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Journal Articles

Oxygen thermochemistry of urania-rare earth system; UO$$_2$$-CeO$$_2$$

Hiroka, Shun; Murakami, Tatsutoshi; Nelson, A. T.*; McClellan, K. J.*

INL/EXT-14-33515, p.34 - 36, 2014/10

Collaborative study has been done on the properties of nuclear materials between the DOE and Japan and the oxygen potential of (U,Ce)O$$_2$$ was measured in this year. Experimental measurements of the oxygen potential were conducted on Ce=20% and 30% composition rates simulating Pu content in advanced MOX fuel in JAEA by gas equilibrium method where oxygen partial pressure in the atmosphere was controlled with mixing dry/wet Ar/H$$_2$$ gas. More than 100 data points were obtained in the O/M range of 1.945 $$sim$$ 2.000 at 1200$$^{circ}$$C, 1400$$^{circ}$$C and 1600$$^{circ}$$C. The experimental results were analyzed by the defect analysis and analytical equations were obtained to calculate O/M as functions of temperature and oxygen potential. From the comparison with that of (U,Pu)O$$_2$$, applicability of the same defect chemistry and S-style curve are common. Also, it is revealed that (U,Ce)O$$_2$$ requires evidently higher oxygen potential for the O/M.

JAEA Reports

Engineering scale development test of MOX fuel fabrication technology to establish commercialized fast reactor fuel, 1; The O/M ratio preparation tests of sintered pellets

Takato, Kiyoto; Murakami, Tatsutoshi; Suzuki, Kiichi; Shibanuma, Kimikazu; Hatanaka, Nobuhiro; Yamaguchi, Bungo; Tobita, Yoshimasa; Shinozaki, Masaru; Iimura, Naoto; Okita, Takatoshi; et al.

JAEA-Technology 2013-026, 42 Pages, 2013/10

JAEA-Technology-2013-026.pdf:3.17MB

In order to cope with making a commercial fast reactor fuel burn-up higher, oxygen-to-metal (O/M) ratio in the fuel specification is designed to 1.95. As the test for the fabrication of such low O/M ratio pellets, two kinds of O/M ratio preparation tests of different reduction mechanism were done. In the first test, we evaluated the technology to prepare the O/M ratio low by annealing the sintered pellets in production scale. In addition, we know from past experience that O/M ratio of the sintered pellets can be reduced by residual carbon when the de-waxed pellets with high carbon content are sintered. Thus, in another test, the green pellets containing a large amount of organic additives were sintered and we evaluated the technology to produce the low O/M ratio sintered pellets by the reduction due to residual carbon. From the first test results, we found a tendency that the higher annealing temperature or the longer annealing time resulted in the lower O/M ratio. However, the amount of O/M ratio reduction was small and it is estimated that a substantial annealing time is necessary to prepare the O/M ratio to 1.95. It is considered that reducing O/M ratio by annealing was difficult because atmosphere gas containing oxygen released from pellets remained and the O/M ratio was changed to the value equilibrated with the gas having high oxygen potential. From another test results, it was confirmed that O/M ratio was reduced by the reduction due to residual carbon. We found that it was important to manage an oxygen potential of atmosphere gas in a sintering furnace low to reduce the O/M ratio effectively.

Journal Articles

Property measurements of (U$$_{0.7}$$,Pu$$_{0.3}$$)O$$_{2-x}$$ in $$P$$$$_{O2}$$-controlled atmosphere

Kato, Masato; Murakami, Tatsutoshi; Sunaoshi, Takeo*; Nelson, A. T.*; McClellan, K.*

Proceedings of International Nuclear Fuel Cycle Conference; Nuclear Energy at a Crossroads (GLOBAL 2013) (CD-ROM), p.852 - 856, 2013/09

Uranium and plutonium mixed oxide (U$$_{0.7}$$,Pu$$_{0.3}$$)O$$_{2-x}$$ which has been developed as a fast reactor fuel is nonstoichiometric compound. The stoichiometry significantly affects various properties. The relationship between oxygen potential and oxygen-to-metal (O/M) ratio has been investigated so far. The measurement results showed that it is essential to control oxygen partial pressure ($$P$$$$_{O2}$$) for holding constant O/M ratio in high temperature range. Therefore, properties of (U$$_{0.7}$$,Pu$$_{0.3}$$)O$$_{2-x}$$ were measured in $$P$$$$_{O2}$$-controlled atmosphere in this work. In this work, properties of O/M change, sintering and thermal expansion were investigated in $$P$$$$_{O2}$$-controlled atmosphere.

Journal Articles

Prevention of segregation of pore former by granulating with MOX powder in low density pellet fabrication for fast breeder reactors

Murakami, Tatsutoshi; Aono, Shigenori

Proceedings of 5th International Granulation Workshop (CD-ROM), 10 Pages, 2011/06

Japan Atomic Energy Agency has been working to advance fabrication technology of mixed plutonium-uranium oxide fuel pellets for fast breeder reactors. In brief, the usual fabrication method of MOX pellets for FBRs consists of granulating raw MOX powder by a tabletting method, followed by pressing into compacts. Then, the compacts are sintered to get the MOX pellets. For the FBR "MONJU", MOX pellets having low density are required as the fuel pellets. The low density pellets are fabricated by adding an organic additive called a "pore former" to the MOX powder. The pore former is thermally decomposed and pores are incorporated into MOX pellets by sintering the compacts containing the pore former. In the past, the pore former was blended with the granulated MOX powder after the granulation process. But the pore former became segregated from the granulated MOX powder during feeding to the press machine, because the specific gravity of pore former is significantly lower than that of granulated MOX powder. In order to solve the problem, blending the raw MOX powder with the pore former was carried out before the granulation process to keep the pore former in the granulated MOX powder. As the result, segregation of pore former was prevented.

Journal Articles

Preparation of low O/M MOX pellets for fast reactors using carbothermic reduction

Murakami, Tatsutoshi; Kato, Masato; Suzuki, Kiichi; Uno, Hiroki*

Proceedings of 2010 International Congress on Advances in Nuclear Power Plants (ICAPP '10) (CD-ROM), p.1859 - 1865, 2010/06

The sintering behavior of the de-waxed pellets containing about 3000 ppm of carbon was analyzed during the sintering process using thermal gravimetry and dilatometer measurements as a parameter of the ratio of hydrogen partial pressure-to-moisture partial pressure (H$$_{2}$$/H$$_{2}$$O) in the sintering atmosphere. The attained O/M ratio and the shrinkage rate increased with decreasing H$$_{2}$$/H$$_{2}$$O ratio in the sintering atmosphere. As a result, it is considered that a carbothermic reduction caused the significant decrease of the O/M ratio in the case of the sintering in the atmosphere of high H$$_{2}$$/H$$_{2}$$O ratio. In contrast, decrement of O/M ratio could be inhibited by keeping the oxygen potential of the atmosphere high in the case of the sintering in the atmosphere of lower H$$_{2}$$/H$$_{2}$$O ratio.

JAEA Reports

Confirmation tests for fabrication of low density MOX pellet for FBR

Murakami, Tatsutoshi; Suzuki, Kiichi; Hatanaka, Nobuhiro; Hanawa, Yukio; Shinozaki, Masaru; Murakami, Shinichi; Tobita, Yoshimasa; Kawasaki, Takeshi; Kobayashi, Yoshihito; Iimura, Naoto; et al.

JAEA-Technology 2008-017, 97 Pages, 2008/03

JAEA-Technology-2008-017.pdf:2.76MB

Low density MOX pellets for FBR "MONJU" have not been fabricated in Plutonium Fuel Fabricating Facility (PFPF) for these 9 years since completion of the first reload fuel for "MONJU" in 1995. In this period, about 60 % of machines in the pellet fabrication process of PFPF have been replaced with new ones, and fabrication of MOX pellets for "JOYO" has been continued using these machines. Concerning the feed MOX powders for "MONJU", the amount of decay heat has been increased with increase of accumulated Am-241 in this period. In addition, powder characteristic of recycled MOX powder which is one of feed powders, MH-MOX powder, UO$$_{2}$$ powder and recycled MOX powder, was significantly changed by replacing former processing machine used for scrap recycling with improved one. Using MOX powder with increased decay heat and recycled MOX powder processed by new machine, a series of low density MOX pellet fabrication tests were conducted to confirm pellet fabrication conditions for current pellet fabrication machines from October in 2004 to August in 2006. As a conclusion, it was confirmed that low density MOX pellets could be fabricated using these feed powders and replaced machines by adjusting pellet fabrication conditions adequately. This report summarizes the results of a series of low density MOX pellet fabrication tests.

Journal Articles

Study on characteristics of recycled MOX powder suitable for low density pellet fabrication

Murakami, Tatsutoshi; Suzuki, Kiichi; Aono, Shigenori

Proceedings of International Conference on Advanced Nuclear Fuel Cycles and Systems (Global 2007) (CD-ROM), p.891 - 896, 2007/09

no abstracts in English

Journal Articles

Parametric studies on nuclear criticality safety design of MOX fuel fabrication facility

Shimizu, Yoshio; Suitsu, Yuichi; Murakami, Tatsutoshi; Yuri, Akiya

Proceedings of 8th International Conference on Nuclear Criticality Safety (ICNC 2007), p.335 - 340, 2007/05

Nuclear criticality safety evaluations for the fast breeder reactor's MOX fuel fabrication facility were performed. In the parametric studies made with SCALE, following three cases are here introduced. (1) The effect of the plutonium isotopic ratio on Pu$$^{*}$$ ($$^{235}$$U, $$^{239}$$Pu, $$^{241}$$Pu) mass control were evaluated. The design conditions of the plutonium isotopic ratio under the operating condition were adjusted from the evaluation. (2) The moderation effects of organic materials in MOX fuel fabrication facility were evaluated. The water contents equivalent moderation effects to organic contents were obtained from the evaluation. (3) The effects of nonuniform mixture of MOX powder and water were evaluated by two-phase model and SMORES. The $$Delta$$k, which differ from the k$$_{eff}$$ of uniform model, were evaluated.

Oral presentation

Nuclear criticality safety for the MOX fuel facility, 2; Parametric evaluation of plutonium isotopic composition for mass control limits

Shimizu, Yoshio; Suitsu, Yuichi; Murakami, Tatsutoshi; Yuri, Akiya

no journal, , 

no abstracts in English

Oral presentation

Nuclear criticality safety for the MOX fuel facility, 1; Establishing critical limits

Suitsu, Yuichi; Shimizu, Yoshio; Murakami, Tatsutoshi; Yuri, Akiya

no journal, , 

no abstracts in English

Oral presentation

Nuclear criticality safety for the mox fuel facility, 3; Commitment to the double contingency principle

Yuri, Akiya; Shimizu, Yoshio; Suitsu, Yuichi; Murakami, Tatsutoshi; Ninagawa, Junichi

no journal, , 

no abstracts in English

Oral presentation

Recovered MOX powder suitable for low density pellet fabrication

Murakami, Tatsutoshi; Suzuki, Kiichi; Aono, Shigenori

no journal, , 

no abstracts in English

Oral presentation

Resintering characteristics of low density pellet

Suzuki, Kiichi; Murakami, Tatsutoshi; Aono, Shigenori

no journal, , 

no abstracts in English

Oral presentation

Fire and explosion safety in the MOX fuel facility, 2; Accident analysis

Suitsu, Yuichi; Murakami, Tatsutoshi; Yuri, Akiya

no journal, , 

We assumed fire and explosion accidents would occur in the MOX fuel facility of JAEA and reevaluated the radiation dose to the public with a recent method.

Oral presentation

Fire and explosion safety in the MOX fuel facility, 1; Safety design review

Murakami, Tatsutoshi; Suitsu, Yuichi; Yuri, Akiya

no journal, , 

no abstracts in English

Oral presentation

Sintering behavior of MOX pellets containing carbon

Murakami, Tatsutoshi; Kato, Masato; Suzuki, Kiichi; Uno, Hiroki*

no journal, , 

no abstracts in English

Oral presentation

Development of cooling hopper for high heat generating MOX powder

Murakami, Tatsutoshi; Shibanuma, Kimikazu; Hanawa, Yukio; Yamaki, Takao; Suzuki, Mitsuru; Aono, Shigenori

no journal, , 

MOX powder containing organic additives is loaded in a hopper. The hopper has a cooling function to mitigate heat deterioration of organic additives, but its cooling may not be enough for higher order plutonium in the future. So temperature measurement of MOX powder in the hopper was carried out as a preliminarily test for development of cooling hopper.

Oral presentation

Sintering characteristics of MOX powder prepared by mechanical blending method

Suzuki, Kiichi; Takeuchi, Kentaro; Murakami, Tatsutoshi; Kato, Masato; Uno, Hiroki*; Sunaoshi, Takeo*

no journal, , 

no abstracts in English

Oral presentation

Effect of recycled MOX powder added to granulated MOX powder on the density of sintered MOX pellets for FBR

Murakami, Tatsutoshi; Suzuki, Kiichi; Shibanuma, Kimikazu; Aono, Shigenori

no journal, , 

no abstracts in English

Oral presentation

O/M ratio adjustment of sintered MOX pellet on an engineering scale

Suzuki, Kiichi; Murakami, Tatsutoshi; Aono, Shigenori; Hatanaka, Nobuhiro; Takano, Tatsuo

no journal, , 

no abstracts in English

28 (Records 1-20 displayed on this page)