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  1. Fracture analysis of the heat-affected zone in the NESC-1 spinning cylinder experiment

    This paper presents updated analyses of the cylinder specimen being used in the international Network for Evaluating Steel Components (NESC) large-scale spinning-cylinder project (NESC-1). The NESC was organized as an international forum to exchange information on procedures for structural integrity assessment, to collaborate on specific projects, and to promote the harmonization of international standards. The objective of the NESC-1 project is to focus on a complete procedure for assessing the structural integrity of aged reactor pressure vessels. A clad cylinder containing through-clad and subclad cracks will be tested under pressurized-thermal shock conditions at AEA Technology, Risley, U.K. Three-dimensional finite-element analysesmore » were carried out to determine the effects of including the cladding heat-affected zone (HAZ) in the models. The cylinder was modeled with inner-surface through-clad cracks having a depth of 74 mm and aspect ratios of 2:1 and 6:1. The cylinder specimen was subjected to centrifugal loading followed by a thermal shock and analyzed with a thermoelastic-plastic material model. The peak K{sub 1} values occurred at the clad/HAZ interface for the 6:1 crack and at the HAZ/base interface for the 2:1 crack. The analytical results indicate that cleavage initiation is likely to be achieved for the 6:1 crack, but questionable for the 2:1 crack.« less
  2. The work of the ICRP dose calculational task group: Issues in implementation of the ICRP dosimetric methodology

    Committee 2 of the International Commission on Radiological Protection (ICRP) has had efforts underway to provide the radiation protection community with age-dependent dose coefficients, i.e.g, the dose per unit intake. The Task Group on Dose Calculations, chaired by the author, is responsible for the computation of these coefficients. The Task Group, formed in 1974 to produce ICRP Publication 30, is now international in its membership and its work load has been distributed among the institutions represented on the task group. This paper discusses: (1) recent advances in biokinetic modeling; (2) the recent changes in the dosimetric methodology; (3) the novelmore » computational problems with some of the ICRP quantities; and (4) quality assurance issues which the Task Group has encountered. Potential future developments of the dosimetric framework which might strengthen the relationships with the emerging understanding of radiation risk will also be discussed.« less
  3. Fissile-waste management constraints: Safeguards and criticality

    Radioactive wastes containing fissionable materials must be managed differently than wastes that do not contain fissionable materials because fissionable materials have two unique characteristics: (a) the potential for nuclear criticality and (b) the potential for use in building of nuclear weapons. A study was completed to determine which wastes containing {sup 233}U could be treated as typical radioactive wastes and which wastes would require special handling because of the fissile content. The methodology of the study provides a basis for defining waste thresholds for other wastes containing fissile material.
  4. Weapons-grade MOX PWR benchmark calculations

    A simplified model of a Westinghouse pressurized water reactor (PWR) assembly has been proposed as a weapons-grade mixed-oxide (MOX) benchmark. The bundle design consists of a uniform plutonium loading that would be appropriate for a full MOX core. The benchmark consists of several state point calculations at zero burnup, a multicycle depletion to 45 MWd/kg, and several state point calculations at end of life. Calculations of the PWR MOX benchmark have been performed with the KENO Monte Carlo code and the VENTURE diffusion theory code using cross sections created using the SCALE system and with the HELIOS system. The benchmarkmore » has been proposed as a light water reactor MOX benchmark with initial results being submitted by the participants by September 1998. The complete specifications for the benchmark are available at« less
  5. Macroscopic cross sections for the management of weapons-grade Pu fuels in BWR`s

    One possible method to reduce the enrichment of the surplus of weapons-grade plutonium is to irradiate mixed-oxide fuels (MOX) in commercial nuclear reactors like the boiling water reactors (BWRs) built by General Electric (GE). Contributions to evaluate this possibility are currently made by Oak Ridge National Laboratory (ORNL) and its contractors. Because important decisions are to be made based on calculations, the calculational procedures, in particular the HELIOS two-dimensional Scand-power proprietary code, were benchmarked against available experience with near-weapons-grade Pu fuel and against other codes. In this work the author reports his calculation of a diffusion theory macroscopic cross sectionmore » as a function of burnup, for different combinations of operational parameters. These results are to be input later to the FORMOSA-B code, developed at North Carolina State University (NCSU), to study fuel management strategies in the long-range operation of BWRs with MOX fuels. Seventeen cases for various conditions of the fuel assemblies were specified by NCSU. These correspond to different combinations of void fractions, fuel temperatures, control rods, and history. The middle section of the 9- x 9-rod MOX fuel assembly for the GE-11 BWR design is shown.« less
  6. MCNP-to-TORT radiation transport calculations for the Fissile Materials Disposition Program

    The US Department of Energy Fissile Materials Disposition Program has begun studies for disposal of surplus weapons-grade plutonium (WG-Pu) as mixed uranium-plutonium oxide (MOX) fuel for commercial light water reactors (LWRs). Most MOX fuel experience is with reactor-grade plutonium (RG-Pu). Therefore, to use WG-Pu in MOX fuel, one must demonstrate that the experience with RG-Pu is relevant. Initial tests have been made in an I-hole of the Advanced Test Reactor (ATR) at the Idaho National Engineering and Environmental Laboratory (INEEL) to aid in the investigation of some of the unresolved issues. One of these issues is to understand the impactmore » of gallium on LWR MOX fuel performance since it is present in small amounts in WG-Pu. Initial radiation transport calculations of the test specimens have been made at INEEL using the MCNP Monte Carlo radiation transport code. These calculations were made to determine the linear heating rates in the fuel specimens. Because of the nature of Monte Carlo, it is extremely time consuming and inefficient to show detailed hot spots in the specimens. However, results from discrete ordinates radiation transport calculations could show these spatial details. Therefore, INEEL was tasked with producing an MCNP source at the boundary of a rectangular parallel-piped enclosing the ATR I-hole, and Oak Ridge National Laboratory (ORNL) was tasked with transforming this boundary source into a discrete ordinates boundary source for the Three dimensional Oak Ridge radiation Transport (TORT) code. The results of this work are discussed.« less
  7. Data from thermal-hydraulic experiments at Oak Ridge National Laboratory

    Thermal-hydraulic separate effects experimentation in support of nuclear reactor licensing was initiated in the mid-1970s at Oak Ridge National Laboratory (ORNL) and ended in the mid-1980s. A variety of facilities were designed, built, and operated in support of the US Nuclear Regulatory Commission (NRC). These facilities were used to examine a wide variety of thermal-hydraulic phenomena applicable to commercial power reactors. More recently, in the early 1990s, experiments supporting research reactor design were also performed. A summary of the major nuclear reactor experimental efforts is shown in Table I. Each of these experiments generated a significant amount of raw datamore » and also a significant amount of reduced data that have been stored in a variety of ways which are discussed here. Technology has quickly overtaken database archival methods of the past and offers a significant opportunity to improve both the quantity and quality of the thermal-hydraulic information available, while allowing access to a much broader community. Incorporation of future and existing data in a uniform database would greatly benefit principal investigators who access this information.« less
  8. Optimization of the SNS neutron beam current

    The proposed Spallation Neutron Source (SNS) facility will consist of two parts: (a) a high-energy (1-GeV) and high-powered (1-MW) proton accelerator (linac) and accumulator ring and (b) a target station that converts the protons to low-energy (<2 eV) neutrons and delivers them to the neutron-scattering instruments. It will be a 60-Hz facility delivering 6 {times} 10{sup 15} protons each second in 60-{micro}s pulses with a linac length of 490 m and an accumulator ring circumference of 220 m. Work is now under way to optimize the neutron beam current. Both the intensity and the time pulse characteristics are important withmore » different requirements for different instruments. The effect of varying the reflector material, the moderator poison location, and the moderator dimensions has been considered. In addition, the impact on the current when a premoderator or a composite moderator is used has been assessed. Two reflector materials were picked to be studied in detail: beryllium and lead. A beryllium reflector gave a greater thermal neutron current but a wider pulse width, with the peak currents about the same. A simple figure of merit (FOM) (intensity/pulse width squared) favored the lead reflector.« less
  9. Geochemistry of hypabyssal rocks of the Midcontinent Rift system in Minnesota, and implications for a Keweenawan magmatic ``family tree``

    The hypabyssal rocks associated with the Keweenawan (1.1 Ga) Midcontinent Rift along the Minnesota shore of Lake Superior are a distinct suite within the rock associations of this region. These rocks are found predominantly as ophitic diabase dikes and sills of various sizes, ranging from a few meters to several hundred meters across. Chilled margins were sampled and analyzed by neutron activation analysis and microprobe fused-bead techniques for bulk chemistry. Mineral compositions were obtained by electron microprobe. Variations in composition were found that are consistent with fractionation. Major-element modeling of fractionation indicates that the majority of the hypabyssal rocks formedmore » at moderate pressures ({approximately}6 kbar), although a number show evidence of fractionation at near-surface levels, and some deeper ({approximately}10 kbar). Resorption features seen in plagioclase phenocrysts are evidence for magmatic evolution at varying levels in the crust. It is possible to relate the varied hypabyssal rocks to a single primary parent through polybaric fractionation. This parent is a high-Al primitive olivine tholeiite--a magma composition common among the volcanic rocks associated with the Midcontinent Rift. Trace-element modeling with this same parent composition yields results consistent with the formation of some hypabyssal rocks as products of a periodically tapped and replenished, constantly fractionating magma chamber, which can decouple the behavior of major and trace elements.« less
  10. Instantaneous phasor method for obtaining instantaneous balanced fundamental components for power quality control and continuous diagnostics

    Poor power quality not only causes additional energy losses, it may also cause detrimental interruptions to business and manufacturing operations. The growing popularity of electronic equipment, such as computers, televisions, electronic ballasts, solid-state motor controllers, and electronically controlled industry loads pollutes the power quality. In 1995, EPRI reported that the revenue losses due to poor power quality to US business alone were $400 billion per year. A new instantaneous phasor method for obtaining instantaneous balanced fundamental components is introduced. An example is presented. This technique may be used for active power quality control and for continuous diagnostics.

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