[en] Full text: Since the start of operation of the first commercial nuclear power plant in 1966, Japan has gradually and steadily increased nuclear power plants. At present, 52 commercial nuclear power plants with the capacity of 45.1TW are being operated and supplying 34% of total electricity generated in FY2001. To ensure stable and reliable long-term energy supply and to reduce environmental effects such as global warming, the fundamental energy policy is to raise the share of nuclear energy in electricity generation to 42% in 2010. Moreover, all the spent fuel will be reprocessed in order to make efficient use of nuclear material and to enable appropriate management and disposal of radioactive waste. Plutonium recovered from the spent fuel will be loaded in LWRs in the form of Plutonium and Uranium Mixed Oxide (MOX) fuel or utilized for R and D of nuclear fuel cycle such as FBR. Utilities have a program to start loading MOX fuel in 16 to 18 commercial LWRs by the year 2010. The amount of spent fuel discharged till September 2002 was 18,800tU, and about 8,000tU of them had been transported to JNC's Tokai Reprocessing Plant or foreign reprocessing plants (COGEMA and BNFL) and the other 10,800tU are being stored in pools or metal casks inside nuclear power plants, which total capacity is about 16,000tU. The Rokkasho Reprocessing Plant of JNFL with the reprocessing capacity of 800tU/y is now under construction and is planned to start commercial operation in July 2005. Its spent fuel storage pool with the capacity of 3,000tU has been already operated since 1999, and is storing spent fuel of 780tU. By the time of start of the said operation, 1,600tU of spent fuel will be stored. At present, total discharge rate of spent fuel in Japan is 900 to 1,000tU/y, and the rate will increase as further expansion of electricity generation by nuclear power. For the appropriate storage and management of the increasing spent fuel, it is important to construct interim storage facilities outside nuclear power plants, which will enable time adjustment till reprocessing them. Amount of spent fuel required off-site storage is estimated at 7,100tU by the year 2010. The Law for Regulations of Nuclear Source Material, Nuclear Fuel Material and Reactors was amended in June 1999, to establish a legal basis for private organizations which construct and operate interim spent fuel storage facilities outside nuclear power plants. The Nuclear Safety Commission issued a safety evaluation guideline for the facilities in October 2002 and the utilities have started preparatory activities including the siting efforts for the off-site interim storage facilities. (author)