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Nishina, Masahiro; Takeuchi, Kentaro; Murakami, Shinichi
Proceedings of International Conference on Fast Reactors and Related Fuel Cycles; Sustainable Clean Energy for the Future (FR22) (Internet), 8 Pages, 2022/04
no abstracts in English
Sato, Isamu; Arima, Tatsumi*; Nishina, Masahiro*; Tanaka, Kosuke; Onose, Shoji; Idemitsu, Kazuya*
JAEA-Research 2012-006, 66 Pages, 2012/05
JAEA-Research-2012-006.pdf:13.55MB
As one of the important properties for fuel manufacturability and burning behavior, the diffusion behavior of actinides in oxide fuels was investigated by both the experimental and the molecular dynamics simulation (MD). Using diffusion couples consisted of an Am containing mixed oxide fuel and a UO
fuel, the diffusion tests were performed. The diffusion coefficients were estimated to be 10
m
/s 
10
m/s. In addition, the difference between Pu and Am diffusion coefficients was vanishingly small. The temperature dependence of bulk diffusion coefficients of actinides in mixed oxide fuels could be evaluated by MD. An evaluation technique for the grain boundary diffusion could be established based on the coincidence site lattice theory. The practical diffusion coefficients were obtained by combining data from the experiments with those predicted from MD. The practical diffusion coefficients obtained was discussed for use of a fuel behavior analysis code.
Nishina, Masahiro; Suzuki, Kiichi; Takeuchi, Kentaro; Kato, Masato; Uno, Hiroki*
no journal, ,
Sintering behavior of MOX pellets prepared by the mechanical blending method was evaluated from measurement results of the O/M ratio and dimensional shrinkage of the pellets during sintering. Change of the O/M ratio occurred when approaching the equilibrium condition which was decided from oxygen potential depending on the P
/P
ratio in the sintering atmosphere. The O/M ratio increased and the MOX pellets shrank at lower temperatures with decreasing P/P ratio. The MOX pellets sintered near O/M = 2.0 showed more homogeneous distribution of uranium and plutonium than those of other specimens.
Akashi, Masatoshi; Nishina, Masahiro; Kato, Masato; Tanaka, Tatsuya*; Shimosaka, Atsuko*; Shirakawa, Yoshiyuki*; Hidaka, Jusuke*
no journal, ,
Nishina, Masahiro; Hirooka, Shun; Morimoto, Kyoichi
no journal, ,
no abstracts in English
Akashi, Masatoshi; Nishina, Masahiro; Morimoto, Kyoichi; Kato, Yoshiyuki; Kato, Masato
no journal, ,
A die filling experiment was carried out using granulated MOX powder to investigate the condition of MOX granules suitable for constant die filling. It was found that the mean particle diameter and the Hausner ratio gave an indication of the die filling for the granulated MOX powder.
Nishina, Masahiro
no journal, ,
no abstracts in English
Ishii, Katsunori; Segawa, Tomoomi; Kawaguchi, Koichi; Nishina, Masahiro; Makino, Takayoshi; Natori, Yuri*
no journal, ,
JAEA is developing simplified a plutonium and uranium mixed oxide (MOX) pellet fabrication process. In this process, agitation granulator improves flowability of MOX powder with water as binder. This granulation method has issues, including low production capacity due to criticality control for wet nuclear material. A new simple additive-free dry granulation method was proposed recently to produce tritium breeding LiO spheres for nuclear fusion reactor. In this research, results of experiments to investigate the applicability of the new granulation method to MOX powder is reported.
Segawa, Tomoomi; Kawaguchi, Koichi; Ishii, Katsunori; Nishina, Masahiro; Makino, Takayoshi; Natori, Yuri*; Ikemoto, Norihiro*; Yonehara, Kazuo*; Tatenuma, Katsuyoshi*
no journal, ,
Japan Atomic Energy Agency has researched and developed a simplified MOX pellet fabrication process. the flowability of MOX powder is improved by a tumbling granulation method using water as a binder. However, in this granulation method, improvement of the production capacity under criticality control for wet nuclear material is an issue. In recent years, an additive-free dry granulation technology has proposed as a novel granulation method for producing tritium breeding LiO spheres for nuclear fusion reactor. In this study, to confirm the applicability of this method to the MOX fuel fabrication process, CeO powder was used as a simulated material of MOX powder as a basic test for mechanization, and the influence of mechanical external force on granulation was confirmed and evaluated. As a result of the test, good granulation property was obtained by applying a mechanical external force of vertical vibration, and it was possible to obtain the prospect of mechanization of the dry granulation process.
Segawa, Tomoomi; Kawaguchi, Koichi; Ishii, Katsunori; Nishina, Masahiro; Makino, Takayoshi; Iimura, Kenji*; Satone, Hiroshi*; Suzuki, Michitaka*; Natori, Yuri*
no journal, ,
Japan Atomic Energy Agency has developed a simplified pelletizing fuel fabrication system. In this system, the flowability of a MOX raw powder is improved by wet granulation for the pelletizing process, and the die wall lubrication method directly presses the granulated MOX powder into green pellets without adding any lubricant into the powder. The homogeneous compression is important to fabricate high-density green pellets. However, it is difficult to observe the compaction behavior in situ. Therefore, the capping phenomenon was investigated by using X-ray computed tomography and alumina powder that is highly transparent against X-rays. When lubricant was used, the breakage of the particles extended to the bottom compared with not used. This result indicates that the die wall lubrication is effective for the homogeneous compression of granulated powders.
Nishina, Masahiro; Takato, Kiyoto; Nakamichi, Shinya; Segawa, Tomoomi; Kawaguchi, Koichi; Ishii, Katsunori; Makino, Takayoshi; Okumura, Kazuyuki
no journal, ,
no abstracts in English
Takato, Kiyoto; Nishina, Masahiro; Tsuchimochi, Ryota; Hayashizaki, Kohei; Segawa, Tomoomi; Kawaguchi, Koichi; Ishii, Katsunori; Makino, Takayoshi; Okumura, Kazuyuki
no journal, ,
no abstracts in English