Decommissioning project feedback experience in the Japan Atomic Energy Research Institut

Since starting the research and development program for peaceful use of nuclear energy in 1950's, various research and demonstration facilities have been constructed in research organizations, universities and commercial sectors in Japan. Some of the nuclear facilities constructed in the early stage of research and development have been retired to be decommissioned because of completion of the initial objectives in the Japan Atomic Energy Research Institute (JAERI). On the other hand, since the first commercial operation of nuclear power plant (1968), the number of nuclear power plants has increased up to 52 plants operating as of August 2003 in Japan. The shear of nuclear energy accounts approximately for 35% of electricity generation in total at present time. However, several nuclear power plants have been operated for more than 25 years and two nuclear power plants are expected to be finally shutdown by 2010 to be eventually decommissioned. The Tokai Power Station, the oldest Japanese nuclear power plant operated by the Japan Atomic Power Company, was permanently shutdown from March 1998 and it is in decommissioning stage at this time. The Fugen, which is advanced thermal reactor operated by the Japan Nuclear Cycle Development Institute (JNC), was finally shutdown on March, 2003 after 25 years operation to be decommissioned. In addition, relating to planned unification between JAERI and JNC in 2005, the studies have been in progress on decommissioning and radioactive waste treatment and disposal; the cost was estimated to be 10 to 30 billion Japanese yens per year during 80 years for decommissioning of nearly 200 nuclear facilities. Decommissioning of nuclear facilities is thus getting to be one of important issues in Japan. Decommissioning of nuclear facilities might be possible using conventional and/or partially improved technology. However, reviewing project feedback experience on decommissioning and decontamination might contribute to solve various issues and to implement a decommissioning project in safe and economical manner. The Japan Power Demonstration Reactor (JPDR) decommissioning project was completed by March, 1996, accumulating various data, experience and know-how on dismantling activities. The data and project experience were analyzed for future decommissioning of commercial and research nuclear facilities, in which the lessons learnt are categorized into three groups: safety case, waste management and work efficiency. The feedback experience was good for planning and implementing decommissioning projects. This paper deals with the decommissioning projects and the feedback experience in JAERI. At present more than 20 research nuclear facilities are listed for decommissioning in the near future in JAERI, and some of the facilities are in dismantling stage. In addition, nearly 200 nuclear facilities will be decommissioned in JAERI and JNC for 80 years after unification of both research organizations. Consequently, it has been required to implement the decommissioning projects in safe and economical manner by effectively referring the past decommissioning experience. JPDR and JRTF decommissioning projects were set up as demonstration programs for future decommissioning of large nuclear facilities. The JPDR decommissioning project was completed successfully without serious problems, accumulating various data and know-how. The JRTF decommissioning project has also been in progress, in which the experience of JPDR dismantling activities are referred and various data and experience are collected to characterize the dismantling activities in fuel cycle facilities. In case of JRR-2 decommissioning project, it has been decided that the building will be used for a centralized fuel storage facility for the time before dismantling the core part. Various lessons learnt have been accumulated through these projects, including technology application, project management and organizational matters. The project data and the experience are shared by other decommissioning projects and studies on decommissioning issues. Further, it might be necessary to study on the most rational way of applying the feedback experience to the future decommissioning of nuclear facilities