The Anodic Reactions on Simulated Spent Fuel (SIMFUEL) in H2O2 Solutions: Effect of Carbonate/Bicarbonate

Abstract

The anodic behavior of simulated nuclear fuel (SIMFUEL) in solutions containing H2O2 and HCO3−/CO32− has been studied electrochemically and using surface analytical techniques, in particular X-ray photoelectron spectroscopy. Two anodic reactions are possible, the oxidative dissolution of UO2 and H2O2 oxidation. The rates of both reactions are controlled by the chemical release of UVI surface species, and can both be increased by the addition of HCO3−/CO32−. Under anodic conditions the dominant reaction is H2O2 oxidation, although UO2 dissolution may also be accelerated by the formation of a uranyl peroxocarbonate complex. Similarly, under open circuit (corrosion) conditions both UO2 corrosion and H2O2 decomposition are also controlled by the rate of release of UVI surface species which blocks access of H2O2 to the underlying conductive UIV1–2xUV2xO2+x surface. Presently, the balance between these two reactions is not known.