Radiolytic Corrosion of238Pu-doped UO2Pellets in 5 M NaCl Solution

Abstract

AbstractDeaerated 5 M NaCl solution is alpha-irradiated up to 700 days in the presence of UO2pellets. Experiments are conducted with238Pu-doped pellets in pure brine and with undoped UO2pellets in a238Pu containing brine. The long-lived radiolysis products H2, O2and ClO3-are formed in all cases proportional to the dose applied on the solution and with yields corresponding to 200, 80 and 7 nMol/(L*Gy).The U concentrations increase with time but do not exceed about 10−4Mol/L thus indicating Uranium to be solubility limited. Moreover, the rinse solutions of the vessels at the end of the experiments contain up to one order of magnitude more U than found in the solutions. The total amounts of mobilized U deviate by less than a factor 10 from each other regardless of the large ratio of surface dose rates (ratio up to 2300) or mean dose rates (ratio up to 100), applied while the reference experiment (UO2pellet in pure brine) yields only some 10−7Mol/L U which is over 3 orders of magnitude lower than observed in experiments with radiation present.The simulation of the radiation chemical processes using a kinetic reaction model can reasonably reproduce the findings of the experiments with respect to the formation of H2and O2and give the order of magnitude for the concentrations of chlorine species and of oxidized UO2.