A THEORETICAL INVESTIGATION OF RADIOLYTIC H2 GENERATION FROM SOLIDS

Abstract

Hydrogen generation from materials in nuclear materials storage is of critical interest due to the potential for pressurization and/or flammability issues. Studies have focused on aqueous systems or those with minor amounts of physisorbed water, since conventional knowledge identifies the radiolytic decomposition of water as the source of H{sub 2} gas. Furthermore, the approach to characterize gas generation is typically strictly empirical, relying on determination of G-values from which production in systems is estimated. Interestingly, exploratory work at SRNL1 on gamma exposure to fully-dried solids with chemically-bound water that are typical of those produced on aluminium-clad nuclear fuel in reactor and post-discharge storage has shown a profound production of hydrogen (as the sole gaseous species) from fully dried boehmite ({gamma}-AlOOH or Al{sub 2}O{sub 3} {center_dot} H{sub 2}O) powders and no observable hydrogen from gibbsite ({gamma}-Al(OH){sub 3} or Al{sub 2}O{sub 3} {center_dot} 3H{sub 2}O) under gamma irradiation from cobalt-60. This observation is significant in that gibbsite is known to thermally decompose at 80 C whereas boehmite is stable to 400 C. Radiation damage can have various effects on solids, including heating, bond breaking, and rearrangements in the bonding structure. For example, a molecule can be ionized resulting in the generation ofmore » free electrons which can, in turn, ionize another molecule. Alternately, reactive radical species such as {lg_bullet}OH or cation species may be formed, which can go on to change bonding structures.« less