Oxidation of UO2 by radiolytic oxidants

The kinetics of UO2 oxidation by H2O2 has been studied using aqueous suspensions Of UO2-powder. The second order,rate constant for the reaction between H2O2 and UO2 has been determined to 8 x 10(-7) m/min (based on the surface to solution volume ratio) in the absence of carbonate. By studying the reaction between UO2 and other oxidants, it is possible to draw conclusions concerning the mechanism. The logarithm of the second order rate constant, ln k, for UO2 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 UO2 is one-electron transfer. A Fenton like mechanism is plausible for the reaction between UO2 and H2O2. The diffusion controlled rate constant in this particular system is approximately 10(3) m/min, and therefore the reactions with OH- and CO3- are estimated to be diffusion controlled. (C) 2003 Elsevier B.V. All rights reserved.