Development of an Uncertainty Analysis Methodology Associated with the Characterization of the Geological Environment: S
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Development of an Uncertainty Analysis Methodology Associated with the Characterization of the Geological Environment: Study on its Applicability in the Tono area K. Yanagizawa1, S. Takeda2, H. Osawa1, Y. Suyama3, H. Takase4, M. Toida3, Metcalfe R. 4 1 Tono Geoscience Center, Japan Nuclear Cycle Development Institute (JNC), Gifu, Japan. 2 Horonobe Underground Reserch Center, Japan Nuclear Cycle Development Institute (JNC), Hokkaido, Japan. 3 Kajima Technical Research Institute, Kajima Corporation, Tokyo, Japan. 4 Quintessa Japan, Yokohama, Japan. ABSTRACT JNC has developed an uncertainty analysis methodology for application to the spatially heterogeneous characteristics of a geological environment. The developed methodology adopts a new approach that identifies all the possible options in concepts and parameter ranges that cannot be excluded in the light of evidence available. This approach enables uncertainties associated with the understanding at a given stage of the site characterization to be made explicit, using probability theory and possibility theory. The uncertainties could be reduced by screening, to exclude concepts and parameter ranges that can be denied in the light of additional evidence obtained in subsequent investigation stages. This paper describes an outline of the developed methodology and its applicability in the Tono area.
INTRODUCTION The ICRP publication 81 [1] mentions that uncertainties are inherent in the performance assessment of the geological disposal of HLW, but that all reasonable means must be taken to reduce potential exposure, so that the expected potential exposure or corresponding risk would be below a certain constraint. In order to specify all reasonable means to reduce potential exposure in each phase of the geological disposal program, it will be necessary to reduce uncertainties associated with the performance assessment. Additionally the multi-barrier system’s performance will need to be optimized. The following specific measures should be taken: (1) evaluation of uncertainties associated with understanding and/or long-term estimation of heterogeneous characteristics of a geological environment in each investigation phase; (2) investigating the geological environment effectively so as to reduce the uncertainties in subsequent investigation phases; (3) designing an underground repository layout to optimize the expected functions of a natural barrier (selection of optimum disposal site, location, and depth, and improvement of the host rock); and (4) designing engineered barriers that are robust with respect to uncertainties. Focusing on heterogeneous characteristics of a geological environment, JNC has developed an “uncertainty analysis methodology associated with the characterization of the geological environment (see figure 1)” in the light of (1) and (2) above. This paper describes an outline of
the developed methodology and its applicability in the Tono area.
UNCERTAINTY ANALYSIS METHODOLOGY The developed methodology adopts a new approach, whereby all the possible opt
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