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R7T7 Nuclear Waste Glass Behavior in Moist Clay: Role of the Clay Mass/Glass Surface Area Ratio

Published online by Cambridge University Press:  21 February 2011

N. Godon  and
E. Vernaz
N. Godon
Affiliation:
CEN-Valrhô, SDHA, BP 171, 30205 Bagnols-sur-Cèze Cedex, France
E. Vernaz
Affiliation:
CEN-Valrhô, SDHA, BP 171, 30205 Bagnols-sur-Cèze Cedex, France
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Abstract

R7T7 glass alteration was investigated in the presence of various moist clays. In contact with smectite 4a, selected in France as a potential engineered barrier material, the glass was significantly corroded: after 6 months the glass corrosion rate was practically the same as the initial alteration rate in double-distilled water. Substantially lower alteration was observed in contact with bentonite 6 activated by sodium carbonate.

Smectite 4a consumes silicon released by glass corrosion, and thus retards the rise to high silicon concentrations in solution at which the glass corrosion rate diminishes. Glass can therefore in some cases be altered as much in moist clay as in water with high renewal rates. Other experiments with smaller quantities of smectite 4a showed that the phenomenon becomes less important in time: its duration is proportional to the ratio between the clay mass (C) and the glass surface area (SA). Comparing the results of studies at different C/SA ratios indicates that low glass corrosion rates are obtained more slowly at higher C/SA ratios.

Tests with 239Pu-doped R7T7 glass also showed that the radionuclide retention factor in the alteration film at the glass surface is only 6, compared with a factor of nearly 50 in double-distilled water.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 176: Symposium U – Scientific Basis for Nuclear Waste Management XIII , 1989 , 319
Copyright
Copyright © Materials Research Society 1990

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References

REFERENCES

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