The corrosion of nuclear fuel under waste disposal conditions is likely to be influenced by the bicarbonate/carbonate content of the groundwater since it increases the solubility of the U-VI corrosion product, [UO2](2+). As one of the half reactions involved in the corrosion process, the anodic dissolution of SIMFUEL (UO2) has been studied in bicarbonate/carbonate solutions (pH 9.8) using voltammetric and potentiostatic techniques and electrochemical impedance spectroscopy. The reaction proceeds by two consecutive one electron transfer reactions (U-IV -> U-V -> U-VI). At low potentials (<= 250 mV (vs. SCE) the rate of the first electron transfer reaction is rate determining irrespective of the total carbonate concentration. At potentials >250 mV (vs. SCE) the formation of a (UO2CO3)-O-VI surface layer begins to inhibit the dissolution rate and the current becomes independent of potential indicating rate control by the chemical dissolution of this layer. (C) 2010 Elsevier Ltd. All rights reserved.