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Compréhension de l'altération à long terme des colis de verre R7T7 : étude du couplage chimie transport dans un milieu fissuré

Laure Chomat 1
1 LCLT - Laboratoire d'Etudes du Comportement à Long Terme des matériaux de conditionnement
DE2D - Département de recherche sur les technologies pour l'enrichissement, le démantèlement et les déchets : DEN/DE2D
Abstract : The long term behavior of nuclear waste glass blocks depends highly on chemical reactions which occur at the surface in contact with water. Studies carried out on inactive fractured glass blocks show that fracture networks play a significant part in reactive surface area. Nevertheless, the complexity of available experiments interpretation, due to a weak knowledge of fracture networks and local lixiviation conditions, doesn't allow us to comprehend the whole physical and chemical mechanisms involved.
Model cracks are a key step to studying chemical and transport coupling in fractured media. Crack lixiviation in aggressive conditions (pH>11) show that the crack's position (horizontal or vertical) determines the dominant transport mechanism (respectively diffusion or convection induced by gravity). This gravity driven flow seems to be negligible in lower pH conditions. The convective velocity is estimated by a 1D model of reactive transport.
Two other parameters are studied: the influence of thermal gradient and the influence of interconnected cracks on alteration. A strong retroactive effect of convection, due to thermal gradient, on the alteration kinetic is observed inside the crack.
These works lead to a complete alteration experiment of a 163 crack network subject to a thermal gradient.
The use of the geochemical software, HYTEC, within the framework of this study shows the potential of the software; however the kinetics law model must be improved.
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Submitted on : Monday, June 8, 2009 - 10:14:23 AM
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  • HAL Id : tel-00392439, version 1

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Laure Chomat. Compréhension de l'altération à long terme des colis de verre R7T7 : étude du couplage chimie transport dans un milieu fissuré. Chimie. Université Pierre et Marie Curie - Paris VI, 2008. Français. ⟨tel-00392439⟩

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