Supporting Development of Practical Designs for a Japanese HLW Repository
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Supporting Development of Practical Designs for a Japanese HLW Repository Hitoshi Makino , Hiroyuki Umeki , Yasuhiro Ochi , Kazumasa Hioki , Hiroo Okubo2, Masaaki Matsumoto2, Osamu Sato2, Sumio Masuda3 and Ian G. McKinley4 1. Japan Atomic Energy Agency, Tokyo, 100-8577, Japan 2. Mitsubishi Research Institute Inc., Tokyo, 100-8141, Japan 3. Nuclear Safety Research Association, Tokyo, 105-0004, Japan 4. McKinley Consulting, 5405 Baden / Dättwil, Switzerland ABSTRACT In preparation for actual repository implementation, designs that could be tailored to specific sites need to be considered. This requires a paradigm shift in design philosophy, moving away from a single reference design towards a flexible and systematic “catalogue” of engineered barrier components and associated repository infrastructure. To support this development, novel methodology for both developing and comparing repository design options for Japanese vitrified high-level radioactive waste (HLW) has been examined. This paper will outline the background of the project and, in particular, some novel approaches examined for facilitating optimisation of practical repository designs. It is complemented by a companion paper - Matsumoto et al: Application of Formal Knowledge Engineering Approaches to Develop A Design Catalogue for A Japanese HLW Repository -, which describes the repository design process in more detail and illustrates results of first dry runs of the methodology. INTRODUCTION The year 2000 represented a turning-point in the Japanese geological disposal programme, with a move from generic R&D into the implementation phase. Following the technical demonstration of the fundamental feasibility of geological disposal of HLW in Japan in the “H12” report [1], the “Specified Radioactive Waste Final Disposal Act” (the “Act”) was promulgated and the Nuclear Waste Management Organization of Japan (NUMO) was established. NUMO is responsible for selection of a disposal site for HLW and for the construction, operation and closure of the repository. Recently, the Act and the Final Disposal Plan were amended and NUMO has now responsibility for geological disposal of not only HLW but also TRU waste. Here, radioactive waste generated during the operation and dismantling of reprocessing facilities and MOX fuel fabrication facilities, containing long-lived radionuclides such as C-14, I-129, Pu-239 and Np-237, is defined as ‘TRU waste’ in Japan and broadly equates to long-lived intermediate-level waste (ILW) and low-level waste (LLW) with significant alpha content [2]. To initiate the siting process, NUMO issued an open call for volunteers to host the repository to all municipalities in Japan. This volunteering approach was chosen due to the high priority assigned to public acceptance, but brings special challenges for the site characterisation teams – and also requires particular flexibility on the side of the repository engineers. Nomination procedures have tended to favour sites where characterisation and design will be easiest – with emphasis on choosing “b
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