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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, Tomomi; 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

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, Tomomi; 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.

Oral presentation

Visualization of relative temperature distribution in conductive materials during microwave heating

Kawaguchi, Koichi; Segawa, Tomomi; Suzuki, Masahiro; Tominaga, Setsuo; Kitazawa, Toshihide*

no journal, , 

In order to visualize the detailed temperature distribution of electrolyte aqueous solution by microwave heating, agar containing KCl was microwave-heated and observed by using thermography. The results of agar containing KCl were compared with appearance of denitration product from cobalt(II) nitrate solution. The heating region agreed with appearance of denitration product. The reasonable agreement was observed and it was conformed that agar containing KCl can be used as a substitute for the denitration product.

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, Tomomi; 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

Criteria and mechanism of transient boiling phenomena induced by microwave heating

Yamaki, Tatsunori*; Abe, Yutaka*; Kaneko, Akiko*; Kanagawa, Tetsuya*; Kitazawa, Toshihide*; Segawa, Tomomi; 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.

Oral presentation

Evaluation on the denitration characteristics heated by the circular polarized microwave

Segawa, Tomomi; Tanigawa, Masafumi; Kato, Yoshiyuki; Kawaguchi, Koichi; Ishii, Katsunori; Suzuki, Masahiro; Kitazawa, Toshihide*; Taguchi, Kenji*; Kashiwa, Tatsuya*

no journal, , 

For the purpose of improving the microwave heating denitration technology, the denitration characteristics of cobalt nitrate aqueous solutions as a simulated materials were analyzed and evaluated by using the microwave heating equipment whichi was controlled to circular polarized wave. Numerical simulation confirmed that the circular polarized wave controlled microwave irradiation uniformed the absorbed power distribution in the circumferential direction. Moreover, it was confirmed that the denitration proceeded uniformly even in the radial direction by the microwave heating denitration experiments of cobalt nitrate aqueous solutions. From these results, it was revealed that favorable heating and denitration characteristics can be obtained by the circularly polarized wave controlled microwave heating equipment.

Oral presentation

Electromagnetic field analysis for the development of the microwave heating equipment capable of uniform heating of a metal nitrate aqueous solution and the metal oxide powder with circular polarization control

Segawa, Tomomi; Tanigawa, Masafumi; Kato, Yoshiyuki; Kawaguchi, Koichi; Ishii, Katsunori; Suzuki, Masahiro; Kitazawa, Toshihide*; Kashiwa, Tatsuya*

no journal, , 

To improve the handling and sinterability of raw powder of a uranium and plutonium mixed oxide produced in the reprocessing process of spent fuels, the microwave heating equipment has been developed considering the microwave property of linear polarization and circularly polarization that contribute to the uniformization of the microwave heating denitration by JAEA. The electromagnetic field simulation analysis was carried out by the Finite-Difference Time-Domain method, and the experimental results were evaluated. An analysis model was developed based on the obtained physical property data which were measured by the cylindrical cavity resonator method. The liquid phase state, microwave was concentrated on the upper surface and bottom surface due to the high loss of the cobalt nitrate aqueous solution, while in the solid phase state, microwave energy was absorbed inside. The absorption electric power distribution became uniform in the circumferential direction.

Oral presentation

Evaluation on the denitration characteristics of metal nitrate aqueous mixed solution by microwave heating and the complex relative permittivity

Segawa, Tomomi; Kawaguchi, Koichi; Ishii, Katsunori; Suzuki, Masahiro; Fukasawa, Tomonori*; Fukui, Kunihiro*; Kitazawa, Toshihide*

no journal, , 

In the process of the spent fuel reprocessing, a mixture of uranyl nitrate and plutonium nitrate is converted to a mixed oxide powder by the microwave heating direct denitration method. In the case of assuming the heterogeneous cycle in the Na-cooled fast reactor, it is required to denitrate a solution containing mainly MA for which microwave heating denitration characteristics have not been clarified, therefore, it is necessary to obtain microwave heating denitration characteristics data for metal nitrate mixed aqueous solutions. In this study, microwave heating denitration characteristics of copper nitrate and nickel nitrate mixed solution and the complex relative permittivity of the final and intermediate products were evaluated. It was clarified that the mixing ratio and the microwave energy loss of metal oxides as final products remarkably affect the denitration characteristics.

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