Tritium Aging of LaNi_4.15Al_0.85 (LANA.85)

The Savannah River Tritium Enterprise (SRTE) has used hydride beds to store and process hydrogen isotopes for over two decades. New beds are being designed to use a hydride material – LaNi_4.15Al_0.85 (LANA.85) – that has a lower plateau pressure than the material previously employed. LANA.85 is expected to have a limited service life due to radiolytic decay of tritium to He-3 within the metal matrix, which will result in degradation of hydride performance. Tritium aging was initiated on a LANA.85 metal hydride sample to look for changes in desorption isotherm performance which occur with aging. Desorption isotherms were collected at 120°C, and 160°C annually. A lower temperature isotherm was collected at 100°C after 2 years of aging. A single absorption isotherm was collected each year at 120°C. After testing, each sample was reloaded with tritium for quiescent aging until the following year. Samples were stored in the beta phase.

Results collected on the virgin material and annually for 2 years of tritium exposure are presented and discussed. The results have shown no unexpected behavior of the LANA.85 materials over the course of tritium exposure. As the service life of a the new hydride bed being designed is greater than 8 years, further annual monitoring and evaluation is recommended to track the effects of tritium exposure on isotherm behavior. Continued evaluation of will reduce the likelihood that unanticipated behaviors will be encountered in full scale production beds within the SRTE Tritium Facility.