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JAEA Reports

Research on diffusion behavior in oxide fuels (Joint research)

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$$_{2}$$ fuel, the diffusion tests were performed. The diffusion coefficients were estimated to be 10$$^{-12}$$m$$^{2}$$/s $$sim$$ 10$$^{-14}$$m$$^{2}$$/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.

Oral presentation

Sintering behavior of MOX pellets prepared by mechanical blending method

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$$_H$$$$_2$$/P$$_H$$$$_2$$$$_O$$ ratio in the sintering atmosphere. The O/M ratio increased and the MOX pellets shrank at lower temperatures with decreasing P$$_H$$$$_2$$/P$$_H$$$$_2$$$$_O$$ ratio. The MOX pellets sintered near O/M = 2.0 showed more homogeneous distribution of uranium and plutonium than those of other specimens.

Oral presentation

Effect of particle properties on die filling behavior in nuclear oxide fuel pellet production

Akashi, Masatoshi; Nishina, Masahiro; Kato, Masato; Tanaka, Tatsuya*; Shimosaka, Atsuko*; Shirakawa, Yoshiyuki*; Hidaka, Jusuke*

no journal, , 

Oral presentation

Characterization of fuel debris (28'A), 9; Oxidation behavior of simulated fuel debris

Nishina, Masahiro; Hiroka, Shun; Morimoto, Kyoichi

no journal, , 

no abstracts in English

Oral presentation

Study on the condition of MOX granules suitable for constant die filling in MOX fuel pellet production

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.

Oral presentation

Evaluation of diffusion behavior simulated MOX powder in air flow

Nishina, Masahiro

no journal, , 

no abstracts in English

Oral presentation

Study on development of additive-free dry granulation technology and evaluation of granulation characteristics

Ishii, Katsunori; Segawa, Tomomi; 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 Li$$_{2}$$O 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.

Oral presentation

Granulation characteristics confirmation test of additive-free dry granulation technology for fast reactor fuel fabrication

Segawa, Tomomi; 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 Li$$_{2}$$O spheres for nuclear fusion reactor. In this study, to confirm the applicability of this method to the MOX fuel fabrication process, CeO$$_{2}$$ 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.

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