Effects of Radiation on Corrosive Environments for Overpack in Geological Disposal of Radioactive Waste

ABSTRACT The corrosion of overpacks in geological disposal is influenced by radiolysis products generated in groundwater during the early post‑closure period. In this study, the effects of groundwater composition and bentonite buffer material on radiolysis behavior were investigated through gamma‑ray irradiation experiments and calculations. Simulated groundwaters with low and high dissolved species concentrations were examined to evaluate hydrogen peroxide (H 2 O 2 ) and gas behavior. The experiments showed that bentonite significantly accelerates H 2 O 2 decomposition while having little effect on hydrogen (H 2 ) generation. A comprehensive groundwater radiolysis model incorporating major ionic species was developed and validated against experimental data. Good agreement was obtained for systems with high dissolved species concentrations, whereas discrepancies were observed under low‑concentration conditions, suggesting increased contributions of pure water radiolysis and uncertainties in reaction rate constants. Long‑term calculations at an absorbed dose rate of 1 Gy h −1 indicate quasi‐steady‐state oxidant concentrations, with dissolved oxygen (O 2 ) accumulation under high‑chloride conditions.