NAGRA Opalinus Clay (…002 - Version 1
FEP 5.2.7 Alpha-radiolysis - production of oxidants and hydrogen, and recombination​

No significant radiolysis of water around the SF canisters occurs prior to canister breaching, because of the shielding effects of the canisters. Following breaching and ingress of water into the canisters, radioloytic decomposition of water close to the fuel matrix will occur, giving rise to a range of radiolysis products, although some recombination of radiolytic oxidants and reductants may occur. Radiolysis produces oxidants that may influence the rate of fuel matrix dissolution. Furthermore, it produces hydrogen gas that may also influence matrix dissolution, as well as the transport of radionuclides that form volatile species.