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Journal Articles

Study on optimizing microwave heating denitration method and powder characteristics of uranium trioxide

Segawa, Tomoomi; Kawaguchi, Koichi; Kato, Yoshiyuki; Ishii, Katsunori; Suzuki, Masahiro; Fujita, Shunya*; Kobayashi, Shohei*; Abe, Yutaka*; Kaneko, Akiko*; Yuasa, Tomohisa*

Proceedings of 2019 International Congress on Advances in Nuclear Power Plants (ICAPP 2019) (Internet), 9 Pages, 2019/05

A solution of plutonium nitrate and uranyl nitrate is converted into a mixed oxide by microwave heating denitration method. In the present study, for improving the efficiency of microwave heating and achieving high-temperature uniformity to produce homogeneous UO$$_{3}$$ powder, the microwave heating test of potassium chloride and uranyl nitrate solution, and numerical simulation analysis were conducted. The potassium chloride agar was adjusted to the dielectric loss, which is close to that of the uranyl nitrate solution and the optimum support table height was estimated to be 50 mm for denitration of the uranyl nitrate solution by microwave heating. The adiabator improved the efficiency of microwave heating denitration. Moreover, the powder yield was improved by using the adiabator owing to ease of scraping of the denitration product from the bottom of the denitration vessel.

Journal Articles

Development of granulation system for simplified MOX pellet fabrication process

Ishii, Katsunori; Segawa, Tomoomi; Kawaguchi, Koichi; Suzuki, Masahiro

Proceedings of 2019 International Congress on Advances in Nuclear Power Plants (ICAPP 2019) (Internet), 5 Pages, 2019/05

Japan Atomic Energy Agency (JAEA) is developing a simplified pelletizing process for MOX fuel fabrication. In this process, the flowability of MOX powder produced by de-nitration conversion based on microwave heating, calcination, and reduction is improved using the wet granulation method. In a previous paper, to produce MOX granules of appropriate sizes for pelletizing them effectively, we proposed a granulation system composed of a wet granulator and a sizing machine. In the present work, we modernized the wet granulator, completed the granulation system by adding auxiliary equipment, and conducted performance tests of the granulation system with WO$$_{3}$$ powder. The results of a performance test indicated that it is possible to convert raw powder into granules characterized by appropriate size and excellent flowability. The time required to process 5 kg of WO$$_{3}$$ powder was about 70 min, which almost satisfies the target time.

Journal Articles

Mechanism of flashing phenomena by microwave heating and influence of high dielectric constant solution

Fujita, Shunya*; Abe, Yutaka*; Kaneko, Akiko*; Yuasa, Tomohisa*; Segawa, Tomoomi; Kato, Yoshiyuki; Kawaguchi, Koichi; Ishii, Katsunori

Proceedings of 11th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-11) (Internet), 7 Pages, 2018/11

Mixed uranium oxide and plutonium oxide powder is produced from uranyl nitrate and plutonium nitrate mixed solution by the microwave heating denitration method in the spent fuel reprocessing process. Since the microwave heating method is accompanied by a boiling phenomenon, it is necessary to fully grasp the operating conditions in order to avoid flashing and spilling in the mass production of denitrification technology for the future. In this research, it was clarified that the heat transfer coefficient became lower as the dielectric constant increased. The dominant factor of the blowing up phenomena is supposed to be generation of the innumerable bubble rather than bubble's growth.

Journal Articles

Development of synthesis and morphology control method of metallic oxide particles using microwave heating

Segawa, Tomoomi

Funtai Kogaku Kaishi, 55(10), P. 547, 2018/10

no abstracts in English

Journal Articles

Mechanism of flashing phenomena induced by microwave heating

Fujita, Shunya*; Abe, Yutaka*; Kaneko, Akiko*; Yuasa, Tomohisa*; Segawa, Tomoomi; Yamada, Yoshikazu; Kato, Yoshiyuki; Ishii, Katsunori

Proceedings of 26th International Conference on Nuclear Engineering (ICONE-26) (Internet), 8 Pages, 2018/07

Mixed uranium oxide and plutonium oxide powder is produced from uranyl nitrate and plutonium nitrate mixed solution by the microwave heating denitration method in the spent fuel reprocessing process. Since the microwave heating method is accompanied by a boiling phenomenon, it is necessary to fully grasp the operating conditions in order to avoid flashing and spilling in the mass production of denitrification technology for the future. In this research, it was confirmed that a potassium chloride aqueous solution as a simulant of uranyl nitrate aqueous solution with high dielectric loss cause loss of microwave at the solution surface as the dielectric loss increased with the increase of KCl concentration by experimental and electromagnetic field analysis, and revealed that the change in the heating condition affects the generation of flushing.

Journal Articles

Flushing phenomena and flow structure by microwave heating

Fujita, Shunya*; Abe, Yutaka*; Kaneko, Akiko*; Chonan, Fuminori*; Yuasa, Tomohisa*; Yamaki, Tatsunori*; Segawa, Tomoomi; Yamada, Yoshikazu

Proceedings of 25th International Conference on Nuclear Engineering (ICONE-25) (CD-ROM), 8 Pages, 2017/07

From the observation results, in the process of flushing, the behaviors leading to flushing were classified divided into three types. First type is that first generation bubble from heating leads to flushing. Second type is that nucleate boiling continues during heating and stop, finally single bubble generates and leads to flushing. Third type is defined that gradual evaporation occurs without bubbles. It was revealed that the total quantities of heat released by flushing are approximately equal when assuming the flushing mechanism, it can be triggered that a large amount of micro bubbles are instantaneously generated and grew.

Journal Articles

Conceptual design of engineering-scale plant applied the simplified MA-bearing fuel fabrication process

Yamada, Yoshikazu; Segawa, Tomoomi; Kato, Masato

Proceedings of International Conference on Fast Reactors and Related Fuel Cycles; Next Generation Nuclear Systems for Sustainable Development (FR-17) (USB Flash Drive), 8 Pages, 2017/06

Japan Atomic Energy Agency (JAEA) have proposed the transmutation of minor actinides by fast reactors as a way to contribute significantly to the reduction of the volume and the potential radiotoxicity of radioactive wastes. In order to achieve this goal, it is important to introduce a fully automated and remote operation fuel fabrication plant with shielded hot cells and manipulators. JAEA's facilities including Plutonium Fuel Production Facility (PFPF) have fabricated MOX fuel. On the basis of the operational and technical experience obtained in above facilities, the conceptual design of engineering-scale plant applied the simplified MA-bearing fuel fabrication process with shielded hot cells and manipulator was done. It will be able to fabricate high MA-bearing fuel and to perform the maintenance and repairing of each equipment with manipulators. This plant will be constructed based on this concept and development plan.

Journal Articles

Validation of measured microwave absorption and temperature change for development of a single-mode-type microwave heating thermogravimetry apparatus

Karisma, A. D.*; Hamaba, Taishu*; Fukasawa, Tomonori*; Huang, A.-N.*; Segawa, Tomoomi; Fukui, Kunihiro*

Review of Scientific Instruments, 88(2), p.024101_1 - 024101_8, 2017/02

 Times Cited Count:1 Percentile:78.44(Instruments & Instrumentation)

Microwave heating direct denitration method is used in the nuclear fuel reprocessing process. In order to develop a single-mode-type microwave heating thermogravimetry apparatus which can perform detailed analysis of the characteristics of microwave heating, the temperature dependence of microwave absorption is verified. The temperature distribution, microwave absorption efficiency, and dielectric properties of a CuO pellet that was heated by the microwave irradiation were investigated. The temperature distribution in the CuO pellet due to one-way travel of the microwave in the apparatus was accurately reproduced by a three-dimensional numerical simulation of the electromagnetic field. The numerically determined temperature dependency of the CuO absorption efficiency was found to be in very good agreement with published data.

Journal Articles

Influence of the heating method on the particle characteristics of copper oxide powders synthesized from copper nitrate aqueous solutions

Segawa, Tomoomi; Fukasawa, Tomonori*; Huang, A.-N.*; Yamada, Yoshikazu; Suzuki, Masahiro; Fukui, Kunihiro*

Chemical Engineering Science, 153, p.108 - 116, 2016/10

 Times Cited Count:1 Percentile:88.21(Engineering, Chemical)

The influence of the heating method and rate on the morphology of CuO powders synthesized from Cu(NO$$_{3}$$)$$_{2}$$$$cdot$$3H$$_{2}$$O aqueous solutions by denitration was investigated. The median diameter of the obtained powder was found to decrease as the heating rate increased, independent of the heating method. The microwave heating method remarkably reduced the particle size and enhanced the irregularity and disorder of the shape and surface of the particles, which were found to be more widely distributed. In contrast, the microwave hybrid heating method yielded the most spherical particles with the smoothest surface. It was also found that this heating method sharpened the particle size distribution and had higher energy efficiency than the MW method. Numerical simulations also indicated a difference in the energy efficiency between these two methods. The simulations also revealed that the hybrid method could heat the whole reactor more uniformly with a lower microwave output.

Journal Articles

Influence of heating method on size and morphology of metallic oxide powder synthesized from metallic nitrate solution

Segawa, Tomoomi; Fukasawa, Tomonori*; Yamada, Yoshikazu; Suzuki, Masahiro; Yoshida, Hideto*; Fukui, Kunihiro*

Proceedings of Asian Pacific Confederation of Chemical Engineering 2015 (APCChE 2015), 8 Pages, 2015/09

A mixed solution of uranyl nitrate and plutonium nitrate is converted to MOX raw powder by the microwave heating de-nitration method in nuclear reprocessing. Copper oxide synthesized by heating de-nitration was used as a model for the de-nitration process. The microwave heating method (MW) and infrared heating method (IR) were used, and how they and their heating rate influence the obtained particle morphology and size were investigated. The particles obtained by the MW and IR were sufficiently similar in the surface morphology and the mass median diameter was decreased by the increased heating rate. The mass median diameters by the MW were the heating rate and smaller than those obtained by IR. The particle size distribution of the particle obtained by the MW was broader than that by the IR. The relationship of the temperature distribution and particle size distribution by the MW was discussed by the numerical simulation.

Journal Articles

Nickel oxide powder synthesis from aqueous solution of nickel nitrate hexahydrate by a microwave denitration method

Segawa, Tomoomi; Kawaguchi, Koichi; Ishii, Katsunori; Suzuki, Masahiro; Arimitsu, Naoki*; Yoshida, Hideto*; Fukui, Kunihiro*

Advanced Powder Technology, 26(3), p.983 - 990, 2015/05

 Times Cited Count:3 Percentile:76.15(Engineering, Chemical)

Denitration of the aqueous solution of nickel nitrate hexahydrate (Ni(NO$$_{3}$$)$$_{2}$$$$cdot$$6H$$_{2}$$O) by a microwave heating method was investigated. Since Ni(NO$$_{3}$$)$$_{2}$$$$cdot$$6H$$_{2}$$O aqueous solution cannot be heated to over 300 $$^{circ}$$C by microwave irradiation owing to the low microwave absorptivity of its intermediate, NiO could not previously be obtained by microwave heating. We propose a novel NiO synthesis method that uses microwave heating without the risk of chemical contamination. A NiO powder reagent was added to the solution as a microwave acceptor. The denitration efficiency to NiO could be improved by an adiabator around the reactor to increase the temperature homogeneity in the reactor. Numerical simulations also reveal that the use of the adiabator results in remarkable changes in the electromagnetic field distribution in the reactor, temperature inhomogeneity decreases.

Journal Articles

The Criteria of flushing phenomena under microwave heating

Yamaki, Tatsunori*; Abe, Yutaka*; Kaneko, Akiko*; Segawa, Tomoomi; Kawaguchi, Koichi; Yamada, Yoshikazu; Fujii, Kanichi*

Journal of Nuclear Science and Technology, 52(2), p.241 - 250, 2015/02

 Times Cited Count:3 Percentile:53.75(Nuclear Science & Technology)

In the Microwave Heating de-nitration method developed in Japan, a mixed solution of uranyl nitrate and plutonium nitrate recovered from the spent fuel in the reprocessing plant is converted directly to mixed oxide (MH-MOX) powder. This MH-MOX powder is utilized to fabricate MOX fuel with UO$$_{2}$$ powder for FBR. The MH method is accompanied with transient boiling phenomena such as overflow and flushing. Toward high-speed and high-capacity conversion by MH-method in the future, it is required to avoid overflow and flushing and to understand optimal design conditions for design and operation. At the first step for these objectives, basic knowledge of transient boiling phenomena by the MH-method has been acquired with using distilled water. It was observed that generation of singular bubble triggered flushing and distilled water just before flushing was superheated by a temperature 10 degrees centigrade higher than boiling temperature. Based on these results, it is clarified that the occurrence criteria of flushing correlate with absorbed power in the water and released power from the water surface.

Journal Articles

Effect of spacer in microwave oven cavity to heat uniformly Pu/U mixed nitrate solution for producing MOX Fuels

Imai, Suguru*; Taguchi, Kenji*; Kashiwa, Tatsuya*; Kitazawa, Toshihide*; Kato, Yoshiyuki; Segawa, Tomoomi; Suzuki, Masahiro

Denki Gakkai Rombunshi, A, 133(5), p.271 - 272, 2013/05

As a part of the nuclear fuel cycle in Japan, the mixed oxide (MOX) fuels are produced through the microwave heating of the Pu/U mixed nitrate solution obtained from spent fuels. In this work, we investigate the effect of a spacer between the bottom of cavity and solution dish in microwave oven cavity to heat unifomly Pu/U mixed nitrate solution for making MOX fuels. As a result, we show the effectiveness of inserting the spacer for a uniform heating of the solution by evaluating the top-to-bottom ratio.

Journal Articles

Mechanism of synthesis of metallic oxide powder from aqueous metallic nitrate solution by microwave denitration method

Fukui, Kunihiro*; Igawa, Yusuke*; Arimitsu, Naoki*; Suzuki, Masahiro; Segawa, Tomoomi; Fujii, Kanichi*; Yamamoto, Tetsuya*; Yoshida, Hideto*

Chemical Engineering Journal, 211-212, p.1 - 8, 2012/11

 Times Cited Count:8 Percentile:58.73(Engineering, Environmental)

The process for synthesizing metallic oxide powders by the microwave denitration method was investigated using hexahydrated nickel nitrate and trihydrated copper nitrate aqueous solutions, and the electrical field and the temperature distributions in the reactor were numerically simulated. Although CuO powder can be obtained from a trihydrated copper nitrate aqueous solution by the microwave denitration method, a hexahydrated nickel nitrate aqueous solution cannot be heated up to over 270 $$^{circ}$$C by microwave irradiation. It was also found that the reaction routes for microwave heating are the same as those for conventional external heating. This finding indicates that the success of producing oxide particles by microwave denitration depends not only on the microwave absorptivity of the intermediate and the metallic oxide, but also on the temperature difference.

Journal Articles

Microwave heating of solid Pu/U mixed nitrate medium in cylindrical cavity for nuclear fuel cycle

Imai, Suguru*; Nakajima, Yuki*; Taguchi, Kenji*; Kashiwa, Tatsuya*; Kitazawa, Toshihide*; Suzuki, Masahiro; Segawa, Tomoomi; Fujii, Kanichi

Proceedings of 2011 International Symposium on Antennas and Propagation (ISAP 2011) (USB Flash Drive), 4 Pages, 2011/10

As a part of the nuclear fuel cycle in Japan, the mixed oxide (MOX) fuels are produced through the microwave heating of the Pu/U mixed nitrate solution obtained from spent fuels. This paper investigated the electric power absorption of the solid Pu/U mixed nitrate medium in a cylindrical oven cavity and the effect of the input polarized waves. The numerical simulations have revealed that the incidence of the circularly polarized wave improves the uniformity of the absorbed power of the medium placed in the cylindrical cavity.

Journal Articles

Development of an advanced fabrication process for fast reactor MOX fuel pellets

Kato, Masato; Segawa, Tomoomi; Takeuchi, Kentaro; Kashimura, Motoaki; Kihara, Yoshiyuki

Proceedings of International Conference on Advanced Nuclear Fuel Cycle; Sustainable Options & Industrial Perspectives (Global 2009) (CD-ROM), p.2051 - 2058, 2009/09

In the Fast Reactor Cycle technology Development (FaCT) project conducted by Japan Atomic Energy Agency, minor actinide-containing MOX (MA-MOX) fuel has been developed. The fuel is a homogeneous MOX fuel which contains a maximum of 5% MA such as Am and Np. The oxygen-to-metal (O/M) ratio of the fuel is adjusted to less than 1.97 to control fuel and cladding chemical interaction in a high burn-up of 150 GWd/t. In this paper, the thermal properties of raw powder and sintering behavior of oxidized powder were investigated. In addition the O/M ratio adjustment procedure was established.

JAEA Reports

Feasibility study of oxygen getter for FBR MOX fuel; Selection of material and examination of loading method into a cladding

Morihira, Masayuki; Segawa, Tomoomi

JAEA-Research 2007-085, 29 Pages, 2008/02

JAEA-Research-2007-085.pdf:2.88MB

The "FaCT project" is a program toward the commercialization of FBR cycle carried out in JAEA. High burn-up of 250 GWd/HMt at bundle peak is targeted in the project. To restrain the fuel cladding chemical interaction (FCCI) in a high burn-up, adoption of low O/M ratio pellets is chosen. Considering the difficulty of accurate oxygen potential control in a commercial scale electric furnace as well as the difficulty of keeping O/M ratio of sintered pellets under the high decay heat from the low decontaminated TRU MOX, it may be difficult to realize commercial mass production of low O/M ratio pellets. If so, excess oxygen released during irradiation should be absorbed by an oxygen getter not but in the matrix of low O/M ratio MOX pellets. Then MOX pellets with higher initial O/M ratio can be acceptable. In this research, a selection of oxygen getter candidates was carried out with the examination of their loading method in a cladding.

Oral presentation

The Influence of the O/M ratios of MOX powders on the sintering properties of pellets

Segawa, Tomoomi; Kato, Masato; Morimoto, Kyoichi; Kashimura, Motoaki; Morihira, Masayuki; Uno, Hiroki*; Tamura, Tetsuya*; Sunaoshi, Takeo*

no journal, , 

no abstracts in English

Oral presentation

Development of simplified pelletizing fuel production technology, 8; Physical properties of TRU-fuel produced

Segawa, Tomoomi; Nakamichi, Shinya; Komeno, Akira; Morimoto, Kyoichi; Kato, Masato; Kashimura, Motoaki; Suzuki, Masahiro; Kihara, Yoshiyuki

no journal, , 

JAEA has been researching in the fundamental properties of MOX fuel including Minor Actinides(Am and Np). In this presentation, melting point, thermal conductivity, oxygen potential and lattice constant of (Am, Np, Pu, U)O$$_{2}$$ are reported.

Oral presentation

Study of oxygen getter materials for the restraining of FCCI in high burn-up FBR MOX fuels

Morihira, Masayuki; Segawa, Tomoomi; Matsuyama, Shinichiro*; Yuda, Ryoichi*; Namekawa, Takashi

no journal, , 

Removal of excess oxygen in a MOX fuel element during the irradiation is required to attain a high burn up of FBR fuel because the increase of the oxygen potential in a fuel element during the irradiation accelerates FCCI. The oxygen getter method is an alternative to the low O/M ratio pellet option. Preliminary surveillance suggested Zr and Ti were most expecting candidates. In this study, the compatibility of these candidate materials with MOX, UO$$_{2}$$ and FMS as well as their oxygen uptake abilities were evaluated.

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