Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Yamada, Yoshikazu; Shibanuma, Kimikazu
Proceedings of International Nuclear Fuel Cycle Conference / Light Water Reactor Fuel Performance Conference (Global/Top Fuel 2019) (USB Flash Drive), p.648 - 654, 2019/09
During a periodic inspection, multiple spot-like nuclear material contamination (maximum 21.7 Bq) was detected at the outer surface of a glove-box (GB) body used to install equipment for fabricating mixed oxide (MOX) fuel at the Japan Atomic Energy Agency. The inspection confirmed a total of 13 cracks passing through the thickness direction of the GB and a bleeding phenomenon was observed on the polyvinyl chloride (PVC) cables in the GB. These cracks were judged as stress corrosion cracking induced by the generation of chlorine gas by irradiation of PVC cables lying against the inner surface of the GB.
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.
Yamada, Yoshikazu; Segawa, Tomoomi; Kato, Masato
Proceedings of International Conference on Fast Reactors and Related Fuel Cycles; Next Generation Nuclear Systems for Sustainable Development (FR-17) (USB Flash Drive), 8 Pages, 2017/06
Japan Atomic Energy Agency (JAEA) have proposed the transmutation of minor actinides by fast reactors as a way to contribute significantly to the reduction of the volume and the potential radiotoxicity of radioactive wastes. In order to achieve this goal, it is important to introduce a fully automated and remote operation fuel fabrication plant with shielded hot cells and manipulators. JAEA's facilities including Plutonium Fuel Production Facility (PFPF) have fabricated MOX fuel. On the basis of the operational and technical experience obtained in above facilities, the conceptual design of engineering-scale plant applied the simplified MA-bearing fuel fabrication process with shielded hot cells and manipulator was done. It will be able to fabricate high MA-bearing fuel and to perform the maintenance and repairing of each equipment with manipulators. This plant will be constructed based on this concept and development plan.
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; Fukasawa, Tomonori*; Yamada, Yoshikazu; Suzuki, Masahiro; Yoshida, Hideto*; Fukui, Kunihiro*
Proceedings of Asian Pacific Confederation of Chemical Engineering 2015 (APCChE 2015), 8 Pages, 2015/09
A mixed solution of uranyl nitrate and plutonium nitrate is converted to MOX raw powder by the microwave heating de-nitration method in nuclear reprocessing. Copper oxide synthesized by heating de-nitration was used as a model for the de-nitration process. The microwave heating method (MW) and infrared heating method (IR) were used, and how they and their heating rate influence the obtained particle morphology and size were investigated. The particles obtained by the MW and IR were sufficiently similar in the surface morphology and the mass median diameter was decreased by the increased heating rate. The mass median diameters by the MW were the heating rate and smaller than those obtained by IR. The particle size distribution of the particle obtained by the MW was broader than that by the IR. The relationship of the temperature distribution and particle size distribution by the MW was discussed by the numerical simulation.
Yamaki, Tatsunori*; Abe, Yutaka*; Kaneko, Akiko*; Segawa, Tomoomi; Kawaguchi, Koichi; Yamada, Yoshikazu; Fujii, Kanichi*
Journal of Nuclear Science and Technology, 52(2), p.241 - 250, 2015/02
Times Cited Count：3 Percentile：25.85(Nuclear Science & Technology)In the Microwave Heating de-nitration method developed in Japan, a mixed solution of uranyl nitrate and plutonium nitrate recovered from the spent fuel in the reprocessing plant is converted directly to mixed oxide (MH-MOX) powder. This MH-MOX powder is utilized to fabricate MOX fuel with UO powder for FBR. The MH method is accompanied with transient boiling phenomena such as overflow and flushing. Toward high-speed and high-capacity conversion by MH-method in the future, it is required to avoid overflow and flushing and to understand optimal design conditions for design and operation. At the first step for these objectives, basic knowledge of transient boiling phenomena by the MH-method has been acquired with using distilled water. It was observed that generation of singular bubble triggered flushing and distilled water just before flushing was superheated by a temperature 10 degrees centigrade higher than boiling temperature. Based on these results, it is clarified that the occurrence criteria of flushing correlate with absorbed power in the water and released power from the water surface.
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.
Nakayama, Shigeru*; Kawaguchi, Koichi; Segawa, Tomoomi; Yamada, Yoshikazu
Proceedings of 19th International Symposium on Artificial Life and Robotics (AROB 2014) (CD-ROM), p.246 - 249, 2014/01
In the nuclear fuel fabrication process, moisture content is very important parameter because of criticality safety control. Considering future commercial nuclear fuel fabrication plant, rapid and durable moisture sensor is required. We have developed an open-ended semi-coaxial microwave sensor to measure moisture involved in a substance. This sensor has no semiconductor tips, so it can be used in strong radiation field. In this paper, we carry out a preliminary experiment for measuring moisture of MOX(UO+PuO) in granulation process, in which water is added as a binder. In our preliminary experiment, to simulate granulated MOX powder, granulated tungsten trioxide powder, which has similar dielectric constant to MOX and has voids to hold water inside, was used. The principle of microwave measurement of moisture is as follows. When the tungsten trioxide contained in a pyrex beaker is placed at the open end of the cavity, the resonant frequency is shifted by a variation in the end of capacitance which results from the difference in the dielectric constant of tungsten trioxide from that of air. Furthermore, the peak value of the resonance curve is attenuated by the absorption of microwave in the tungsten trioxide. Therefore, the moisture content of tungsten trioxide can be estimated by measuring either the frequency shift or attenuation. They are measured using a tracking generator and a spectrum analyzer. In our presentation, we will show the experimental results in detail.
Yamada, Yoshikazu; Kurita, Ichiro; Suzuki, Kazunori; Shinada, Kenta; Kato, Mitsuaki*
Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 5 Pages, 2005/10
None
Yamada, Yoshikazu; Suzuki, Yoshihiro*
no journal, ,
no abstracts in English
Sudo, Katsuo; Okita, Takatoshi; Takeuchi, Kentaro; Takano, Tatsuo; Kato, Akebumi*; Haga, Tetsuya; Yamada, Yoshikazu; Kihara, Yoshiyuki
no journal, ,
no abstracts in English
Yamaki, Tatsunori*; Kaneko, Akiko*; Abe, Yutaka*; Segawa, Tomoomi; Kawaguchi, Koichi; Yamada, Yoshikazu; Suzuki, Masahiro; Fujii, Kanichi*
no journal, ,
To use recovered uranium and plutonium as raw material of nuclear fuel, reprocessing solution (uranium and plutonium mixed nitrate solution) of the spent nuclear fuel is converted to uranium and plutonium mixed oxide (MOX) powder. Microwave heating direct denitration method is one of such methods to convert nitrate solution to MOX powder. The cylindrical denitration vessel can be expected to realize high-speed and high-capacity processing against traditional shallow vessel. Flushing and overflow phenomena of solution have been confirmed in cylindrical vessel. The research was conducted in order to clarify mechanism of the flushing and overflow phenomena during microwave heating. It was found that there was tendency of flushing in the case of short vessel diameter and high initial water level when magnetron power was constant. It was confirmed that the liquid temperature just before flushing was superheat.
Yamaki, Tatsunori*; Kaneko, Akiko*; Abe, Yutaka*; Segawa, Tomoomi; Kawaguchi, Koichi; Yamada, Yoshikazu
no journal, ,
In Japan, the microwave heating method is adopted in the conversion process of reprocessing facility for spent fuels of a nuclear reactor. When the scale-up of the conversion process is considered, visualization observation of flushing phenomena by microwave heating was experimented in order to optimize the structure of denitration containers depending on the scale of throughput. Evaluation of the effects of the diameter of a container, initial level of liquid, and microwave power on the conditions for the generation of flusing was conducted, and it was clarified that the mechanism of the generation of flushing and dominant factor.
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.
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
Yamada, Yoshikazu; Kawaguchi, Koichi; Segawa, Tomoomi; Matsumura, Tatsuro; Kato, Masato
no journal, ,
Researchers at Japan Atomic Energy Agency (JAEA) have proposed the transmutation of minor actinides (MAs) by both fast reactors (FRs) and accelerator driven systems (ADSs) as a way to contribute significantly to the reduction of the volume and the potential radiotoxicity of radioactive wastes. Pu-U mixed oxide with small amount of MA is adopted as fuel of FRs, while U-free nitride and mixed oxide of MA, Pu and inert element are candidates for fuel of ADSs. JAEA researchers have also studied the simplified MOX fuel fabrication process to decrease the fabrication cost. This report describes a technological investigation of the simplified MA-bearing fuel fabrication process that prepares fuel suitable for both FRs and ADSs. Furthermore, this report includes an analysis of the feasibility of fabricating MA macro-dispersion pellets and MA micro-dispersion pellets for ADSs by using the simplified MOX fabrication process. The flowabilities of both de-nitrated raw powders were improved with the tumbling granulator, and the Carr flowability index was more than 70 for both. The green pellets had no defects in their appearance such as cracks. The CeO particles were dispersed homogeneously in both macro-dispersion and micro-dispersion pellets. As a result, it was judged that the simplified MOX fuel fabrication process is applicable to fabrication of MOX pellets for ADSs as well as FRs.
Fujita, Shunya*; Abe, Yutaka*; Kaneko, Akiko*; Chonan, Fuminori*; Yuasa, Tomohisa*; Yamaki, Tatsunori*; Segawa, Tomoomi; Yamada, Yoshikazu
no journal, ,
no abstracts in English
