic load. Low carbon Alloy 600, or Alloy 182 high in titanium and niobium versus carbon, cracked at lower rates than material with high carbon activity. Materials with low concentrations of phosphorus and sulfur cracked slower than those high in these elements in clean environment, but no such effect was found in environment with sulfate. Alloy 182 weld metal generally cracked at higher rates than Alloy 600.

  15. Deep-Burn Modular Helium Reactor Fuel Development Plan

    SciTech Connect (OSTI)

    McEachern, D

    2002-12-02

    This document contains the workscope, schedule and cost for the technology development tasks needed to satisfy the fuel and fission product transport Design Data Needs (DDNs) for the Gas Turbine-Modular Helium Reactor (GT-MHR), operating in its role of transmuting transuranic (TRU) nuclides in spent fuel discharged from commercial light-water reactors (LWRs). In its application for transmutation, the GT-MHR is referred to as the Deep-Burn MHR (DB-MHR). This Fuel Development Plan (FDP) describes part of the overall program being undertaken by the U.S. Department of Energy (DOE), utilities, and industry to evaluate the use of the GT-MHR to transmute transuranic nuclides from spent nuclear fuel. The Fuel Development Plan (FDP) includes the work on fuel necessary to support the design and licensing of the DB-MHR. The FDP is organized into ten sections. Section 1 provides a summary of the most important features of the plan, including cost and schedule information. Section 2 describes the DB-MHR concept, the features of its fuel and the plan to develop coated particle fuel for transmutation. Section 3 describes the knowledge base for fabrication of coated particles, the experience with irradiation performance of coated particle fuels, the database for fission product transport in HTGR cores, and describes test data and calculations for the performance of coated particle fuel while in a repository. Section 4 presents the fuel performance requirements in terms of as-manufactured quality and performance of the fuel coatings under irradiation and accident conditions. These requirements are provisional because the design of the DB-MHR is in an early stage. However, the requirements are presented in this preliminary form to guide the initial work on the fuel development. Section 4 also presents limits on the irradiation conditions to which the coated particle fuel can be subjected for the core design. These limits are based on past irradiation experience. Section 5 describes

  16. Dependence of dynamic fracture resistance on crack velocity in tungsten: Pt. 1. Single crystals

    SciTech Connect (OSTI)

    Liv, J.M.; Shen, B.W.

    1984-06-01

    The dependence of dynamic fracture resistance on crack propagation velocity on (100) in tungsten has been examined. A correlation is obtained between the measured local crack velocity with the surfac and subsurface deformations. Based on the experimental results on one pass, two passes, and prestrained, electron beam zone refined single crystals, a discussion is given on the slip modes activated at the crack tip, the contributions to the dynamic fracture resistance from dislocations and surface features and from the preexisting deformed microstructure.

  17. On the approximation of crack shapes found during inservice inspection

    SciTech Connect (OSTI)

    Bhate, S.R.; Chawla, D.S.; Kushwaha, H.S.

    1997-04-01

    This paper addresses the characterization of axial internal flaw found during inservice inspection of a pipe. J-integral distribution for various flaw shapes is obtained using line spring finite, element method. The peak J-value and its distribution across the crack is found to be characteristic feature of each shape. The triangular shape yields peak J-value away from the center, the point of depth. The elliptic approximation results in large overestimate of J-value for unsymmetric flaws. Triangular approximation is recommended for such flaws so that further service can be obtained from the component.

  18. Sulfide stress-cracking resistance of nitrogen-strengthened stainless steels

    SciTech Connect (OSTI)

    Gaugh, R.R.

    1982-03-01

    A description is given of sulfide stress-cracking tests performed on a number of these alloys. Most were found to be somewhat susceptible to cracking, depending on the stress level. It was determined that this was due to their high manganese content. The mechanism responsible for cracking was not firmly established. One commercial nitrogen-strengthened stainless steel, XM19, was highly resistant to sulfide stress cracking despite a manganese content of 5%. This difference is attributed to the superior corrosion resistance of the alloy. 6 refs.

  19. Stress corrosion cracking of Alloy 600 using the constant strain rate test

    SciTech Connect (OSTI)

    Bulischeck, T.S.; Van Rooyen, D.

    1981-10-01

    Nuclear grade production tubing of Alloy 600 was evaluated for stress corrosion cracking (SCC) susceptibility in high purity water at 365, 345, 325, and 290 C. Reverse tube U-bend specimens provided crack initiation data and constant extension rate tests were employed to determine the crack velocities experienced in th crack propagation stage. Initial results indicate that a linear extrapolation of data received from high temperature tests can be used to predict the service life of steam generator tubing that has been plastically deformed or is continually deforming by ''denting.''

  20. J-integral for a semi-elliptical surface crack at a bimaterial interface

    SciTech Connect (OSTI)

    Sharobeam, M.H.; Landes, J.D.

    1995-12-31

    Surface cracks are common defects in welded, bonded, and composite structures. The elastic-plastic fracture of these defects may be analyzed using the J-integral. The authors have recently developed a new approach to evaluate the J-integral for semi-elliptical surface cracks in panels made of homogeneous materials and subject to remote tension. This approach, which is based on load separation, allows the evaluation of J for such a three-dimensional geometry using a single specimen test record. It is analogous to the single specimen technique in two-dimensional geometries. In this article, the authors extend their study to surface cracks at bimaterial interfaces. A three-dimensional finite element model is developed to model such a crack. The J-integral is evaluated along the crack front using the virtual crack extension method. The elastic-plastic fracture behavior of the crack is studied. Load separation is also examined and the new single specimen approach for surface cracks in single material panels is extended to those at bimaterial interfaces. The study also includes a comparison between the results of surface cracks in single material panels and those at bimaterial interfaces.

  1. Effects of weld residual stresses on crack-opening area analysis of pipes for LBB applications

    SciTech Connect (OSTI)

    Dong, P.; Rahman, S.; Wilkowski, G.

    1997-04-01

    This paper summarizes four different studies undertaken to evaluate the effects of weld residual stresses on the crack-opening behavior of a circumferential through-wall crack in the center of a girth weld. The effect of weld residual stress on the crack-opening-area and leak-rate analyses of a pipe is not well understood. There are no simple analyses to account for these effects, and, therefore, they are frequently neglected. The four studies involved the following efforts: (1) Full-field thermoplastic finite element residual stress analyses of a crack in the center of a girth weld, (2) A comparison of the crack-opening displacements from a full-field thermoplastic residual stress analysis with a crack-face pressure elastic stress analysis to determine the residual stress effects on the crack-opening displacement, (3) The effects of hydrostatic testing on the residual stresses and the resulting crack-opening displacement, and (4) The effect of residual stresses on crack-opening displacement with different normal operating stresses.

  2. Ordinary SQUID interferometers and superfluid helium matter wave interferometers: The role of quantum fluctuations

    SciTech Connect (OSTI)

    Golovashkin, A. I.; Zherikhina, L. N. Tskhovrebov, A. M.; Izmailov, G. N.; Ozolin, V. V.

    2010-08-15

    When comparing the operation of a superfluid helium matter wave quantum interferometer (He SQUID) with that of an ordinary direct-current quantum interferometer (dc SQUID), we estimate their resolution limitation that correspond to quantum fluctuations. An alternative mode of operation of the interferometer as a unified macroquantum system is considered.

  3. RECONCILING THE GALACTIC BULGE TURNOFF AGE DISCREPANCY WITH ENHANCED HELIUM ENRICHMENT

    SciTech Connect (OSTI)

    Nataf, David M.; Gould, Andrew P.

    2012-06-01

    We show that the factor {approx}2 discrepancy between spectroscopic and photometric age determinations of the Galactic bulge main-sequence turnoff can be naturally explained by positing an elevated helium enrichment for the bulge relative to that assumed by standard isochrones. Helium enhancement relative to standard isochrones is confirmed at the 2.3{sigma} level. We obtain an upper bound on the helium enrichment for the metal-rich ([Fe/H] Almost-Equal-To +0.30) stars of {Delta}Y Almost-Equal-To +0.11 relative to canonical expectations, given the requirement that the spectroscopic and photometric ages be consistent and the limiting condition of instantaneous star formation. We discuss phenomenological evidence that the bulge may have had a chemical evolution that is distinct from the solar neighborhood in this manner, and we make several testable predictions. Should this emerging picture of the bulge as helium-enhanced hold, it will require the development of new isochrones, new model atmospheres, and modified analysis and cosmological interpretation of the integrated light of other bulges and elliptical galaxies.

  4. Helium, Iron and Electron Particle Transport and Energy Transport Studies on the TFTR Tokamak

    DOE R&D Accomplishments [OSTI]

    Synakowski, E. J.; Efthimion, P. C.; Rewoldt, G.; Stratton, B. C.; Tang, W. M.; Grek, B.; Hill, K. W.; Hulse, R. A.; Johnson, D .W.; Mansfield, D. K.; McCune, D.; Mikkelsen, D. R.; Park, H. K.; Ramsey, A. T.; Redi, M. H.; Scott, S. D.; Taylor, G.; Timberlake, J.; Zarnstorff, M. C. (Princeton Univ., NJ (United States). Plasma Physics Lab.); Kissick, M. W. (Wisconsin Univ., Madison, WI (United States))

    1993-03-01

    Results from helium, iron, and electron transport on TFTR in L-mode and Supershot deuterium plasmas with the same toroidal field, plasma current, and neutral beam heating power are presented. They are compared to results from thermal transport analysis based on power balance. Particle diffusivities and thermal conductivities are radially hollow and larger than neoclassical values, except possibly near the magnetic axis. The ion channel dominates over the electron channel in both particle and thermal diffusion. A peaked helium profile, supported by inward convection that is stronger than predicted by neoclassical theory, is measured in the Supershot The helium profile shape is consistent with predictions from quasilinear electrostatic drift-wave theory. While the perturbative particle diffusion coefficients of all three species are similar in the Supershot, differences are found in the L-Mode. Quasilinear theory calculations of the ratios of impurity diffusivities are in good accord with measurements. Theory estimates indicate that the ion heat flux should be larger than the electron heat flux, consistent with power balance analysis. However, theoretical values of the ratio of the ion to electron heat flux can be more than a factor of three larger than experimental values. A correlation between helium diffusion and ion thermal transport is observed and has favorable implications for sustained ignition of a tokamak fusion reactor.

  5. Non-local thermodynamic equilibrium effects on isentropic coefficient in argon and helium thermal plasmas

    SciTech Connect (OSTI)

    Sharma, Rohit; Singh, Kuldip

    2014-03-15

    In the present work, two cases of thermal plasma have been considered; the ground state plasma in which all the atoms and ions are assumed to be in the ground state and the excited state plasma in which atoms and ions are distributed over various possible excited states. The variation of Z?, frozen isentropic coefficient and the isentropic coefficient with degree of ionization and non-equilibrium parameter ?(= T{sub e}/T{sub h}) has been investigated for the ground and excited state helium and argon plasmas at pressures 1?atm, 10?atm, and 100?atm in the temperature range from 6000?K to 60?000?K. For a given value of non-equilibrium parameter, the relationship of Z? with degree of ionization does not show any dependence on electronically excited states in helium plasma whereas in case of argon plasma this dependence is not appreciable till degree of ionization approaches 2. The minima of frozen isentropic coefficient shifts toward lower temperature with increase of non-equilibrium parameter for both the helium and argon plasmas. The lowering of non-equilibrium parameter decreases the frozen isentropic coefficient more emphatically in helium plasma at high pressures in comparison to argon plasma. The increase of pressure slightly reduces the ionization range over which isentropic coefficient almost remains constant and it does not affect appreciably the dependence of isentropic coefficient on non-equilibrium parameter.

  6. Statistical Properties of Inter-Series Mixing in Helium: From Integrability to Chaos

    SciTech Connect (OSTI)

    Pu''ttner, R.; Gremaud, B.; Delande, D.; Domke, M.; Martins, M.; Schlachter, A. S.; Kaindl, G.

    2001-04-23

    The photoionization spectrum of helium shows considerable complexity close to the double-ionization threshold. By analyzing the results from both our recent experiments and ab initio three- and one-dimensional calculations, we show that the statistical properties of the spacings between neighboring energy levels clearly display a transition towards quantum chaos.

  7. Thermal analysis of a coaxial helium panel of a cryogenic vacuum pump for advanced divertor of DIII-D tokamak

    SciTech Connect (OSTI)

    Baxi, C.B.; Langhorn, A.; Schaubel, K.; Smith, J.

    1991-08-01

    It is planned to install a 50,000 1/s cryogenic pump for particle removal in the D3-D tokamak. A critical component of this cryogenic pump will be a helium panel which has to be maintained at a liquid helium temperature. The outer surface area of the helium panel has an area of 1 m{sup 2} and consists of a 2.5 cm diameter, 10 m long tube. From design considerations, a coaxial geometry is preferable since it requires a minimum number of welds. However, the coaxial geometry also results in a counter flow heat exchanger arrangement, where the outgoing warm fluid will exchange heat with incoming cold fluid. This is of concern since the helium panel must be cooled from liquid nitrogen temperature to liquid helium temperature in less than 5 minutes for successful operation of the cryogenic pump. In order to analyze the thermal performance of the coaxial helium panel, a finite difference computer model of the geometry was prepared. The governing equations took into account axial as well as radial conduction through the tube walls. The variation of thermal properties was modeled. The results of the analysis showed that although the coaxial geometry behaves like a counter flow heat exchanger, within the operating range of the cryogenic pump a rapid cooldown of the helium panel from liquid nitrogen temperature to the operating temperature is feasible. A prototypical experiment was also performed at General Atomics (GA) which verified the concept and the analysis. 4 refs., 8 figs.

  8. Apparatus and method for prevention of cracking in welded brittle alloys

    DOE Patents [OSTI]

    Kronberg, James W.; Younkins, Robert M.

    2000-01-01

    An apparatus and method for reducing cracking in a heated material as the material cools. The apparatus includes a variable frequency electric signal generator that is coupled to a transducer. The transducer produces a variable frequency acoustic signal in response to the variable frequency electric signal, which is applied to the heated material to reduce cracking as the material cools.

  9. Laser Peening of Alloy 600 to Improve Intergranular Stress Corrosion Cracking Resistance in Power Plants

    SciTech Connect (OSTI)

    Chen, H; Rankin, J; Hackel, L; Frederick, G; Hickling, J; Findlan, S

    2004-04-20

    Laser peening is an emerging modern process that impresses a compressive stress into the surface of metals or alloys. This treatment can reduce the rate of intergranular stress corrosion cracking and fatigue cracking in structural metals or Alloy 600 needed for nuclear power plants.

  10. Key results for the NRC`s Short Cracks in Piping and Piping Welds Research Program

    SciTech Connect (OSTI)

    Wilkowski, G.; Krishnaswamy, P.; Brust, F.

    1995-04-01

    The overall objective of the Short Cracks in Piping and Piping Welds Program is to verify and improve engineering analyses to predict the fracture behavior of circumferentially cracked pipe under quasi-static loading with particular attention to crack lengths typically used in LBB or flaw evaluation criteria. The USNCRC program at Battelle was initiated in March 1990 and is scheduled to be completed in December 1994. This paper discusses key results from the overall program with particular emphasis on the efforts since the last WRSIM meeting. The program consists of eight technical tasks as listed below: task 1 short through-wall-cracked (TWC) pipe evaluations; task 2 short surface-cracked (SC) pipe evaluations; task 3 bi-metallic weld crack evaluations; task 4 dynamic strain aging and crack instabilities; task 5 fracture evaluations of anisotropic pipe; task 6 crack-opening-area evaluations; task 7 NRCPIPE code improvements; task 8 additional efforts. Task 8 is a collection of new efforts initiated during the coarse of the program. A list of the full-scale pipe experiments in this program is given in Table 1. All of the experiments have been completed. The most recent accomplishments in each of the tasks listed above are discussed below. The details of all the results in the eight tasks are published in the semiannual reports as well as topical reports from the program.

  11. Weld solidification cracking in cast Ni[sub 3]Al alloys

    SciTech Connect (OSTI)

    Santella, M.L. )

    1993-06-01

    Most of the cast Ni[sub 3]Al alloys currently under study have marginal resistance to solidification cracking, and therefore, they have poor weldability. Crack-free welds can be made on the alloys only with difficulty, and with poor reproducibility. Based on metallographic analysis of solidification cracks in welds of one such alloy, identified as IC221M, modest composition modifications were made to the base alloy to improve solidification-cracking resistance. The tensile properties and fabricability of the modified alloy, IC221W to denote improved weldability, were evaluated and found to be comparable to those of the base alloy and used to weld plates of cast IC221M. A crack-free weldment was obtained, which had good tensile properties up to 900 C.

  12. Stress corrosion crack detection in alloy 600 in high temperature caustic. Master`s thesis

    SciTech Connect (OSTI)

    Brisson, B.W.

    1996-06-01

    Alloy 600, the material used for pressurized water reactor steam generator tubing, is susceptible to environmentally assisted stress corrosion cracking. Intergranular stress corrosion cracking (IGSCC) attacks the tubes in areas of high residual stress, and in crevice regions. No method has been successfully developed to monitor steam generator tubing in-situ for crack initiation and growth. Essentially all available published IGSCC crack growth data for alloy 600 is based on non-tubing material. Although it is very likely that the current data base is applicable to tubing processing, differences between tube and other geometries make a comparison between tubing and other data important for verification purposes. However, obtaining crack initiation and growth data from tubing is difficult due to the geometry and the thin wall thickness.

  13. Fundamental understanding and life prediction of stress corrosion cracking in BWRs and energy systems

    SciTech Connect (OSTI)

    Andresen, P.L.; Ford, F.P.

    1998-03-01

    The objective of this paper is to present an approach for design and lifetime evaluation of environmental cracking based on experimental and fundamental modeling of the underlying processes operative in crack advance. In detailed this approach and its development and quantification for energy (hot water) systems, the requirements for a life prediction methodology will be highlighted and the shortcomings of the existing design and lifetime evaluation codes reviewed. Examples are identified of its use in a variety of cracking systems, such as stainless steels, low alloy steels, nickel base alloys, and irradiation assisted stress corrosion cracking in boiling water reactor (BWR) water, as well as preliminary use for low alloy steel and Alloy 600 in pressurized water reactors (PWRs) and turbine steels in steam turbines. Identification of the common aspects with environmental cracking in other hot water systems provides a secure basis for its extension to related energy systems. 166 refs., 49 figs.

  14. About the mechanism of stress corrosion cracking of Alloy 600 in high temperature water

    SciTech Connect (OSTI)

    Rebak, R.B.; Szklarska-Smialowska, Z.

    1995-12-31

    Alloy 600 is a material commonly used to construct the tubing in the steam generators (SG) of pressurized light water reactors (PWR) and of CANDU heavy water reactors. It is well established which variables and to which extent they influence the crack growth rate (CGR) in Alloy 600 exposed to high temperature (deaerated) water (HTW), especially in very aggressive conditions. There is evidence that the same variables that influence CGR also control the crack induction time. However, there are only a few data on crack induction time and no detailed explanation of the events that lead to the nucleation of a crack on an apparent smooth tube surface. In this paper, a critical review of the mechanisms of stress corrosion cracking (SCC) is given and, an interpretation of the events occurring during the long ({approx} 15 y) induction times observed in plant is postulated.

  15. Critical analysis of alloy 600 stress corrosion cracking mechanisms in primary water

    SciTech Connect (OSTI)

    Rios, R. |; Noel, D.; Bouvier, O. de; Magnin, T.

    1995-04-01

    In order to study the mechanisms involved in the stress-corrosion cracking (SCC) of Alloy 600 in primary water, the influence of the relevance of physicochemical and metallurgical parameters was assessed: hydrogen and oxygen overpressures, microstructure, and local chemical composition. The obtained results show that, even if the dissolution/oxidation seems to be the first and necessary step responsible for crack initiation and if hydrogen effects can also be involved in cracking, neither a dissolution/oxidation model nor a hydrogen model appears sufficient to account for cracking. Moreover, fractographic examinations performed on specimens` fracture surfaces lead to the fact that attention should be paid to a cleavage like microcracking mechanism involving interactions between corrosion and plasticity at the vicinity of grain boundaries. A corrosion-enhanced plasticity model is proposed to describe the intergranular and transgranular cracking in Alloy 600.

  16. Repair welding of fusion reactor components. Second year technical report

    SciTech Connect (OSTI)

    Chin, B.A.

    1993-05-15

    Experiments have shown that irradiated Type 316 stainless steel is susceptible to heat-affected-zone (HAZ) cracking upon cooling when welded using the gas tungsten arc (GTA) process under lateral constraint. The cracking has been hypothesized to be caused by stress-assisted helium bubble growth and rupture at grain boundaries. This study utilized an experimental welding setup which enabled different compressive stresses to be applied to the plates during welding. Autogenous GTA welds were produced in Type 316 stainless steel doped with 256 appm helium. The application of a compressive stress, 55 MPa, during welding suppressed the previously observed catastrophic cracking. Detailed examinations conducted after welding showed a dramatic change in helium bubble morphology. Grain boundary bubble growth along directions parallel to the weld was suppressed. Results suggest that stress-modified welding techniques may be used to suppress or eliminate helium-induced cracking during joining of irradiated materials.

  17. Repair welding of fusion reactor components

    SciTech Connect (OSTI)

    Chin, B.A.

    1993-05-15

    Experiments have shown that irradiated Type 316 stainless steel is susceptible to heat-affected-zone (HAZ) cracking upon cooling when welded using the gas tungsten arc (GTA) process under lateral constraint. The cracking has been hypothesized to be caused by stress-assisted helium bubble growth and rupture at grain boundaries. This study utilized an experimental welding setup which enabled different compressive stresses to be applied to the plates during welding. Autogenous GTA welds were produced in Type 316 stainless steel doped with 256 appm helium. The application of a compressive stress, 55 MPa, during welding suppressed the previously observed catastrophic cracking. Detailed examinations conducted after welding showed a dramatic change in helium bubble morphology. Grain boundary bubble growth along directions parallel to the weld was suppressed. Results suggest that stress-modified welding techniques may be used to suppress or eliminate helium-induced cracking during joining of irradiated materials.

  18. WARM BREEZE FROM THE STARBOARD BOW: A NEW POPULATION OF NEUTRAL HELIUM IN THE HELIOSPHERE

    SciTech Connect (OSTI)

    Kubiak, M. A.; Bzowski, M.; Sokół, J. M.; Swaczyna, P.; Grzedzielski, S.; Alexashov, D. B.; Izmodenov, V. V.; Möbius, E.; Leonard, T.; Fuselier, S. A.; McComas, D. J.; Wurz, P.

    2014-08-01

    We investigate the signals from neutral helium atoms observed in situ from Earth orbit in 2010 by the Interstellar Boundary Explorer (IBEX). The full helium signal observed during the 2010 observation season can be explained as a superposition of pristine neutral interstellar He gas and an additional population of neutral helium that we call the Warm Breeze. The Warm Breeze is approximately 2 times slower and 2.5 times warmer than the primary interstellar He population, and its density in front of the heliosphere is ∼7% that of the neutral interstellar helium. The inflow direction of the Warm Breeze differs by ∼19° from the inflow direction of interstellar gas. The Warm Breeze seems to be a long-term, perhaps permanent feature of the heliospheric environment. It has not been detected earlier because it is strongly ionized inside the heliosphere. This effect brings it below the threshold of detection via pickup ion and heliospheric backscatter glow observations, as well as by the direct sampling of GAS/Ulysses. We discuss possible sources for the Warm Breeze, including (1) the secondary population of interstellar helium, created via charge exchange and perhaps elastic scattering of neutral interstellar He atoms on interstellar He{sup +} ions in the outer heliosheath, or (2) a gust of interstellar He originating from a hypothetic wave train in the Local Interstellar Cloud. A secondary population is expected from models, but the characteristics of the Warm Breeze do not fully conform to modeling results. If, nevertheless, this is the explanation, IBEX-Lo observations of the Warm Breeze provide key insights into the physical state of plasma in the outer heliosheath. If the second hypothesis is true, the source is likely to be located within a few thousand AU from the Sun, which is the propagation range of possible gusts of interstellar neutral helium with the Warm Breeze characteristics against dissipation via elastic scattering in the Local Cloud. Whatever the

  19. Stress Corrosion Cracking Issues in Light Metals for Automotive Applications

    SciTech Connect (OSTI)

    Jones, Russell H.; Danielson, Michael J.; Baer, Donald R.; Windisch, Charles F.; Vetrano, John S.; Edwards, Daniel J.

    2000-12-31

    The Partnership for New Generation Vehicle has the goal of producing lightweight automobiles that achieve 80 mpg. To accomplish this will require liberal use of Al and Mg alloys such as AA5083 and AZ91D. The corrosion and stress corrosion of alloy AA5083 is controlled by the precipitation of the b-phase (Al3Mg2) at grain boundaries and by the precipitation of the g-phase (Mg17Al12) in AZ91D. The b-phase is anodic to the Al matrix while the g-phase is cathodic to the Mg matrix. The effects of crack propagation along grain boundaries with electrochemically active particles is a key factor in the SCC performance of these materials.

  20. Benefits of hydroprocessing pressure on fluid catalytic cracking performance

    SciTech Connect (OSTI)

    Reid, T.A.; Asim, M.Y.; Keyworth, D.A.; Wiseman, S.L.

    1995-09-01

    Hydroprocessing provides a higher quality feed for the fluid catalytic cracking unit. As refiners face deteriorating crude quality and stricter environmental constraints for transportation fuels, hydroprocessing of the FCCU feed becomes more attractive. The benefits of high pressure operation of FCC pretreaters have been poorly defined. Proper selection of the hydroprocessing pressure, hydroprocessing catalyst and operating philosophy can result in increased profits relative to non-optimal operation. This paper first discusses the benefit resulting from FCC feed pretreatment and specifically evaluates for the first time the benefits of hydrogen partial pressure for FCC pretreatment at low, moderate and high pressures at two temperatures. Once the refiner has chosen pretreatment, further optimization of hydroprocessing unit operation and FCCU operation is illustrated.

  1. CRACK GROWTH ANALYSIS OF SOLID OXIDE FUEL CELL ELECTROLYTES

    SciTech Connect (OSTI)

    S. Bandopadhyay; N. Nagabhushana

    2003-10-01

    Defects and Flaws control the structural and functional property of ceramics. In determining the reliability and lifetime of ceramics structures it is very important to quantify the crack growth behavior of the ceramics. In addition, because of the high variability of the strength and the relatively low toughness of ceramics, a statistical design approach is necessary. The statistical nature of the strength of ceramics is currently well recognized, and is usually accounted for by utilizing Weibull or similar statistical distributions. Design tools such as CARES using a combination of strength measurements, stress analysis, and statistics are available and reasonably well developed. These design codes also incorporate material data such as elastic constants as well as flaw distributions and time-dependent properties. The fast fracture reliability for ceramics is often different from their time-dependent reliability. Further confounding the design complexity, the time-dependent reliability varies with the environment/temperature/stress combination. Therefore, it becomes important to be able to accurately determine the behavior of ceramics under simulated application conditions to provide a better prediction of the lifetime and reliability for a given component. In the present study, Yttria stabilized Zirconia (YSZ) of 9.6 mol% Yttria composition was procured in the form of tubes of length 100 mm. The composition is of interest as tubular electrolytes for Solid Oxide Fuel Cells. Rings cut from the tubes were characterized for microstructure, phase stability, mechanical strength (Weibull modulus) and fracture mechanisms. The strength at operating condition of SOFCs (1000 C) decreased to 95 MPa as compared to room temperature strength of 230 MPa. However, the Weibull modulus remains relatively unchanged. Slow crack growth (SCG) parameter, n = 17 evaluated at room temperature in air was representative of well studied brittle materials. Based on the results, further work

  2. Nonlinear ultrasonic assessment of stress corrosion cracking damage in sensitized 304 stainless steel

    SciTech Connect (OSTI)

    Morlock, Florian Jacobs, Laurence J. Kim, Jin-Yeon; Singh, Preet; Wall, James J.

    2015-03-31

    This research uses nonlinear Rayleigh surface waves to characterize stress corrosion cracking (SCC) damage in welded 304 Stainless Steel (304 SS). 304 SS is widely used in reactor pressure vessels, where a corrosive environment in combination with applied stress due to high internal pressures can cause SCC. Welds and the nearby heat affected zones (HAZ) in the vessel material are especially sensitive to SCC damage. SCC damage results in microstructural changes such as dislocation formation and microcrack initiation that in the long term lead to reduced structural integrity and material failure. Therefore, the early detection of SCC is crucial to ensure safe operation. It has been shown that the microstructural changes caused by SCC can generate higher harmonic waves when excited harmonically. This research considers different levels of SCC damage induced in samples of welded 304 SS by applying stress to a specimen held in a corrosive medium (Sodium Thiosulfate). A nonlinear Rayleigh surface wave is introduced in the material and the fundamental and the second harmonic waves are measured using wedge detection. The nonlinearity parameter that relates the fundamental and the second harmonic amplitudes, is computed to quantify the SCC damage in each sample. These results are used to demonstrate the feasibility of using nonlinear Rayleigh waves to characterize SCC damage.

  3. Field and laboratory investigations of coring-induced damage in core recovered from Marker Bed 139 at the waste isolation pilot plant underground facility

    SciTech Connect (OSTI)

    Holcomb, D.J.; Zeuch, D.H.; Morin, K.; Hardy, R.; Tormey, T.V.

    1995-09-01

    A combined laboratory and field investigation was carried out to determine the extent of coring-induced damage done to samples cored from Marker Bed 139 at the WIPP site. Coring-induced damage, if present, has the potential to significantly change the properties of the material used for laboratory testing relative to the in situ material properties, resulting in misleading conclusions. In particular, connected, crack-like damage could make the permeability of cored samples orders of magnitude greater than the in situ permeabilities. Our approach compared in situ velocity and resistivity measurements with laboratory measurements of the same properties. Differences between in situ and laboratory results could be attributed to differences in the porosity due to cracks. The question of the origin of the changes could not be answered directly from the results of the measurements. Pre-existing cracks, held closed by the in situ stress, could open when the core was cut free, or new cracks could be generated by coring-induced damage. We used core from closely spaced boreholes at three orientations (0{degree}, {plus_minus}45{degrees} relative to vertical) to address the origin of cracks. The absolute orientation of pre-existing cracks would be constant, independent of the borehole orientation. In contrast, cracks induced by coring were expected to show an orientation dependent on that of the source borehole.

  4. The effect of helium from tritium decay on the gas-solid equilibrium constant for La-Ni-Al tritides

    SciTech Connect (OSTI)

    Walters, R.T.

    1988-01-01

    Change in the equilibrium vapor pressure over LaNi/sub 4.25/ Al/sub 0.75/ tritide with helium in-growth has been observed for helium concentrations up to 10,000 appm. The change is a decrease in pressure from about 500 torr to 90 torr at 80/degree/C. This decrease is believed to be associated with a crystal lattice expansion due to helium, and is similar to the plateau pressure decrease as function of aluminum concentration for the family of LaNi/sub 5-x/Al/sub x/ alloys with O < x < 1. Subsequent tritium cycling recovers the plateau pressure. These data suggest that helium has very short range diffusion for the time of these observations. 18 refs., 4 figs., 2 tabs.

  5. Stress-corrosion crack initiation process for Alloy 182 weld metal in simulated BWR environments

    SciTech Connect (OSTI)

    Nakayama, Guen; Akashi, Masatsune

    1995-09-01

    For preventing SCC from occurring in the internal structure of materials of the BWR plant, the injection of hydrogen into the core-water so as to reduce the free corrosion potential of the materials were proposed. Because of the lack of basic data of stress-corrosion cracking susceptibility in BWR environment on Ni-based alloys in comparison with stainless steels, the slow strain-rate tensile (SSRT) tests and the creviced bent-beam (CBB) test were conducted for a sensitized Alloy 182 weld metal in high-purity water environments containing dissolved oxygen (DO) and hydrogen (DH) to varied concentrations at 288 C, and the SCC initiation process were examined. The susceptibility of a material to SCC was discussed in terms of the electrode potential effect, and the effects of impurities of the testing water were examined by adding slightly Na{sub 2}, SO{sub 4}. In high purity waters and in the electrode potential region higher than {minus} 0.2 V vs. SHE, the interdendritic stress-corrosion cracks were observed both in the slow strain-rate test and the creviced bent-beam test. SEM observations of sub-cracks at the specimen surfaces revealed that stress-corrosion cracks were initiated when the oxide film had cracked to under-hundred {micro}m wide, that no such individual cracks could grow per se, but that those micro-cracks which happened to be formed in each other`s vicinity would coalesce into large cracks, one of which made propagated as stress-corrosion cracking, and that the stress-corrosion cracking sensitivity became more acute on addition of impurity. In the electrode potential region lower than 0 V, on the other hand, the stress-corrosion cracks were observed to be initiated at bottoms of corrosion pits formed on the specimen surfaces in the former, whereas both type of stress-corrosion cracks were observed between 0 to {minus}0.2V. No stress-corrosion crack was observed even though much the same corrosion pits in the CBB test at {minus}0.4 V.

  6. Supply and Demand of Helium-3| U.S. DOE Office of Science (SC)

    Office of Science (SC) Website

    Supply and Demand of Helium-3 Nuclear Physics (NP) NP Home About Research Facilities Science Highlights Benefits of NP Funding Opportunities Nuclear Science Advisory Committee (NSAC) Community Resources Contact Information Nuclear Physics U.S. Department of Energy SC-26/Germantown Building 1000 Independence Ave., SW Washington, DC 20585 P: (301) 903-3613 F: (301) 903-3833 E: Email Us More Information » Isotope Development & Production for Research and Applications (IDPRA) Supply and Demand

  7. The role of correlation in the ground state energy of confined helium atom

    SciTech Connect (OSTI)

    Aquino, N.

    2014-01-14

    We analyze the ground state energy of helium atom confined by spherical impenetrable walls, and the role of the correlation energy in the total energy. The confinement of an atom in a cavity is one way in which we can model the effect of the external pressure on an atom. The calculations of energy of the system are carried out by the variational method. We find that the correlation energy remains almost constant for a range values of size of the boxes analyzed.

  8. Final Technical Report for the Neutron Detection without Helium-3 Project

    SciTech Connect (OSTI)

    Ely, James H.; Bliss, Mary; Kouzes, Richard T.; Lintereur, Azaree T.; Robinson, Sean M.; Siciliano, Edward R.; Swinhoe, Martyn T.; Woodring, Mitchell L.

    2013-11-01

    This report details the results of the research and development work accomplished for the ‘Neutron Detection without Helium-3’ project conducted during the 2011-2013 fiscal years. The primary focus of the project was to investigate commercially available technologies that might be used in safeguards applications in the relatively near term. Other technologies that are being developed may be more applicable in the future, but were outside the scope of this study.

  9. Modeling and Simulation Optimization and Feasibility Studies for the Neutron Detection without Helium-3 Project

    SciTech Connect (OSTI)

    Ely, James H.; Siciliano, Edward R.; Swinhoe, Martyn T.; Lintereur, Azaree T.

    2013-01-01

    This report details the results of the modeling and simulation work accomplished for the ‘Neutron Detection without Helium-3’ project during the 2011 and 2012 fiscal years. The primary focus of the project is to investigate commercially available technologies that might be used in safeguards applications in the relatively near term. Other technologies that are being developed may be more applicable in the future, but are outside the scope of this study.

  10. Double, Double Toil and Trouble: Tungsten Burns and Helium Bubbles | U.S.

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    DOE Office of Science (SC) Double, Double Toil and Trouble: Tungsten Burns and Helium Bubbles Advanced Scientific Computing Research (ASCR) ASCR Home About Research Facilities Science Highlights Benefits of ASCR Funding Opportunities Advanced Scientific Computing Advisory Committee (ASCAC) Community Resources Contact Information Advanced Scientific Computing Research U.S. Department of Energy SC-21/Germantown Building 1000 Independence Ave., SW Washington, DC 20585 P: (301) 903-7486 F: (301)

  11. Radiation and gas conduction heat transport across a helium dewer multilayer insulation system

    SciTech Connect (OSTI)

    Green, M.A.

    1995-02-01

    This report describes a method for calculating mixed heat transfer through the multilayer insulation used to insulated a 4K liquid helium cryostat. The method described permits one to estimate the insulation potential for a multilayer insulation system from first principles. The heat transfer regimes included are: radiation, conduction by free molecule gas conduction, and conduction through continuum gas conduction. Heat transfer in the transition region between the two gas conduction regimes is also included.

  12. A Study of Thermocurrent Induced Magnetic Fields in ILC Cavities

    SciTech Connect (OSTI)

    Crawford, Anthony C.; Cooley, Victoria

    2014-03-31

    The case of axisymmetric ILC type cavities with titanium helium vessels is investigated. A first order estimate for magnetic field within the SRF current layer is presented. The induced magnetic field is found to be not more than 1.4x10-8 Tesla = 0.14 milligauss for the case of axial symmetry. Magnetic fields due to symmetry breaking effects are discussed.

  13. Investigation of helium ion production in constricted direct current plasma ion source with layered-glows

    SciTech Connect (OSTI)

    Lee, Yuna; Chung, Kyoung-Jae; Park, Yeong-Shin; Hwang, Y. S.; Center for Advance Research in Fusion Reactor Engineering, Seoul National University, Seoul 151-744

    2014-02-15

    Generation of helium ions is experimentally investigated with a constricted direct current (DC) plasma ion source operated at layered-glow mode, in which electrons could be accelerated through multiple potential structures so as to generate helium ions including He{sup 2+} by successive ionization collisions in front of an extraction aperture. The helium discharge is sustained with the formation of a couple of stable layers and the plasma ball with high density is created near the extraction aperture at the operational pressure down to 0.6 Torr with concave cathodes. The ion beam current extracted with an extraction voltage of 5 kV is observed to be proportional to the discharge current and inversely proportional to the operating pressure, showing high current density of 130 mA/cm{sup 2} and power density of 0.52 mA/cm{sup 2}/W. He{sup 2+} ions, which were predicted to be able to exist due to multiple-layer potential structure, are not observed. Simple calculation on production of He{sup 2+} ions inside the plasma ball reveals that reduced operating pressure and increased cathode area will help to generate He{sup 2+} ions with the layered-glow DC discharge.

  14. Improvements of fuel failure detection in boiling water reactors using helium measurements

    SciTech Connect (OSTI)

    Larsson, I.; Sihver, L.; Grundin, A.; Helmersson, J. O.

    2012-07-01

    To certify a continuous and safe operation of a boiling water reactor, careful surveillance of fuel integrity is of high importance. The detection of fuel failures can be performed by off-line gamma spectroscopy of off-gas samples and/or by on-line nuclide specific monitoring of gamma emitting noble gases. To establish the location of a leaking fuel rod, power suppression testing can be used. The accuracy of power suppression testing is dependent on the information of the delay time and the spreading of the released fission gases through the systems before reaching the sampling point. This paper presents a method to improve the accuracy of power suppression testing by determining the delay time and gas spreading profile. To estimate the delay time and examine the spreading of the gas in case of a fuel failure, helium was injected in the feed water system at Forsmark 3 nuclear power plant. The measurements were performed by using a helium detector system based on a mass spectrometer installed in the off-gas system. The helium detection system and the results of the experiment are presented in this paper. (authors)

  15. Benchmarking density functionals for hydrogen-helium mixtures with quantum Monte Carlo: Energetics, pressures, and forces

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Clay, Raymond C.; Holzmann, Markus; Ceperley, David M.; Morales, Maguel A.

    2016-01-19

    An accurate understanding of the phase diagram of dense hydrogen and helium mixtures is a crucial component in the construction of accurate models of Jupiter, Saturn, and Jovian extrasolar planets. Though DFT based rst principles methods have the potential to provide the accuracy and computational e ciency required for this task, recent benchmarking in hydrogen has shown that achieving this accuracy requires a judicious choice of functional, and a quanti cation of the errors introduced. In this work, we present a quantum Monte Carlo based benchmarking study of a wide range of density functionals for use in hydrogen-helium mixtures atmore » thermodynamic conditions relevant for Jovian planets. Not only do we continue our program of benchmarking energetics and pressures, but we deploy QMC based force estimators and use them to gain insights into how well the local liquid structure is captured by di erent density functionals. We nd that TPSS, BLYP and vdW-DF are the most accurate functionals by most metrics, and that the enthalpy, energy, and pressure errors are very well behaved as a function of helium concentration. Beyond this, we highlight and analyze the major error trends and relative di erences exhibited by the major classes of functionals, and estimate the magnitudes of these e ects when possible.« less

  16. Coupling a Supercritical Carbon Dioxide Brayton Cycle to a Helium-Cooled Reactor.

    SciTech Connect (OSTI)

    Middleton, Bobby; Pasch, James Jay; Kruizenga, Alan Michael; Walker, Matthew

    2016-01-01

    This report outlines the thermodynamics of a supercritical carbon dioxide (sCO2) recompression closed Brayton cycle (RCBC) coupled to a Helium-cooled nuclear reactor. The baseline reactor design for the study is the AREVA High Temperature Gas-Cooled Reactor (HTGR). Using the AREVA HTGR nominal operating parameters, an initial thermodynamic study was performed using Sandia's deterministic RCBC analysis program. Utilizing the output of the RCBC thermodynamic analysis, preliminary values of reactor power and of Helium flow rate through the reactor were calculated in Sandia's HelCO2 code. Some research regarding materials requirements was then conducted to determine aspects of corrosion related to both Helium and to sCO2 , as well as some mechanical considerations for pressures and temperatures that will be seen by the piping and other components. This analysis resulted in a list of materials-related research items that need to be conducted in the future. A short assessment of dry heat rejection advantages of sCO2> Brayton cycles was also included. This assessment lists some items that should be investigated in the future to better understand how sCO2 Brayton cycles and nuclear can maximally contribute to optimizing the water efficiency of carbon free power generation

  17. Design guidelines for avoiding thermo-acoustic oscillations in helium piping systems

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Gupta, Prabhat Kumar; Rabehl, Roger

    2015-04-02

    Thermo-acoustic oscillations are a commonly observed phenomenon in helium cryogenic systems, especially in tubes connecting hot and cold areas. The open ends of these tubes are connected to the lower temperature (typically at 4.5 K), and the closed ends of these tubes are connected to the high temperature (300 K). Cryogenic instrumentation installations provide ideal conditions for these oscillations to occur due to the steep temperature gradient along the tubing. These oscillations create errors in measurements as well as an undesirable heat load to the system. The work presented here develops engineering guidelines to design oscillation-free helium piping. This workmore » also studies the effect of different piping inserts and shows how the proper geometrical combinations have to be chosen to avoid thermo-acoustic oscillations. The effect of an 80 K intercept is also studied and shows that thermo-oscillations can be dampened by placing the intercept at an appropriate location. As a result, the design of helium piping based on the present work is also verified with the experimental results available in open literature.« less

  18. Comparison between a propane-air combustion front and a helium-air simulated combustion front

    SciTech Connect (OSTI)

    Barraclough, S.

    1983-12-01

    Turbulent combustion experiments were performed in a right cylindrical combustion bomb using a premixed propane-air gaseous fuel. The initial conditions inside the combustion chamber were three psig and room temperature. Prior to spark firing, the turbulence intensity inside the combustion chamber was measured and could be varied over a ten fold range. The effect of initial turbulence intensity on turbulent flame propagation was investigated. Two regimes of turbulent combustion were identified, which is in agreement with a previous investigator's results. One of them, a ''transition regime'' occurs when the turbulence intensity is approximately twice the laminar flame speed. Within the transition regime, the turbulent burning speed is linearly proportional to initial turbulence intensity and independent of laminar flame speed and turbulence length scale. A high pressure helium front was injected into the combustion chamber to simulate the combustion front. Since the helium front is isothermal, hot-wire anemometry can be used to quantify the change in turbulence intensity ahead of the propagating front. The helium front was found to have different characteristics than the combustion front.

  19. Design guidelines for avoiding thermo-acoustic oscillations in helium piping systems

    SciTech Connect (OSTI)

    Gupta, Prabhat Kumar; Rabehl, Roger

    2015-04-02

    Thermo-acoustic oscillations are a commonly observed phenomenon in helium cryogenic systems, especially in tubes connecting hot and cold areas. The open ends of these tubes are connected to the lower temperature (typically at 4.5 K), and the closed ends of these tubes are connected to the high temperature (300 K). Cryogenic instrumentation installations provide ideal conditions for these oscillations to occur due to the steep temperature gradient along the tubing. These oscillations create errors in measurements as well as an undesirable heat load to the system. The work presented here develops engineering guidelines to design oscillation-free helium piping. This work also studies the effect of different piping inserts and shows how the proper geometrical combinations have to be chosen to avoid thermo-acoustic oscillations. The effect of an 80 K intercept is also studied and shows that thermo-oscillations can be dampened by placing the intercept at an appropriate location. As a result, the design of helium piping based on the present work is also verified with the experimental results available in open literature.

  20. Design guidelines for avoiding thermo-acoustic oscillations in helium piping systems

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Gupta, Prabhat Kumar; Rabehl, Roger

    2015-04-02

    Thermo-acoustic oscillations are a commonly observed phenomenon in helium cryogenic systems, especially in tubes connecting hot and cold areas. The open ends of these tubes are connected to the lower temperature (typically at 4.5 K), and the closed ends of these tubes are connected to the high temperature (300 K). Cryogenic instrumentation installations provide ideal conditions for these oscillations to occur due to the steep temperature gradient along the tubing. These oscillations create errors in measurements as well as an undesirable heat load to the system. The work presented here develops engineering guidelines to design oscillation-free helium piping. This workmorealso studies the effect of different piping inserts and shows how the proper geometrical combinations have to be chosen to avoid thermo-acoustic oscillations. The effect of an 80 K intercept is also studied and shows that thermo-oscillations can be dampened by placing the intercept at an appropriate location. As a result, the design of helium piping based on the present work is also verified with the experimental results available in open literature.less

  1. A MEASUREMENT OF THE ADIABATIC COOLING INDEX FOR INTERSTELLAR HELIUM PICKUP IONS IN THE INNER HELIOSPHERE

    SciTech Connect (OSTI)

    Saul, Lukas; Wurz, Peter; Kallenbach, Reinald

    2009-09-20

    Interstellar neutral gas enters the inner heliosphere where it is ionized and becomes the pickup ion population of the solar wind. It is often assumed that this population will subsequently cool adiabatically, like an expanding ideal gas due, to the divergent flow of the solar wind. Here, we report the first independent measure of the effective adiabatic cooling index in the inner heliosphere from SOHO CELIAS measurements of singly charged helium taken during times of perpendicular interplanetary magnetic field. We use a simple adiabatic transport model of interstellar pickup helium ions, valid for the upwind region of the inner heliosphere. The time averaged velocity spectrum of helium pickup ions measured by CELIAS/CTOF is fit to this model with a single free parameter which indicates an effective cooling rate with a power-law index of gamma = 1.35 +- 0.2. While this average is consistent with the 'ideal-gas' assumption of gamma = 1.5, the analysis indicates that such an assumption will not apply in general, and that due to observational constraints further measurements are necessary to constrain the cooling process. Implications are discussed for understanding the transport processes in the inner heliosphere and improving this measurement technique.

  2. A novel scheme to handle highly pulsed loads with a standard helium refrigerator

    SciTech Connect (OSTI)

    Slack, D.S.

    1993-06-30

    Helium refrigerator performance degrades rapidly when it has to handle a varying or pulsed heat load. A novel scheme is presented to handle highly pulsed 4.5 K cryogenic loads with a standard helium refrigerator by isolating it from these pulses. The scheme uses a relatively simple arrangement of control valves, heat exchangers, and a storage dewar. Applications include pulsed tokamak machines such as TPX (Tokamak Physics Experiment) and ITER (International Thermonuclear Experimental Reactor). For example, the TPX (currently in the conceptual design phase in a DoE contract) requires an average 4.5 K refrigerator capacity of about 10 kW; however, pulsed loads caused by eddy current and nuclear heating will exceed 100 kW. The scheme presented here provides a method for handling these pulsed loads. Because of the simple and proven nature of the components involved and the thermodynamic properties of the helium, the system could be implemented for projects such as TPX or ITER with little or no development.

  3. Helium in chirped laser fields as a time-asymmetric atomic switch

    SciTech Connect (OSTI)

    Kaprlov-?nsk, Petra Ruth; Moiseyev, Nimrod

    2014-07-07

    Tuning the laser parameters exceptional points in the spectrum of the dressed laser helium atom are obtained. The weak linearly polarized laser couples the ground state and the doubly excited P-states of helium. We show here that for specific chirped laser pulses that encircle an exceptional point one can get the time-asymmetric phenomenon, where for a negative chirped laser pulse the ground state is transformed into the doubly excited auto-ionization state, while for a positive chirped laser pulse the resonance state is not populated and the neutral helium atoms remains in the ground state as the laser pulse is turned off. Moreover, we show that the results are very sensitive to the closed contour we choose. This time-asymmetric state exchange phenomenon can be considered as a time-asymmetric atomic switch. The optimal time-asymmetric switch is obtained when the closed loop that encircles the exceptional point is large, while for the smallest loops, the time-asymmetric phenomenon does not take place. A systematic way for studying the effect of the chosen closed contour that encircles the exceptional point on the time-asymmetric phenomenon is proposed.

  4. Fracture analysis of axially cracked pressure tube of pressurized heavy water reactor

    SciTech Connect (OSTI)

    Krishnan, S.; Bhasin, V.; Mahajan, S.C.

    1997-04-01

    Three Dimensional (313) finite element elastic plastic fracture analysis was done for through wall axially cracked thin pressure tubes of 220 MWe Indian Pressurized Heavy Water Reactor. The analysis was done for Zr-2 and Zr-2.5Nb pressure tubes operating at 300{degrees}C and subjected to 9.5 Mpa internal pressure. Critical crack length was determined based on tearing instability concept. The analysis included the effect of crack face pressure due to the leaking fluid from tube. This effect was found to be significant for pressure tubes. The available formulae for calculating J (for axially cracked tubes) do not take into account the effect of crack face pressure. 3D finite element analysis also gives insight into variation of J across the thickness of pressure tube. It was observed that J is highest at the mid-surface of tube. The results have been presented in the form of across the thickness average J value and a peak factor on J. Peak factor on J is ratio of J at mid surface to average J value. Crack opening area for different cracked lengths was calculated from finite element results. The fracture assessment of pressure tubes was also done using Central Electricity Generating Board R-6 method. Ductile tearing was considered.

  5. Recent Observation of Hydrogen-Induced Cracking of High-Strength Steels

    SciTech Connect (OSTI)

    McMahon, Jr, C J; Liu, Xinyu; Kameda, Jun; Morgan, Michael J

    2008-09-14

    The present progress report shows that the ultra-high-strength 4340-type steel, even if ideally pure, cannot safely be used for service in a hydrogen environment. Some of the strength must be given up in favor of more toughness, which can be achieved by reducing the carbon content and increasing the nickel content. The 5%NiCrMoV steel with about 0.1% carbon shows promise in this regard, especially in an aqueous environment and in hydrogen at around atmospheric pressure. However, we have not yet achieved a purity level high enough to establish the baseline behavior of an ideally pure version of this steel in high-pressure hydrogen.

  6. Simulations of Failure via Three-Dimensional Cracking in Fuel Cladding for Advanced Nuclear Fuels

    SciTech Connect (OSTI)

    Lu, Hongbing; Bukkapatnam, Satish; Harimkar, Sandip; Singh, Raman; Bardenhagen, Scott

    2014-01-09

    Enhancing performance of fuel cladding and duct alloys is a key means of increasing fuel burnup. This project will address the failure of fuel cladding via three-dimensional cracking models. Researchers will develop a simulation code for the failure of the fuel cladding and validate the code through experiments. The objective is to develop an algorithm to determine the failure of fuel cladding in the form of three-dimensional cracking due to prolonged exposure under varying conditions of pressure, temperature, chemical environment, and irradiation. This project encompasses the following tasks: 1. Simulate 3D crack initiation and growth under instantaneous and/or fatigue loads using a new variant of the material point method (MPM); 2. Simulate debonding of the materials in the crack path using cohesive elements, considering normal and shear traction separation laws; 3. Determine the crack propagation path, considering damage of the materials incorporated in the cohesive elements to allow the energy release rate to be minimized; 4. Simulate the three-dimensional fatigue crack growth as a function of loading histories; 5. Verify the simulation code by comparing results to theoretical and numerical studies available in the literature; 6. Conduct experiments to observe the crack path and surface profile in unused fuel cladding and validate against simulation results; and 7. Expand the adaptive mesh refinement infrastructure parallel processing environment to allow adaptive mesh refinement at the 3D crack fronts and adaptive mesh merging in the wake of cracks. Fuel cladding is made of materials such as stainless steels and ferritic steels with added alloying elements, which increase stability and durability under irradiation. As fuel cladding is subjected to water, chemicals, fission gas, pressure, high temperatures, and irradiation while in service, understanding performance is essential. In the fast fuel used in advanced burner reactors, simulations of the nuclear

  7. Stress corrosion cracking of pressurizer instrumentation nozzles in the French 1300 MWe units

    SciTech Connect (OSTI)

    Alter, D.; Robin, Y.; Pichon, M.; Teissier, A.; Thomeret, B.

    1992-12-31

    The 1300 MWE French PWR pressurizers are equipped with nozzles through which instruments penetrate the pressure vessel. The nozzles are made from forged and bored bars of Inconel 600 mechanically expanded in the pressurizer wall. They are then manually welded with Inconel 182 coated electrodes to the internal stainless steel cladding of the pressuriser. To understand the origin of leaks occurring early in life and to assess the extent of the problem we undertook an analysis of the fabrication conditions. Field investigations were carried out by dye penetrant testing on the nozzle bore. Cracks have been found on 35 percent of the 119 tested penetrations. Destructive examination performed on 3 nozzles showed that the circumferential cracks did not go through the wall thickness. Laboratory investigations of the nozzle pulled from Nogent 1 confirmed that the crack morphology corresponded to that of primary water stress corrosion cracking. No correlation has been found between microstructure of the different heats of Alloy 600 and cracking. Nozzle mock-ups investigations allowed residual stress measurements by X-ray diffraction. Stress corrosion cracking tests, showed that only longitudinal cracks can be through-wall while both longitudinal and circumferential cracks are initiated on the internal surface. As a result, Electricite De France decided to replace the Inconel 600 nozzles by stainless steel ones with austenitic st. st. weld. Furthermore, a full inventory of the Alloy 600 parts contained in the primary circuit has been performed. For each localized parts an assessment of the risk of stress corrosion cracking is under progress by studying material structures, stress level, operating conditions and safety point of view.

  8. Causes and solutions for cracking of coextruded and weld overlay floor tubes in black liquor recovery boilers

    SciTech Connect (OSTI)

    Keiser, J.R.; Taljat, B.; Wang, X.L.

    1998-09-01

    Cracking of coextruded, black liquor recovery boiler floor tubes is both a safety and an economic issue to mill operators. In an effort to determine the cause of the cracking and to identify a solution, extensive studies, described in this and three accompanying papers, are being conducted. In this paper, results of studies to characterize both the cracking and the chemical and thermal environment are reported. Based on the results described in this series of papers, a possible mechanism is presented and means to lessen the likelihood of cracking or to totally avoid cracking of floor tubes are offered.

  9. On the Use of the Polynomial Annihilation Edge Detection for Locating Cracks in Beam-Like Structures

    SciTech Connect (OSTI)

    Saxena, Rishu; Surace, Cecilia; Archibald, Richard K

    2013-01-01

    A crack in a structure causes a discontinuity in the first derivative of the mode shapes: On this basis, a numerical method for detecting discontinuities in smooth piecewise functions and their derivatives, based on a polynomial annihilation technique, has been applied to the problem of crack detection and localisation in beam-like structures for which only post-damage mode shapes are available. Using a finite-element model of a cracked beam, the performance of this methodology has been analysed for different crack depths and increasing amounts of noise. Given the crack position, a procedure to estimate its depth is also proposed and corresponding results shown.

  10. Effect of cold work on the growth rates of stress corrosion cracks in structural materials of nuclear systems

    SciTech Connect (OSTI)

    Magdowski, R.; Speidel, M.O.

    1996-10-01

    The growth rates of stress corrosion cracks in austenitic stainless steels and nickel base alloy 600 exposed to simulated boiling water reactor coolant were measured by fracture mechanics testing techniques. Cold work may increase the crack growth rates up to one hundred times. In both, the annealed condition and the cold worked condition, the stress corrosion crack growth rates are independent of stress intensity over a wide K-range and crack growth rates correlate well with yield strength and hardness. In the annealed condition the fracture path is intergranular, but higher degrees of cold work introduce higher proportions of transgranular stress corrosion cracking.

  11. Technique development for field inspection of cracking in seam welded ducts

    SciTech Connect (OSTI)

    Shell, Eric B.; Benson, Craig; Liljestrom, Greg C.; Shanahan, Stephen

    2014-02-18

    The resistance seam weld interfaces between alloyed and pure titanium are an in service concern due to precipitation of titanium hydride and resulting embrittlement and cracking. Several inspection techniques were developed and evaluated for field use to characterize the damage in the fleet. Electromagnetic, ultrasonic, florescent penetrant, thermographic, and radiographic techniques were considered. The ultrasonic and electromagnetic approaches were both found suitable. However, the electromagnetic approach is more desirable for field inspections, due to consistency and ease of use. The electromagnetic inspection procedure is able to discriminate between precursor damage and through cracking with sufficient sensitivity to small cracks.

  12. 1987 EPRI workshop on mechanisms of primary water intergranular stress corrosion cracking: Proceedings

    SciTech Connect (OSTI)

    Gorman, J.A.; Partridge, M.J.

    1988-09-01

    A meeting on ''Mechanisms of Primary Water IGSCC'' (PWSCC) was organized to give those working in this area an opportunity to share their results, ideas, and plans in regard to investigations of fundamental aspects of the PWSCC phenomenon affecting alloy 600 steam generator tubes. Topics discussed included: (1) General reviews of hydrogen embrittlement and film rupture - anodic dissolution mechanisms of stress corrosion cracking, (2) environmental factors involved in PWSCC, (3) the influence of microstructure on PWSCC, and (4) the influence of stress and plastic strain on PWSCC. A significant portion of the discussions of all of these topics was devoted to the subject of modelling of crack initiation and crack growth.

  13. VEBA-cracking-processes for upgrading heavy oils and refinery residues

    SciTech Connect (OSTI)

    Graeser, U.; Niemann, K.

    1983-03-01

    More than 20 different heavy oils and residues have been processed by the VEBA-Combi-Cracking and VEBA-LQ-Cracking high pressure hydrocracking processes, in a bench scale unit. Conversions up to 99 wt % of to a syncrude, consisting of naphtha middle distillate and vacuum gas oil were obtained. Conversions correlate with space velocity at a given temperature and product pattern depends upon degree of conversion. The VEBA-LQ-Cracking process produces a stable syncrude whereas the products of the VEBA-Combi process are very low in sulfur and nitrogen.

  14. Comparative study of stress corrosion cracking of steam generator tube materials in water at 315 C

    SciTech Connect (OSTI)

    De, P.K.; Ghosal, S.K.

    1981-06-01

    Stress corrosion cracking (SCC) of Type 304 and 304L stainless steels, Inconel 600, Incoloy 800, and Monel 400 has been studied in water at 315 C, with or without 0.6 ppm Pb and 0.05 or 8 ppm O/sub 2/. Under mill annealed, cold worked (25%) and stress relieved (675 C, 1 hour) conditions, Type 304L, Incoloy 800, and Monel 400 were resistant to cracking, whereas highly stressed Inconel 600 cracked intergranularly. Inconel 600, heat treated at 600 C for 24 hours or more following annealing, was resistant to SCC. The effects of microstructural changes on SCC behavior are discussed. 20 refs.

  15. Coolant Sub-Channel and Smeared-Cracking Models in BISON | Department of

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Energy Coolant Sub-Channel and Smeared-Cracking Models in BISON Coolant Sub-Channel and Smeared-Cracking Models in BISON January 29, 2013 - 10:45am Addthis Coolant Sub-Channel and Smeared-Cracking Models in BISON A single-pin coolant sub-channel model was implemented in BISON, the pin-scale simulation code. This enables BISON to compute the heat transfer coefficient and coolant temperature as a function of axial position along the fuel pin (rather than requiring this information to be

  16. Studies on the disbonding initiation of interfacial cracks.

    SciTech Connect (OSTI)

    McAdams, Brian J.; Pearson, Raymond A.

    2005-08-01

    With the continuing trend of decreasing feature sizes in flip-chip assemblies, the reliability tolerance to interfacial flaws is also decreasing. Small-scale disbonds will become more of a concern, pointing to the need for a better understanding of the initiation stage of interfacial delamination. With most accepted adhesion metric methodologies tailored to predict failure under the prior existence of a disbond, the study of the initiation phenomenon is open to development and standardization of new testing procedures. Traditional fracture mechanics approaches are not suitable, as the mathematics assume failure to originate at a disbond or crack tip. Disbond initiation is believed to first occur at free edges and corners, which act as high stress concentration sites and exhibit singular stresses similar to a crack tip, though less severe in intensity. As such, a 'fracture mechanics-like' approach may be employed which defines a material parameter--a critical stress intensity factor (K{sub c})--that can be used to predict when initiation of a disbond at an interface will occur. The factors affecting the adhesion of underfill/polyimide interfaces relevant to flip-chip assemblies were investigated in this study. The study consisted of two distinct parts: a comparison of the initiation and propagation phenomena and a comparison of the relationship between sub-critical and critical initiation of interfacial failure. The initiation of underfill interfacial failure was studied by characterizing failure at a free-edge with a critical stress intensity factor. In comparison with the interfacial fracture toughness testing, it was shown that a good correlation exists between the initiation and propagation of interfacial failures. Such a correlation justifies the continuing use of fracture mechanics to predict the reliability of flip-chip packages. The second aspect of the research involved fatigue testing of tensile butt joint specimens to determine lifetimes at sub

  17. STRESS CORROSION CRACK GROWTH RESPONSE FOR ALLOY 152/52 DISSIMILAR METAL WELDS IN PWR PRIMARY WATER

    SciTech Connect (OSTI)

    Toloczko, Mychailo B.; Olszta, Matthew J.; Overman, Nicole R.; Bruemmer, Stephen M.

    2015-08-15

    As part of ongoing research into primary water stress corrosion cracking (PWSCC) susceptibility of alloy 690 and its welds, SCC tests have been conducted on alloy 152/52 dissimilar metal (DM) welds with cracks positioned with the goal to assess weld dilution and fusion line effects on SCC susceptibility. No increased crack growth rate was found when evaluating a 20% Cr dilution zone in alloy 152M joined to carbon steel (CS) that had not undergone a post-weld heat treatment (PWHT). However, high SCC crack growth rates were observed when the crack reached the fusion line of that material where it propagated both on the fusion line and in the heat affected zone (HAZ) of the carbon steel. Crack surface and crack profile examinations of the specimen revealed that cracking in the weld region was transgranular (TG) with weld grain boundaries not aligned with the geometric crack growth plane of the specimen. The application of a typical pressure vessel PWHT on a second set of alloy 152/52 – carbon steel DM weld specimens was found to eliminate the high SCC susceptibility in the fusion line and carbon steel HAZ regions. PWSCC tests were also performed on alloy 152-304SS DM weld specimens. Constant K crack growth rates did not exceed 5x10-9 mm/s in this material with post-test examinations revealing cracking primarily on the fusion line and slightly into the 304SS HAZ.

  18. Intergranular attack and stress corrosion cracking propagation behavior of alloy 600 in high-temperature caustic solution

    SciTech Connect (OSTI)

    Kawamura, H.; Hirano, H. . Komae Research Lab.)

    1999-06-01

    The effect of stress intensity factors (K) at the intergranular attack and stress corrosion crack (IGA/SCC) tips on the IGA/SCC propagation behavior of steam generator (SG) tubing was studied under accelerated test conditions. Values of K at the IGA/SCC crack tips were calculated using the statically indeterminate model. Based upon analysis of those factors, the double-cantilever beam (DCB) and SG model boiler tests were carried out to evaluate the effect of stress intensity on IGA/SCC crack propagation. K at the crack tips increased with increasing crack length. For a long crack, K decreased with an increasing number of cracks. However, for a short crack, K decreased slightly with an increasing number of cracks. DCB test results showed the IGA/SCC crack velocity of alloy 600 (UNS N06600) increased gradually with increasing K in the range from 15 MPa[radical]m to [approximately]60 MPa[radical]m. This is the range relevant to IGA/SCC crack tips of typical SG tubes under operating conditions of Pressurized-water reactors. Metallographic examination of tubes removed from the SG model boiler, fouled with 10 ppm sodium hydroxide (NaOH), showed IGA/SCC propagation rates were almost constant in the tested range of K.

  19. Influence of Radiation-Induced Voids and Bubbles on Physical Properties of Austenitic Structural Alloys

    SciTech Connect (OSTI)

    Shcherbakov, E. N.; Kozlov, A. V.; Portnykh, I. A.; Balachov, Iouri I.; Garner, Francis A.

    2004-08-01

    Void swelling in austenitic stainless steels induces significant changes in their electrical resistivity and elastic moduli, as demonstrated in this study using a Russian stainless steel irradiated as fuel pin cladding in BN-600. Precipitation induced by irradiation also causes second-order changes in these properties. When cavities are full of helium as expected under some fusion irradiation conditions, additional second-order changes are expected but they will be small enough to exclude from the analysis.

  20. Methodology for extracting local constants from petroleum cracking flows

    DOE Patents [OSTI]

    Chang, Shen-Lin; Lottes, Steven A.; Zhou, Chenn Q.

    2000-01-01

    A methodology provides for the extraction of local chemical kinetic model constants for use in a reacting flow computational fluid dynamics (CFD) computer code with chemical kinetic computations to optimize the operating conditions or design of the system, including retrofit design improvements to existing systems. The coupled CFD and kinetic computer code are used in combination with data obtained from a matrix of experimental tests to extract the kinetic constants. Local fluid dynamic effects are implicitly included in the extracted local kinetic constants for each particular application system to which the methodology is applied. The extracted local kinetic model constants work well over a fairly broad range of operating conditions for specific and complex reaction sets in specific and complex reactor systems. While disclosed in terms of use in a Fluid Catalytic Cracking (FCC) riser, the inventive methodology has application in virtually any reaction set to extract constants for any particular application and reaction set formulation. The methodology includes the step of: (1) selecting the test data sets for various conditions; (2) establishing the general trend of the parametric effect on the measured product yields; (3) calculating product yields for the selected test conditions using coupled computational fluid dynamics and chemical kinetics; (4) adjusting the local kinetic constants to match calculated product yields with experimental data; and (5) validating the determined set of local kinetic constants by comparing the calculated results with experimental data from additional test runs at different operating conditions.

  1. Primary side stress corrosion cracking and remedial measures

    SciTech Connect (OSTI)

    Theus, G.J.

    1986-01-01

    Primary side stress corrosion cracking (SCC) of Alloy 600 stream generator tubing in some recirculating pressurized water reactor steam generators has usually occurred in two locations: at the roll transition and expansion locations within the tube-sheets and at the apex and tangent areas of the tight radius U bends. Occasionally, other highly stressed areas have also suffered primary side SCC: at support plate tube intersections where secondary side denting has occurred and at the steam generator tube transition areas of explosively installed mini-sleeves. Laboratory data and operating performances of Alloy 600 tubing indicate that the factors affecting the susceptibility to this type of SSC, in decreasing order of importance, are high stresses, material microstructures, and operating temperatures. Remedial measures to correct these problems in newer plants include changing design and fabrication procedures, thus avoiding highly stressed areas of tubing, and changing tube manufacturing heat treating requirements, thus improving the microstructures. Alternate tube materials, such as Alloy 800, Monel 400, or austenitic stainless steels, have not suffered this type of failure.

  2. Nucleosynthesis in helium-enriched asymptotic giant branch models: Implications for heavy element enrichment in ω Centauri

    SciTech Connect (OSTI)

    Karakas, Amanda I.; Marino, Anna F.; Nataf, David M.

    2014-03-20

    We investigate the effect of helium enrichment on the evolution and nucleosynthesis of low-mass asymptotic giant branch (AGB) stars of 1.7 M {sub ☉} and 2.36 M {sub ☉} with a metallicity of Z = 0.0006 ([Fe/H] ≈–1.4). We calculate evolutionary sequences with the primordial helium abundance (Y = 0.24) and with helium-enriched compositions (Y = 0.30, 0.35, 0.40). For comparison, we calculate models of the same mass but at a lower metallicity Z = 0.0003 ([Fe/H] ≈–1.8) with Y = 0.24. Post-processing nucleosynthesis calculations are performed on each of the evolutionary sequences to determine the production of elements from hydrogen to bismuth. Elemental surface abundance predictions and stellar yields are presented for each model. The models with enriched helium have shorter main sequence and AGB lifetimes, and they enter the AGB with a more massive hydrogen-exhausted core than the primordial helium model. The main consequences are as follows: (1) low-mass AGB models with enhanced helium will evolve more than twice as fast, giving them the chance to contribute sooner to the chemical evolution of the forming globular clusters, and (2) the stellar yields will be strongly reduced relative to their primordial helium counterparts. An increase of ΔY = 0.10 at a given mass decreases the yields of carbon by up to ≈60% and of fluorine by up to 80%; it also decreases the yields of the s-process elements barium and lanthanum by ≈45%. While the yields of first s-process peak elements strontium, yttrium, and zirconium decrease by up to 50%, the yields of rubidium either do not change or increase.

  3. Infrared spectroscopy of Mg–CO{sub 2} and Al–CO{sub 2} complexes in helium nanodroplets

    SciTech Connect (OSTI)

    Thomas, Brandon J.; Harruff-Miller, Barbara A.; Bunker, Christopher E.; Lewis, William K.

    2015-05-07

    The catalytic reduction of CO{sub 2} to produce hydrocarbon fuels is a topic that has gained significant attention. Development of efficient catalysts is a key enabler to such approaches, and metal-based catalysts have shown promise towards this goal. The development of a fundamental understanding of the interactions between CO{sub 2} molecules and metal atoms is expected to offer insight into the chemistry that occurs at the active site of such catalysts. In the current study, we utilize helium droplet methods to assemble complexes composed of a CO{sub 2} molecule and a Mg or Al atom. High-resolution infrared (IR) spectroscopy and optically selected mass spectrometry are used to probe the structure and binding of the complexes, and the experimental observations are compared with theoretical results determined from ab initio calculations. In both the Mg–CO{sub 2} and Al–CO{sub 2} systems, two IR bands are obtained: one assigned to a linear isomer and the other assigned to a T-shaped isomer. In the case of the Mg–CO{sub 2} complexes, the vibrational frequencies and rotational constants associated with the two isomers are in good agreement with theoretical values. In the case of the Al–CO{sub 2} complexes, the vibrational frequencies agree with theoretical predictions; however, the bands from both structural isomers exhibit significant homogeneous broadening sufficient to completely obscure the rotational structure of the bands. The broadening is consistent with an upper state lifetime of 2.7 ps for the linear isomer and 1.8 ps for the T-shaped isomer. The short lifetime is tentatively attributed to a prompt photo-induced chemical reaction between the CO{sub 2} molecule and the Al atom comprising the complex.

  4. Stress-corrosion cracking of sensitized stainless steel by sulfur-containing compounds

    SciTech Connect (OSTI)

    Isaacs, H.S.; Vyas, B.; Kendig, M.W.

    1981-01-01

    The stress corrosion cracking (SCC) of sensitized Type 304 stainless steel in thiosulfate solutions has been studied using constant extension rate tests. Very low concentrations of about 6.10/sup -7/M Na/sub 2/S/sub 2/O/sub 3/ (0.1ppm) gave cracking. With boric acid added, higher concentrations (1ppm) were required. The SCC was shown to be electrochemically controlled. Below -0.5v/sub SCE/ (-0.75/sub SHE/) no SCC took place; above this potential the rate of SCC increased with potential. An induction period was required before SCC continued above -0.5v if the potential was held at or below this value for extended times. This period was associated with the build up of an aggressive solution of thiosulfate decomposition products within the crack. The cracking process has been considered to be controlled by rupture of a salt layer and not a passivating oxide.

  5. Cracked lifting lug welds on ten-ton UF{sub 6} cylinders

    SciTech Connect (OSTI)

    Dorning, R.E.

    1991-12-31

    Ten-ton, Type 48X, UF{sub 6} cylinders are used at the Portsmouth Gaseous Diffusion Plant to withdraw enriched uranium hexafluoride from the cascade, transfer enriched uranium hexafluoride to customer cylinders, and feed enriched product to the cascade. To accomplish these activities, the cylinders are lifted by cranes and straddle carriers which engage the cylinder lifting lugs. In August of 1988, weld cracks on two lifting lugs were discovered during preparation to lift a cylinder. The cylinder was rejected and tagged out, and an investigating committee formed to determine the cause of cracking and recommend remedial actions. Further investigation revealed the problem may be general to this class of cylinder in this use cycle. This paper discusses the actions taken at the Portsmouth site to deal with the cracked lifting lug weld problem. The actions include inspection activities, interim corrective actions, metallurgical evaluation of cracked welds, weld repairs, and current monitoring/inspection program.

  6. Prediction of crack propagation paths in the unit cell of SOFC stacks

    SciTech Connect (OSTI)

    Joulaee, N.; Makradi, A.; Ahzi, Said; Khaleel, Mohammad A.; Koeppel, Brian J.

    2009-08-01

    Planar Solid Oxide Fuel Cells (SOFC) stacks are multi-material layered systems with different thermo-mechanical properties. Due to their severe thermal loading, these layers have to meet high demands to preserve their mechanical integrity without initiation and propagation of fracture. Here, we focus on a typical unit cell of the stack which consists of positive electrode-electrolyte-negative electrode (PEN). Based on the mechanical properties of each layer and their interfaces, an energy criterion as a function of crack length is used for the prediction of possible crack extensions in the PEN. This criterion is a pure local criterion, independent of applied loads and geometry of the specimen. An analysis of the competition between crack deflections in the interfaces and crack penetration in layers is presented.

  7. Assessment of Initial Test Conditions for Experiments to Assess Irradiation Assisted Stress Corrosion Cracking Mechanisms

    Broader source: Energy.gov [DOE]

    Irradiation-assisted stress corrosion cracking is a key materials degradation issue in today’s nuclear power reactor fleet and affects critical structural components within the reactor core. The...

  8. Webinar: Impacts of Impurities on Hydrogen Assisted Fatigue Crack Growth in Structural Steels

    Broader source: Energy.gov [DOE]

    The Energy Department will present a live webinar titled "Impacts of Impurities on Hydrogen Assisted Fatigue Crack Growth in Structural Steels" on Tuesday, January 12, from 12 to 1 p.m. EST.

  9. Tensile cracking of a brittle conformal coating on a rough substrate

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Reedy, Jr., E. D.

    2016-04-07

    This note examines the effect of interfacial roughness on the initiation and growth of channel cracks in a brittle film. A conformal film with cusp-like surface flaws that replicate the substrate roughness is investigated. This type of surface flaw is relatively severe in the sense that stress diverges as the cusp-tip is approached (i.e., there is a power-law stress singularity). For the geometry and range of film properties considered, the analysis suggests that smoothing the substrate could substantially increase the film’s resistance to the formation of the through-the-thickness cracks that precede channel cracking. Furthermore, smoothing the substrate’s surface has amore » relatively modest effect on the film stress needed to propagate a channel crack.« less

  10. Aluminum nitride transitional layer for reducing dislocation density and cracking of AIGan epitaxial films

    DOE Patents [OSTI]

    Allerman, Andrew A.; Crawford, Mary H.; Koleske, Daniel D.; Lee, Stephen R.

    2011-03-29

    A denticulated Group III nitride structure that is useful for growing Al.sub.xGa.sub.1-xN to greater thicknesses without cracking and with a greatly reduced threading dislocation (TD) density.

  11. Fatigue crack damage detection using subharmonic component with nonlinear boundary condition

    SciTech Connect (OSTI)

    Wu, Weiliang Qu, Wenzhong E-mail: xiaoli6401@126.com; Xiao, Li E-mail: xiaoli6401@126.com; Shen, Yanfeng Giurgiutiu, Victor

    2015-03-31

    In recent years, researchers have focused on structural health monitoring (SHM) and damage detection techniques using nonlinear vibration and nonlinear ultrasonic methods. Fatigue cracks may exhibit contact acoustic nonlinearity (CAN) with distinctive features such as superharmonics and subharmonics in the power spectrum of the sensing signals. However, challenges have been noticed in the practical applications of the harmonic methods. For instance, superharmonics can also be generated by the piezoelectric transducers and the electronic equipment; super/subharmonics may also stem from the nonlinear boundary conditions such as structural fixtures and joints. It is hard to tell whether the nonlinear features come from the structural damage or the intrinsic nonlinear boundary conditions. The objective of this paper is to demonstrate the application of nonlinear ultrasonic subharmonic method for detecting fatigue cracks with nonlinear boundary conditions. The fatigue crack was qualitatively modeled as a single-degree-of-freedom (SDOF) system with non-classical hysteretic nonlinear interface forces at both sides of the crack surfaces. The threshold of subharmonic generation was studied, and the influence of crack interface parameters on the subharmonic resonance condition was investigated. The different threshold behaviors between the nonlinear boundary condition and the fatigue crack was found, which can be used to distinguish the source of nonlinear subharmonic features. To evaluate the proposed method, experiments of an aluminum plate with a fatigue crack were conducted to quantitatively verify the subharmonic resonance range. Two surface-bonded piezoelectric transducers were used to generate and receive ultrasonic wave signals. The fatigue damage was characterized in terms of a subharmonic damage index. The experimental results demonstrated that the subharmonic component of the sensing signal can be used to detect the fatigue crack and further distinguish it from

  12. Tests and analyses for fully plastic fracture mechanics of plane strain mode I crack growth

    SciTech Connect (OSTI)

    McClintock, F.A.; Parks, D.M.; Kim, Y.J.

    1995-12-31

    Under monotonic loading, structures should ideally be ductile enough to provide continued resistance during crack growth. For fully plastic crack growth in low strength alloys, existing asymptotic solutions for elastic-plastic growing cracks are not applicable because they reach the fracture strain only in regions small compared to the inhomogeneities of the actual fracture process. For the limiting case of non-hardening fully-plastic plane strain crack growth, in a number of geometries and loadings the near-tip fields are characterized in terms of three parameters: an effective angle 2{theta}{sub s} between a pair of slip planes, and the normal stress {sigma}{sub s} and the increment of displacement {delta}u{sub s} across the planes. This three-parameter characterization is in contrast to the one- or two-parameter (K or J and T or Q) characterization in linear or non-linear elastic fracture mechanics. These {theta}{sub s}, {sigma}{sub s}, and {delta}u{sub s} parameters are found form the far-field geometries and loadings through slip line fields or least upper bound analyses based on circular arcs. The resulting crack growth, in terms of the crack tip opening angle (CTOA), is a function of {theta}{sub s}, {sigma}{sub s}, and the material. The geometry of the crack growing between two moving slip planes emanating from its tip reduces this function to the critical fracture shear strain left behind the slip planes, {gamma}f, as a function of {sigma}{sub s}. {gamma}f({sigma}{sub s}) is found theoretically from a hole initiation and growth model. It is also found from preliminary fully plastic crack growth experiments on unequally grooved specimens with fixed-grip extension or 4-point bending of a 1018 CF steel.

  13. In situ investigation of high humidity stress corrosion cracking of 7075 aluminum alloy by three-dimensional (3D) X-ray synchrotron tomography

    SciTech Connect (OSTI)

    Singh, S. S.; Williams, J. J.; Lin, M. F.; Xiao, X.; De Carlo, F.; Chawla, N.

    2014-05-14

    In situ X-ray synchrotron tomography was used to investigate the stress corrosion cracking behavior of under-aged Al–Zn–Mg–Cu alloy in moisture. The discontinuous surface cracks (crack jumps) mentioned in the literature are actually a single continuous and tortuous crack when observed in three dimension (3D). Contrary to 2D measurements made at the surface which suggest non-uniform crack growth rates, 3D measurements of the crack length led to a much more accurate measurement of crack growth rates.

  14. In situ investigation of high humidity stress corrosion cracking of 7075 aluminum alloy by three-dimensional (3D) X-ray synchrotron tomography

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Singh, S. S.; Williams, J. J.; Lin, M. F.; Xiao, X.; De Carlo, F.; Chawla, N.

    2014-05-14

    In situ X-ray synchrotron tomography was used to investigate the stress corrosion cracking behavior of under-aged Al–Zn–Mg–Cu alloy in moisture. The discontinuous surface cracks (crack jumps) mentioned in the literature are actually a single continuous and tortuous crack when observed in three dimension (3D). Contrary to 2D measurements made at the surface which suggest non-uniform crack growth rates, 3D measurements of the crack length led to a much more accurate measurement of crack growth rates.

  15. Fatigue-crack propagation in aluminum-lithium alloys processed by power and ingot metallurgy

    SciTech Connect (OSTI)

    Venkateswara Rao, K.T.; Ritchie, R.O. ); Kim, N.J. ); Pizzo, P.P. )

    1990-04-01

    Fatigue-crack propagation behavior in powder-metallurgy (P/M) aluminum-lithium alloys, namely, mechanically-alloyed (MA) Al-4.0Mg-1.5Li-1.1C-0.80{sub 2} (Inco 905-XL) and rapid-solidification-processed (RSP) Al-2.6Li-1.0Cu-0.5Mg-0.5Zr (Allied 644-B) extrusions, has been studied, and results compared with data on an equivalent ingot-metallurgy (I/M) Al-Li alloy, 2090-T81 plate. Fatigue-crack growth resistance of the RSP Al-Li alloy is found to be comparable to the I/M Al-Li alloy; in contrast, crack velocities in MA 905-XL extrusions are nearly three orders of magnitude faster. Growth-rate response in both P/M Al-Li alloys, however, is high anisotropic. Results are interpreted in terms of the microstructural influence of strengthening mechanism, slip mode, grain morphology and texture on the development of crack-tip shielding from crack-path deflection and crack closure. 14 refs., 7 figs., 2 tabs.

  16. Random polycrystals of grains containing cracks: Model ofquasistatic elastic behavior for fractured systems

    SciTech Connect (OSTI)

    Berryman, James G.; Grechka, Vladimir

    2006-07-08

    A model study on fractured systems was performed using aconcept that treats isotropic cracked systems as ensembles of crackedgrains by analogy to isotropic polycrystalline elastic media. Theapproach has two advantages: (a) Averaging performed is ensembleaveraging, thus avoiding the criticism legitimately leveled at mosteffective medium theories of quasistatic elastic behavior for crackedmedia based on volume concentrations of inclusions. Since crack effectsare largely independent of the volume they occupy in the composite, sucha non-volume-based method offers an appealingly simple modelingalternative. (b) The second advantage is that both polycrystals andfractured media are stiffer than might otherwise be expected, due tonatural bridging effects of the strong components. These same effectshave also often been interpreted as crack-crack screening inhigh-crack-density fractured media, but there is no inherent conflictbetween these two interpretations of this phenomenon. Results of thestudy are somewhat mixed. The spread in elastic constants observed in aset of numerical experiments is found to be very comparable to the spreadin values contained between the Reuss and Voigt bounds for thepolycrystal model. However, computed Hashin-Shtrikman bounds are much tootight to be in agreement with the numerical data, showing thatpolycrystals of cracked grains tend to violate some implicit assumptionsof the Hashin-Shtrikman bounding approach. However, the self-consistentestimates obtained for the random polycrystal model are nevertheless verygood estimators of the observed average behavior.

  17. Sonic IR crack detection of aircraft turbine engine blades with multi-frequency ultrasound excitations

    SciTech Connect (OSTI)

    Zhang, Ding; Han, Xiaoyan; Newaz, Golam

    2014-02-18

    Effectively and accurately detecting cracks or defects in critical engine components, such as turbine engine blades, is very important for aircraft safety. Sonic Infrared (IR) Imaging is such a technology with great potential for these applications. This technology combines ultrasound excitation and IR imaging to identify cracks and flaws in targets. In general, failure of engine components, such as blades, begins with tiny cracks. Since the attenuation of the ultrasound wave propagation in turbine engine blades is small, the efficiency of crack detection in turbine engine blades can be quite high. The authors at Wayne State University have been developing the technology as a reliable tool for the future field use in aircraft engines and engine parts. One part of the development is to use finite element modeling to assist our understanding of effects of different parameters on crack heating while experimentally hard to achieve. The development has been focused with single frequency ultrasound excitation and some results have been presented in a previous conference. We are currently working on multi-frequency excitation models. The study will provide results and insights of the efficiency of different frequency excitation sources to foster the development of the technology for crack detection in aircraft engine components.

  18. Effects of hydrogen on electropotential monitoring of stress corrosion crack growth

    SciTech Connect (OSTI)

    Thompson, C.D.; Carey, D.M.; Perazzo, N.L.

    1997-08-01

    Electropotential monitoring (EPM) has a crack growth measurement resolution that is an order of magnitude greater than methods that rely on crack mouth opening displacement. However, two phenomena have been identified that compromise the accuracy of the EPM technique. Coolant hydrogen concentrations above those needed to chemically reduce nickel oxide to metallic nickel cause EPM to underestimate the true crack length. The metallic nickel provides an electrical conduction path at contact points across the irregular crack surface thereby lowering the EPM potential. The coolant hydrogen concentration at which this reduction occurs is temperature dependent and correlates with an abrupt decrease in the rate of SCC crack growth. It was also found that EPM can indicate large crack growth when none actually exists. At temperatures > 315 C (600 F) the electrical resistivity of mill annealed Alloy 600 increased by as much as 5% in a period of weeks or months. Each 1% increase in resistivity results in a bias in the EPM indicated cracklength of about 0.2 mm (0.008 inches). Smaller changes in the electrical resistivity of other alloys have been measured which rank as EN52> X-750> 304SS> nickel. It has been shown that these resistivity changes occur during exposure to high temperature water or inert gas. Strategies to minimize the effects of these two phenomena on EPM measurement are discussed.

  19. Use of Multiple Reheat Helium Brayton Cycles to Eliminate the Intermediate Heat Transfer Loop for Advanced Loop Type SFRs

    SciTech Connect (OSTI)

    Haihua Zhao; Hongbin Zhang; Samuel E. Bays

    2009-05-01

    The sodium intermediate heat transfer loop is used in existing sodium cooled fast reactor (SFR) plant design as a necessary safety measure to separate the radioactive primary loop sodium from the water of the steam Rankine power cycle. However, the intermediate heat transfer loop significantly increases the SFR plant cost and decreases the plant reliability due to the relatively high possibility of sodium leakage. A previous study shows that helium Brayton cycles with multiple reheat and intercooling for SFRs with reactor outlet temperature in the range of 510°C to 650°C can achieve thermal efficiencies comparable to or higher than steam cycles or recently proposed supercritical CO2 cycles. Use of inert helium as the power conversion working fluid provides major advantages over steam or CO2 by removing the requirement for safety systems to prevent and mitigate the sodium-water or sodium-CO2 reactions. A helium Brayton cycle power conversion system therefore makes the elimination of the intermediate heat transfer loop possible. This paper presents a pre-conceptual design of multiple reheat helium Brayton cycle for an advanced loop type SFR. This design widely refers the new horizontal shaft distributed PBMR helium power conversion design features. For a loop type SFR with reactor outlet temperature 550°C, the design achieves 42.4% thermal efficiency with favorable power density comparing with high temperature gas cooled reactors.

  20. A passively-safe fusion reactor blanket with helium coolant and steel structure

    SciTech Connect (OSTI)

    Crosswait, K.M.

    1994-04-01

    Helium is attractive for use as a fusion blanket coolant for a number of reasons. It is neutronically and chemically inert, nonmagnetic, and will not change phase during any off-normal or accident condition. A significant disadvantage of helium, however, is its low density and volumetric heat capacity. This disadvantage manifests itself most clearly during undercooling accident conditions such as a loss of coolant accident (LOCA) or a loss of flow accident (LOFA). This thesis describes a new helium-cooled tritium breeding blanket concept which performs significantly better during such accidents than current designs. The proposed blanket uses reduced-activation ferritic steel as a structural material and is designed for neutron wall loads exceeding 4 MW/m{sup 2}. The proposed geometry is based on the nested-shell concept developed by Wong, but some novel features are used to reduce the severity of the first wall temperature excursion. These features include the following: (1) A ``beryllium-joint`` concept is introduced, which allows solid beryllium slabs to be used as a thermal conduction path from the first wall to the cooler portions of the blanket. The joint concept allows for significant swelling of the beryllium (10 percent or more) without developing large stresses in the blanket structure. (2) Natural circulation of the coolant in the water-cooled shield is used to maintain shield temperatures below 100 degrees C, thus maintaining a heat sink close to the blanket during the accident. This ensures the long-term passive safety of the blanket.

  1. Helium transport and ash control studies. Annual progress report, 1 June 1991--31 March 1992

    SciTech Connect (OSTI)

    Miley, G.H.

    1992-06-01

    The Primary goal of this research is to develop a helium (ash) transport scaling law based on experimental data from devices such as TFTR and JET. To illustrate the importance of this, we have studied ash accumulation effects on ignition requirements using a O-D transport model. Ash accumulation is characterized in the model by the ratio of the helium particle confinement time to the energy confinement time t{sub {alpha}}/t{sub E}. Results show that the ignition ``window`` shrinks rapidly as t{sub {alpha}}/t{sub E} increases, closing for high t{sub {alpha}}/t{sub E} increases, closing for high t{sub {alpha}}/t{sub E}. A ``best`` value for t{sub {alpha}}/t{sub E} will ultimately be determined from our scaling law studies. A helium transport scaling law is being sought that expresses the transport coefficients (D{sub {alpha}}, V{sub {alpha}}) as a function of the local plasma parameters. This is necessary for use in transport code calculations, e.g. for BALDUR. Based on experimental data from L-mode plasma operation in TFTR, a scaling law to a power law expression has been obtained using a least-square fit method. It is found that the transport coefficients are strongly affected by the local magnetic field and safety factor q. A preliminary conclusion from this work is that active control of ash buildup must be developed. To study control, we have developed a O-D plasma model which employs a simple pole-placement control model. Some preliminary calculations with this model are presented.

  2. Deep Burn Develpment of Transuranic Fuel for High-Temperature Helium-Cooled Reactors - July 2010

    SciTech Connect (OSTI)

    Snead, Lance Lewis; Besmann, Theodore M; Collins, Emory D; Bell, Gary L

    2010-08-01

    The DB Program Quarterly Progress Report for April - June 2010, ORNL/TM/2010/140, was distributed to program participants on August 4. This report discusses the following: (1) TRU (transuranic elements) HTR (high temperature helium-cooled reactor) Fuel Modeling - (a) Thermochemical Modeling, (b) 5.3 Radiation Damage and Properties; (2) TRU HTR Fuel Qualification - (a) TRU Kernel Development, (b) Coating Development, (c) ZrC Properties and Handbook; and (3) HTR Fuel Recycle - (a) Recycle Processes, (b) Graphite Recycle, (c) Pyrochemical Reprocessing - METROX (metal recovery from oxide fuel) Process Development.

  3. Fabrication of carbon nanotube nanogap electrodes by helium ion sputtering for molecular contacts

    SciTech Connect (OSTI)

    Thiele, Cornelius; Vieker, Henning; Beyer, André; Gölzhäuser, Armin; Flavel, Benjamin S.; Hennrich, Frank; Muñoz Torres, David; Eaton, Thomas R.; Mayor, Marcel; Kappes, Manfred M.; Löhneysen, Hilbert v.; and others

    2014-03-10

    Carbon nanotube nanogaps have been used to contact individual organic molecules. However, the reliable fabrication of a truly nanometer-sized gap remains a challenge. We use helium ion beam lithography to sputter nanogaps of only (2.8 ± 0.6) nm size into single metallic carbon nanotubes embedded in a device geometry. The high reproducibility of the gap size formation provides a reliable nanogap electrode testbed for contacting small organic molecules. To demonstrate the functionality of these nanogap electrodes, we integrate oligo(phenylene ethynylene) molecular rods, and measure resistance before and after gap formation and with and without contacted molecules.

  4. Numerical simulation of alumina spraying in argon-helium plasma jet

    SciTech Connect (OSTI)

    Chang, C.H.

    1992-01-01

    A new numerical model is described for simulating thermal plasmas containing entrained particles, with emphasis on plasma spraying applications. The plasma is represented as a continuum multicomponent chemically reacting ideal gas, while the particles are tracked as discrete Lagrangian entities coupled to the plasma. Computational results are presented from a transient simulation of alumina spraying in a turbulent argon-helium plasma jet in air environment, including torch geometry, substrate, and multiple species with chemical reactions. Particle-plasma interactions including turbulent dispersion have been modeled in a fully self-consistent manner. Interactions between the plasma and the torch and substrate walls are modeled using wall functions. (15 refs.)

  5. Numerical simulation of alumina spraying in argon-helium plasma jet

    SciTech Connect (OSTI)

    Chang, C.H.

    1992-08-01

    A new numerical model is described for simulating thermal plasmas containing entrained particles, with emphasis on plasma spraying applications. The plasma is represented as a continuum multicomponent chemically reacting ideal gas, while the particles are tracked as discrete Lagrangian entities coupled to the plasma. Computational results are presented from a transient simulation of alumina spraying in a turbulent argon-helium plasma jet in air environment, including torch geometry, substrate, and multiple species with chemical reactions. Particle-plasma interactions including turbulent dispersion have been modeled in a fully self-consistent manner. Interactions between the plasma and the torch and substrate walls are modeled using wall functions. (15 refs.)

  6. Alkaline intergranular corrosion and stress corrosion cracking of Alloy 600

    SciTech Connect (OSTI)

    Nagano, N.

    1996-12-31

    Intergranular corrosion (IGC), often termed IGA, and intergranular stress corrosion cracking (IGSCC) have continued to occur on mill-annealed (MA) Alloy 600 tubing in the secondary side of steam generators, which are still serious corrosion instances in operating pressurized water reactors. The IGC and IGSCC phenomena have occurred on MA Alloy 600 at the crevice between the tube and tube support plate, in which a high concentration of caustic solution is formed under dry and wet conditions at high temperature. A review of technical articles has been performed concerning environmental and metallurgical factors affecting the IGC and IGSCC, and their mechanistic aspects. A combination of IGC and IGSCC, one of the most common modes of corrosion on the secondary side of steam generators, occurs in a specific potential region, at the active-passive transition potential, in a concentrated caustic solution at elevated temperature. The anodic dissolution of Alloy 600 increases as the temperature of caustic solutions is increased. The corrosion rate for each constituent of Alloy 600 such as nickel, chromium, iron or chromium carbide is influenced differently by temperature, resulting in various effects on the characteristics of corrosion protective surface films. Increase in chromium content and thermal treatment at 700 C are beneficial for IGC and IGSCC resistance. IGC is intergranular corrosion, and IGSCC is initiated above a critical applied stress. Grain boundary chromium carbides such as Cr{sub 7}C{sub 3} and Cr{sub 23}C{sub 6} have been formed to increase resistance to IGC and IGSCC. Several theories have been proposed concerning the roles of chromium carbides at grain boundaries. Some specific theories are focused on in this paper with supporting data.

  7. An experimental and numerical analysis of hydrogen assisted cracking and weldability test methodology. Ph.D. Thesis

    SciTech Connect (OSTI)

    Dighde, R.M.

    1993-12-31

    The preferred method for increasing resistance to hydrogen-assisted cracking (HAC) is the application of an adequate preheating temperature, T(sub ph). The suitability of given welding conditions, including T(sub ph), in avoiding HAC is generally assessed through the use of Tekken and Lehigh weldability restraint tests. The safe welding conditions determined from these tests are then applied in industrial fabrication. It is observed that these safe welding conditions do not always avoid HAC in actual weldments. Therefore, it is necessary to evaluate the weldability testing procedure in its entirety against the more general industrial fabrication practice and understand the inherent differences. The differences arising, at different stages of weldability testing procedure, from weld hydrogen measurement technique, weldability testing procedure, hydrogen diffusion behavior, residual stress development, and dimensional differences in weldability tests and actual weldments were analyzed in detail using an experimental and numerical approach. The weld hydrogen measurement results indicated that the existing hydrogen measurement standards do not measure the weld hydrogen levels in actual weldments, and should, therefore, be modified for use in weldability testing procedure. The Tekken and Lehigh weldability test results suggested that weld induced variation at stress concentration locations strongly influences the HAC tendency and crack propagation behavior. Finite element analysis (FEA) of hydrogen diffusion behavior in weldability tests and actual weld grooves indicated that hydrogen diffusion is a strong function of the groove shape and the weld thermal cycle, and hence, direct applicability of weldability test results to actual weldments can be misleading. Elasto-plastic thermo-mechanical behavior of Tekken and Lehigh weldability tests during welding was carried out using FEA.

  8. Cracking of n-butane catalyzed by iron- and maganese-promoted sulfated zirconia

    SciTech Connect (OSTI)

    Cheung, T.K.; d`Itri, J.L.; Gates, B.C.

    1995-05-01

    Fe- and Mn-promoted sulfated zirconia was used to catalyze the conversion of n-butane at atmospheric pressure and n-butane partial pressures in the range of 0.0025-0.01 atm. At temperatures <225{degrees}C, the significant reactions were isomerization and disproportionation; in the range of 225-300{degrees}C, these reactions were accompanied by cracking, and at temperatures >350{degrees}C, cracking and isomerization occurred. Catalyst deactivation, resulting at least in part from coke formation, was rapid. The primary cracking products were methane, ethane, ethylene, and propylene. The observation of these products along with an ethane/ethylene molar ratio of nearly 1 at 450{degrees}C is consistent with cracking occurring, at least in part, by the Haag-Dessau mechanism, whereby the strongly acidic catalyst protonates n-butane to give carbonium ions. The rate of methane formation from n-butane cracking catalyzed by Fe- and Mn-promoted sulfated zirconia at 450{degrees}C was about 3 x 10{sup {minus}9}mol/(g of catalyst {center_dot}s). This comparison suggests that the catalytic activity of the promoted sulfated zirconia at 450{degrees}C is about the same as that of the zeolite, although its activity for n-butane isomerization and disproportionation at temperatures <100{degrees}C is orders of magnitude greater than those of zeolites. Thus the indication of superacidity of the promoted sulfated zirconia does not extend to high temperatures. The results raise questions about the nature of the presumed superacidity: perhaps the low-temperature reactions may involve catalyst functions other than the acidic function responsible for high-temperature cracking reactions or perhaps superacidic sites may be very rapidly poisoned at cracking temperatures. 14 refs., 8 figs., 3 tabs.

  9. Irradiation-Assisted Stress Corrosion Cracking of Austenitic Stainless Steels in BWR Environments

    SciTech Connect (OSTI)

    Chen, Y.; Chopra, O. K.; Gruber, Eugene E.; Shack, William J.

    2010-06-01

    The internal components of light water reactors are exposed to high-energy neutron irradiation and high-temperature reactor coolant. The exposure to neutron irradiation increases the susceptibility of austenitic stainless steels (SSs) to stress corrosion cracking (SCC) because of the elevated corrosion potential of the reactor coolant and the introduction of new embrittlement mechanisms through radiation damage. Various nonsensitized SSs and nickel alloys have been found to be prone to intergranular cracking after extended neutron exposure. Such cracks have been seen in a number of internal components in boiling water reactors (BWRs). The elevated susceptibility to SCC in irradiated materials, commonly referred to as irradiation-assisted stress corrosion cracking (IASCC), is a complex phenomenon that involves simultaneous actions of irradiation, stress, and corrosion. In recent years, as nuclear power plants have aged and irradiation dose increased, IASCC has become an increasingly important issue. Post-irradiation crack growth rate and fracture toughness tests have been performed to provide data and technical support for the NRC to address various issues related to aging degradation of reactor-core internal structures and components. This report summarizes the results of the last group of tests on compact tension specimens from the Halden-II irradiation. The IASCC susceptibility of austenitic SSs and heat-affected-zone (HAZ) materials sectioned from submerged arc and shielded metal arc welds was evaluated by conducting crack growth rate and fracture toughness tests in a simulated BWR environment. The fracture and cracking behavior of HAZ materials, thermally sensitized SSs and grain-boundary engineered SSs was investigated at several doses (?3 dpa). These latest results were combined with previous results from Halden-I and II irradiations to analyze the effects of neutron dose, water chemistry, alloy compositions, and welding and processing conditions on IASCC

  10. Analysis of stress corrosion cracking in alloy 718 following commercial reactor exposure

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Leonard, Keith J.; Gussev, Maxim N.; Stevens, Jacqueline N.; Busby, Jeremy T.

    2015-08-24

    Alloy 718 is generally considered a highly corrosion-resistant material but can still be susceptible to stress corrosion cracking (SCC). The combination of factors leading to SCC susceptibility in the alloy is not always clear enough. In this paper, alloy 718 leaf spring (LS) materials that suffered stress corrosion damage during two 24-month cycles in pressurized water reactor service, operated to >45 MWd/mtU burn-up, was investigated. Compared to archival samples fabricated through the same processing conditions, little microstructural and property changes occurred in the material with in-service irradiation, contrary to high dose rate laboratory-based experiments reported in literature. Though the lackmore » of delta phase formation along grain boundaries would suggest a more SCC resistant microstructure, grain boundary cracking in the material was extensive. Crack propagation routes were explored through focused ion beam milling of specimens near the crack tip for transmission electron microscopy as well as in polished plan view and cross-sectional samples for electron backscatter diffraction analysis. It has been shown in this study that cracks propagated mainly along random high-angle grain boundaries, with the material around cracks displaying a high local density of dislocations. The slip lines were produced through the local deformation of the leaf spring material above their yield strength. Also, the cause for local SCC appears to be related to oxidation of both slip lines and grain boundaries, which under the high in-service stresses resulted in crack development in the material.« less

  11. Stepped-anneal and total helium/hydrogen measurements in high-energy proton-irradiated tungsten

    SciTech Connect (OSTI)

    Oliver, B.M.; Hamilton, M.L.; Garner, F.A.; Sommer, W.F.; Maloy, S.A.; Ferguson, P.D.

    1998-12-31

    To provide structural material design data for the Accelerator Production of Tritium (APT) project, a 1 mA, 800 MeV proton beam at the Los Alamos Neutron Science Center (LANSCE) was used to irradiate a large number of metal samples, including a tungsten target similar to that being considered as the neutron source for the tritium production. The maximum proton fluence to the tungsten target was {approximately} 10{sup 21} protons/cm{sup 2}. An unavoidable byproduct of spallation reactions is the formation of large amounts of hydrogen and helium. Postulated accident scenarios for APT involving the use of tungsten rods clad with Alloy 718, raise concerns as to the amount and rate of release of these gases due to temperatures increases from afterheat accumulation, with the major concern being pressurizing and possibly failure of the cladding. To address these issues, portions of the LANSCE tungsten rods were subjected to temperature histories calculated as likely to occur, and the time-dependent evolution of helium and hydrogen gases was measured. Stepped-anneal and total helium/hydrogen measurements were conducted on multiple samples of the tungsten material. Helium measurements were conducted at Pacific Northwest National Laboratory (PNNL) using a high-sensitivity magnetic-sector isotope-dilution helium analysis system. Stepped-anneal measurements were conducted at temperatures from {approximately} 25 C to {approximately} 1,600 C in {approximately} 100 C steps. Total helium measurements were conducted by rapid vaporization after completion of the stepped-anneal process, and are compared with Monte Carlo calculations performed at Los Alamos National Laboratory (LANL) using the LAHET code system. Hydrogen measurements were conducted between {approximately} 750 C and {approximately} 1,200 C using a high-temperature furnace that had been extensively modified for the application. Hydrogen detection was accomplished by periodic sampling of the furnace gas using a separate

  12. Multi-component catalyst mixture and process for catalytic cracking of heavy hydrocarbon feed to lighter products

    SciTech Connect (OSTI)

    Herbst, J.A.; Owen, H.; Schipper, P.H.

    1991-10-08

    This paper describes a catalytic cracking catalyst. It comprises: a bulk conversion cracking catalyst containing at least one component with an equivalent pore size of at least about 7 angstroms in a matrix, the bulk conversion cracking catalyst having physical properties which permit use in a fluidized or moving bed catalytic cracking reactor; a light paraffin upgrading catalyst comprising at least one zeolite having a constraint index of 1--12 and paraffin cracking/isomerization activity; and a light paraffin upgrading catalyst comprising at least one zeolite having a constraint index of 1--12 and paraffin aromatization activity, and wherein the upgrading catalysts have substantially the same physical properties as the bulk conversion cracking catalyst.

  13. Mode I and mixed I/III crack initiation and propagation behavior of V-4Cr-4Ti alloy at 25{degrees}C

    SciTech Connect (OSTI)

    Li, H.X.; Kurtz, R.J.; Jones, R.H.

    1997-04-01

    The mode I and mixed-mode I/III fracture behavior of the production-scale heat (No. 832665) of V-4Cr-4Ti has been investigated at 25{degrees}C using compact tension (CT) specimens for a mode I crack and modified CT specimens for a mixed-mode I/III crack. The mode III to mode I load ratio was 0.47. Test specimens were vacuum annealed at 1000{degrees}C for 1 h after final machining. Both mode I and mixed-mode I/III specimens were fatigue cracked prior to J-integral testing. It was noticed that the mixed-mode I/III crack angle decreased from an initial 25 degrees to approximately 23 degrees due to crack plane rotation during fatigue cracking. No crack plane rotation occurred in the mode I specimen. The crack initiation and propagation behavior was evaluated by generating J-R curves. Due to the high ductility of this alloy and the limited specimen thickness (6.35 mm), plane strain requirements were not met so valid critical J-integral values were not obtained. However, it was found that the crack initiation and propagation behavior was significantly different between the mode I and the mixed-mode I/III specimens. In the mode I specimen crack initiation did not occur, only extensive crack tip blunting due to plastic deformation. During J-integral testing the mixed-mode crack rotated to an increased crack angle (in contrast to fatigue precracking) by crack blunting. When the crack initiated, the crack angle was about 30 degrees. After crack initiation the crack plane remained at 30 degrees until the test was completed. Mixed-mode crack initiation was difficult, but propagation was easy. The fracture surface of the mixed-mode specimen was characterized by microvoid coalescence.

  14. Influence of helium puff on divertor asymmetry in Experimental Advanced Superconducting Tokamak

    SciTech Connect (OSTI)

    Liu, S. C., E-mail: lshch@ipp.ac.cn; Xu, G. S.; Wang, H. Q.; Ding, R.; Duan, Y. M.; Gan, K. F.; Shao, L. M.; Chen, L.; Zhang, W.; Chen, R.; Xiong, H.; Ding, S.; Hu, G. H.; Liu, Y. L.; Zhao, N.; Li, Y. L.; Gao, X. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China)] [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Guo, H. Y. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China) [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Tri Alpha Energy, Inc., Post Office Box 7010, Rancho Santa Margarita, California 92688 (United States); Wang, L. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China) [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); School of Physics and Optoelectronic Technology, Dalian university of Technology, Dalian 116024 (China); Yan, N. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China) [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Association Euratom-Ris DTU, DK-4000 Roskilde (Denmark)

    2014-02-15

    Divertor asymmetries with helium puffing are investigated in various divertor configurations on Experimental Advanced Superconducting Tokamak (EAST). The outer divertor electron temperature decreases significantly during the gas injection at the outer midplane. As soon as the gas is injected into the edge plasma, the power deposition drops sharply at the lower outer target while increases gradually at the lower inner target in LSN configuration; the power deposition increases quickly at the upper outer target while remains unchanged at the upper inner target in upper single null configuration; the power deposition increases slightly at the outer targets while shows no obvious variation at the inner targets in double null configuration. The radiated power measured by the extreme ultraviolet arrays increases significantly due to helium gas injection, especially in the outer divertor. The edge parameters are measured by reciprocating probes at the outer midplane, showing that the electron temperature and density increase but the parallel Mach number decreases significantly due to the gas injection. Effects of poloidal E??B drifts and parallel SOL flows on the divertor asymmetry observed in EAST are also discussed.

  15. Constraints on helium enhancement in the globular cluster M4 (NGC 6121): The horizontal branch test

    SciTech Connect (OSTI)

    Valcarce, A. A. R.; De Medeiros, J. R.; Catelan, M.; Alonso-Garca, J.; Corts, C.

    2014-02-20

    Recent pieces of evidence have revealed that most, and possibly all, globular star clusters are composed of groups of stars that formed in multiple episodes with different chemical compositions. In this sense, it has also been argued that variations in the initial helium abundance (Y) from one population to the next are also the rule, rather than the exception. In the case of the metal-intermediate globular cluster M4 (NGC 6121), recent high-resolution spectroscopic observations of blue horizontal branch (HB) stars (i.e., HB stars hotter than the RR Lyrae instability strip) suggest that a large fraction of blue HB stars are second-generation stars formed with high helium abundances. In this paper, we test this scenario by using recent photometric and spectroscopic data together with theoretical evolutionary computations for different Y values. Comparing the photometric data with the theoretically derived color-magnitude diagrams, we find that the bulk of the blue HB stars in M4 have ?Y ? 0.01 with respect to the cluster's red HB stars (i.e., HB stars cooler than the RR Lyrae strip)a result which is corroborated by comparison with spectroscopically derived gravities and temperatures, which also favor little He enhancement. However, the possible existence of a minority population on the blue HB of the cluster with a significant He enhancement level is also discussed.

  16. Large-scale atomistic simulations of helium-3 bubble growth in complex palladium alloys

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Hale, Lucas M.; Zimmerman, Jonathan A.; Wong, Bryan M.

    2016-05-18

    Palladium is an attractive material for hydrogen and hydrogen-isotope storage applications due to its properties of large storage density and high diffusion of lattice hydrogen. When considering tritium storage, the material’s structural and mechanical integrity is threatened by both the embrittlement effect of hydrogen and the creation and evolution of additional crystal defects (e.g., dislocations, stacking faults) caused by the formation and growth of helium-3 bubbles. Using recently developed inter-atomic potentials for the palladium-silver-hydrogen system, we perform large-scale atomistic simulations to examine the defect-mediated mechanisms that govern helium bubble growth. Our simulations show the evolution of a distribution of materialmore » defects, and we compare the material behavior displayed with expectations from experiment and theory. In conclusion, we also present density functional theory calculations to characterize ideal tensile and shear strengths for these materials, which enable the understanding of how and why our developed potentials either meet or confound these expectations.« less

  17. Unusual behavior in magnesium-copper cluster matter produced by helium droplet mediated deposition

    SciTech Connect (OSTI)

    Emery, S. B. Little, B. K.; Xin, Y.; Ridge, C. J.; Lindsay, C. M.; Buszek, R. J.; Boatz, J. A.; Boyle, J. M.

    2015-02-28

    We demonstrate the ability to produce core-shell nanoclusters of materials that typically undergo intermetallic reactions using helium droplet mediated deposition. Composite structures of magnesium and copper were produced by sequential condensation of metal vapors inside the 0.4 K helium droplet baths and then gently deposited onto a substrate for analysis. Upon deposition, the individual clusters, with diameters ∼5 nm, form a cluster material which was subsequently characterized using scanning and transmission electron microscopies. Results of this analysis reveal the following about the deposited cluster material: it is in the un-alloyed chemical state, it maintains a stable core-shell 5 nm structure at sub-monolayer quantities, and it aggregates into unreacted structures of ∼75 nm during further deposition. Surprisingly, high angle annular dark field scanning transmission electron microscopy images revealed that the copper appears to displace the magnesium at the core of the composite cluster despite magnesium being the initially condensed species within the droplet. This phenomenon was studied further using preliminary density functional theory which revealed that copper atoms, when added sequentially to magnesium clusters, penetrate into the magnesium cores.

  18. THE VALUE OF HELIUM-COOLED REACTOR TECHNOLOGIES OF NUCLEAR WASTE

    SciTech Connect (OSTI)

    C. RODRIGUEZ; A. BAXTER

    2001-03-01

    Helium-cooled reactor technologies offer significant advantages in accomplishing the waste transmutation process. They are ideally suited for use with thermal, epithermal, or fast neutron energy spectra. They can provide a relatively hard thermal neutron spectrum for transmutation of fissionable materials such as Pu-239 using ceramic-coated transmutation fuel particles, a graphite moderator, and a non-fertile burnable poison. These features (1) allow deep levels of transmutation with minimal or no intermediate reprocessing, (2) enhance passive decay heat removal via heat conduction and radiation, (3) allow operation at relatively high temperatures for a highly efficient generation of electricity, and (4) discharge the transmuted waste in a form that is highly resistant to corrosion for long times. They also offer the possibility for the use of epithermal neutrons that can interact with transmutable materials more effectively because of the large atomic cross sections in this energy domain. A fast spectrum may be useful for deep burnup of certain minor actinides. For this application, helium is essentially transparent to neutrons, does not degrade neutron energies, and offers the hardest possible neutron energy environment. In this paper, we report results from recent work on materials transmutation balances, safety, value to a geological repository, and economic considerations.

  19. Determination of effective axion masses in the helium-3 buffer of CAST

    SciTech Connect (OSTI)

    Ruz, J

    2011-11-18

    The CERN Axion Solar Telescope (CAST) is a ground based experiment located in Geneva (Switzerland) searching for axions coming from the Sun. Axions, hypothetical particles that not only could solve the strong CP problem but also be one of the favored candidates for dark matter, can be produced in the core of the Sun via the Primakoff effect. They can be reconverted into X-ray photons on Earth in the presence of strong electromagnetic fields. In order to look for axions, CAST points a decommissioned LHC prototype dipole magnet with different X-ray detectors installed in both ends of the magnet towards the Sun. The analysis of the data acquired during the first phase of the experiment yielded the most restrictive experimental upper limit on the axion-to-photon coupling constant for axion masses up to about 0.02 eV/c{sup 2}. During the second phase, CAST extends its mass sensitivity by tuning the electron density present in the magnetic field region. Injecting precise amounts of helium gas has enabled CAST to look for axion masses up to 1.2 eV/c{sup 2}. This paper studies the determination of the effective axion masses scanned at CAST during its second phase. The use of a helium gas buffer at temperatures of 1.8 K has required a detailed knowledge of the gas density distribution. Complete sets of computational fluid dynamic simulations validated with experimental data have been crucial to obtain accurate results.

  20. Commissioning of helium refrigeration system at JLab for 12 GeV upgrade

    SciTech Connect (OSTI)

    Ganni, Venkatarao; Dixon, Kelly D.; Knudsen, Peter N.; Norton, Robert O.; Creel, Jonathan D.

    2014-01-01

    The new 4.5 K refrigerator system added to the Jefferson Lab (JLab) Central Helium Liquefier (CHL) for the 12 GeV upgrade will double its previous capacity. It includes a 4.5 K cold box system and compressor system with associated oil removal and gas management systems. At its maximum capacity condition, this new system supports an additional 238 g/s 30 K 1.16 bar cold compressor return flow, a 15 g/s 4.5 K liquefaction load and a 12.6 kW 35–55 K shield load. Five more design conditions, ranging from liquefaction to refrigeration and a stand-by/reduced load state, were specified for the sizing and selection of its components. The cold box system is comprised of a 300–60 K vertical cold box that incorporates a liquid nitrogen pre-cooler and a 60–4.5 K horizontal cold box housing seven turbines that are configured in four expansion stages including one Joule-Thompson expander. The helium compression system has five compressors to support three pressure levels in the cold box. This paper will briefly review the salient 4.5 K system design features and discuss the recent commissioning results.

  1. OPTIMAL DESIGN AND OPERATION OF HELIUM REFRIGERATION SYSTEMS USING THE GANNI CYCLE

    SciTech Connect (OSTI)

    Venkatarao Ganni, Peter Knudsen

    2010-04-01

    The constant pressure ratio process, as implemented in the floating pressure - Ganni cycle, is a new variation to prior cryogenic refrigeration and liquefaction cycle designs that allows for optimal operation and design of helium refrigeration systems. This cycle is based upon the traditional equipment used for helium refrigeration system designs, i.e., constant volume displacement compression and critical flow expansion devices. It takes advantage of the fact that for a given load, the expander sets the compressor discharge pressure and the compressor sets its own suction pressure. This cycle not only provides an essentially constant system Carnot efficiency over a wide load range, but invalidates the traditional philosophy that the (‘TS’) design condition is the optimal operating condition for a given load using the as-built hardware. As such, the Floating Pressure- Ganni Cycle is a solution to reduce the energy consumption while increasing the reliability, flexibility and stability of these systems over a wide operating range and different operating modes and is applicable to most of the existing plants. This paper explains the basic theory behind this cycle operation and contrasts it to the traditional operational philosophies presently used.

  2. Production of stable, non-thermal atmospheric pressure rf capacitive plasmas using gases other than helium or neon

    DOE Patents [OSTI]

    Park, Jaeyoung; Henins, Ivars

    2005-06-21

    The present invention enables the production of stable, steady state, non-thermal atmospheric pressure rf capacitive .alpha.-mode plasmas using gases other than helium and neon. In particular, the current invention generates and maintains stable, steady-state, non-thermal atmospheric pressure rf .alpha.-mode plasmas using pure argon or argon with reactive gas mixtures, pure oxygen or air. By replacing rare and expensive helium with more readily available gases, this invention makes it more economical to use atmospheric pressure rf .alpha.-mode plasmas for various materials processing applications.

  3. Counter-intuitive experimental evidence on the initiation of radical crack in ceramic thin films at the atomic scale

    SciTech Connect (OSTI)

    Zhuang, Chunqiang Li, Zhipeng; Lin, Songsheng

    2015-10-15

    The basic issue related to radial crack in ceramic thin films has received considerable attention due to the fact that the radial crack plays an important role in evaluating the toughness properties of ceramic materials. In this work, an atomic-scale new experimental evidence is clearly presented to reveal the counter-intuitive initiation, the nucleation and the propagation mechanism of the radial crack in Al-Cr-N ceramic thin films.

  4. Spent Nuclear Fuel (SNF) Project Cask and MCO Helium Purge System Design Review Completion Report Project A.5 and A.6

    SciTech Connect (OSTI)

    ARD, K.E.

    2000-04-19

    This report documents the results of the design verification performed on the Cask and Multiple Canister Over-pack (MCO) Helium Purge System. The helium purge system is part of the Spent Nuclear Fuel (SNF) Project Cask Loadout System (CLS) at 100K area. The design verification employed the ''Independent Review Method'' in accordance with Administrative Procedure (AP) EN-6-027-01.

  5. Grain Boundary Character Along Intergranular Stress Corrosion Crack Paths in Austenitic Stainless Alloys Removed from High-Temperature Water Service

    SciTech Connect (OSTI)

    Gertsman, Valerii Y.; Bruemmer, Stephen M.

    2002-01-01

    Stress-corrosion cracks produced in high-temperature water environments were examined in alloy 600 and stainless steel samples. The alloy 600 samples were removed from pressurized-water reactor (PWR) steam generator tubing after exhibiting cracking in service or after model-boiler stress corrosion cracking tests. The 304 and 316 stainless steel samples also experienced intergranular stress corrosion cracking (IGSCC) in high-temperature-water environments similar to a PWR steam generator. Grain boundary misorientations were measured along IG crack paths as well as in the bulk. In general, only twin Sigma 3 boundaries exhibited improved resistance to crack propagation. If the Sigma 3 were factored out, the fractions of grain boundary types of cracked boundaries corresponded to their frequency of occurrence in the bulk alloy. Other boundaries with coincident site lattice misorientations, including Sigma 9 and Sigma 27, were observed to crack. The cracks were often (but not always) arrested at grain boundary junctions containing Sigma 3 boundaries. The results obtained indicate that grain boundary crystallography does not fully determine its susceptibility to IGSCC in typical commercial alloys. Other factors must be taken into account when assessing material?s propensity to IG failure.

  6. Arrest of propagating brittle cracks in low toughness pipe with clock spring reinforcements. Topical report, December 1992-November 1995

    SciTech Connect (OSTI)

    Block, N.; Kishel, J.; Stephens, D.R.

    1995-12-01

    Results obtained in this project generally correlated with work earlier by NCF Industries in 1990, although a greater number of brittle cracks were generated in most of the tests in this project. They verified that design of an external arrest section is much more stringent for termination of multiple brittle cracks at temperatures providing lower shelf toughness of the pipe steel. Arrest of brittle cracks appears feasible with tightly applied external fiberglass wraps of proper design. According, additional work to define design needed for reproducible arrests of multiple brittle cracks by Clock Spring is warranted.

  7. Overview of recent studies and modifications being made to RHIC to mitigate the effects of a potential failure to the helium distribution system

    SciTech Connect (OSTI)

    Tuozzolo, J.; Bruno, D.; DiLieto, A.; Heppner, G.; Karol, R.; Lessard,E.; Liaw, C-J; McIntyre, G; Mi, C.; Reich, J.; Sandberg, J.; Seberg, S.; Smart, L.; Tallerico, T.; Theisen, C.; Todd, R.; Zapasek R.

    2011-03-28

    In order to cool the superconducting magnets in RHIC, its helium refrigerator distributes 4.5 K helium throughout the tunnel along with helium distribution for the magnet line recoolers, the heat shield, and the associated return lines. The worse case for failure would be a release from the magnet distribution line which operates at 3.5 to 4.5 atmospheres and contains the energized magnet but with a potential energy of 70 MJoules should the insulation system fail or an electrical connection opens. Studies were done to determine release rate of the helium and the resultant reduction in O{sub 2} concentration in the RHIC tunnel and service buildings. Equipment and components were also reviewed for design and reliability and modifications were made to reduce the likelihood of failure and to reduce the volume of helium that could be released.

  8. Fracture behavior of ceramic laminates in bending-I. Modeling of crack propagation

    SciTech Connect (OSTI)

    Phillipps, A.J.; Clegg, W.J.; Clyne, T.W. . Dept. of Materials Science and Metallurgy)

    1993-03-01

    This paper concerns the fracture behavior of specimens made up of ceramic sheets, separated by thin interlayers, which act to deflect cracks and thus to prevent catastrophic failure of the specimen. The treatment is divided into two parts. In this paper, the behavior of this type of material during bending is quantitatively modeled. The model is based on through-thickness cracks propagating when a critical stress is reached and interfacial cracks then advancing a distance dictated by the available energy. The variation in laminae strengths is modeled using a Monte Carlo method to determine the strength of successive laminae for a given Weibull modulus. The model is used to predict load/displacement plots and to explore the effects of changes in loading geometry and specimen variables, including Young's modulus, lamina strength, loading span, interfacial toughness, as well as lamina and sample thickness. A distinction is drawn between the energy actually absorbed in causing complete failure of the specimen as measured from the area under the load/displacement curve, and the amount of energy necessary to cause the crack propagation which occurred. These differ if the energy available to drive the interfacial cracks is more than sufficient for them to reach the ends of the specimen or if energy is dissipated elsewhere in the system. A criterion is derived by which specimens can be designed so as to minimize the difference between these two quantities. The significance of this concept in optimizing the toughness of these laminated materials is briefly discussed.

  9. Simulation of crack propagation in fiber-reinforced concrete by fracture mechanics

    SciTech Connect (OSTI)

    Zhang Jun; Li, Victor C

    2004-02-01

    Mode I crack propagation in fiber-reinforced concrete (FRC) is simulated by a fracture mechanics approach. A superposition method is applied to calculate the crack tip stress intensity factor. The model relies on the fracture toughness of hardened cement paste (K{sub IC}) and the crack bridging law, so-called stress-crack width ({sigma}-{delta}) relationship of the material, as the fundamental material parameters for model input. As two examples, experimental data from steel FRC beams under three-point bending load are analyzed with the present fracture mechanics model. A good agreement has been found between model predictions and experimental results in terms of flexural stress-crack mouth opening displacement (CMOD) diagrams. These analyses and comparisons confirm that the structural performance of concrete and FRC elements, such as beams in bending, can be predicted by the simple fracture mechanics model as long as the related material properties, K{sub IC} and ({sigma}-{delta}) relationship, are known.

  10. Effect of heat treatment on caustic stress corrosion cracking behavior of alloy 600

    SciTech Connect (OSTI)

    Sung, J.K.

    1999-12-01

    Constant elongation rate tests (CERT) were conducted to evaluate the effect of heat treatment on intergranular stress corrosion cracking (IGSCC) susceptibility of alloy 600 (UNS NO6600) in 140 C and 50% caustic solution at {minus}900 mV vs saturated calomel electrode (SCE). Results showed: (1) Heat treatment at low temperature for a long time (600 C for 260 h) led to a material that was not susceptible to caustic intergranular (IG) cracking. Increase in heat treatment temperature enhanced IG cracking susceptibility. Caustic IGSCC susceptibility was at maximum near the carbon solubility limit. However, when the heat treatment temperature was higher than the carbon solubility limit, a significant decrease in crack growth rate was observed. (2) Grain boundaries acted as a preferential crack path when grain boundary carbon segregation was likely. Thermodynamic considerations suggested that severe caustic IGSCC susceptibility near the carbon solubility limit could be explained in terms of carbon segregation at the grain boundaries. (3) IGSCC in caustic solution did not seem to be caused by chromium depletion. (4) Although formation of semi-continuous IG carbides and IGSCC resistance seemed to exhibit a similar chronological response with heat treatment, it was unlikely that grain boundary IG carbides played a role in caustic IGSCC susceptibility.

  11. Fracture toughness results and preliminary analysis for International Cooperative Test Program on specimens containing surface cracks

    SciTech Connect (OSTI)

    Reuter, W.G.; Elfer, N.C.; Hull, D.A.; Newman, J.C. Jr.; Munz, D.; Panontin, T.L.

    1997-12-31

    Specimens containing surface cracks were tested in either tension or bending to compare the stress intensity factor at failure with plane strain fracture toughness (K{sub Ic}) in an International Cooperative Test Program. The material was heat treated to {sigma}{sub ys} = 1 587 MPa and K{sub Ic} = 54 MPa m{sub 1/2}. Because substantial stable crack growth occurred for some specimens, the test plan was modified to include detecting the onset of crack growth. It is shown that P{sub max} and the original fatigue precrack size cannot be employed to calculate K{sub max} for comparison with K{sub Ic} when significant stable crack growth occurs. However, using P{sub init} (load at which stable crack growth is initiated) and the original fatigue precrack size to calculate K{sub max} or K{sub {phi}=30{degree}} provides a very useful comparison with K{sub Ic}. The influence of variations in fatigue precrack configuration on test results are also discussed.

  12. Cracking of simulated oil refinery off-gas over a coal char, petroleum coke, and quartz

    SciTech Connect (OSTI)

    Yuan Zhang; Jin-hu Wu; Dong-ke Zhang

    2008-03-15

    The cracking of oil refinery off-gas, simulated with a gas mixture containing methane (51%), ethylene (21.4%), ethane (21.1%), and propane (6.5%), over a coal char, petroleum coke, and quartz, respectively, has been studied in a fixed bed reactor. The experiments were performed at temperatures between 850 and 1000{sup o}C and at atmospheric pressure. The results show that the conversions of all species considered increased with increasing temperature. Ethane and propane completely decomposed over all three bed materials in the temperature range investigated. However, the higher initial conversion rates of methane and ethylene cracking at all temperatures were observed only over the coal char and not on the petroleum coke and quartz, indicating a significant catalytic effect of the coal char on methane and ethylene cracking. Methane and ethylene conversions decreased with reaction time due to deactivation of the coal char by carbon deposition on the char surface and, in the later stage of a cracking experiment, became negative, suggesting that methane and ethylene had been formed during the cracking of ethane and propane. 16 refs., 13 figs., 2 tabs.

  13. Detection of submicron scale cracks and other surface anomalies using positron emission tomography

    DOE Patents [OSTI]

    Cowan, Thomas E.; Howell, Richard H.; Colmenares, Carlos A.

    2004-02-17

    Detection of submicron scale cracks and other mechanical and chemical surface anomalies using PET. This surface technique has sufficient sensitivity to detect single voids or pits of sub-millimeter size and single cracks or fissures of millimeter size; and single cracks or fissures of millimeter-scale length, micrometer-scale depth, and nanometer-scale length, micrometer-scale depth, and nanometer-scale width. This technique can also be applied to detect surface regions of differing chemical reactivity. It may be utilized in a scanning or survey mode to simultaneously detect such mechanical or chemical features over large interior or exterior surface areas of parts as large as about 50 cm in diameter. The technique involves exposing a surface to short-lived radioactive gas for a time period, removing the excess gas to leave a partial monolayer, determining the location and shape of the cracks, voids, porous regions, etc., and calculating the width, depth, and length thereof. Detection of 0.01 mm deep cracks using a 3 mm detector resolution has been accomplished using this technique.

  14. The effect of residuals on the presence of intergranular surface cracks on continuously cast billets

    SciTech Connect (OSTI)

    Wijngaarden, M.J.U.T. van; Visagie, G.P.

    1996-12-31

    During 1991, Iscor Vereeniging experienced a dramatic increase in the rejection rate of specialty steel bars rolled from continuously cast billets due to the presence of seams on the bars. The seams originated from tearing of the billets during the first 2 passes in the roughing mill during hot rolling. The defective billets were found to contain fine intergranular cracks on the surface. Such cracks have been described in the literature and have been attributed to the presence of high levels of residuals resulting in the well-known phenomenon of surface hot shortness which results from the enrichment of residuals at the grain boundaries after preferential oxidation of iron during scaling of the steel. The present investigation revealed that the effect of residuals on intergranular surface cracking is a complex interaction between steel composition and casting conditions such as casting speed, intensity of secondary cooling, section size, and mold type. This paper quantifies the effect of residuals on the intergranular surface cracking of continuously cast billets and quantitatively relates the incidence of these cracks to parameters which can be controlled during steelmaking and continuous casting.

  15. Petascale Simulations of Stress Corrosion Cracking | Argonne Leadership

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Computing Facility 240 Million Year: 2013 Research Domain: Materials Science Corrosion is a complex technological and economic problem with an annual cost of about 3% of the nation's gross domestic product. The performance and lifetime of materials widely used in energy and nuclear technologies are often limited by corrosion under stress loads. Simulations performed at the Argonne Leadership Computing Facility are revealing the atomistic mechanisms that control stress-induced corrosion

  16. Method for cracking hydrocarbon compositions using a submerged reactive plasma system

    DOE Patents [OSTI]

    Kong, P.C.

    1997-05-06

    A method is described for cracking a liquid hydrocarbon composition (e.g. crude oil) to produce a cracked hydrocarbon product. A liquid hydrocarbon composition is initially provided. An electrical arc is generated directly within the hydrocarbon composition so that the arc is entirely submerged in the composition. Arc generation is preferably accomplished using a primary and secondary electrode each having a first end submerged in the composition. The first ends of the electrodes are separated from each other to form a gap there between. An electrical potential is then applied to the electrodes to generate the arc within the gap. A reactive gas is thereafter delivered to the arc which forms a bubble around the arc. Gas delivery may be accomplished by providing a passageway through each electrode and delivering the gas through the passageways. The arc and gas cooperate to produce a plasma which efficiently cracks the hydrocarbon composition. 6 figs.

  17. Method for cracking hydrocarbon compositions using a submerged reactive plasma system

    DOE Patents [OSTI]

    Kong, Peter C.

    1997-01-01

    A method for cracking a liquid hydrocarbon composition (e.g. crude oil) to produce a cracked hydrocarbon product. A liquid hydrocarbon composition is initially provided. An electrical arc is generated directly within the hydrocarbon composition so that the arc is entirely submerged in the composition. Arc generation is preferably accomplished using a primary and secondary electrode each having a first end submerged in the composition. The first ends of the electrodes are separated from each other to form a gap therebetween. An electrical potential is then applied to the electrodes to generate the arc within the gap. A reactive gas is thereafter delivered to the arc which forms a bubble around the arc. Gas delivery may be accomplished by providing a passageway through each electrode and delivering the gas through the passageways. The arc and gas cooperate to produce a plasma which efficiently cracks the hydrocarbon composition.

  18. A STUDY OF CORROSION AND STRESS CORROSION CRACKING OF CARBON STEEL NUCLEAR WASTE STORAGE TANKS

    SciTech Connect (OSTI)

    BOOMER, K.D.

    2007-08-21

    The Hanford reservation Tank Farms in Washington State has 177 underground storage tanks that contain approximately 50 million gallons of liquid legacy radioactive waste from cold war plutonium production. These tanks will continue to store waste until it is treated and disposed. These nuclear wastes were converted to highly alkaline pH wastes to protect the carbon steel storage tanks from corrosion. However, the carbon steel is still susceptible to localized corrosion and stress corrosion cracking. The waste chemistry varies from tank to tank, and contains various combinations of hydroxide, nitrate, nitrite, chloride, carbonate, aluminate and other species. The effect of each of these species and any synergistic effects on localized corrosion and stress corrosion cracking of carbon steel have been investigated with electrochemical polarization, slow strain rate, and crack growth rate testing. The effect of solution chemistry, pH, temperature and applied potential are all considered and their role in the corrosion behavior will be discussed.

  19. Can surface cracks and unipolar arcs explain breakdown and gradient limits?

    SciTech Connect (OSTI)

    Insepov, Zeke; Norem, Jim

    2013-01-15

    The authors argue that the physics of unipolar arcs and surface cracks can help understand rf breakdown and vacuum arc data. They outline a model of the basic mechanisms involved in breakdown and explore how the physics of unipolar arcs and cracks can simplify the picture of breakdown and gradient limits in accelerators, tokamaks as well as laser ablation, micrometeorites, and other applications. Cracks are commonly seen in SEM images of arc damage and they are produced as the liquid metal cools. They can produce the required field enhancements to explain field emission data and can produce mechanical failure of the surface that would trigger breakdown events. Unipolar arcs can produce currents sufficient to short out rf structures, and can cause the sort of damage seen in SEM images. They should be unstable, and possibly self-quenching, as seen in optical fluctuations and surface damage. The authors describe some details and consider the predictions of this simple model.

  20. Evaluation of cracking in the 241-AZ tank farm ventilation line at the Hanford Site

    SciTech Connect (OSTI)

    ANANTATMULA, R.P.

    1999-10-20

    In the period from April to October of 1988, a series of welding operations on the outside of the AZ Tank Farm ventilation line piping at the Hanford Site produced unexpected and repeated cracking of the austenitic stainless steel base metal and of a seam weld in the pipe. The ventilation line is fabricated from type 304L stainless steel pipe of 24 inch diameter and 0.25 inch wall thickness. The pipe was wrapped in polyethylene bubble wrap and buried approximately 12 feet below grade. Except for the time period between 1980 and 1987, impressed current cathodic protection has been applied to the pipe since its installation in 1974. The paper describes the history of the cracking of the pipe, the probable cracking mechanisms, and the recommended future action for repair/replacement of the pipe.

  1. Measurement of Fatigue Crack Growth Relationships in Hydrogen Gas for Pressure Swing Adsorber Vessel Steels

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Somerday, Brian P.; Barney, Monica

    2014-12-04

    We measured the hydrogen-assisted fatigue crack growth rates (da/dN) for SA516 Grade 70 steel as a function of stress-intensity factor range (ΔK) and load-cycle frequency to provide life-prediction data relevant to pressure swing adsorber (PSA) vessels. For ΔK values up to 18.5 MPa m1/2, the baseline da/dN versus ΔK relationship measured at 1Hz in 2.8 MPa hydrogen gas represents an upper bound with respect to crack growth rates measured at lower frequency. However, at higher ΔK values, we found that the baseline da/dN data had to be corrected to account for modestly higher crack growth rates at the lower frequenciesmore » relevant to PSA vessel operation.« less

  2. Measurement of Fatigue Crack Growth Relationships in Hydrogen Gas for Pressure Swing Adsorber Vessel Steels

    SciTech Connect (OSTI)

    Somerday, Brian P.; Barney, Monica

    2014-12-04

    We measured the hydrogen-assisted fatigue crack growth rates (da/dN) for SA516 Grade 70 steel as a function of stress-intensity factor range (ΔK) and load-cycle frequency to provide life-prediction data relevant to pressure swing adsorber (PSA) vessels. For ΔK values up to 18.5 MPa m1/2, the baseline da/dN versus ΔK relationship measured at 1Hz in 2.8 MPa hydrogen gas represents an upper bound with respect to crack growth rates measured at lower frequency. However, at higher ΔK values, we found that the baseline da/dN data had to be corrected to account for modestly higher crack growth rates at the lower frequencies relevant to PSA vessel operation.

  3. Observations and insights into Pb-assisted stress corrosion cracking of alloy 600 steam generator tubes

    SciTech Connect (OSTI)

    Thomas, L.; Bruemmer, Stephen M.

    2005-08-15

    Pb-assisted stress-corrosion cracking (PbSCC) of Alloy 600 steam-generator tubing in high-temperature-water service and laboratory tests were studied by analytical transmission electron microscopy of cross-sectioned samples. Examinations of pulled tubes from many pressurized water reactors revealed lead in cracks from 11 of 17 samples. Comparisons of the degraded intergranular structures with ones produced in simple laboratory tests with PbO in near-neutral AVT water showed that the PbSCC characteristics in service tubing could be reproduced without complex chemistries and heat-flow conditions that can occur during plant operation. Observations of intergranular and transgranular cracks promoted by Pb in the test samples also provided new insights into the mechanisms of PbSCC in mill-annealed and thermally treated Alloy 600.

  4. Method and apparatus for detecting external cracks from within a metal tube

    DOE Patents [OSTI]

    Caffey, Thurlow W. H.

    2001-08-07

    A method and tool using a continuous electromagnetic wave from a transverse magnetic-dipole source with a coaxial electric-dipole receiver is described for the detection of external sidewall cracks and other anomalies in boiler tubes and other enclosures. The invention utilizes the concept of radar backscatter rather than eddy-currents or ultrasound, which are sometimes used in prior art crack-detection methods. A numerical study of the distribution of the fields shows that the direct transmission from the source to the receiver is reduced from that in free space. Further, if the diameter of the receiver dipole is made sufficiently small, it should be possible to detect cracks with a scattering loss of up to -40 dB in thin-walled boiler tubes.

  5. ISO test method to determine sustained-load-cracking resistance of aluminium cylinders

    SciTech Connect (OSTI)

    Bhuyan, G.S.; Rana, M.D.

    1999-08-01

    Leak as well as rupture types of failures related to sustained-load-cracking (SLC) have been observed in high-pressure gas cylinders fabricated from certain aluminium alloy. The stable crack growth mechanism observed primarily in the cylinder neck and shoulder area have been identified as the SLC mechanism occurring at room temperature without any environmental effect. The International Organization for standardization (ISO) Sub-Committee 3, Working Group 16 has developed a test method to measure the SLC resistance using fracture mechanics specimens along with an acceptance criterion for aluminium cylinders. The technical rationale for the proposed test method and the physical significance of the acceptance criterion to the cylinder performance in terms of critical stress-crack size relationship is presented. Application of the developed test method for characterizing new aluminium alloy for manufacturing cylinders is demonstrated. SLC characteristics of several aluminium cylinders as well as on-board cylinders for natural gas vehicles assessed by the authors are discussed.

  6. Method and means of reducing erosion of components of plasma devices exposed to helium and hydrogen isotope radiation

    DOE Patents [OSTI]

    Kaminsky, Manfred S.; Das, Santosh K.; Rossing, Thomas D.

    1977-01-25

    Surfaces of components of plasma devices exposed to radiation by atoms or ions of helium or isotopes of hydrogen can be protected from damage due to blistering by shielding the surfaces with a structure formed by sintering a powder of aluminum or beryllium and its oxide or by coating the surfaces with such a sintered metal powder.

  7. Keep Customers-and Energy-From Slipping Through the Cracks | Department

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    of Energy Keep Customers-and Energy-From Slipping Through the Cracks Keep Customers-and Energy-From Slipping Through the Cracks A photo of three people standing and talking to each other, two men and a woman, inside a home. The most successful energy efficiency upgrade programs have customers who are willing and able to implement energy efficiency upgrades. This may seem like an obvious statement; however, many upgrade programs are struggling to reach their upgrade goals because they allow

  8. Intrinsic stage I crack propagation in Al-Zn-Mg single crystals

    SciTech Connect (OSTI)

    Petit, J.; Kosche, K.; Gudladt, H.J. Daimler-Benz AG, Stuttgart, Max-Planck-Institut fuer Metallforschung, Stuttgart, )

    1992-04-01

    A clear identification has been achieved for intrinsic stage I fatigue-crack propagation in single crystals of a high-purity Al-Zn-Mg alloy. The intrinsic stage I regime is noted to be much faster than intrinsic stage II for comparable loading conditions. The 'shielding' effect related to stage I-like propagation is significantly more important than anticipated on the basis of the conventional comparison to stage II. The propagation of a small surface crack growing in stage I is comparable to that of intrinsic stage I in single crystals rather than to either stage I or stage II in polycrystals. 11 refs.

  9. Cohesive Modeling of Dynamic Crack Growth in Homogeneous and Functionally Graded Materials

    SciTech Connect (OSTI)

    Zhang Zhengyu; Paulino, Glaucio H.; Celes, Waldemar

    2008-02-15

    This paper presents a Cohesive Zone Model (CZM) approach for investigating dynamic crack propagation in homogeneous and Functionally Graded Materials (FGMs). The failure criterion is incorporated in the CZM using both a finite cohesive strength and work to fracture in the material description. A novel CZM for FGMs is explored and incorporated into a finite element framework. The material gradation is approximated at the element level using a graded element formulation. A numerical example is provided to demonstrate the efficacy of the CZM approach, in which the influence of the material gradation on the crack growth pattern is studied.

  10. A tool to detect external cracks from within a metal tube

    SciTech Connect (OSTI)

    Caffey, T.W.H.

    1997-01-01

    A tool using a continuous electromagnetic wave from a transverse magnetic-dipole source with a coaxial electric-dipole receiver is outlined for the detection of external sidewall cracks in boiler tubes. A numerical study of the distribution of the fields shows that the direct transmission from the source to the receiver is reduced from that in free space. Further, if the diameter of the receiver dipole is made sufficiently small, it should be possible to detect cracks with a scattering loss of up to 40dB in thin-walled boiler tubes.

  11. Cracking Molecular Structures with Bright Lights - and a Few Good Eggs |

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Department of Energy Cracking Molecular Structures with Bright Lights - and a Few Good Eggs Cracking Molecular Structures with Bright Lights - and a Few Good Eggs June 22, 2012 - 11:04am Addthis This rendering shows a lysozyme structural model against its X-ray diffraction pattern from SLAC’s Linac Coherent Light Source (LCLS), a powerful X-ray laser facility. Researchers have achieved high-resolution images of these simple biomolecules using advanced crystallography at LCLS. | Photo by

  12. Mechanisms of stress corrosion cracking for iron-based alloys in high-temperature water

    SciTech Connect (OSTI)

    Zhou, X.Y.; Congleton, J.; Bahraloloom, A.

    1998-11-01

    Stress corrosion cracking (SCC) susceptibilities of a series of iron-based alloys (IBA), including some high-purity irons, were evaluated in lithiated water at temperatures up to 300 C. Inclusion distributions in each material were established using quantitative metallography and energy dispersive x-ray analysis (EDX). Electrochemical measurements were performed to investigate film formation kinetics. Results showed the minimum potential for SCC was a function of the inclusion content. Reducing the inclusion content in IBA moved the minimum potential for SCC in the anodic direction and/or increased the temperature for the onset of cracking but did not eliminate SCC.

  13. The Helium Cooling System and Cold Mass Support System for theMICE Coupling Solenoid

    SciTech Connect (OSTI)

    Wang, L.; Wu, H.; Li, L.K.; Green, M.A.; Liu, C.S.; Li, L.Y.; Jia, L.X.; Virostek, S.P.

    2007-08-27

    The MICE cooling channel consists of alternating threeabsorber focus coil module (AFC) and two RF coupling coil module (RFCC)where the process of muon cooling and reacceleration occurs. The RFCCmodule comprises a superconducting coupling solenoid mounted around fourconventional conducting 201.25 MHz closed RF cavities and producing up to2.2T magnetic field on the centerline. The coupling coil magnetic fieldis to produce a low muon beam beta function in order to keep the beamwithin the RF cavities. The magnet is to be built using commercialniobium titanium MRI conductors and cooled by pulse tube coolers thatproduce 1.5 W of cooling capacity at 4.2 K each. A self-centering supportsystem is applied for the coupling magnet cold mass support, which isdesigned to carry a longitudinal force up to 500 kN. This report willdescribe the updated design for the MICE coupling magnet. The cold masssupport system and helium cooling system are discussed indetail.

  14. A modified heat leak test facility employing a closed-cycle helium refrigerator

    SciTech Connect (OSTI)

    Boroski, W.N.

    1996-01-01

    A Heat Leak Test Facility (HLTF) has been in use at Fermilab for many years. The apparatus has successfully measured the thermal performance of a variety of cryostat components under simulated operating conditions. While an effective tool in the cryostat design process, the HLTF has several limitations. Temperatures are normally fixed at cryogen boiling points and run times are limited to cryogen inventory. Moreover, close personnel attention is required to maintain system inventories and sustain system equilibrium. To provide longer measurement periods without perturbation and to minimize personnel interaction, a new heat leak measurement facility (HLTF-2) has been designed that incorporates a closed-cycle helium refrigerator. The two-stage refrigerator provides cooling to the various temperature stations of the HLTF while eliminating the need for cryogens. Eliminating cryogen inventories has resulted in a reduction of the amount of direct personnel attention required.

  15. Comparison of classical and quantal calculations of helium three-body recombination

    SciTech Connect (OSTI)

    Prez-Ros, Jess Greene, Chris H.; Ragole, Steve; Wang, Jia

    2014-01-28

    A general method to study classical scattering in n-dimension is developed. Through classical trajectory calculations, the three-body recombination is computed as a function of the collision energy for helium atoms, as an example. Quantum calculations are also performed for the J{sup ?} = 0{sup +} symmetry of the three-body recombination rate in order to compare with the classical results, yielding good agreement for E ? 1 K. The classical threshold law is derived and numerically confirmed for the Newtonian three-body recombination rate. Finally, a relationship is found between the quantum and classical three-body hard hypersphere elastic cross sections which is analogous to the well-known shadow scattering in two-body collisions.

  16. Numerical investigation of pulse-modulated atmospheric radio frequency discharges in helium under different duty cycles

    SciTech Connect (OSTI)

    Sun Jizhong; Ding Zhengfen; Li Xuechun; Wang Dezhen [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116023 (China); Wang Qi [Dalian Institute of Semiconductor Technology, School of Electronics Science and Technology, Dalian University of Technology, Dalian 116023 (China)

    2011-12-15

    Experiments observed that the pulse duty cycle has effects on the plasma homogeneity in pulse-modulated radio frequency (rf) discharges. In this paper, pulse-modulated rf (13.56 MHz) helium discharges are theoretically investigated using a two dimensional fluid model. With the pulse period being fixed to 15 {mu}s, it is found that when the pulse-on duration is over 4 {mu}s, i.e., the duty cycle is larger than approximately 27%, the discharge transits from an inhomogeneous to a homogeneous mode in every specific part of each pulse cycle under currently-used simulation parameters. More quantitative analysis shows that the discharge becomes more homogeneous as the duty cycle is increased but does not reach complete homogeneity. Possible reasons for the homogeneity improvement are discussed.

  17. Commissioning and operational results of the 12 GeV helium compression system at Jlab

    SciTech Connect (OSTI)

    Knudsen, Peter N.; Ganni, Venkatarao; Dixon, Kelly D.; Norton, Robert O.; Creel, Jonathan D.

    2015-12-01

    The new compressor system at Jefferson Lab (JLab) for the 12 GeV upgrade was commissioned in the spring of 2013 and incorporates many design changes, discussed in previous publications, to improve the operational range, efficiency, reliability and maintainability as compared to previous compressor skids used for this application. The 12 GeV helium compression system has five compressors configured with four pressure levels supporting three pressure levels in the new cold box. During compressor commissioning the compressors were operated independent of the cold box over a wide range of process conditions to verify proper performance including adequate cooling and oil removal. Isothermal and volumetric efficiencies over these process conditions for several built-involume ratios were obtained. This paper will discuss the operational envelope results and the modifications/improvements incorporated into the skids.

  18. Fast Thermal Helium Beam diagnostic for measurements of edge electron profiles and fluctuations

    SciTech Connect (OSTI)

    Agostini, M. Scarin, P.; Cavazzana, R.; Carraro, L.; Grando, L.; Taliercio, C.; Franchin, L.; Tiso, A.

    2015-12-15

    The edge of fusion experiments is a region where strong gradients develop, together with the presence of strong fluctuations due to turbulence. The thermal helium beam diagnostic developed for the RFX-mod experiment allows the measurements with a single diagnostic of both low frequency time evolution of the edge radial profiles of electron density and temperature (tens of hertz), and the high frequency fluctuations (hundreds of kHz). To maximize the collected light, the three HeI lines necessary to be measured for the evaluation of n{sub e} and T{sub e} are separated with a spectrograph, and multianode photomultipliers are used as light detectors. The paper describes the diagnostic setup, with the interface hardware with the machine and the optical layout, and the characterization of its performances.

  19. First Principles Calculations of Helium Solution Energies in BCC Transition Metals

    SciTech Connect (OSTI)

    Willaime, Francois; Fu, Chu Chun

    2008-07-01

    Density functional theory calculations of the solution energies of helium in substitutional, tetrahedral and octahedral sites have been performed for all BCC transition metals: V, Nb, Ta, Cr, Mo, W and Fe. The effects of exchange correlation functional and of pseudopotential have been investigated in Fe; they are relatively small. The solution energies are found to be weakly dependent on the element for the substitutional site whereas for the interstitial sites they are much smaller in group V than in group VI and they decrease from 3d to 4d and 5d metals. As a result an inversion is observed from V, Nb and Ta - which tend to favor the interstitial site - to Mo and W, which favor the substitutional one, with an intermediate behavior for Cr and Fe. Finally, the results indicate that the tetrahedral site is always energetically more favorable than the octahedral one by 0.2 to 0.3 eV. (authors)

  20. Corrosion and Creep of Candidate Alloys in High Temperature Helium and Steam Environments for the NGNP

    SciTech Connect (OSTI)

    Was, Gary; Jones, J. W.

    2013-06-21

    This project aims to understand the processes by which candidate materials degrade in He and supercritical water/steam environments characteristic of the current NGNP design. We will focus on understanding the roles of temperature, and carbon and oxygen potential in the 750-850 degree C range on both uniform oxidation and selective internal oxidation along grain boundaries in alloys 617 and 800H in supercritical water in the temperature range 500-600 degree C; and examining the application of static and cyclic stresses in combination with impure He environments in the temperature rang 750-850 degree C; and examining the application of static and cyclic stresses in combination with impure He environments in the temperature range 750-850 degree C over a range of oxygen and carbon potentials in helium. Combined, these studies wil elucidate the potential high damage rate processes in environments and alloys relevant to the NGNP.

  1. High-voltage electrical apparatus utilizing an insulating gas of sulfur hexafluoride and helium

    DOE Patents [OSTI]

    Wootton, Roy E.

    1980-01-01

    High-voltage electrical apparatus includes an outer housing at low potential, an inner electrode disposed within the outer housing at high potential with respect thereto, and support means for insulatably supporting the inner electrode within the outer housing. Conducting particles contaminate the interior of the outer housing, and an insulating gas electrically insulates the inner electrode from the outer housing even in the presence of the conducting particles. The insulating gas is comprised of sulfur hexafluoride at a partial pressure of from about 2.9 to about 3.4 atmospheres absolute, and helium at a partial pressure from about 1.1 to about 11.4 atmospheres absolute. The sulfur hexafluoride comprises between 20 and 65 volume percent of the insulating gas.

  2. Electron dynamics and plasma jet formation in a helium atmospheric pressure dielectric barrier discharge jet

    SciTech Connect (OSTI)

    Algwari, Q. Th.; O'Connell, D.

    2011-09-19

    The excitation dynamics within the main plasma production region and the plasma jets of a kHz atmospheric pressure dielectric barrier discharge (DBD) jet operated in helium was investigated. Within the dielectric tube, the plasma ignites as a streamer-type discharge. Plasma jets are emitted from both the powered and grounded electrode end; their dynamics are compared and contrasted. Ignition of these jets are quite different; the jet emitted from the powered electrode is ignited with a slight time delay to plasma ignition inside the dielectric tube, while breakdown of the jet at the grounded electrode end is from charging of the dielectric and is therefore dependent on plasma production and transport within the dielectric tube. Present streamer theories can explain these dynamics.

  3. Transient analysis of an FHR coupled to a helium Brayton power cycle

    SciTech Connect (OSTI)

    Chen, Minghui; Kim, In Hun; Sun, Xiaodong; Christensen, Richard; Utgikar, Vivek; Sabharwall, Piyush

    2015-08-01

    The Fluoride salt-cooled High-temperature Reactor (FHR) features a passive decay heat removal system and a high-efficiency Brayton cycle for electricity generation. It typically employs an intermediate loop, consisting of an intermediate heat exchanger (IHX) and a secondary heat exchanger (SHX), to couple the primary system with the power conversion unit (PCU). In this study, a preliminary dynamic system model is developed to simulate transient characteristics of a prototypic 20-MWth Fluoride salt-cooled High-temperature Test Reactor (FHTR). The model consists of a series of differential conservation equations that are numerically solved using the MATLAB platform. For the reactor, a point neutron kinetics model is adopted. For the IHX and SHX, a fluted tube heat exchanger and an offset strip-fin heat exchanger are selected, respectively. Detailed geometric parameters of each component in the FHTR are determined based on the FHTR nominal steady-state operating conditions. Three initiating events are simulated in this study, including a positive reactivity insertion, a step increase in the mass flow rate of the PCU helium flow, and a step increase in the PCU helium inlet temperature to the SHX. The simulation results show that the reactor has inherent safety features for those three simulated scenarios. It is observed that the increase in the temperatures of the fuel pebbles and primary coolant is mitigated by the decrease in the reactor power due to negative temperature feedbacks. The results also indicate that the intermediate loop with the two heat exchangers plays a significant role in the transient progression of the integral reactor system.

  4. Microstructure-sensitive small fatigue crack growth assessment. Effect of strain ratio multiaxial strain state and geometric discontinuities

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Castelluccio, Gustavo M.; McDowell, David L.

    2015-09-16

    Fatigue crack initiation in the high cycle fatigue regime is strongly influenced by microstructural features. Research efforts have usually focused on predicting fatigue resistance against crack incubation without considering the early fatigue crack growth after encountering the first grain boundary. However, a significant fraction of the variability of the total fatigue life can be attributed to growth of small cracks as they encounter the first few grain boundaries, rather than crack formation within the first grain. Our paper builds on the framework previously developed by the authors to assess microstructure-sensitive small fatigue crack formation and early growth under complex loadingmore » conditions. Moreover, the scheme employs finite element simulations that explicitly render grains and crystallographic directions along with simulation of microstructurally small fatigue crack growth from grain to grain. The methodology employs a crystal plasticity algorithm in ABAQUS that was previously calibrated to study fatigue crack initiation in RR1000 Ni-base superalloy. Our work present simulations with non-zero applied mean strains and geometric discontinuities that were not previously considered for calibration. Results exhibit trends similar to those found in experiments for multiple metallic materials, conveying a consistent physical description of fatigue damage phenomena.« less

  5. Intergranular attack and stress corrosion cracking of Alloy 600 in high-temperature caustic solutions containing contaminants

    SciTech Connect (OSTI)

    Bandy, R.; Roberge, R.; van Rooyen, D.

    1985-06-01

    Concentrated caustic is a primary cause of stress corrosion cracking and intergranular attack of Alloy 600 tubing in PWRs. However, temperature, electrochemical potential, stress, and metallurgical state all play a role. This study provides the quantitative evidence needed to develop models of crack growth and to devise effective countermeasures.

  6. Microstructure-sensitive small fatigue crack growth assessment. Effect of strain ratio multiaxial strain state and geometric discontinuities

    SciTech Connect (OSTI)

    Castelluccio, Gustavo M.; McDowell, David L.

    2015-09-16

    Fatigue crack initiation in the high cycle fatigue regime is strongly influenced by microstructural features. Research efforts have usually focused on predicting fatigue resistance against crack incubation without considering the early fatigue crack growth after encountering the first grain boundary. However, a significant fraction of the variability of the total fatigue life can be attributed to growth of small cracks as they encounter the first few grain boundaries, rather than crack formation within the first grain. Our paper builds on the framework previously developed by the authors to assess microstructure-sensitive small fatigue crack formation and early growth under complex loading conditions. Moreover, the scheme employs finite element simulations that explicitly render grains and crystallographic directions along with simulation of microstructurally small fatigue crack growth from grain to grain. The methodology employs a crystal plasticity algorithm in ABAQUS that was previously calibrated to study fatigue crack initiation in RR1000 Ni-base superalloy. Our work present simulations with non-zero applied mean strains and geometric discontinuities that were not previously considered for calibration. Results exhibit trends similar to those found in experiments for multiple metallic materials, conveying a consistent physical description of fatigue damage phenomena.

  7. Creep and Creep-Fatigue Crack Growth at Structural Discontinuities and Welds

    SciTech Connect (OSTI)

    Dr. F. W. Brust; Dr. G. M. Wilkowski; Dr. P. Krishnaswamy; Mr. Keith Wichman

    2010-01-27

    The subsection ASME NH high temperature design procedure does not admit crack-like defects into the structural components. The US NRC identified the lack of treatment of crack growth within NH as a limitation of the code and thus this effort was undertaken. This effort is broken into two parts. Part 1, summarized here, involved examining all high temperature creep-fatigue crack growth codes being used today and from these, the task objective was to choose a methodology that is appropriate for possible implementation within NH. The second part of this task, which has just started, is to develop design rules for possible implementation within NH. This second part is a challenge since all codes require step-by-step analysis procedures to be undertaken in order to assess the crack growth and life of the component. Simple rules for design do not exist in any code at present. The codes examined in this effort included R5, RCC-MR (A16), BS 7910, API 579, and ATK (and some lesser known codes). There are several reasons that the capability for assessing cracks in high temperature nuclear components is desirable. These include: (1) Some components that are part of GEN IV reactors may have geometries that have sharp corners - which are essentially cracks. Design of these components within the traditional ASME NH procedure is quite challenging. It is natural to ensure adequate life design by modeling these features as cracks within a creep-fatigue crack growth procedure. (2) Workmanship flaws in welds sometimes occur and are accepted in some ASME code sections. It can be convenient to consider these as flaws when making a design life assessment. (3) Non-destructive Evaluation (NDE) and inspection methods after fabrication are limited in the size of the crack or flaw that can be detected. It is often convenient to perform a life assessment using a flaw of a size that represents the maximum size that can elude detection. (4) Flaws that are observed using in-service detection

  8. Trapping helium in Y{sub 2}Ti{sub 2}O{sub 7} compared to in matrix iron: A first principles study

    SciTech Connect (OSTI)

    Yang, Litong; Jiang, Yong E-mail: odette@engineering.ucsb.edu; Robert Odette, G. E-mail: odette@engineering.ucsb.edu; Yamamoto, Takuya; Liu, Zuming; Liu, Yong

    2014-04-14

    Pyrochlore Y{sub 2}Ti{sub 2}O{sub 7} is a primary precipitate phase in nano-structured ferritic alloys (NFAs) for fission and fusion energy applications. We report a theoretical study for assessing the relative stability of trapping helium in Y{sub 2}Ti{sub 2}O{sub 7} versus in matrix iron. Various defect structures and the associated energies are examined and compared. Results reveal that helium can be deeply trapped in Y{sub 2}Ti{sub 2}O{sub 7} and that the corresponding self-interaction is essentially repulsive. Transmutant helium in NFAs prefers to occupy individual octa-interstitial sites in Y{sub 2}Ti{sub 2}O{sub 7}, before forming small clusters in Y{sub 2}Ti{sub 2}O{sub 7}. Helium partitioning in NFAs depends on the number and dispersion of Y{sub 2}Ti{sub 2}O{sub 7}; and thus initially, bubble formation and growth in iron matrix can be largely suppressed. Charge transfer occurs from helium to neighboring oxygen anions, but not to neighboring metal cations, suggesting a general effectiveness of trapping helium in oxides. Reasons for the ultimate fate of helium to form small nm-scale interface bubbles are also discussed.

  9. Free radicals induced in aqueous solution by non-contact atmospheric-pressure cold plasma

    SciTech Connect (OSTI)

    Tani, Atsushi; Fukui, Satoshi; Ono, Yusuke; Kitano, Katsuhisa; Ikawa, Satoshi

    2012-06-18

    To understand plasma-induced chemical processing in liquids, we investigated the formation of free radicals in aqueous solution exposed to different types of non-contact atmospheric-pressure helium plasma using the spin-trapping technique. Both hydroxyl radical (OH{center_dot}) and superoxide anion radical (O{sub 2}{sup -}{center_dot}) adducts were observed when neutral oxygen gas was additionally supplied to the plasma. In particular, O{sub 2}{sup -}{center_dot} can be dominantly induced in the solution via oxygen flow into the afterglow gas of helium plasma. This type of plasma treatment can potentially be used in medical applications to control infectious diseases, because the O{sub 2}{sup -}{center_dot} is crucial for sterilization of liquids via atmospheric-pressure plasma.

  10. Catalytic cracking. (Latest citations from the NTIS data base). Published Search

    SciTech Connect (OSTI)

    Not Available

    1992-05-01

    The bibliography contains citations concerning applications of catalytic cracking in fluidized beds, moving beds, refineries, vacuum distillation, and reformers. Design criteria, models, controls, and operating procedures are also discussed. (Contains 250 citations and includes a subject term index and title list.)

  11. Catalytic cracking. (Latest citations from the NTIS Bibliographic database). Published Search

    SciTech Connect (OSTI)

    Not Available

    1993-09-01

    The bibliography contains citations concerning applications of catalytic cracking in fluidized beds, moving beds, refineries, vacuum distillation, and reformers. Design criteria, models, controls, and operating procedures are also discussed. (Contains 250 citations and includes a subject term index and title list.)

  12. The effect of specimen strength and thickness on cracking susceptibility during the Sigmajig weldability test

    SciTech Connect (OSTI)

    Lippold, J.C.; Shademan, S.S.; Baeslack, W.A. III

    1996-03-01

    The effects of yield strength and specimen thickness on the threshold stress for solidification cracking using the Sigmajig weldability test have been determined for A-286 stainless steel. An increase in test specimen yield strength results in a decrease in the threshold stress for cracking. This decrease is attributed in part to a decrease in the width of the plastically deformed weld zone as the yield strength increases, which enhances strain localization in this region and promotes solidification cracking. Over a range of yield strengths, an increase in specimen thickness generally results in higher threshold stress for cracking, which are attributed to an increased inherent restraint. The relationship between weld pool shape, the solidification grain and the fracture stress during transverse loading has been investigated by performing hot-ductility tests of weld fusion zone specimens. The hot-ductility behavior of specimens produced from welds exhibiting elliptical and teardrop-shaped weld pools is comparable. However, specimens produced from welds that exhibit a teardrop-shaped weld pool fracture along the fusion zone centerline above the nil-ductility temperature, whereas specimens produced from welds that exhibit an elliptical-shaped weld pool fracture in the partially melted zone. A correlation was observed between the fracture stress measured by hot-ductility testing and threshold stresses measured using the Sigmajig test.

  13. Fatigue of polycrystalline silicon for MEMS applications: Crack growth and stability under resonant loading conditions

    SciTech Connect (OSTI)

    Muhlstein, C.L.; Howe, R.T.; Ritchie, R.O.

    2001-12-05

    Although bulk silicon is not known to exhibit susceptibility to cyclic fatigue, micron-scale structures made from silicon films are known to be vulnerable to degradation by fatigue in ambient air environments, a phenomenon that has been recently modeled in terms of a mechanism of sequential oxidation and stress-corrosion cracking of the native oxide layer.

  14. Stress-corrosion cracking of Inconel alloy 600 in high-temperature water: an update. [PWR

    SciTech Connect (OSTI)

    Bandy, R.; van Rooyen, D.

    1983-01-01

    Inconel 600 has been tested in high-temperature aqueous media (without oxygen) in several tests. Data are presented to relate failure times to periods of crack initiation and propagation. Quantitative relationships have been developed from tests in which variations were made in temperature, applied load, strain rate, water chemistry, and the condition of the test alloy.

  15. Numerical modeling and experiments of creep crack growth under cyclic loading

    SciTech Connect (OSTI)

    Brust, F.W.

    1995-12-31

    This paper presents a summary of some recent studies of creep crack growth under history dependent load conditions. The effect of a proper constitutive law is illustrated. Moreover, the asymptotic fields are reconsidered under cyclic creep conditions. In addition, several experiments are modeled and the behavior of integral parameters is discussed.

  16. Stress corrosion cracking of Ni-Cu alloy 400 tubes in feedwater heaters

    SciTech Connect (OSTI)

    Amar, A.S.

    1994-12-31

    This paper presents the results of the inspections and metallurgical evaluations of a high pressure feedwater heater that experienced numerous tube failures after a short service life. Using EPRI NDE Center technical support, tubes were eddy current tested with special probes in the tubesheet region and with conventional probes in the remaining straight portion. Pulled tubes were metallurgically examined. Crack depths were correlated with eddy current indications. Short axial cracks were found on the inner surface of the tubes at roll transitions. Failures were attributed to intergranular stress corrosion cracking. The cold drawn-stress relieved Monel{trademark} (Alloy 400) tube had < 10 KSI hoop residual stress, however the residual stress was probably much higher in the roll transition. A large number of tubes were plugged based on the eddy current indications, however several tubes that showed no indications had leaked a few months later. This suggested that after initiation, crack growth was rapid. The heater was replaced after 4.5 years of service.

  17. Analysis of crack initiation and growth in the high level vibration test at Tadotsu

    SciTech Connect (OSTI)

    Kassir, M.K.; Park, Y.J.; Hofmayer, C.H.; Bandyopadhyay, K.K.; Shteyngart, S.

    1993-08-01

    The High Level Vibration Test data are used to assess the accuracy and usefulness of current engineering methodologies for predicting crack initiation and growth in a cast stainless steel pipe elbow under complex, large amplitude loading. The data were obtained by testing at room temperature a large scale modified model of one loop of a PWR primary coolant system at the Tadotsu Engineering Laboratory in Japan. Fatigue crack initiation time is reasonably predicted by applying a modified local strain approach (Coffin-Mason-Goodman equation) in conjunction with Miner`s rule of cumulative damage. Three fracture mechanics methodologies are applied to investigate the crack growth behavior observed in the hot leg of the model. These are: the {Delta}K methodology (Paris law), {Delta}J concepts and a recently developed limit load stress-range criterion. The report includes a discussion on the pros and cons of the analysis involved in each of the methods, the role played by the key parameters influencing the formulation and a comparison of the results with the actual crack growth behavior observed in the vibration test program. Some conclusions and recommendations for improvement of the methodologies are also provided.

  18. Overlapping double etch technique for evaluation of metallic alloys to stress corrosion cracking

    DOE Patents [OSTI]

    Not Available

    1980-05-28

    A double overlapping etch zone technique for evaluation of the resistance of metallic alloys to stress corrosion cracking is described. The technique involves evaluating the metallic alloy along the line of demarcation between an overlapping double etch zone and single etch zone formed on the metallic alloy surface.

  19. Overlapping double etch technique for evaluation of metallic alloys to stress corrosion cracking

    DOE Patents [OSTI]

    Steeves, Arthur F.; Stewart, James C.

    1981-01-01

    A double overlapping etch zone technique for evaluation of the resistance of metallic alloys to stress corrosion cracking. The technique involves evaluating the metallic alloy along the line of demarcation between an overlapping double etch zone and single etch zone formed on the metallic alloy surface.

  20. Cracking catalysts comprising phosphorus and method of preparing and using the same

    SciTech Connect (OSTI)

    Absil, R.P.L.; Herbst, J.A.

    1993-07-27

    A zeolite catalyst is described for cracking hydrocarbons formed by a process comprising the steps of: forming a slurry comprising clay, a source of phosphorus and an acid stable zeolite; and spray drying said slurry in the absence of other non-zeolitic inorganic oxide matrices at a pH which is sufficiently low to provide a calcined attrition index of [<=] 10.