Refine your search:     
Report No.
 - 
Search Results: Records 1-11 displayed on this page of 11
  • 1

Presentation/Publication Type

Initialising ...

Refine

Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...

Keyword

Initialising ...

Language

Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

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

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

Evaporation of liquids in vacuum and preventive measures against eruptive boiling

Murakami, Yoshio

Hyomen Kagaku, 12(8), p.520 - 524, 1991/00

no abstracts in English

Oral presentation

Effect of dielectric characteristics on transient boiling phenomena induced by microwave heating

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.

Oral presentation

Mechanism of flushing phenomena induced by microwave heating

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

no journal, , 

no abstracts in English

Oral presentation

Mechanism of the flashing phenomena induced by microwave heating

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.

Oral presentation

Mechanism of flashing phenomena in microwave heating

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 $$^{circ}$$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 $$^{circ}$$C.

Oral presentation

Mechanism of flashing induced by microwave heating

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.

Oral presentation

Effect of permittivity on microwave heating characteristics

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.

Oral presentation

Effect of high dielectric solution on microwave heating characteristics

Kobayashi, Shohei*; Abe, Yutaka*; Kaneko, Akiko*; Futsuta, Akihiro*; Fujiwara, Kota*; Segawa, Tomoomi; Kawaguchi, Koichi; Ishii, Katsunori

no journal, , 

To investigate the influence of the dielectric properties of a solution or a spacer on the heating process of the solution, a low dielectric Teflon or an airogel having a very low dielectric property almost equivalent to air was placed as a spacer directly below the vessel. And the influence of the geometry and the dielectric properties of the sample and the spacer on the heating properties of the sample were evaluated. The heating efficiency obtained by the experiment tended to decrease as the spacer height increased. It was confirmed that the heating efficiency obtained by the electromagnetic analysis almost agreed with the experimental results by a support height of 50 mm. When Teflon was used as a spacer, microwaves entered from the bottom of the solution, whereas when airogel was used as a spacer, microwaves tended to enter from the top of the solution, and it was clarified that the dielectric characteristics of the spacer were the heating characteristics of the sample.

11 (Records 1-11 displayed on this page)
  • 1