Influence of groundwater composition on the reductive precipitation of U(VI) on corroding iron foil surfaces

In order to assess the disposal of spent nuclear fuel in a deep geological nuclear waste repository, the interactions between U(VI) and corroded iron present in the canister material are of importance. It is important to correctly model the fate of the oxidatively dissolved uranium in order to correctly estimate radium releases from the canister in the long term. The release of radionuclides into the environment depends on the dissolution of the UO2 matrix which is dependent on the redox conditions at the fuel surface. The effect of metallic iron on the reduction of U(VI) was studied under anoxic conditions using synthetic groundwaters with different compositions, chosen to investigate the influence of calcium-uranyl-carbonato complexes on the thermodynamics and kinetics of U(VI) reduction on anoxically corroding iron. The corrosion products formed on the iron surface were investigated using SEM-EDS and XPS to identify elemental composition and oxidation states of uranium and iron on the surface. The iron foils efficiently reduced U(VI) to U(IV) causing its significant sorption and precipitation on the iron foil surfaces in the form of U(IV).