OXIDATION OF NUCLEAR-FUEL (UO2) BY THE PRODUCTS OF WATER RADIOLYSIS -DEVELOPMENT OF A KINETIC-MODEL

Radiolysis of groundwater will produce oxidants and reductants which c an affect the oxidation and dissolution of used fuel (UO2) placed in a geological disposal vault. A kinetic model to describe the oxidation of UO2 by the products of radiolysis of water is described. This model assumes that a monomolecular surface layer of UO2 reacts as if it wer e dissolved in a thin layer of water of a thickness corresponding to t he diffusion range of the radicals formed during radiolysis. In this m anner we can use the rate constants for the reactions of radiolytic sp ecies with dissolved uranium as an analog of the heterogeneous system for which rate constants are unknown. The refinement of this model, ba sed on a series of electrochemical and open-circuit corrosion experime nts, is described. Model predictions are compared with dissolution rat es measured in these experiments.