Performance Restoration of a Tritium-Aged LaNi _4.25Al _0.75 Sample

Journal Article · Mon May 18 00:00:00 EDT 2020 · Fusion Science and Technology

DOI:https://doi.org/10.1080/15361055.2020.1718839· OSTI ID:1637907

Staack, Gregory C. ^[1]; James, David W.  ^[1]

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1. Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

Hydride beds containing LaNi _4.25Al _0.75 (LANA.75) are used to store significant quantities of tritium. These hydride beds have a limited service life due to radiolytic decay of tritium to 3He within the metal matrix. The crystal structure of the hydride is altered by trapped ³He, which has a very low solubility in the metal. The altered structure induces the formation of a heel of trapped hydrogen isotopes and diminishes the reversible capacity of the hydride. With sufficient tritium exposure, the bed loses the ability to deliver 3He-free tritium, and replacement is needed. Demonstration of a means to regenerate tritium-aged LANA.75 in situ would delay or even eliminate the need to replace lanthanum nickel aluminum (LANA) hydride beds. This paper presents test results obtained during regeneration testing. The efficacy of regeneration testing was evaluated by comparing tritium desorption isotherms collected on the hydride before and after exposure to regeneration conditions. Testing was performed on a bench-scale tritium-aged LANA.75 sample that was previously isotopically exchanged (from tritium to deuterium), passivated, and recovered. Once transferred to a high-temperature test cell, the deuterium heel of the sample was isotopically exchanged with tritium, and a baseline desorption isotherm was collected for comparison purposes. The sample was then heated under vacuum, and comparative isotherms were gathered between regeneration evolutions. Shifts in isotherms show progressive improvements with higher-temperature exposure over the tritium-aged baseline. The heel was significantly reduced, and the reversible capacity of the hydride was essentially restored to near virgin values. For all tested conditions, the plateau pressure remained higher than virgin LANA.75.

• Research Organization: Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)
• Sponsoring Organization: USDOE Office of Environmental Management (EM)
• Grant/Contract Number: AC09-08SR22470
• OSTI ID: 1637907
• Report Number(s): SRNL-STI-2018-00688; TRN: US2201685
• Journal Information: Fusion Science and Technology, Vol. 76, Issue 4; Conference: Tritium 2019, 12TH International Conference On Tritium Science & Technology, Busan, Korea, April 22-26, 2019; ISSN 1536-1055
• Publisher: American Nuclear Society
• Country of Publication: United States
• Language: English

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