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Single Idealized Cracks: A Tool for Understanding Fractured Glass Block Leaching

Published online by Cambridge University Press:  01 February 2011

Laure Chomat
Affiliation:
CEA Marcoule, DEN/VRH/DTCD/SECM/LCLT, BP 17171, F-30207 Bagnols-sur-Cèze Cedex
Frédéric Bouyer
Affiliation:
CEA Marcoule, DEN/VRH/DTCD/SECM/LCLT, BP 17171, F-30207 Bagnols-sur-Cèze Cedex
Stéphane Gin
Affiliation:
CEA Marcoule, DEN/VRH/DTCD/SECM/LCLT, BP 17171, F-30207 Bagnols-sur-Cèze Cedex
Stéphane Roux
Affiliation:
LMT Cachan, 61 Avenue du Président Wilson F-94 235 Cachan Cedex
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Abstract

Within the scope of the long term behaviour of the R7T7 glass, which is the French nuclear glass, leaching and its coupling with transport mechanisms is studied. Experiments carried out on a SON 68 glass (inactive R7T7 type glass) model cracks in static basic conditions show a strong coupling between solution transport and glass leaching, depending on crack aperture. Moreover, gravity driven convective transport was evidenced for vertical model cracks, whereas only molecular diffusion was detected for horizontal model cracks under the same alteration conditions. In addition, an original device was developed to study the influence of temperature gradients on alteration kinetics as a convective driving force. These experiments show conclusively that thermally- or gravity-induced convective flow must be taken into account, even if such convective effects have not been established experimentally in neutral condition, which is more realistic condition for geological storage. A modeling, based on a porous geochemical software (HYTEC) accounting for both chemistry and transport, has been successfully applied to describe alteration within simple silicate glass cracks. It will be extended to study SON 68 glass model cracks, and more complex fracture networks.

Type
Research Article
Copyright
Copyright © Materials Research Society 2008

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