THE SWELLING BEHAVIOUR OF BENTONITE BUFFER MATERIAL CONSIDERING THE EFFECT OF TEMPERATURE

In the nuclear fuel cycle of nuclear power generation, reprocessing generates high-level radioactive waste. Geological disposal is a widely accepted disposal method for high-level radioactive waste. This method can isolate waste from the human environment for a very long time. Geological disposal utilizes bentonite as a buffer material in order to suppress the transfer of radioactive materials to groundwater. In practice, waste may be exposed to a high-temperature environment due to decay heat or geothermal heat, or heated groundwater may permeate the water. Nonetheless, few studies consider the effect of heat on bentonite, and it is difficult to understand the long-term swelling performance of bentonite material under these conditions. Therefore, it is necessary to investigate the effect of temperature on bentonite. In this study, swelling properties of bentonite were investigated by performing a swelling pressure test considering temperature history and temperature change. Results demonstrated that swelling pressure tended to increase with increasing temperature. Furthermore, a threshold value for the equilibrium swelling pressure may exist.