Milestone 1.2.12: The Fate of Oxygen Radical Species in Corroded Aluminum Alloys under Irradiation

Abstract

The U.S. Department of Energy tasked Idaho National Laboratory to evaluate the feasibility of extended dry storage of aluminum-clad spent nuclear fuel (ASNF) in heliumbackfilled canisters. A significant research effort has been devoted to determining the amount of radiation-induced molecular hydrogen (H2) generation from corrosion layers that would be present on the fuel assembly surfaces. However, limited attention has been directed to the oxygen radical species that are concurrently generated in these H2 producing radiation environments. This report collates and summarizes the available experimental and computational studies on the fate of these reactive oxygen radicals during the irradiation of aluminum oxyhydroxide and hydroxide polymorphs typically formed on ASNF. Based on this review, it is determined that radiation-induced oxygen-centered radicals do not react to give molecular oxygen gas (O2), but rather remain trapped in the aluminum corrosion layers in their original crystal lattice positions. Overall, O2 generation will not be a concern for extended storage of ASNF in helium-backfilled canisters. That is, no O2 contribution to pressurization of sealed dry storage systems or creation of a flammable atmosphere is anticipated.

Modeling DOE Standard Canister Configurations with Updated Surface Chemistry

“…The new chemistry model assumes that the water adsorbed in the oxyhydroxide matrix undergoes basic water radiolysis reactions, and that the aluminum oxyhydroxide breakdown into a series of reactions involving stable Oand O3groups. Horne, 2023 &Conrad et al, 2022 present an overview of the literature for these mechanisms that involve the formation of an electron and hole pair (𝑒 ! , ℎ " ) form in the solid from ionization and excitation.…”