Erosion phenomenon evaluation of bentonite buffer material; Generation behavior of bentonite colloid

Matsumoto, Kazuhiro; Iijima, Kazuki  ; Tanai, Kenji 

In the geological disposal of High Level Radioactive Waste (HLW), buffer material composed of engineered barriers system is expected to play important roles for the post-closure safety, for example, retardation of radionuclide migration. After overpack is breached, vitrified waste is considered to be dissolved by groundwater, followed by radionuclide dissolution into the groundwater and migration through the buffer material, as a reference scenario of safety assessment. It is also concerned about that bentonite colloids generated from the buffer may sorb radionuclides released from the buffer and consequently facilitate the radionuclide migration due to forming stable pseudo-colloids. In this study, erosion experiments of bentonite were carried out under the flow condition simulating groundwater flow and the generation rate of bentonite colloid from buffer materials is also discussed.