Research on evaluation of buffer materials in the engineered barrier

Chijimatsu, Masakazu*; Amemiya, Kiyoshi*; Yamashita, Ryo*

In order to achieve the geological disposal of radioactive waste in safe, it is necessary to ensure the stability of the engineered barrier system (EBS). One of the most important factors for the stability of the EBS is the disposal technology. It is considered that the stability of the EBS is secured by the properly emplacement based on the design requirement. In this research, the methods filling the gap between buffer and rock or buffer and overpack were examined. Bentonite pellets were tested as the filling materials. After emplacement of the engineered barrier system, it is expected that the near-field environment will be impacted by phenomena such as heat dissipation by conduction and other heat transfer mechanisms, infiltration of groundwater from the surrounding in to the engineered barrier system, stress imposed by the overburden pressure and generation of swelling pressure in the buffer due to water infiltration. In order to recognize and evaluate these coupled phenomena, it is necessary to make a confidence of the mathematical models and computer codes based on the information about the in-situ experimats regarding the engineered barrier system. In this research, technical investigation about the in-situ full-scale experiment (called Prototype Repository Project) in Aspo HRL facility by SKB of Sweden were performed. Fathermore, the thermo-hydro-mechanical (THM) code named THAMES was validated at the international project, DECOVALEX III.