Abstract: In order to study the interaction influence of bentonite and water on safety of geological disposal for high-level radioactive waste, two bentonites of different montmorillonite contents were immersed in water for 3 000 hours. Test results showed that their swell indexes increased with the increase of montmorillonite content, and a linear relationship was observed between the biggest swell index and logarithm of montmorillonite content. After swelling reached equilibrium, the concentration of univalent cation was larger than the concentration of divalent cation in supernatant and it increased with the increase of montmorillonite content; and there was also a linear relationship between sodium concentration and logarithm of montmorillonite content in two bentonites. The amount of dried residue of the supernatant also increased with the increase of montmorillonite content, and the XRD test results indicated that montmorillonite was present in dried residue of liquid supernatant. These experimental results can be a basis for further studies on interaction of buffer material and groundwater in geological disposal.

Key words: bentonite, swell index, water chemistry, ionic concentration, colloid