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 U-VI 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 U-VI surface species which blocks access of H2O2 to the underlying conductive (U1-2xU2xO2+xV)-U-IV surface. Presently, the balance between these two reactions is not known. (C) 2014 The Electrochemical Society. All rights reserved.