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Dissolution Studies of Soddyite as a Long-Term Analogue of theOxidative Alteration of the Spent Nuclear Fuel Matrix

Published online by Cambridge University Press:  03 September 2012

I. Pérez
Affiliation:
Polytechnic University of Catalunya, Dept. of Chem. Eng., Avd. Diagonal 647, 08028 Barcelona (Spain)
I. Casas
Affiliation:
Polytechnic University of Catalunya, Dept. of Chem. Eng., Avd. Diagonal 647, 08028 Barcelona (Spain)
M. E. Torrero
Affiliation:
Polytechnic University of Catalunya, Dept. of Chem. Eng., Avd. Diagonal 647, 08028 Barcelona (Spain)
E. Cera
Affiliation:
QuantiSci, Pare Tecnologie del Vallés, 08290 Cerdanyola (Spain)
L. Duro
Affiliation:
QuantiSci, Pare Tecnologie del Vallés, 08290 Cerdanyola (Spain)
J. Bruno
Affiliation:
QuantiSci, Pare Tecnologie del Vallés, 08290 Cerdanyola (Spain)
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Abstract

The thermodynamic and kinetic dissolution properties of a syntheticallyobtained soddyite have been determined at different bicarbonateconcentrations. This uranium-silicate is expected to be a secondary solidphase of the oxidative alteration pathway of uranium dioxide in waters withlow phosphate content and, consequently, it is likely to constitute one ofthe long-term uranium solubility limiting solid phases.

The experimental data obtained at the end of the experiments correspondfairly well to the theoretical model calculated with a log K0S0 of 3.9±0.7.

On the other hand, the general trend of the total uranium in solutionmeasured in the experiments as a function of time has been fitted by using akinetic equation obtained from the principle of detailed balancing of thedissolution reaction. In addition, the EQ3/6 code has also been used tomodel the uranium concentrations as a function of time. In both modelingexercises comparable results were obtained. The dissolution rate, normalizedto the total surface area used in the experiments as measured with the BETmethod, gave an average value of 6.8 (±4.4) 10−14 mol cm−2 s−1.

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Type
Research Article
Copyright
Copyright © Materials Research Society 1997

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References

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