Uranium Dissolution and Geochemical Modeling in Anoxic and Oxic Solutions

Abstract

ABSTRACTHigh Level Waste (HLW) glasses are to be stored in deep geologic repositories around the world. Some potential repository geologies have oxidizing groundwaters while some have reducing or anoxic groundwaters. The differences in the oxidizing potential of the groundwater, expressed as groundwater Eh, which has a profound impact on the release of multivalent species such as iron and uranium from the glass. Static leach testing of monolithic glass samples (ASTM C1220) doped with uranium were performed at 90°C in an Ar glovebox under anoxic and oxic conditions. Tests were performed in both deionized water and in simulated basaltic groundwater that was pre-equilibrated at low Eh. Geochemical modeling of the measured Eh-pH conditions from the oxic and anoxic experiments using Geochemist’s Workbench software, suggested that different colloidal species control the release of uranium species under oxic and anoxic conditions.