Short term aging of LaNi{sub 4.25}Al{sub 0.75} tritide storage material
In support of the Tritium Facilities at the Savannah River Site (SRS), the Tritium Exposure Program (TEP) was initiated in 1986 to investigate the effects of tritium aging on metal hydride materials used in tritium processing applications. The primary material selected for tritium storage was the substituted LaNi{sub 5} alloy, LaNi{sub 4.25}Al{sub 0.75} (LANA.75). The substitution of Al for Ni served to lower the plateau pressure of the tritide, and to stabilize the material to cycling and tritium aging effects. The sub-atmospheric plateau pressure, of LANA.75 tritide at room temperature, made it a safe tritium storage medium, and the tritium aging effects were reduced from that of LaNi{sub 5} tritide, but not eliminated. LANA.75 tritides retain the {sup 3}He decay product of absorbed tritium in the metal lattice. As the concentration of {sup 3}He grows, the lattice becomes strained due to the insoluble species. This strain is manifest in tritium aging effects. These effects include (1) a decrease in the equilibrium plateau pressure, (2) an increase in the plateau slope, (3) a reduction in the reversible storage capacity, and (4) the evolution of a tritium heel. The long term aging effects have been studied over the years, however the short term (less than one year) tritium aging effects have not been investigated until now. The acquisition of desorption isotherms at more than one temperature allows the thermodynamic parameters of change in enthalpy, {Delta}H, and change in entropy, {Delta}S, for the {beta}-{alpha} phase transition of the metal tritide to be determined. These parameters are related to the equilibrium pressure, P, and the isothermal temperature, T, through the following relation: where R is the gas constant, and the factor of 1/2 yields results per mole of atomic tritium. A van`t Hoff plot of 1/2 Ln(P) versus 1/T may be fitted to a straight line, with the slope and intercept used to determine {Delta}H and {Delta}S through equation.
- Research Organization:
- Westinghouse Savannah River Co., Aiken, SC (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC09-89SR18035
- OSTI ID:
- 10188188
- Report Number(s):
- WSRC-MS-94-0477; CONF-9409181-7; ON: DE95001238; TRN: 94:021097
- Resource Relation:
- Conference: 19. Department of Energy conference on compatibility, aging and service life,Los Alamos, NM (United States),28-30 Sep 1994; Other Information: PBD: [1994]
- Country of Publication:
- United States
- Language:
- English
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