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Sensitivity Analysis of Uranium Solubility Under Strongly Oxidizing Conditions

Published online by Cambridge University Press:  10 February 2011

L. Liu  and
I. Neretnieks
L. Liu
Affiliation:
Department of Chemical Engineering and Technology, Royal Institute of Technology, Stockholm, Sweden
I. Neretnieks
Affiliation:
Department of Chemical Engineering and Technology, Royal Institute of Technology, Stockholm, Sweden
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Abstract

To evaluate the effect of geochemical conditions in the repository on the solubility of uranium under strongly oxidizing conditions, a mathematical model has been developed to determine the solubility, by utilizing a set of non linear algebraic equations to describe the chemical equilibria in the groundwater environment. The model takes into account the predominant precipitation-dissolution reactions, hydrolysis reactions and complexation reactions that may occur under strongly oxidizing conditions. The model also includes the solubilitylimiting solids induced by the presence of carbonate, phosphate, silicate, calcium, and sodium in the groundwater. The thermodynamic equilibrium constants used in the solubility calculations are essentially taken from the NEA Thermochemical Data Base of Uranium, with some modification and some uranium minerals added, such as soddyite, rutherfordite, uranophane, uranyl orthophosphate, and becquerelite. By applying this model, the sensitivities of uranium solubility to variations in the concentrations of various groundwater component species are systematically investigated. The results show that the total analytical concentrations of carbonate, phosphate, silicate, and calcium in deep groundwater play the most important role in determining the solubility of uranium under strongly oxidizing conditions.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 556: Symposium QQ – Scientific Basis for Nuclear Waste Management XXII , 1999 , 1001
Copyright
Copyright © Materials Research Society 1999

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