Anodic Dissolution Characteristics of UO2 Electrode in the Potential Ranges over Oxygen Evolution in Carbonate Solutions at Several pHs

This work studied the anodic dissolution characteristics of a UO2 electrode at several potentials which were much higher than the corrosion potential in carbonate solutions of a high concentration at several pHs. The cyclic voltammograms with several wide potential windows and dissolution rates at several constant applied potentials were measured in the carbonate solutions. The corrosion product at the electrode and the current efficiencies of the electrolytic dissolution were evaluated. The peak occurring after the potential region of the oxygen evolution in the voltammogram of the UO2 electrode was ascribed to the suppression of the oxygen evolution by a corrosion product of UO2CO3. The effective dissolution of UO2 in a carbonate solution could be obtained at an applied potential such as +4 V (vs SSE) or more, which was with an overpotential of oxygen evolution high enough to rupture the corrosion product at the electrode surface, rather than the potential for the oxidation of UO2 grain as UO22+ before the oxygen evolution. The corrosion potential of UO2 decreased with pH in the carbonate solution. And the dissolution rate and current efficiency of UO2 increased with decrease of pH in the carbonate solution. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3474950] All rights reserved.