Radiation-induced molecular hydrogen gas generation in the presence of aluminum alloy 1100.

The United States government currently manages nearly 13 metric tons of aluminum-clad spent nuclear fuel (SNF) without a long-term storage solution, so a fundamental understanding of corrosion processes occurring on aluminum alloy surfaces is of utmost importance to plan for extended (>50 years) interim dry storage of aluminum-clad SNF. While thermal and chemical corrosion processes are well characterized for aluminum, radiation effects are not. To help understand the impacts of radiation on aluminum-clad SNF, the radiation-induced molecular hydrogen gas (H 2) generation from pristine and pre-corroded aluminum alloy 1100 (Al-1100) coupons has been studied. Corrosion of coupons was achieved by submerging coupons in water at 95 °C for 29 days, yielding a ~5 μm boehmite/bayerite oxide film. Pre-corroded coupons were exposed to cobalt-60 gamma radiation to absorbed doses of up to 1.0 MGy under a variety of conditions: cover-gas composition (argon, nitrogen, or air), relative humidity (0, 50, and 100%), and temperature (ambient, 100, and 200 °C). Post-irradiation measurements demonstrated that the yield of H 2 was directly attributable to the presence of the Al-1100 coupons and their physisorbed water with dependence on absorbed gamma dose, relative humidity, and cover-gas composition. No H 2 was quantified in the presence of air, while both nitrogen and argon environments afforded higher H 2 yields with increasing relative humidities. This was attributed to the greater availability of adsorbed water for radiolytic processes. Irradiation of pre-corroded Al-1100 coupons at different temperatures under 0% relative humidity argon conditions yielded statistically equivalent H 2 yields for ambient temperatures and 100 °C. However, irradiation at 200 °C promoted a 3 to 4-fold increase in the yield of H 2 , possibly due to the transformation of bayerite to boehmite and/or improved efficiency of H• and H 2 release from oxide surfaces. • Pristine and pre-corroded Al-1100 coupons were exposed to gamma radiation in argon, nitrogen, and air gaseous environments. • Absorption of γ-radiation energy by the Al-1100 coupons generated H 2 but did not significantly alter the aluminum surface. • The presence of oxyhydroxide corrosion deposits promoted H 2 generation, relative to the assumed alumina on pristine coupons. • The H 2 generation rate followed argon > nitrogen > air coupon environments. [ABSTRACT FROM AUTHOR]