Review of the studies on the effect of ionizing radiation for redox front migration in HLW repository

Yamaguchi, Makoto; Yui, Mikazu

Studies on the effect of ionizing radiation for redox front migration in HLW repository were reviewed. The concept of the redox front by groundwater radiolysis around HLW was proposed by Neretnieks in 1982, and it was employed in the performance assessment of spent fuel disposal system executed by Swedish regulatory organization (SKI) in early 90s. With very conservative assumption that all the radiolytic oxidants diffuse into engineered barrier, the redox front reached the bedrock after several hundred years after canister failure, which increased the dose rate of redox-sensitive radioactive elements. However, dissolution tests of spent fuels under various redox conditions indicated that dissolved hydrogen strongly suppress the oxidative dissolution of UO matrix and redox front migration by radiolytic oxidants has not been mentioned in performance assessments since late 90s.