Simulation of Radionuclide Transport in the Engineered Barrier System of a Geological Repository

After closure of the geological repository, the coupled thermal, hydrological and mechanical processes such as the heat generation from a waste, the intrusion of groundwater from a surrounding rock, and the stress changes due to the swelling of a buffer will be occurred in the engineered barrier system. The thermal gradient in a buffer due to decay heat can accelerate the migration of radionuclides through the buffer, and the drying and resaturation processes occurring in the buffer may have a critical impact on the release of radionuclides from the disposed waste. In investigating the migration of ions and contaminants in a porous medium, a saturated condition has been commonly assumed, and several works have considered the transport of ions in an unsaturated porous medium. However, the migration of radionuclides through a partially saturated medium with a thermal gradient has not been fully studied. In this study, the simulation results of the coupled thermal, hydrological, and chemical processes occurring in the engineered barrier system of a geological repository using the TOUGH2 computer code are presented