Current status of development of small and medium sized reactor in Japan

Current status of development of small and medium sized reactors (SMRs) was reviewed based on IAEA-TECDOC, the recent publications and proceedings of international conferences. There are around twenty reactor concepts which can be categorized in SMRs. The results of statistics of these concepts are discussed. For example, the designers are classified into four groups such as the plant manufacturers, research institutes, universities and independent research groups. The reactor types range from light water reactors to molten salt reactors. It is believed that such discussion would give general trend of the developmental efforts in Japan and show different ideas which might be helpful for those who are interested in developing new reactor concepts. From this point of view, some unique concepts were also discussed. The uniqueness means that each concept has only one and rather new feature among the concepts. It was the author who decided the uniqueness form the other concepts. For example, a concept which can utilize natural uranium to more than 40% without any fuel reprocessing is explained. Other one is such that it can operate completely automatically. They might also give incentives of developing new ideas for reactor concepts after Generation IV. (author)