The oxidative dissolution of unirradiated UO2 by hydrogen peroxide as a function of pH

The dissolution of non-irradiated UO2 was studied as a function of both pH and hydrogen peroxide concentration (simulating radiolytic generated product). At acidic pH and a relatively low hydrogen peroxide concentration (10(-5) mol dm(-3)), the UO2 dissolution rate decreases linearly with pH while at alkaline pH the dissolution rate increases linearly with pH. At higher H2O, concentrations (10(-3) mol dm(-3)) the dissolution rates are lower than the ones at 10(-5) mol dm(-3) H2O2, which has been attributed to the precipitation at these conditions of studtite (UO(4)(.)4H(2)O, which was identified by X-ray diffraction), together with the possibility of hydrogen peroxide decomposition. In the literature, spent fuel dissolution rates determined in the absence of carbonate fall in the H2O2 concentration range 5 x 10(-7)- 5 x 10(-5) mol dm(-3) according to our results, which is in agreement with H2O2 concentrations determined in spent fuel leaching experiments. (c) 2005 Elsevier B.V. All rights reserved.