Abstract
For the safety assessment of a geological disposal system for high-level radioactive waste, it is necessary to quantify coupled thermo-hydro-mechanical-chemical (THMC) processes in the near-field. The current study investigated the geochemical changes arising from the infiltration of groundwater into the bentonite buffer under a thermal regime of radiogenic heating arising from the vitrified waste with the computer simulated assistance of a developed THMC model. In the case of infiltration by a saline groundwater, sulfate precipitates as gypsum around the overpack in the bentonite buffer and the Na-type bentonite changes to Ca-type by exposure to Ca ions released from concrete supports. In addition, the temporal evolution of the bentonite buffer porewater composition can be obtained to assess its contribution to the corrosion of the overpack.
