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Uranium(IV) Solubility and Hydrolysis Constants Under Reduced Conditions

Published online by Cambridge University Press:  15 February 2011

Tatsuya Yajima ,
Yuji Kawamura  and
Shinzo Ueta
Tatsuya Yajima
Affiliation:
Naka Energy Research Center, Mitsubishi Materials Corporation. 1002-14 Naka-machi, Naka-gun, Ibaraki, 311-01Japan.
Yuji Kawamura
Affiliation:
Naka Energy Research Center, Mitsubishi Materials Corporation. 1002-14 Naka-machi, Naka-gun, Ibaraki, 311-01Japan.
Shinzo Ueta
Affiliation:
Naka Energy Research Center, Mitsubishi Materials Corporation. 1002-14 Naka-machi, Naka-gun, Ibaraki, 311-01Japan.
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Abstract

The solubility of UO2 (s) was examined in dilute NaCl solutions at room temperature and in the pH range from 2 to 12. Dissolution equilibrium showed good agreements between the data obtained by oversaturation and undersaturation experiments.

The dissolution reactions that control the solubility of U[IV] are estimated as UO2 (s) + 4H+ → U4+ + 2H2O and UO2 (s) + 2H2O → U(OH)4°. The log K at zero ionic strength are yielded 0.34 ± 0.4 and −8.7 ± 0. 4, respectively. The hydrolysis constant (log β14) is calculated −9.0 ± 0.5 for the hydrolysis reaction of U4+ + 4H2) → U(OH)4° + 4H+. Contribution of the other uranium species to the solubility are of minor importance.

The crystallization of the precipitations of U02 (s) progressed gradually in the oversaturation experiments. Nevertheless the progress of crystallization had little effect on the solubility.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 353: Symposium – Scientific Basis for Nuclear Waste Management XVIII , 1994 , 1137
Copyright
Copyright © Materials Research Society 1995

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References

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