An electrochemical and radiolytic study of the effects of H2 on the corrosion of UO2-based materials

Abstract

The influence of γ-radiation in the presence of dissolved hydrogen on the corrosion of uranium dioxide has been compared to the electrochemical behavior of uranium dioxide in aqueous chloride solutions. Hydrogen atoms, produced either electrochemically or by water radiolysis were shown to reduce UV in the oxide leading to suppression of its corrosion. The removal of electrochemical polarization, and of hydrogen when γ-radiation was present, allowed re-oxidation of the uranium dioxide accompanied by the reformation of hydrogen. These results are consistent with published studies which show the corrosion of spent nuclear fuel can be suppressed in the presence of hydrogen. H2 effect in suppressing the corrosion of UO2-based materials without catalysis of noble metal particles is studied by producing H radicals electrochemically and radiolytically. Reactive H radicals produced by H2O reduction at cathodic potentials, lead to the reduction of UV states which are present due either to the DyIII doping or the non-stoichiometry within the UO2 based materials. When the cathodic potential is switched to open circuit, the relaxation of ECORR (corrosion potential) indicates that the electrochemically reduced surface is unstable. The combination of γ-irradiation and H2 can also lead to the reduction of UO2. In the absence of dissolved H2, a similar relaxation of ECORR indicates that reactive H radicals produced electrochemically or radiolytically are responsible for the reduction of the UO2 matrix.