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[AGE31-P07] Effect of Moisture Content on the Thermal and Gas Transport Properties of Granulated Bentonite Mixture
Keywords:Radioactive waste disposal, granulated bentonite mixture (GBM), moisture content, thermal parameters, gas transport parameters
The deep geological repository concept comprises emplacement of radioactive waste in the bedrock with the help of a buffer material. Granulated bentonite mixtures (GBM) are being considered as a candidate buffer material due to high compaction properties and ease of emplacement operations in the repository. After emplacement, the GBM buffer will be subjected to complex hydro-mechanical processes as a result of water infiltration from the surrounding bedrock. These hydro-mechanical changes will affect the heat transfer and gas transport processes in the repository. Understanding of the thermal and gas transport processes at changing water saturation is essential for the design optimization of buffer and safety-related calculations. This study investigated the effect of moisture content on the thermal and gas transport parameters. The GBM was prepared from a Japanese bentonite, trade name, OK Bentonite, Kunimine Industries, Japan. First, air-dried OK bentonite grains were sieved and graded to obtain a grain size distribution between 0.075 mm and 9.5 mm. The material was packed in the acrylic cores of 100 cm3 volume at dry density 1.2 and 1.3 g/cm3 and the samples were then kept in a relative humidity (RH) and temperature (T) controlled chamber at constant RH = 95% and T = 20º C. The samples were prepared for measurements at different time intervals (t = 0, 1, 2 and 4 weeks). The thermal parameters were measured using a portable dual-needle probe analyzer (KD2-Pro, Decagon Devices Inc., Pullman, WA, USA). The gas transport parameters such as air permeability (ka) and gas diffusivity (Dp/Do) were measured by an air permeameter and gas diffusion chamber apparatus respectively. The results provided a better insight to understand the thermal and gas transport properties of GBM under the effect of moisture saturation.