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Journal Articles

Experience in MOX fuel fabrication at the PFPF for the fast reactor

Suzuki, Kiichi; Okita, Takatoshi; Aono, Shigenori

Proceedings of International Conference on Fast Reactors and Related Fuel Cycles; Next Generation Nuclear Systems for Sustainable Development (FR-17) (USB Flash Drive), 10 Pages, 2017/06

Japan Atomic Energy Agency has developed mixed plutonium-uranium oxide (MOX) fuel fabrication technologies in large-scale and fabricated MOX fuel assemblies for experimental fast reactor "JOYO" and prototype fast reactor "MONJU" at Plutonium Fuel Production Facility (PFPF) since 1988. Low density pellet is adopted as MONJU fuel. For the low density pellet fabrication in large-scale, various challenges were encountered. In order to resolve these challenges, countermeasures such as new pore former with high softening temperature and improved granulation method for MOX powder were considered. In this presentation, accumulated MOX fuel fabrication technologies as mentioned above and recent R&D activity such as new pelletizing method, or die wall lubrication pelletizing, for low-decontaminated TRU fuel fabrication will be discussed.

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.

JAEA Reports

Operating and maintenance experiences of rebottling equipment for plutonium dioxide powder received from foreign country

Ono, Takanori; Hatanaka, Nobuhiro; Okita, Takatoshi; Aono, Shigenori

JAEA-Technology 2012-042, 96 Pages, 2013/02

JAEA-Technology-2012-042.pdf:2.6MB

In January of 1993, plutonium dioxide powder was received from the reprocessing plant "La Hague" of COGEMA in France to Plutonium Fuel Production Facility (PFPF) of JAEA to use as feed powder of MOX fuel for FBR prototype "Monju". Since the plutonium dioxide powder was contained in COGEMA type canisters, the powder had to be rebottled from CCGEMA type canisters to JAEA type canisters which can be handled in the PFPF. Therefore feed powder rebottling equipment and temporary feed storage equipment were developed and installed in the PFPF. Rebottling work with their equipments was started from March of 1993 and completed in March of 2006. This report summarizes operating and maintenance experiences on feed powder rebottling equipment and temporary feed storage equipment. It's important to reflect the operating and maintenance experiences of the rebottling equipment into design of a new rebottling equipment for uranium-plutonium mixed oxide powder.

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

Oxygen chemical diffusion in hypo-stoichiometric MOX

Kato, Masato; Morimoto, Kyoichi; Tamura, Tetsuya*; Sunaoshi, Takeo*; Konashi, Kenji*; Aono, Shigenori; Kashimura, Motoaki

Journal of Nuclear Materials, 389(3), p.416 - 419, 2009/06

 Times Cited Count:11 Percentile:59.93(Materials Science, Multidisciplinary)

Plutonium and uranium mixed oxide (MOX) has been developed to use as a core fuel of the fast reactor. The oxygen to metal ratio (O/M) of the MOX fuel is an important parameter to control the FCCI. The oxygen potential and the oxygen diffusion coefficient of the MOX are essential data to understand the oxygen behaviour in MOX. The oxygen potentials of the MOX were measured with accuracy as a function of O/M and temperatures in the previous work. In this work the oxygen chemical diffusion coefficient in (Pu$$_{0.2}$$U$$_{0.8}$$)O$$_{2-x}$$ and (Pu$$_{0.3}$$U$$_{0.7}$$)O$$_{2-x}$$ were investigated using thermo gravimetric technique. The kinetics of the reduction processes of (Pu$$_{0.2}$$U$$_{0.8}$$)O$$_{2-x}$$ and (Pu$$_{0.3}$$U$$_{0.7}$$)O$$_{2-x}$$ were measured by TG-DTA method. The oxygen chemical diffusion coefficients have been estimated from the reduction curves. It was concluded that the oxygen chemical diffusion coefficient in (Pu$$_{0.3}$$U$$_{0.7}$$)O$$_{2-x}$$ is a smaller than that of (Pu$$_{0.2}$$U$$_{0.8}$$)O$$_{2-x}$$.

Journal Articles

Effective thermal conductivity of MOX raw powder

Takeuchi, Kentaro; Kato, Masato; Sunaoshi, Takeo*; Aono, Shigenori; Kashimura, Motoaki

Journal of Nuclear Materials, 385(1), p.103 - 107, 2009/03

 Times Cited Count:4 Percentile:30.6(Materials Science, Multidisciplinary)

The effective thermal conductivities were evaluated by measuring radial temperature distribution in MH-MOX powder. The effective thermal conductivities were very small and they changed significantly with O/M, bulk density and atmosphere gas. The results in this work were analyzed by the model of Hamilton and Crosser and the new model for the effective thermal conductivity for MH-MOX powder was derived as a function of powder properties, thermal conductivity of atmosphere gas and temperature.

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

The Oxidation rate of (U$$_{0.7}$$Pu$$_{0.3}$$)O$$_{2-x}$$ with two fcc phases

Suzuki, Kiichi; Kato, Masato; Tamura, Tetsuya*; Aono, Shigenori; Kashimura, Motoaki

Journal of Alloys and Compounds, 444-445, p.590 - 593, 2007/10

 Times Cited Count:5 Percentile:38(Chemistry, Physical)

It was reported that sintered MOX pellet of hypostoichiometric composition was oxidized at room temperature in an atmosphere of inert gas and air. The region of two fcc phases exist at room temperature in the (U,Pu)O$$_{2-X}$$ with Pu content of greater than 20%. In this study, the oxidation rate of (U$$_{0.7}$$Pu$$_{0.3}$$)O$$_{2-X}$$ with two fcc phases was investigated to contribute to understanding of the oxidation behavior using thermogravimetric technique. The sintered pellets of (U$$_{0.7}$$Pu$$_{0.3}$$)O$$_{2-X}$$ were prepared by mechanical blending method and were sliced into disc-like sample with about 1 mm thick and 85-93% theoretical density. The oxidation rate of the samples were measured at 60, 125 and 150$$^{circ}$$C in an atmosphere of Air, N$$_{2}$$ and Air/N$$_{2}$$ gas mixture containing moisture of 1 - 700ppm using thermal gravity and differential thermal analysis. The curve of the isothermal oxidation was analyzed by the model of diffusion in a system consisting of two phases. The diffusion model can represent the oxidation curve as a function of time and temperature. In the results of X-ray diffraction measurement, fcc phase with O/M $$approx$$ 2.00 was observed to increase by oxidation of sample. These results indicate that the oxidation of the (U$$_{0.7}$$Pu$$_{0.3}$$)O$$_{2-X}$$ with two fcc phases proceeds by diffusion of the phase with O/M $$approx$$ 2.00 which is formed on the sample surface.

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

Effect of ball milling condition on powder properties and pellet characteristics for fast reactor MOX fuel fabrication

Takeuchi, Kentaro; Okita, Takatoshi; Aono, Shigenori

Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 4 Pages, 2005/10

In the FBR MOX pellet fabrication process, the characteristics such as specific surface area and homogeneity of the ball milled powder depend on the ball milling condition. The qualities of the MOX pellet such as sintered density and homogeneity are influenced by the characteristics of the ball milled powder. In this work, correlations relationship between properties of milled powder, ball milling condition and characteristic of the MOX pellet have been evaluated.

Journal Articles

Development of the simplified MOX pellet fabrication process (short process); Improvement of MOX powder lowability

Makino, Takayoshi; Okita, Takatoshi; Kato, Yoshiyuki; Kurita, Tsutomu; Takahashi, Yoshiharu; Aono, Shigenori

Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 5 Pages, 2005/10

A simplified MOX pellet fabrication process, called short process, has been developed to drastically reduce fuel fabrication cost.The MH powder has characteristic of fine particle and low flowability. It is difficult to pelletize the MH powder directly without granulation into smaller size FR pellet compared with LWR fuel. Therefore, small-scale hot tests to improve the flowability of the MH powder has been carried out using two kinds of methods, and quality of the pellet was evaluated.

Journal Articles

Oxygen Potentials of Plutonium and Uranium Mixed Oxide

Kato, Masato; Aono, Shigenori; Tamura, Tetsuya*; Konashi, Kenji*

Journal of Nuclear Materials, 344, p.235 - 239, 2005/00

 Times Cited Count:35 Percentile:90.27(Materials Science, Multidisciplinary)

The oxygen potentials of (Pu$$_{0.3}$$U$$_{0.7}$$)O$$_{2-X}$$ near stoichiometric region were measured by thermogravimetric technique which was used to establish the equilibrium between the oxide phases and H$$_{2}$$/H$$_{2}$$O system gas. The experimental results of (Pu$$_{0.3}$$U$$_{0.7}$$)O$$_{2-X}$$ give a consistent picture variation in Po$$_{2}$$ with O/M and the temperature with other works. The relationship between the partial oxygen pressure and X in MO$$_{2-X}$$was evaluated by the lattice defect theory. The relation in hypo-stoichiometric region is x$$mu$$Po$$_{2}$$$$^{-1/2}$$ near stoichiometric composition, and changes to x$$mu$$Po$$_{2}$$$$^{-1/3}$$ with a decrease in O/M.

JAEA Reports

Melting Temperature Measurement Of Nuclear Fuel, 1; Development of the Melting Temperature Measurement Technology for MOX Fuel and the Melting Temperature Measurement of MOX Fuel

Morimoto, Kyoichi; Kato, Masato; Aono, Shigenori; Uno, Hiroki*

JNC TN8400 2004-017, 64 Pages, 2004/11

JNC-TN8400-2004-017.pdf:4.79MB

The use of high plutonium concentration MOX fuel is considered because of an increase of high-order plutonium from high burnup fuel, the shortage of the enriched uranium etc. The melting temperature and the thermal conductivity etc are necessary for the using of MOX fuel from the viewpoint of the safety evaluation and the fuel design. But reports about the melting temperature of MOX are few, so it is necessary to obtain more melting temperature data. This report describes the melting temperature measurement of MOX fuel whose compositions are from 0 to 100 atom% PuO2 (O/M is 2.00) and that whose O/M are from 1.922 to 1.983 (Pu concentration is 28 atom%). The result of the former experiment agree approximately with that of previous reports. About the later experiment, the variance of melting temperature by O/M is so complicated that this behavior did not show a simple increasing tendency or decreasing tendency. In these experiments, it is found that MOX samples with high O/M reacts with tungsten which is a material of sample container. In order to prevent this reaction, the sample container was made from alloy of tungsten and rhenium. And the applicability of this container was evaluated.

JAEA Reports

Effective Thermal Conductivity of Plutonium and Uranium Mixed Raw Powder

Kato, Masato; Sunaoshi, Takeo*; Aono, Shigenori

JNC TN8400 2004-013, 47 Pages, 2004/07

JNC-TN8400-2004-013.pdf:1.43MB

The effective thermal conductivity of plutonium and uranium mixed raw powder (1:1 MOX) together with thermal conductivity of gas in atmosphere was measured using self heat genelation of plutonium. The effective thermal conductivity was evaluated the influence of thermal conductivity of gas and powder properties. The experimental results in Ar, air and He atmosphere are very small value which are 0.00060$$sim$$0.0011, 0.00077$$sim$$0.0013 and 0.0014$$sim$$0.0024 w/cm$$^{circ}$$C, respectively. The data in this work were analyzed by Hamilton's equation, which made the equation reproducing the effective thermal conductivity for MOX powder as a function of O/M, specific surface area, average particle size and temperature. The equation reproduce the experimental data in range of $$pm$$205 error.

Journal Articles

Model of Oxygen Potential of (Pu$$_{0.3}$$U$$_{0.7}$$)O$$_{2pm X}$$ and (Np$$_{0.02}$$Am$$_{0.02}$$Pu$$_{0.3}$$U$$_{0.66}$$)O$$_{2-X}$$ based on Lattice Defect Theory

Kato, Masato; Aono, Shigenori; Kihara, Yoshiyuki; Konashi, Kenji*

Materials Models and Simulations for Nuclear Fuels MMSNF-3, CD-ROM, 13p., 13 Pages, 2004/00

The model of oxygen potential of (Pu$$_{0.3}$$U$$_{0.7}$$)O$$_{2pm X}$$ was derived by experimental data set based on the lattice defect theory. In the model, the oxygen potential is calculated as a function of O/M and the temperature of fuel. The oxygen potential was evaluated by the crossed point of two lines of oxygen potential in the hypo-stoichiometric region and in the hyper-stoichiometric region. The oxygen potential of (Np$$_{0.02}$$Am$$_{0.02}$$Pu$$_{0.3}$$U$$_{0.66}$$)O$$_{2-X}$$was also evaluated and compared with that of (Pu$$_{0.3}$$U$$_{0.7}$$)O2-X

Journal Articles

Oxygen Potentials of Pultonium and Uranium Mixed Oxide

Kato, Masato; Tamura, Tetsuya*; Aono, Shigenori

Proceedings of 11th Symposium on Thermodynamics of Nuclear Materials (STNM-11), P. 81, 2004/00

The oxygen potentials of (Pu$$_{0.3}$$U$$_{0.7}$$)O$$_{2-X}$$were measured by thermogravimetric equilibrium measurement in the range of the temperature from 800 to 1350 in Ar/H$$_{2}$$/H$$_{2}$$O or He/H$$_{2}$$/H$$_{2}$$O mixture gas flow. The experimental results of (Pu$$_{0.3}$$U$$_{0.7}$$)O$$_{2-X}$$are in good agree with the other works. The relationship between the partial oxygen pressure (PO$$_{2}$$) and X in MO$$_{2-X}$$ was analized based on lattice defect theory. The oxygen potential of (Pu$$_{0.3}$$U$$_{0.7}$$)O$$_{2-X}$$was modeled by lattice defect theory using the data of the literature and this work. The resulting equation well reproduces the oxygen potential-temperature data for (Pu$$_{0.3}$$U$$_{0.7}$$)O$$_{2-X}$$.

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

Oxidation rate of (U$$_{0.7}$$Pu$$_{0.3}$$)O$$_{2-x}$$

Suzuki, Kiichi; Kato, Masato; Tamura, Tetsuya*; Uno, Hiroki*; Kashimura, Motoaki; Aono, Shigenori

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.

24 (Records 1-20 displayed on this page)