Solubility of Uranium Dioxide during Underground Disposal of Radioactive Wastes and Spent Nuclear Fuel
O. L. Gaskova1 and M. B. Bukaty2
1Institute of Mineralogy and Petrography, Siberian Branch of the Russian Academy of Sciences,
Pr. Akademika Koptyuga 3, Novosibirsk 630090 (Russia), E-mail: gaskova@uiggm.nsc.ru
2Institute of Gas and Petroleum Geology, Tomsk Affiliation,
Siberian Branch of the Russian Academy of Sciences,
Pr. Akademicheskiy 3, Tomsk 634055 (Russia)
Pages: 649-655
Abstract
The problem of reliable prediction of the safety of burial of the spent nuclear fuel in the environmental components is connected with the reliability of quantitative models describing solubility/precipitation of uranium dioxide UO2(s) as the major component, depending on a number of physicochemical parameters, such as temperature, Eh-pH, salt composition and concentration of electrolyte solutions. In the present paper we report on the free Gibbs' energy of formation of this phase and the accompanying complexes in the solutions of different composition. The reported values of Gibbs' energy allow reliable model reproduction of the experimental results on solubility and the concentrations of dissolved uranium observed in nature. In addition, the reasons that may cause local non-equilibrium fluctuations of the concentrations of this element under the conditions conjugated with the radioactive decay of short- and medium-lived isotopes are discussed.
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