Status of assessment tools on the performance guarantee contents of buffer material

Tanai, Kenji ; Jintoku, Takashi*; Kikuchi, Hirohito*; Nishimura, Mayuka; Matsumoto, Kazuhiro*; Aoyanagi, Shigeo; Yui, Mikazu

In order to contribute to the safety standards and guidelines which a regulator decides, state-of the art assessment method is investigated and summarized in the table about performance guarantee contents of buffer material related to the mechanical support and protection of the overpack and rock matrix, and the retardation of radionuclide. In addition, examples of the assessment tool are described. In this report, summary of (1) basic properties of bentonite, including swelling properties, mechanical properties and hydraulic properties, (2) long-term behavior of bentonite, including creep deformation, penetration into host rock, erosion and alteration, (3) gas permeability, (4) colloid filtration and (5) mechanical stability of the near-field is described. Check points, assessment methods (based on the data obtained from the experimental results, the estimation value obtained from empirical equations and database, and the modeling calculations) and latest results of these R&D programs were also summarized.