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Effects of pH and Uranium Valence State on the Aqueous Dissolution of Brannerite

Published online by Cambridge University Press:  01 February 2011

Y. Zhang ,
E. Loi ,
M. Blackford ,
T. McLeod ,
H. Li  and
B. Begg
Y. Zhang
Affiliation:
Materials and Engineering Science, ANSTO, PMB 1, Menai, NSW 2234, Australia
E. Loi
Affiliation:
Materials and Engineering Science, ANSTO, PMB 1, Menai, NSW 2234, Australia
M. Blackford
Affiliation:
Materials and Engineering Science, ANSTO, PMB 1, Menai, NSW 2234, Australia
T. McLeod
Affiliation:
Materials and Engineering Science, ANSTO, PMB 1, Menai, NSW 2234, Australia
H. Li
Affiliation:
Materials and Engineering Science, ANSTO, PMB 1, Menai, NSW 2234, Australia
B. Begg
Affiliation:
Materials and Engineering Science, ANSTO, PMB 1, Menai, NSW 2234, Australia
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Abstract

The dissolution of the thorium analogue of brannerite (ThTi2O6-I) and U(IV)/U(V) doped Th-brannerite (Th0.97U0.03Ti2O6-II and Th0.955U0.03Ca0.015Ti2O6-III) in aqueous media under atmospheric conditions has been studied to elucidate the effects of pH and uranium valence state on the dissolution rate.

The dissolution of I is nearly stoichiometric but slightly preferential release of U occurs for II and preferential release of Ca and U occur for III. The V-shape pH dependence previously observed for U-brannerite only occurs for U (not other matrix elements) for II, indicating that the pH dependence is related to the U oxidation state upon dissolution. The normalised U dissolution rates of III are nearly an order of magnitude higher than those of II for pH values over 3, suggesting brannerite is less durable with U(V) doping. TEM examination of specimens after leaching revealed few surface alteration products, which is consistent with the nearly stoichiometric dissolution of thorium brannerite.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 807: Symposium Scientific Basis for Nuclear Waste Management XXVII , 2003 , 279
Copyright
Copyright © Materials Research Society 2004

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References

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