Design of J-PARC transmutation experimental facility

After the Fukushima accident, the management of spent fuel received a great deal of attention and then, reduction of radioactive wastes became increasingly important. Partitioning and transmutation technology using fast reactors or accelerator-driven systems (ADS) was noted as part of the re-evaluation of the national fuel cycle policy, discussed by the Atomic Energy Commission of Japan. To realise the transmutation of minor actinides and long-lived fission products, basic studies for various research fields are needed and therefore, equipment to obtain the experimental data using spallation target and minor actinides is required. In the framework of the J-PARC Project, the Japan Atomic Energy Agency (JAEA) promoted the construction of the experimental facility for transmutation systems and the design of the Transmutation Experimental Facility (TEF). The facility consists of two buildings, the Transmutation Physics Experimental Facility (TEF-P) to perform critical experiments using minor actinide bearing fuels and the ADS Target Test Facility (TEF-T) for irradiation of various structural material candidates in flowing lead-bismuth environment. According to the latest time schedule, TEF-T will be constructed rather faster than the licensing of TEF-P to facilitate the construction. TEF-T will be operated within 5 years and TEF-P needs another 5 years to finish the construction, after budget approbation by the government. Based on this time schedule and facility layout, concepts of the facility, namely TEF-T should be revised to accept proton beam up to 400 MeV-133 kW. Sealed-annular tube type spallation target filled with lead-bismuth eutectic alloy is considered for both low-power proton irradiation target and full stop length target for proton/neutron simultaneous irradiation. Both targets were designed to simulate the operating condition of actual lead-bismuth-cooled ADS transmuter (800 MWt). The temperature range of lead-bismuth can be set around 300-500 degree centigrade and systematic data accumulation is planned for various structural materials and irradiation damage rate indicated by DPA (displacement per atom) at various operation temperatures under the structural stressed environment. Even though the irradiation sample is limited to a very small size, the annual irradiation rates can be set to several tens of DPA. TEF-P is designed to reflect the structure of existing critical assembly FCA located in JAEA/Tokai site to take over a lot of experimental data and experience at FCA. The required amount of minor actinides to perform the significant critical/subcritical experiments is specified and is reflected in the design of the critical assembly itself. Remote devices and related facility layout are also designed for the safe handling of the minor actinide bearing fuels. (authors)