Abstract:

In the deep disposal of highly radioactive waste, the engineering barrier made by densely compacted bentonite is used to prevent the groundwater infiltrating and the radioactive waste diffusing; and the gap between the bedrock and nuclear waste canister can be filled up by the hydro swelling bentonite. The permeability and swelling behavior of bentonite are needed to be carefully studied. It is Gaomiaozi (GMZ) bentonie from China to be investigated here. A series of laboratory tests were conducted including test for determining water retention curve, permeability coefficient test in swelling condition and mercury; intrusion porosimetry (MIP) test after that. A mathematical model is established for the relationship among permeability, swelling volumetric strain, void ratio and suction of GMZ bentonite. Equations of the model indicate that the permeability coefficient and swelling volumetric strain increase with suction decrease. The reason is that the decrease of suction can cause the increase of void ratio of bentonite which will cause the increase of permeability coefficient. This discovery can facilitate the design of deep disposal of highly radioactive waste.

Key words: deep disposal of highly radioactive waste, highly compacted Gaomiaozi bentonite, free swelling condition