The effect of Y 2O 3 on the dynamics of oxidative dissolution of UO 2

Abstract

In this work, we have studied the impact of Y 2O 3 on the kinetics of oxidative dissolution of UO 2 and the consumption of H 2O 2. The second order kinetics of catalytic consumption of H 2O 2 on Y 2O 3 was investigated in aqueous Y 2O 3 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 H 2O 2 and UO 2. Powder experiments with mixtures of UO 2 and Y 2O 3 show that Y 2O 3 has no effect on the oxidative dissolution of UO 2, whereas the consumption of H 2O 2 seems to be slightly slower in the presence of Y 2O 3 and H 2 respectively. UO 2 pellets with solid inclusions of Y 2O 3 show a decrease in oxidative dissolution by a factor of 3.3 and 5.3 under inert and hydrogen atmosphere, respectively. The rate of H 2O 2 consumption is similar for all cases and is well in line with kinetic data from powder experiments. The effects of H 2 and Y 2O 3 on the oxidative dissolution of UO 2 under gamma irradiation are similar to those found in experiments with H 2O 2. No significant difference in dissolution between inert and reducing atmosphere can be observed for pure UO 2.