Physicochemical Characteristics and Radiation-Chemical Processes in the System PuO2-Sorbed Water

The experimental data on formation of H-2 and O-2 during storage of PuO2 samples containing sorbed water were analyzed. It was shown that the rates of formation of these gases, all other factors being the same, are governed by the procedure of water sorption: in sorption from the liquid phase these rates are significantly higher than those in sorption from the gas phase. To elucidate the conditions of safe storage of PuO2, it is necessary to obtain systematic quantitative data on the kinetics of H-2 and O-2 formation in the system consisting of PuO2 and water sorbed from moist air. The optimized mathematical model of sorbed water radiolysis adequately describing the experimental data on the formation of H-2 and O-2 at room temperature in the system consisting of PuO2 and water sorbed from the liquid phase is presented. The rate constant of H-2 and O-2 recombination in the presence of PuO2 containing 2-3% water was found to be <= 1 x 10(-5) mol(-1) s(-1). With the knowledge of the reaction rate constants, the model allows calculation of the amounts of H-2 and O-2 and the pressure in the storage vessel depending on the amount of sorbed water, radiation dose rate, and storage duration.