Dissolution of studtite [UO2(O2)(H2O)4] in various geochemical conditions

Jungjum Kim, HyunJu Kim, Won-Seok Kim, Wooyong Um

Journal of Environmental Radioactivity, 2018, 189, 57-66

https://doi.org/10.1016/j.jenvrad.2018.01.010

Abstract

This study determined the dissolution rate of studtite, (UO2)O2(H2O)4, which can be formed by reaction between H2O2 and UO22+ that leaks from spent nuclear fuel (SNF) in deep geological repositories. The batch dissolution experiments were conducted using synthesized studtite under different solution conditions with varying pHs and concentrations of HCO3− and [H2O2] in synthetic groundwater. The experimental results suggested that carbonate ligand and H2O2 in groundwater accelerated the dissolution of studtite and uranium (U) release. Above 10−5 M of H2O2 initial concentration, the released uranium concentration in solution decreased, possibly as a result of reprecipitation of studtite due to reaction between uranium and H2O2. The results will be useful to assess the comprehensive transport of uranium from both nuclear waste and SNF stored in deep geological repositories.