Assessment of sorption and diffusion in the rock matrix in the NUMO safety case

NUMOのセーフティケースにおける岩石中の収着・拡散の評価

浜本 貴史*; 澁谷 早苗*; 石田 圭輔*; 藤崎 淳*; 山田 基幸*; 舘 幸男  

Hamamoto, Takafumi*; Shibutani, Sanae*; Ishida, Keisuke*; Fujisaki, Kiyoshi*; Yamada, Motoyuki*; Tachi, Yukio

NUMOでは日本における地層処分の成立性と安全性を示すためのジェネリックなセーフティケースを開発している。このセーフティケースにおける安全評価のために、3種類の母岩を対象として分配係数及び実効拡散係数パラメータを設定するとともに、その不確実性や今後の課題について議論した。

NUMO has developed a generic safety case to demonstrate the feasibility and safety of geological disposal of HLW and TRU in Japan and to provide a basic structure for the safety case which will be applicable to any potential site. In this safety case, the safety assessment was carried out for the repositories tailored to site descriptive models developed for three representative rock groups (plutonic, Neogene sedimentary and Pre-Neogene sedimentary rocks). Radionuclide migration parameters in rocks, i.e. distribution coefficients (Kds) and effective diffusion coefficients (Des), were derived to allow safety analysis for a range of scenarios. In this generic stage, the values of these parameter were given as the statistical values derived from laboratory data for certain rock types. The data were extracted from the latest database, with interpretation based on radionuclide speciation derived from relevant groundwater thermodynamic modelings.