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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.
Chonan, Fuminori*; Abe, Yutaka*; Yuasa, Tomohisa*; Kaneko, Akiko*; Segawa, Tomoomi; Yamada, Yoshikazu
no journal, ,
In a reprocessing process of nuclear fuel cycle, an uranium-plutonium mixed oxide (MOX) raw powder is converted from a mixture solution of uranyl nitrate and plutonium nitrate by the microwave heating denitration method (MH method). The MH method is applied to remove water and nitric acid from a metallic nitrate solution, and a metallic oxide is obtained. In order to improve the efficiency of MH method, optimizing the equipment and conditions is needed to prevent flushing of a mixture solution during microwave heating. In our group, we have been studied that the influence of height of supporter which placed under the mixture solution in the vessel on its heating phenomena. Also we have been analyzed simulation of electromagnetic field during microwave heating in microwave oven. From those results, we considered the appropriate height of supporter in the oven. It was clarified that height of supporter was one of the important parameter for the efficiency of microwave heating.
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
Fujita, Shunya*; Abe, Yutaka*; Kaneko, Akiko*; Yuasa, Tomohisa*; Segawa, Tomoomi; Yamada, Yoshikazu
no journal, ,
A mixed solution of uranyl nitrate and plutonium nitrate is converted to MOX raw powder by the microwave heating de-nitration method in nuclear fuel reprocessing. Since the microwave heating causes a boiling phenomenon, it is necessary to sufficiently confirm operating conditions to prevent flushing and overflow phenomena of solution. In this study, visualization observation of the microbubble generation and growth behavior near the liquid surface, measuring of bubble diameters, calculating the frequency of nucleation and estimating the quantity of heat of required for generation and growth of microbubbles were performed for the purpose of clarifying the generation mechanism of the flushing phenomena caused by microwave heating. As a result of comparative study with the amount of heat of released by flushing, it was confirmed that the quantities of the heat of released by flushing and the heat of required for generation and growth of microbubbles agree on the order.
Fujita, Shunya*; Abe, Yutaka*; Kaneko, Akiko*; Yuasa, Tomohisa*; Segawa, Tomoomi; Kato, Yoshiyuki; Yamada, Yoshikazu
no journal, ,
A mixed solution of uranyl nitrate and plutonium nitrate is converted to MOX raw powder by the microwave heating de-nitration method in nuclear fuel reprocessing. Since the microwave heating causes a boiling phenomenon, it is necessary to sufficiently confirm operating conditions to prevent flushing and overflow phenomena of solution, and it is necessary to evaluate the influence of the dielectric property of the object on the microwave heating characteristics and to optimize the equipment and operating conditions. In this study, the visualization observation using a potassium chloride aqueous solution and agar as a high dielectric constant solution and evaluation of a heating portion, and the electromagnetic field analysis are performed for the purpose of evaluating the influence of the dielectric constant of the material and the installation position on microwave heating characteristics.
Fujita, Shunya*; Abe, Yutaka*; Kaneko, Akiko*; Yuasa, Tomohisa*; Segawa, Tomoomi; Yamada, Yoshikazu; Kato, Yoshiyuki; Ishii, Katsunori
no journal, ,
Mixed uranium oxide and plutonium oxide (MOX) 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 MH 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, for the purpose of clarifying the mechanism of flashing phenomenon during microwave heating, the generation mechanism of bubbles that innumerably occur at the time of flashing is considered. When the contact angle at the heterogeneous nucleation of bubbles was 177 
C, the theoretical value of the heterogeneous nucleation approximately agreed with the experimental value at the time the superheat degree was found to be close to 35 C.
