The effect of Y2O3 on the dynamics of oxidative dissolution of UO2

In this work, we have studied the impact of Y2O3 on the kinetics of oxidative dissolution of UO2 and the consumption of H2O2. The second order kinetics of catalytic consumption of H2O2 on Y2O3 was investigated in aqueous Y2O3 powder suspensions by varying the solid surface area to solution volume ratio. The resulting second order rate constant is 10(-8) m s(-1), which is of the same magnitude as for the reaction between H2O2 and UO2. Powder experiments with mixtures of UO2 and Y2O3 show that Y2O3 has no effect on the oxidative dissolution of UO2, whereas the consumption of H2O2 seems to be slightly slower in the presence of Y2O3 and H-2 respectively. UO2 pellets with solid inclusions of Y2O3 show a decrease in oxidative dissolution by a factor of 3.3 and 5.3 under inert and hydrogen atmosphere, respectively. The rate of H2O2 consumption is similar for all cases and is well in line with kinetic data from powder experiments. The effects of H-2 and Y2O3 on the oxidative dissolution of UO2 under gamma irradiation are similar to those found in experiments with H2O2. No significant difference in dissolution between inert and reducing atmosphere can be observed for pure UO2.