How inorganic anions in groundwater influence the mechanism of oxidativedissolution of nuclear fuels in geological repositories in case of barrier failure.

• H2O2 has previously been shown to be the main oxidant responsible for driving the process of radiation-induced dissolution of spent nuclear fuel in geological repositories for spent nuclear fuel. As the groundwater composition will vary depending on geographical location as well as on the age of the repository (in relation to glacial cycles, etc.), it is important to elucidate the impact of different groundwater constituents. While several studies have addressed the impact of HCO3- and halide ions on the radiation chemistry of water in general and radiation-induced oxidative dissolution of spent nuclear fuel in particular, very few studies have addressed the impact of halide ions on the mechanism of the reaction between H2O2 and UO2. In this work, the impact of Cl-, Br- and ClO4- on the mechanism and kinetics of H2O2-induced oxidative dissolution of UO2-powder in aqueous suspensions with and without added HCO3- has been studied experimentally. The experiments show that for systems containing 10 mM HCO3- and an initial H2O2-concentration of 0.15 mM, the presence of 1 M Cl-, Br- or ClO4- does not influence the kinetics of the reaction. At higher initial H2O2-concentrations, the presence of 1 M Br- appears to increase the rate of H2O2 consumption as well as the rate of UO22+ release. In solutions without added HCO3-, the presence of 1 M Cl-, Br- or ClO4- has an impact on the overall kinetics of the process at all initial H2O2-concentrations. This is partly attributed to an ionic strength effect enhancing adsorption of UO22+ to UO2 and partly attributed to stabilization of soluble uranyl-peroxo complexes mainly by Cl- and Br-.

Ämnesord

NATURVETENSKAP  -- Kemi -- Oorganisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Inorganic Chemistry (hsv//eng)

Nyckelord

Kemi

Chemistry

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vet (ämneskategori)

ovr (ämneskategori)