When spent fuel eventually comes into contact with groundwater, fuel matrix dissolution will be strongly influenced by redox conditions in the near field. The most significant factors influencing redox conditions at the fuel surface in a reducing environment are alpha-radiolysis of water and the presence of reductants such as Fe(II) and H2 arising principally from canister corrosion. The radiolytic yield (G) of molecular oxidants, generally considered to be ~1 molecule of hydrogen peroxide per 100 eV for alpha-radiolysis, is expected to be considerably lower in the presence of reductants but the overall effect on the rate of matrix dissolution cannot yet be reliably quantified. We have attempted to estimate the effective yield of oxidants by examining the results from various studies of spent fuel and UO2 dissolution, including alpharadiolysis experiments. The analysis suggests that the effective yield (G eff) is likely to be no greater than 0.01 in the repository environment. The implications of low Geff values are discussed in relation to fuel dissolution rates. Some other aspects of radiolysis relevant to nearfield redox chemistry are also examined, including the potential significance of alpha emitters sorbed in the repository near field in producing radiolytic oxidants.
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Smith, P.A., Johnson, L.H. Spent Fuel Dissolution: An Examination of the Impacts of Alpha-Radiolysis. MRS Online Proceedings Library 608, 29 (1999). https://doi.org/10.1557/PROC-608-29