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Title: Update on Titanium Drip Shield


No abstract prepared.

; ;
Publication Date:
Research Org.:
Yucca Mountain Project, Las Vegas, Nevada
Sponsoring Org.:
OSTI Identifier:
Report Number(s):
MOL.20060626.0011, DC# 47633; TRN: US0606040
DOE Contract Number:
Resource Type:
Resource Relation:
Conference: NA
Country of Publication:
United States

Citation Formats

G.M. Gordon, K. Mon, and F. Hua. Update on Titanium Drip Shield. United States: N. p., 2006. Web.
G.M. Gordon, K. Mon, & F. Hua. Update on Titanium Drip Shield. United States.
G.M. Gordon, K. Mon, and F. Hua. Mon . "Update on Titanium Drip Shield". United States. doi:.
title = {Update on Titanium Drip Shield},
author = {G.M. Gordon and K. Mon and F. Hua},
abstractNote = {No abstract prepared.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon May 08 00:00:00 EDT 2006},
month = {Mon May 08 00:00:00 EDT 2006}

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  • Both qualitative and quantitative assessments have been conducted to evaluate the effects of hydrogen induced cracking on the drip shield. The basic premise of the assessments is that failure will occur once the hydrogen content exceeds a certain limit or critical value, H{sub c}. Potential mechanisms for hydrogen absorption in the drip shield have been identified to be general passive corrosion and galvanic couple with steel components. Both qualitative and quantitative evaluations indicated that hydrogen concentration in the drip shield will be below the critical value by a considerable margin. The choice of the mathematical models and associated parameters appearsmore » to be reasonable. Continued effort in data collection and development should provide validation and improved level of confidence of the proposed models.« less
  • The Engineered Barrier System (EBS) represents one system in the performance of the Yucca Mountain high-level radioactive waste (HLW) repository to isolate and prevent the transport of radionuclides from the site to the accessible environment. Breached Waste Package and Drip Shield Experiments (BWPDSE) were performed at the Department of Energy's National Nuclear Security Administration Nevada Support Facility in North Las Vegas, NV in the A-1 lowbay between May 2, 2002 and July 25, 2002. Data collected from the BWPDSE will be used to support the flux splitting model used in Analysis and Modeling Report ANL-WIS-PA-000001 REV 00 ICN 03 ''EBSmore » Radionuclide Transport Abstraction'' (BSC 2001a). Tests were conducted by dripping water from heights representing the drift crown or wall on a full-scale section of a drip shield with both smooth and rough surfaces. The drip shields had machined square breaches that represent the general corrosion breaches or nodes in the ''WAPDEG Analysis of Waste Package and Drip Shield Degradation'' AMR (CRWMS M&O 2000d). Tests conducted during the BWPDSE included: initial tests to determine the splash radius distances and spread factor from the line of drip impact, single patch tests to determine the amount of water collected in target breaches from splashing or rivulet flow, multiple patch tests to determine the amount of water collected in several breaches from both splashing and rivulet flow, and bounding flow rate tests. Supplemental data were collected to provide additional information for rivulet spread, pan evaporation in the test chamber, and water temperatures of the input water and drip shield surface water. The primary flow mechanism observed on both smooth and rough surfaces was rivulet flow, not film flow. Lateral rivulet spread distances were, in general, wider on the smooth drip shield surface than on the rough drip shield surface. There were substantial differences between the mechanisms of rivulet formation and movement on smooth and rough drip shield surfaces. Water collected in breaches was a function of the location of drip impact upstream from the target breach, i.e., impact breaches must be directly above or slightly to the side of the breaches in order for a substantial volume of water to collect in breaches. Splash droplets contributed a small portion of the water collected in breaches. Mass balances showed that evaporation from the drip shield was a large component of water loss. This was particularly manifested during low flow runs of the bounding flow rate tests where test duration was around five hours.« less
  • A simple and conservative model has been developed to evaluate the effects of hydrogen-induced cracking on the drip shield. The basic premise of the model is that failure will occur once the hydrogen content exceeds a certain limit or critical value, HC. This model is very conservative because it assumes that, once the environmental and material conditions can support that particular corrosion process, failure will be effectively instantaneous. In the description of the HIC model presented in Section 6.1, extensive evidence has been provided to support a qualitative assessment of Ti-7 as an excellent choice of material for the dripmore » shield with regard to degradation caused by hydrogen-induced cracking. LTCTF test data observed at LLNL, although unqualified, provides additional indication beyond a qualitative level that hydrogen concentration appears to be low in titanium materials. Quantitative evaluation based on the HIC model described in Section 6.1 indicates that the hydrogen concentration does not exceed the critical value. It is concluded that drip shield material (Ti-7) is able to sustain the effects of hydrogen-induced cracking.« less
  • Ti Gr 7 is an extremely corrosion resistant material, with a very stable passive film. Based upon exposures in the LTCTF, it has been determined that the general corrosion and oxidation rates of Ti Gr 7 are essentially below the level of detection. In any event, over the 10,000 year life of the repository, general corrosion and oxidation should not be life limiting. The large separation between measured corrosion and threshold potentials indicate that localized breakdown of the passive film is unlikely under plausible conditions, even in SSW at 120 C. In the future, the pH and current in crevicesmore » formed from Ti Gr 7 should be determined experimentally. With exposures of two years, no significant evidence of crevice corrosion has been observed with Ti Gr 16 in SDW, SCW, and SAW at temperatures up to 9O C, though many of the samples have a beautiful green patina. An abstracted model has been presented, with parameters determined experimentally, that should enable performance assessment to account for the general and localized corrosion of this material. A feature of this model is the use of the materials specification to limit the range of corrosion and threshold potentials, thereby making sure that substandard materials prone to localized attack are avoided.« less
  • The environments on the drip shield and waste package outer barrier are controlled by the compositions of the waters that contact these components. the temperature (T) of these components, and the effective relative humidity (RH) at these components. Because the composition of the waters that are expected to enter the emplacement drifts (either by seepage flow or by episodic flow) have not been specified: well J13 water was chosen as the reference water (Harrar 1990). Section 6.2 discusses the accessible RH for the temperatures of interest at the repository horizon. Section 6.3 discusses the adsorption of water on metal alloysmore » in the absence of hygroscopic salts. Because the temperatures of the DSs and the WPOBs are higher than those of the surrounding near-field environment, the relative humidity at the DSs and the WPOBs will be lower than that of the surrounding near-field environment. This difference is a result of the water partial pressure in the drift being constant and no higher than the equilibrium water vapor pressure at the temperature of the drift wall.« less