Hydration behaviour of uranyl chloride: from fundamental chemistry to environmental applications

In water uranium exists almost exclusively as the uranyl ion [UO2]2+. In the presence of halides these can form complexes of the type [UO2(H2O)nClx]2-x, whose thermodynamics and structures in solution are not fully understood. This is important as high halide concentrations are expected to be found in spent nuclear fuels or under certain environmental conditions. In this work we propose to study the reaction of uranyl chloride [UO2(H2O)5][Cl]2 with LiCl under increasing halide concentrations to determine the structures and formation constants. The latter are important as these feed into thermodynamic databases but are experimentally unknown. These databases are used as prediction tools that underpin safety cases for storage of spent nuclear fuels so it is of importance to have robust, experimentally determined values.