Moisture movement under a temperature gradient in highly compacted bentonite

The heat induced moisture movement in buffer materials to be used for the geologic disposal of high-level radioactive waste is investigated by a series of experiments and numerical simulations. Highly compacted blocks of Japanese Na bentonite are used in the experiments as the buffer materials. Mechanistic models including those proposed by Philip et al. and Ewen et al. are formulated to the finite-element program which are applied to interpret the experimental results. The applicability of the mechanistic models to the compacted bentonite is examined. The numerical results agree well with the experimental results qualitatively, though a few quantitative discrepancies are found. Those discrepancies demand better descriptions for material properties on compacted bentonite and introducing an effect of volume change associated with change in water content.