Sensitivity Analysis for the Scenarios on Deterioration or Loss of Safety Functions Expected in Disposal System Due to H
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Sensitivity Analysis for the Scenarios on Deterioration or Loss of Safety Functions Expected in Disposal System Due to Human Error on Application of Engineering Technology Seiji Takeda 1, Yoshihisa Inoue 1 and Hideo Kimura 1 Nuclear Safety Research Center, Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki, 3191195 Japan
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ABSTRACT The sensitive analysis of radionuclide migration for the scenarios on deterioration or loss of safety functions expected in HLW disposal system due to the human error (initial defective scenarios) is performed in this study. Release rates for Cs-135 and Se-79 are estimated from Monte Carlo-based analysis. Maximum release rates of Se-79 and Cs-135 from natural barrier in initial defective scenarios for vitrified waste and overpack are approximately equivalent to that in normal scenario on all safety function working. Maximum release rate of Se-79 in initial defective scenario of buffer under the condition of colloidal migration is about 30 times as high as that in normal scenario. Maximum release rate of Cs-135 in initial defective scenario of plugs is about two orders of magnitude higher than that in normal scenario. These results especially indicate the need to understand the feasibility on two types of initial defective scenario, leading to the loss of restraint for colloidal migration in buffer and the loss of restraint with plugs from short-circuit migration. INTRODUCTION Nuclear Safety Research Center of Japan Atomic Energy Agency has carried out regulatory research to provide technical support for safety review of the license application for candidate sites of final disposal of high-level radioactive waste (HLW), in which Nuclear Waste Management Organization of Japan (NUMO) as an implementer will propose through the stepwise setting process. NUMO will concretely provide a repository design and engineering technology of repository construction tailored to a specific site. From a viewpoint of safety regulation, it is important to review suitably the progress of engineering technical development applied for stepwise implementation of safety geological disposal towards a future safety review and to grasp the safety function of the engineered barrier materials, namely vitrified waste, overpack, sand-bentonite buffer material and sealing plugs, affected by various factors. The human error on application of engineering technology is one of important factors. The sensitive analysis of radionuclide migration for the scenarios on deterioration or loss of expected safety functions of the engineered barrier materials due to the human error on the application of engineering technology (hereinafter referred to as “initial defective scenarios”) is performed in this study. The analysis specifies the initial defective scenario, which should be especially focused toward future safety review. ANALYTICAL METHOD
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Scenario description In this analysis, disposal site is not specific, and geological disposal system is basically the same design as in the H12 Project report [1] of Japan Nuclear Cycle
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