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Segawa, Tomoomi; Kawaguchi, Koichi; Ishii, Katsunori; Suzuki, Masahiro; Fukasawa, Tomonori*; Fukui, Kunihiro*
Funtai Kogakkai-Shi, 57(9), p.485 - 494, 2020/09
In the spent fuel reprocessing process, a mixed solution of uranyl nitrate and plutonium nitrate is converted into mixed oxide powder by the microwave heating. To evaluate the applicability to the industrial-scale and acquire the characteristics data of the microwave heating denitration of various metal nitrate aqueous solutions based on the knowledge studied in the development of laboratory-scale basic experiments, the microwave heating characteristics and metal oxide powder properties were investigated using cerium nitrate, cobalt nitrate and copper nitrate aqueous solutions. The progress rate of the denitration reaction was depended on the position, and the denitration reaction proceeded faster at the periphery than at the center. The morphologies of the synthesized products were porous and hard dry solid with cerium nitrate aqueous solution, foamed dry solid with cobalt nitrate aqueous solution, and powdery particles with copper nitrate aqueous solution. The denitration ratio and average particle size of the synthesized products increased in the order of the cerium nitrate aqueous solution, the cobalt nitrate aqueous solution, and the copper nitrate aqueous solution. The numerical simulations revealed that the periphery of the bottom surface of the metal nitrate aqueous solution was heated by microwaves. This results consistent with the experimental results in which the denitration reaction started from the periphery of the metal nitrate aqueous solution.
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
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.
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.
Segawa, Tomoomi
Funtai Kogakkai-Shi, 55(10), P. 547, 2018/10
no abstracts in English
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.
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.
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：4 Percentile：21.22(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.
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：7 Percentile：26.49(Engineering, Chemical)The influence of the heating method and rate on the morphology of CuO powders synthesized from Cu(NO)
3HO 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.
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：8 Percentile：27.86(Engineering, Chemical)Denitration of the aqueous solution of nickel nitrate hexahydrate (Ni(NO)6HO) by a microwave heating method was investigated. Since Ni(NO)6HO aqueous solution cannot be heated to over 300 
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.
Yamaki, Tatsunori*; Abe, Yutaka*; Kaneko, Akiko*; Segawa, Tomoomi; Kawaguchi, Koichi; Yamada, Yoshikazu
Proceedings of the 22nd International Conference on Nuclear Engineering 2014 (ICONE-22), Vol.2A, p.V02AT09A011_1 - V02AT09A011_10, 2014/07
Uranium and plutonium mixed nitrate solution of the spent nuclear fuel is converted to uranium and plutonium mixed oxide (MOX) powder by the microwave heating direct denitration method in co-conversion process of the nuclear fuel cycle. The cylindrical denitration vessel can be expected to realize high-speed and high-capacity processing against traditional shallow vessel. However, flushing and overflow phenomena of solution have been confirmed in cylindrical vessel. Thus, It is required to be clarified that the generation condition and generation mechanism of flushing phenomena during microwave heating for the safety of the operating condition and the optimum design of the equipment. The craiteria of flushing phenomena and the relationship between the released power by evaporation and the absorbed power in water is confirmed by the experimental results from the microwave heating. It is found that the flow structure is changed and the outer surface is heated according to the increase of the concentration of KCl by the microwave heating experiment with using the KCl solution and KCl jelly as a simulated solution of the uranium and plutonium mixed nitrate solution.
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：13 Percentile：41.13(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 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.
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Solid Wastes by Microwave Heating; *; ; ; ; ; *; *
JAERI-M 84-001, 76 Pages, 1984/02
no abstracts in English
Yamaki, Tatsunori*; Abe, Yutaka*; Kaneko, Akiko*; Kanagawa, Tetsuya*; Kitazawa, Toshihide*; Segawa, Tomoomi; Kawaguchi, Koichi; Yamada, Yoshikazu
no journal, ,
For practical application of high-volume production of microwave heating denitration method, it is required to avoid the transient boiling phenomena of overflow and flushing during microwave heating and to optimize the design condition of vessel shape and microwave outpot. The boiling phenomena and flow structure of KCl aqueous solution by microwave heating were measured with the KCl concentration as a parameter. Flushing phenomena does not become difficult to occur and flow structure becomes disordered to be created the vortex structure according to increase of the KCl concentration. From the results of measuring the temperature distribution of side cross-section surface of the KCl jelly, near the center is mainly heated in the case of the water jelly. On the other hand, around the jelly is mainly heated in the KCl jelly. It is clarified that the generation condition of flushing and the boiling phenomena are significantly influenced by the difference of water and KCl solution.
Yamaki, Tatsunori*; Abe, Yutaka*; Kaneko, Akiko*; Kanagawa, Tetsuya*; Kitazawa, Toshihide*; Segawa, Tomoomi; Kawaguchi, Koichi; Yamada, Yoshikazu
no journal, ,
A mixed solution of uranyl nitrate and plutonium nitrate recovered from the spent fuel is converted directly to mixed oxide (MOX) powder in the microwave heating de-nitration process of the reprocessing plant. This research aimed at elucidating occurrence criteria and mechanism of flushing phenomena in order to avoid transient boiling phenomena such as overflow and flushing, and understand optimal design conditions. Flushing conditions were clarified by evaluating the correlation between absorbed power in the distilled water and released power by evaporation.
Hamaba, Taishu*; Segawa, Tomoomi; Fukasawa, Tomonori*; Yoshida, Hideto*; Fukui, Kunihiro*
no journal, ,
no abstracts in English
Chonan, Fuminori*; Abe, Yutaka*; Kaneko, Akiko*; Kanagawa, Tetsuya*; Yuasa, Tomohisa*; Segawa, Tomoomi; Yamada, Yoshikazu
no journal, ,
no abstracts in English
Fujita, Shunya*; Abe, Yutaka*; Kaneko, Akiko*; Chonan, Fuminori*; Yuasa, Tomohisa*; Yamaki, Tatsunori*; Segawa, Tomoomi; Yamada, Yoshikazu
no journal, ,
no abstracts in English
Chonan, Fuminori*; Abe, Yutaka*; Kaneko, Akiko*; Kanagawa, Tetsuya*; Fujita, Shunya*; Yuasa, Tomohisa*; Segawa, Tomoomi; Yamada, Yoshikazu
no journal, ,
no abstracts in English
