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Hydrolysis of R7T7 Nuclear Waste Glass in Dilute Media: Mechanisms and Rate as a function of Ph

Published online by Cambridge University Press:  28 February 2011

T. Advocat ,
J. L. Crovisier ,
E. Vernaz ,
G. Ehret  and
H. Charpentier
T. Advocat
Affiliation:
CEA-CEN Valrhô/SCD/SEMC, BP 171, 30205 Bagnols-sur-Cèze Cedex, France
J. L. Crovisier
Affiliation:
CGS, Institut de Géologie, 1 rue Blessig, 67000 Strasbourg, France
E. Vernaz
Affiliation:
CEA-CEN Valrhô/SCD/SEMC, BP 171, 30205 Bagnols-sur-Cèze Cedex, France
G. Ehret
Affiliation:
CGS, Institut de Géologie, 1 rue Blessig, 67000 Strasbourg, France
H. Charpentier
Affiliation:
CEA-CEN Grenoble, DMG/SEM/LECM, 38000 Grenoble, France
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Abstract

R7T7 nuclear waste glass dissolution in highly dilute aqueous media under static conditions at 90°C occurs according to two different mechanisms depending on the solution acidity. In acid media (pH 4.8 and 5.5), preferential extraction of glass network modifiers results in the formation of an alkali metal-depleted surface region on which amorphous and crystallized (phosphate) compounds rich in transition elements precipitate. Steady-state dissolution conditions are not reached, as attested by variable normalized SI, B and Na mass losses. Glass dissolution is stoichiometric in basic media (pH 7 to 10): the strong bonds of the silicated network are broken at a rate that increases with the pH: the glass dissolution rate increases by a factor of 15 between pH 7 and 10. Under these conditions, alteration products at the glass/solution interface do not constitute a short-term kinetic barrier against the release of the major glass components.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 212: Symposium P – Scientific Basis for Nuclear Waste Management XIV , 1990 , 57
Copyright
Copyright © Materials Research Society 1991

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References

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