Abstract The kinetics of UO 2 oxidation by H 2O 2 has been studied using aqueous suspensions of UO 2-powder. The second order rate constant for the reaction between H 2O 2 and UO 2 has been determined to 8 × 10 −7 m/min (based on the surface to solution volume ratio) in the absence of carbonate. By studying the reaction between UO 2 and other oxidants, it is possible to draw conclusions concerning the mechanism. The logarithm of the second order rate constant, ln k, for UO 2 oxidation appears to be linearly related to the one-electron reduction potential, E 0, of the oxidant. This indicates that the rate limiting step in the oxidation of UO 2 is one-electron transfer. A Fenton like mechanism is plausible for the reaction between UO 2 and H 2O 2. The diffusion controlled rate constant in this particular system is approximately 10 3 m/min, and therefore the reactions with OH and CO 3 − are estimated to be diffusion controlled.