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Sasa, Toshinobu; Oigawa, Hiroyuki
Proceedings of 8th International Topical Meeting on Nuclear Applications and Utilization of Accelerators (AccApp '07), p.949 - 955, 2007/00
Construction of the Transmutation Experimental Facility which has a critical assembly and a lead-bismuth target is planned within the framework of J-PARC project. We are planning to install the critical assembly with a 30kW beam dump at the first phase and the target facility will be built at the latter phase. Based on this construction plan, JAEA collected the preliminary Letters Of Intent for TEF. More than 30 research programs by about one hundred researchers were proposed. The proposals spread over wide research fields such as innovative reactor concepts, nuclear data, medical application, and so on. According to these many valuable proposals, the re-arrangement of facility layout and the new experimental equipment design are now underway. One of the important R&Ds is to prepare for the application of minor actinide fuels to critical assembly. The development of the technology to handle the high-background minor actinide fuel is being performed. A sensitivity analysis was also performed to determine the efficient fuel composition.
Sasa, Toshinobu; Oigawa, Hiroyuki
Proceedings of 8th International Topical Meeting on Nuclear Applications and Utilization of Accelerators (AccApp '07), p.628 - 632, 2007/00
A lead-bismuth target/cooled ADS for transmutation of minor actinides adopts a vertical injection of proton beam. In this configuration, the beam duct acts a streaming path toward the upper section of subcritical core. In this analysis, two issues for radiation shielding related to ADS beam transport are discussed. Several magnets to control the proton beam are located above the subcritical core and the workmen might access the high-dose area. We determined the allowable maintenance time and obtained the several tens minutes for maintenance per person can be allowable according to the Japanese regulations. To enhance the maintenance time, additional shield must be located. Our proposed ADS are designed as a tank-type layout of the subcritical core because of the usage of heavy liquid metal coolant. So, the steam generators which are located beside the beam duct have a potential of heavy irradiation by escaped neutron through the beam duct space. We investigated the activation of secondary coolant and found that no specific addition of shields was required.
Sasa, Toshinobu; Nishihara, Kenji; Sugawara, Takanori; Oigawa, Hiroyuki
Proceedings of 8th International Topical Meeting on Nuclear Applications and Utilization of Accelerators (AccApp '07), p.904 - 909, 2007/00
The nuclear fuel cycles based on MOX-fueled LWRs and FRs, americium (Am) and curium (Cm) should be carefully managed because they may affect the soundness of nuclear fuels if they are recycled with plutonium. On the other hand, if we dispose of Am and Cm, they will affect the design of the geological repository because of their long half-lives. We propose a new system concept called an "Actinide Reformer", whose purpose is the effective transmutation of Am and Cm. In the concept, Am and Cm are separated from the spent fuel by the advanced aqueous reprocessing and converted to chloride molten-salt fuel which has many experiences for developing pyrochemical reprocessing process. Using such liquid-type fuel, many defects on Am and Cm such as high radioactivity and heat release and chemical incompatibility can be overcome. The Actinide Reformer is designed as an accelerator-driven system which consists of a 10MW-class cyclotron, tungsten target and subcritical core. The system is designed to recover overall electricity to drive system itself.
Toyokawa, Hiroyuki*; Hirade, Tetsuya; Kuroda, Ryunosuke*; Suzuki, Ryoichi*; Odaira, Toshiyuki*
Proceedings of 8th International Topical Meeting on Nuclear Applications and Utilization of Accelerators (AccApp '07) (CD-ROM), p.331 - 335, 2007/00
A novel radiographic method for nondestructive testing of industrial products based on positron annihilation was presented. High-energy 
-ray beam, which was generated via the laser-Compton scattering was used for the present method. An experimental study using a reinforced concrete block, as a sample, showed that the method was suitable for nondestructive testing of industrial products containing metals. Tomographic method was also applied, and a cross-sectional image of the sample was obtained. By use of high-energy -ray beam, we can detect not only the decay of -ray beam and also the decay of annihilation -rays from positrons formed in the samples. By shifting and rotating the sample, it is possible to obtain PET (positron emission tomography) image. It is also expected that positron annihilation method can be applied for the certain cite in the sample.