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Conference Papers Year : 2000

Assessment of a clay barrier resaturation in isothermal conditions

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François Cany
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Abstract

Many projects of underground repositories for high level radioactive wastes involve an engineered clay barrier, placed between the waste canister and the surrounding rock. By hydrating progressively, the barrier swells, seals the gaps and provides a good global watertightness. In a high level radioactive waste repository, the maximum admissible temperature for the barrier governs the space between canisters and consequently the cost of the civil engineering works. Thus a precise assessment of this criterion is compulsory. Even though the barrier behaviour depends on the thermal-hydro-mechanical interactions with the canister and the host rock, the study is only focused on the hydraulic behaviour of the barrier without phase change in a first step. A chamber containing one high level radioactive waste canister is simulated for the East of France repository site. A 2D-plane computation is done with the CASTEM2000 code. A cylindrical geometry, composed of a barrier layer surrounded by a site layer, is represented. Two kinds of clay are studied for the barrier. The clay foreseen for the french repository sites is the FoCa clay. But in order to compare our results with those of other european countries, we studied the spanish La Serrata clay too for the barrier. The East of France site is made of a clay, different from the barrier one. To understand the influence of the boundary conditions on the barrier resaturation time, two sorts of boundary conditions are considered for the external site limit: an imposed water pressure or no water flow. On the internal barrier limit, we enforce a water flow equal to zero. Initially, the site is saturated whereas the barrier is partially unsaturated. Neglecting the initial ventilation phase in the repository site, we suppose that the barrier is in thermal equilibrium with the surrounding site. Their average temperature is 50°C. The models implemented in the CASTEM-2000 code are based on the mixed-hybrid finite element formulation. The numerical model used for this computation supposes that air remains at a constant pressure and water only exists in a liquid state. This paper is devoted to the analysis of the barrier resaturation by the site water. A parametric study on the barrier material and the boundary conditions is realised. The results are the water pressure and the saturation versus time and along a radius.
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Dates and versions

cea-03956851 , version 1 (25-01-2023)

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  • HAL Id : cea-03956851 , version 1

Cite

Marie-France Robbe, François Cany. Assessment of a clay barrier resaturation in isothermal conditions. ICONE 8 - 8th International Conference on Nuclear Engineering, Apr 2000, Baltimore, United States. pp.8269. ⟨cea-03956851⟩
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