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Mechanism of Unirradiated UO2 (S) Dissolution in Nacl and Mgcl2 Brines at 25°C

Published online by Cambridge University Press:  15 February 2011

Joan de Pablo ,
J. Giménez ,
M. E. Torrero  and
I. Casas
Joan de Pablo
Affiliation:
Department of Chemical Engineering. Universitat Politècnica de Catalunya E-08028 Barcelona, Spain.
J. Giménez
Affiliation:
Department of Chemical Engineering. Universitat Politècnica de Catalunya E-08028 Barcelona, Spain.
M. E. Torrero
Affiliation:
Department of Chemical Engineering. Universitat Politècnica de Catalunya E-08028 Barcelona, Spain.
I. Casas
Affiliation:
Department of Chemical Engineering. Universitat Politècnica de Catalunya E-08028 Barcelona, Spain.
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Abstract

The dissolution of unirradiated UO2 (s) has been studied in NaCl and MgCl2 brines under both reducing and oxidizing conditions.

The initial uranium release under reducing conditions has been attributed to the dissolution of an initial oxidized layer. The final uranium concentrations have been modeled by using the PHRQPITZ computer program giving the solubility of the solid phase UO2 (s).

Under oxidizing conditions, the initial release is the sum of the oxidized layer dissolution and the oxidation/dissolution of the UO2. The release rates calculated are 1.4·10−5 mol d−1 m−2 in NaCl2-brine and 3.6·10−5 mol d−1 m−2 in MgCl2-brine. After the initial release, uranium concentration in the NaCI-brine reaches a constant value, which has been attributed to the formation of a secondary solid phase. In MgCl2-brine, the uranium concentration increases slowly indicating, in this case, no control by secondary phase formation.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 353: Symposium – Scientific Basis for Nuclear Waste Management XVIII , 1994 , 609
Copyright
Copyright © Materials Research Society 1995

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References

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