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[2D18] Measurements of Thermodynamic Data of Water in Ca-Bentonite by Relative Humidity Method
Keywords:Radioactive waste disposal, Buffer material, Ca-montmorillonite, Thermodynamic Data
Buffer material (compacted bentonite), one of the engineered barrier elements in the geological disposal of a high-level radioactive waste, develops swelling stress due to groundwater penetration from the surrounding rock mass. Even previous studies provide almost no thermodynamic data on Ca-montmorillonite. In this study, thermodynamic data on Ca-montmorillonite were obtained by measuring relative humidity (RH) and temperature. The activities of water and the relative partial molar Gibbs free energies decreased with decreasing water content in water contents lower than about 25%. This trend was similar to that of Na-montmorillonite. The swelling stress calculated based on the thermodynamic model was approximately 17MPa at a montmorillonite partial density of 1.5Mg/m3, and similar level as that of Na-montmorillonite.
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