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

In this work, we have studied the impact of Y sub(2)O sub(3) on the kinetics of oxidative dissolution of UO sub(2) and the consumption of H sub(2)O sub(2). The second order kinetics of catalytic consumption of H sub(2)O sub(2) on Y sub(2)O sub(3) was investigated in aqueous Y sub(2)O sub(3) powder suspensions by varying the solid surface area to solution volume ratio. The resulting second order rate constant is 10 super(-8) m s super(-1), which is of the same magnitude as for the reaction between H sub(2)O sub(2) and UO sub(2). Powder experiments with mixtures of UO sub(2) and Y sub(2)O sub(3) show that Y sub(2)O sub(3) has no effect on the oxidative dissolution of UO sub(2), whereas the consumption of H sub(2)O sub(2) seems to be slightly slower in the presence of Y sub(2)O sub(3) and H sub(2) respectively. UO sub(2) pellets with solid inclusions of Y sub(2)O sub(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 sub(2)O sub(2) consumption is similar for all cases and is well in line with kinetic data from powder experiments. The effects of H sub(2) and Y sub(2)O sub(3) on the oxidative dissolution of UO sub(2) under gamma irradiation are similar to those found in experiments with H sub(2)O sub(2). No significant difference in dissolution between inert and reducing atmosphere can be observed for pure UO sub(2).