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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.
Fujita, Shunya*; Abe, Yutaka*; Kaneko, Akiko*; Yuasa, Tomohisa*; Segawa, Tomoomi; Kato, Yoshiyuki; Kawaguchi, Koichi; Ishii, Katsunori
no journal, ,
The microwave heating denitration method is used in the spent fuel reprocessing process of the nuclear fuel cycle. Since the microwave heating method is accompanied by a transient boiling phenomenon, it is necessary to grasp the operating conditions and to clarify the mechanism of flashing and spilling in order to avoid it. In this study, by assuming the flashing model for the purpose of the clarification of the flashing mechanism by microwave heating, the flashing mechanism of instantaneous generation and growth is considered by calculating the generation frequency and volume of bubble from the visualization result at flushing. The mechanism of flashing phenomenon during microwave heating is thought that the significant flushing phenomenon occurs by the process that a large amount of nanobubbles are generated at a solid-fluid interface in a overheated liquid phase, the bubble group grows exponentially and collapses, and its internal pressure releases.
Kobayashi, Shohei*; Fujita, Shunya*; Abe, Yutaka*; Kaneko, Akiko*; Yuasa, Tomohisa*; Segawa, Tomoomi; Kato, Yoshiyuki; Kawaguchi, Koichi; Ishii, Katsunori
no journal, ,
The microwave heating denitration method is used in the spent fuel reprocessing process. In order to develop the mass production of denitrification technology for the future, it is necessary to fully grasp the operating conditions to avoid flashing and overflow phenomena of solution. In this research, the conditions of the generation of flashing are evaluated using the potassium chloride aqueous solution as the simulated solution, and the concentration of potassium chloride and the microwave output as parameters. It is found that it is difficult to occur the flashing phenomenon as the concentration of potassium chloride increases.