The Role of Dissolved Hydrogen on Rare Earth–Doped Uranium Dioxide Corrosion in the Presence of Hydrogen Peroxide

Abstract

Electrochemical and X-ray photoelectron spectroscopic (XPS) methods have been used to study the combined influence of H2O2 and H2 on the oxidation of SIMFUEL (UO2) electrodes in 0.1 mol·dm−3 KCl (pH = 9.5) at 60°C. The SIMFUEL electrodes contain REIII (rare earth) ions at UIV lattice sites within the UO2 matrix. In both Ar-purged and H2/Ar-purged solutions the final corrosion potential values were dependent on [H2O2]; however, the XPS analyses showed no differences in the degree of oxidation of uranium, indicating no enduring effect of H2 on the oxidation of UO2 in H2O2– containing solutions. However, in H2/Ar-purged solutions the corrosion potential achieves considerably more positive transient values than in Ar-purged solutions before relaxing to the final value. A possible reason is that the UIV ⇄ UVI redox cycle induced by hydrogen peroxide oxidation and hydrogen reduction activates the UO2 surface, leading to a temporary enhancement of UO2 dissolution (as UO22+).