Research and development for geological disposal of radioactive waste; High-level radioactive waste as an example

Kamei, Gento 

High-level radioactive waste (HLW) refers to vitrified waste which is solidified high-level radioactive liquid waste after reproccessing with glass material. After interim storage for several decades, HLW is sealde with metal container (overpack) and with buffer material (bentonite), then is laid into a geologic formation (or bedrock). This is called as "multi-barrier system". Indicator of the safety assessment is dose rate when the migrating radionuclides reach to the earth's surface. Long-term stability of the multi-barrier system is assessed based on analyses of radionuclide migration in bentonite and the host rock in consideration of long-term behaviors of glass, metal container, bentonite and the geologic environment.