The conceptual design of the disposal of spent nuclear fuel in Sweden is based on a multibarrier system. In the KBS-3 concept, the bentonite buffer is a barrier with the primary purpose of surrounding and protecting the canister. The bentonite buffer is expected to prevent or minimise the water exchange with the surrounding rock and protect the canister against mechanical damages caused by possible shear movements in the immediate surroundings.
For a number of years, the researchers at Chalmers University of Technology have studied the buffer, with special emphasis on the drying and saturation phases of the buffer evolution. As a complement to the detailed numerical models for coupled thermal-hydrological-mechanicalchemical (THMC) processes, simplified models have been developed within the current project in order to improve the conceptual understanding of relevant physical processes and their interactions.