Air Passivation of Metal Hydride Beds for Waste Disposal

One waste acceptance criteria for hydride bed waste disposal is that the bed be non-pyrophoric. Batch-wise air ingress tests were performed which determined the amount of air consumed by a metal hydride bed. A desorbed, 4.4 kg titanium prototype hydride storage vessel (HSV) produced a 4.4°C internal temperature rise upon the first air exposure cycle and a 0.1°C temperature rise upon a second air exposure. A total of 346 scc air was consumed by the bed (0.08 scc per gram Ti). A desorbed, 9.66 kg LaNi_4.25Al_0.75 prototype storage bed experienced larger temperature rises over successive cycles of air ingress and evacuation. The cycles were performed over a period of days with the bed effectively passivated after the 12^th cycle. Nine to ten STP-L of air reacted with the bed producing both oxidized metal and water.