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Hamamoto, Takafumi*; Shibutani, Sanae*; Ishida, Keisuke*; Fujisaki, Kiyoshi*; Yamada, Motoyuki*; Tachi, Yukio
Proceedings of 6th East Asia Forum on Radwaste Management Conference (EAFORM 2017) (Internet), 6 Pages, 2017/12
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.
Tsuji, Masakuni*; Okihara, Mitsunobu*; Nakashima, Hitoshi*; Sato, Toshinori; Aoyagi, Kazuhei
Proceedings of 6th East Asia Forum on Radwaste Management Conference (EAFORM 2017) (Internet), 6 Pages, 2017/12
Regarding the engineering technology, the rock grouting has been recently studied as one of the most important technologies. Although the cement grout has not been reported to be affected by the sea water, the latest grouting material called colloidal silica grout is known to be sensitive to the saline water. The mechanism of its affection by sea water is not clear and its grouting methodology in such condition is not yet established either. Therefore, we studied on the latest grouting technologies for geological disposal in Nordic countries and Japan by article survey and a grouting workshop. As a result, it was found that the approach for countermeasures in grouting under sea water is different between Japan, Sweden, and Finland, which are based respectively on the mixture, on the design method, and on the controlling method. It seems that the best solution against this problem is to establish a hybrid and optimal grouting methodology under sea water by combining each country's developed grouting technology in the near future for saline condition, which is respectively based on mixing, design, and controlling method.
Hama, Katsuhiro
Proceedings of 6th East Asia Forum on Radwaste Management Conference (EAFORM 2017) (Internet), 6 Pages, 2017/12
The Mizunami Underground Research Laboratory project is being pursued by the JAEA in the crystalline host rock at Mizunami City in Gifu Prefecture. The project proceeds in three overlapping phases, Surface-based investigation Phase (Phase I), Construction Phase (Phase II) and Operation Phase (III). During Phase I, a step-wise investigation was conducted by iterating investigation, interpretation, and assessment, thereby understanding of geologic environment was progressively and effectively improved with progress of investigation. During Phase II, we have evaluated adequacy of techniques for investigation, analysis and assessment of the deep geological environment established in the Phase I. For Phase III, three important issues were identified based on the latest results. Development of countermeasure technologies for reducing groundwater inflow, Development of modeling technologies for mass transport, Development of drift backfilling technologies.