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

Abstract The dissolution of non-irradiated UO 2 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 UO 2 dissolution rate decreases linearly with pH while at alkaline pH the dissolution rate increases linearly with pH. At higher H 2 O 2 concentrations (10 −3 mol dm −3 ) the dissolution rates are lower than the ones at 10 −5 mol dm −3 H 2 O 2 , 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 H 2 O 2 concentration range 5 × 10 −7 – 5 × 10 −5 mol dm −3 according to our results, which is in agreement with H 2 O 2 concentrations determined in spent fuel leaching experiments.