ABSTRACT
Disposal tunnels excavated into deep bedrock are used to store high-level radioactive waste from nuclear power plants. Bentonite-based backfills are placed in the tunnels to isolate waste from human areas, where groundwater infiltrates and saturates the backfills. As the saturation increases, the swelling pressure increases and the hydraulic conductivity decreases, sealing the waste. The hydraulic conductivity of backfill depends on factors such as mineral composition, dry density, and groundwater conditions. When groundwater flows through granite fissures, it carries kaolinite formed by weathering, which interacts with the bentonite-based backfill and alters its hydraulic properties. This study investigates the impact of kaolinite (up to 10% in mass) on the hydraulic conductivity of bentonite-sand backfills through laboratory tests under saturated conditions. The results demonstrate that increased kaolinite content increases the hydraulic conductivity, which can affect the long-term safety of deep disposal tunnels.
