Final report on the surface-based investigation (phase 1) at the Mizunami Underground Laboratory project


Saegusa,-Hiromitsu; Seno,-Yasuhiro; Nakama,-Shigeo; Tsuruta,-Tadahiko; Amano,-Kenji; Takeuchi,-Ryuji; Matsuoka,-Toshiyuki; Onoe,-Hironori; Mizuno,-Takashi; Ohyama,-Takuya; Hama,-Katsuhiro; Sato,-Toshinori; Kuji,-Masayoshi; Kuroda,-Hidetaka; Semba,-Takeshi; Uchida,-Masahiro; Sugihara,-Kozo; Sakamaki,-Masanori (Japan Atomic Energy Agency, Geological Isolation Research and Development Directorate, Mizunami, Gifu (Japan)); Iwatsuki,-Teruki (Japan Atomic Energy Agency, Horonobe Underground Research Center, Mizunami, Gifu (Japan)The Mizunami Underground Laboratory (MIU) Project is a comprehensive research project investigating the deep underground environment within crystalline rock being conducted by Japan Atomic Energy Agency at Mizunami City in Gifu Prefecture, central Japan and its role is defined in 'Framework for Nuclear Energy Policy' by Japan Atomic Energy Commission. The MIU Project has three overlapping phases: Surface-based Investigation phase (Phase I), Construction phase (Phase II), and Operation phase (Phase III), with a total duration of 20 years. The overall project goals of the MIU Project from Phase I through to Phase III are: 1) to establish techniques for investigation, analysis and assessment of the deep geological environment, and 2) to develop a range of engineering for deep underground application. During Phase I, the overall project goals were supported by Phase I goals. For the overall project goals 1), the Phase I goals were set to construct models of the geological environment from all surface-based investigation results that describe the geological environment prior to excavation and predict excavation response. For the overall project goals 2), the Phase I goals were set to formulate detailed design concepts and a construction plan for the underground facilities. This report summarizes the Phase I investigation which was completed in March 2005. The authors believe this report will make an important milestone, since this report clarifies how the Phase I goals are achieved and evaluate the future issues thereby direct the research which will be conducted during Phase II. With regard to the overall project goals 1), 'To establish techniques for investigation, analysis and assessment of the deep geological environment,' 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. An optimal procedure from investigation to assessment was compiled as a set of geosynthesis data flow diagram for each investigation step. With regard to the overall project goals 2), 'To formulate detailed design concepts and a construction plan for the underground facilities,' an optimal design of MIU was completed with the aim to provide a foundation for engineering technologies in deep underground to safely construct and operate an underground facility which will be built for the purpose of acquiring data and demonstrating disposal technologies. Thus, this report summarizes geosynthesis procedures to investigate and assess the crystalline rock, and development of individual investigation and assessment methods. At the same time, technical findings and know-how which can serve as foundation to disposal business were compiled. Also, this report clarified the necessity for the Phase II and Phase III investigation by compiling unresolved issues during the Phase I investigation. The results described in this report will be utilized as technical knowledge of disposal technology and effectively used to enhance technical foundation which will support disposal business and safety regulations.