Inert Blanketing of a Hydride Bed Using Typical Grade Protium

The reduction in hydride absorption rate due to ”blanketing” can be explained in terms of a reduced hydrogen partial pressure in the bed due to the accumulation of inerts (i.e. non-hydrogen isotopes) in the bed void volume.  Literature results show reduced absorption rates when protium for bed absorption contains helium with low-end inert compositions in the 0.6 to 1% range. A hydride bed containing 9.66 kg of LaNi_4.25Al_0.75 (LANA0.75) metal hydride - a nominal capacity of 1400 STP-L, was cycled repeatedly to decrepitate the hydride material into smaller particles for bed strain measurement. The hydride cycles added and removed nominally 1000 to 1100 STP-L of protium per hydride cycle. Consistent and repeatable absorptions results were observed for different absorption cycles. During one of the absorption tests, slower absorption results were obtained due to the use of typical grade (500 ppm inerts), instead of research grade, protium which blanketed the bed. The impact of 0.05% inerts in protium on bed absorption rate is shown and explained in terms of an increase in inert partial pressure as the bed was loaded.