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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; 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.
Kato, Yoshiyuki
Nihon Genshiryoku Gakkai Wabun Rombunshi, 14(2), p.75 - 85, 2015/06
In the MOX pellet fabrication process, the MOX powder is mixed, granulated and is pressed and finally sintered MOX pellet. In addition only a little part of MOX powder disperses in a globe box and adheres to its wall and floor. The scattered MOX powder becomes dirty. This waste MOX powders have been called as dirty MOX powders and stored. MOX powders which do not meet the specification are rejected from the MOX pellet fabrication process. By the conventional method, MOX powder is pelletized once. The pellet was dissolved with hot nitric acid. Recovery is possible by extracting plutonium out of a nitric acid solution. In this study, a simple method to recover MOX was developed. Generally, MOX powders cannot dissolved in a nitric acid at room temperature. And then, MOX powders are reacted with silicon compound (SiC) and dissolved in a nitric acid at room temperature. Nearly 70% of plutonium was recovered with uranium.
Kato, Yoshiyuki
Nihon Genshiryoku Gakkai Wabun Rombunshi, 13(2), p.62 - 73, 2014/05
A mixture of plutonium nitrate and uranyl nitrate solution is co-converted to MOX by the microwave heating method developed by JAEA. The heating efficiency is very important to improve throughput or energy-saving performance in this conversion process. In this study, the efficiencies were measured using both experimental and engineering scale microwave ovens, changing the chemical form of solution and its location in the oven. In addition, the distributions of electromagnetic field strength and its absorption concentration in the solution were numerically evaluated by an electromagnetic field analysis code, MWS 2009. The experimental results could almost be explained by the numerical analyses.
Imai, Suguru*; Taguchi, Kenji*; Kashiwa, Tatsuya*; Kitazawa, Toshihide*; Kato, Yoshiyuki; Segawa, Tomoomi; 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.
Kato, Yoshiyuki
Journal of Nuclear Science and Technology, 49(10), p.999 - 1009, 2012/10
Times Cited Count：2 Percentile：17.8(Nuclear Science & Technology)Performance of wet granulation for MOX powder de-nitrated by the microwave heating de-nitration method was investigated in order to fabricate MOX fuel pellets for FBR at an extremely simplified process. An agitating granulator equipped with three blades and a chopper was used and the performance was evaluated. Characteristics of raw powder and granules were evaluated from SEM observation, granulometry and flow-ability measurement. We could obtain the granules of 120-140 
m in diameter from the raw powder of several micron in a narrow range of water addition ratio 12.5-13.5 wt% with a flow-ability 
73 and a product yield 90%. Specific surface area which is the index of sintering performance was almost same as the one of raw powder. When the ratio was 
9 wt%, flow-ability did not change from the one of raw powder 30 and no granule was observed. It was estimated from an additional experiment that the reason was capillaries (or voids) in the raw powder. When the ratio was larger than 14 wt%, flow-ability saturated and product yield decreased. This narrow range of water addition ratio and strong binding force were successfully understood based on the standard theory of granulation supposing a pendular state and Gorge method.
Asakura, Koichi; Takeuchi, Kentaro; Makino, Takayoshi; Kato, Yoshiyuki
Nuclear Technology, 167(3), p.348 - 361, 2009/09
Times Cited Count：4 Percentile：30.49(Nuclear Science & Technology)Technological feasibility of a simplified MOX pellet fabrication process, the short process, was studied. About 300 g MH-MOX powder with adjusted plutonium content to 30% could be successfully processed by a tumbling-granulator for subsequent pelletizing and sintering processes. The granulated 30%PuO
-MOX powder could be pressed into green annular pellets directly and smoothly when using a die wall lubrication method. The pellet tensile strengths were compared for a granulated molybdenum powder and they were higher for pellets obtained when using the die wall lubrication method than when using the conventional powder mixing method. The amount of additives in the green pellets could be controlled at 0.06wt% in this process. It is therefore, possible to carry out de-waxing and sintering of green pellets in the same furnace. By controlling the average particle sizes of granulated 30%PuO-MOX powders, pellets with more than 95% theoretical density could be obtained after 1700 
C for 2 h. As a result, it can be concluded that the short process is technoligically feasible to fabricate MOX annular pellets.
Kurita, Tsutomu; Kato, Yoshiyuki; Yoshimoto, Katsunobu; Suzuki, Masahiro; Kihara, Yoshiyuki; Fujii, Kanichi
Proceedings of International Conference on Advanced Nuclear Fuel Cycle; Sustainable Options & Industrial Perspectives (Global 2009) (CD-ROM), p.94 - 102, 2009/09
With regard to advanced MOX fuel fabrication, a new concept in which one vessel especially designed to meet microwave de-nitration is utilized also for crushing and for granulation, without organic lubricant nor powder transfer across the processes, was introduced for innovative MOX powder production. In order to realize this concept, two attempts were made: A specially designed three blade impeller coupled with auxiliary blade. A uniquely shaped mixing blade coupled with an auxiliary blade having auto-orbital hybrid rotation. The mixing blade promotes the growth of particles, whereas the auxiliary blade suppresses the overgrowth by chopping larger particles. These granulators use a little water as binder. As a result, major diameter of granule 400-1000 micron and flow-ability 82-85 was obtained with fine WO model powder. Therefore, a prospect to satisfy both desirable powder properties and simplified nuclear material production was opened, as well as improvement of working efficiency and cut down on costs.
Ishii, Katsunori; Suzuki, Masahiro; Yamamoto, Takuma; Kihara, Yoshiyuki; Kato, Yoshiyuki; Kurita, Tsutomu; Yoshimoto, Katsunobu; Yasuda, Masatoshi*; Matsusaka, Shuji*
Journal of Chemical Engineering of Japan, 42(5), p.319 - 324, 2009/05
Times Cited Count：7 Percentile：29.75(Engineering, Chemical)The flowability of coarse particles has been experimentally investigated using the vibrating tube method, to evaluate the applicability of this method to MOX (mixed oxide of PuO and UO) particles which are nuclear fuel used for electric power production. Five sizes of non-radioactive model particles, smaller than 850 micrometers, made of ZrO were prepared, and the experiments were carried out using vibrating tubes with an outlet diameter from 2 to 4 mm. The outlet diameter significantly affected the flowability measurements. When using the tube with a 4-mm-outlet diameter, the flowability of all the model particles was successfully measured. The inclination angle of the tube, also, affected the flowability measurements. From the advantages of high sensitivity, short measurement time, simple structure, and easy operation, the vibrating tube method is expected to be applied to the remote flowability measurement of the MOX particles.
by the first-principles and lattice vibrationMinamoto, Satoshi*; Kato, Masato; Konashi, Kenji*; Kawazoe, Yoshiyuki*
Journal of Nuclear Materials, 385(1), p.18 - 20, 2009/03
Times Cited Count：32 Percentile：88.55(Materials Science, Multidisciplinary)Plutonium dioxide (PuO) is the key compounds which will take effect the thermal properties for MOX fuels. But due to the lack of experimental data on plutonium dioxide, computational thermodynamics data were not established. In recently, the coupling of first-principle calculation and lattice dynamics theory, computational thermodynamics data could be obtained numerically. We applied first principle plane-wave calculation and lattice dynamics theory to estimate thermal properties of plutonium oxide for perfect crystal. Total energy calculation for perfect crystal reproduced experimental lattice parameter well. And after phonon dispersion calculation for plutonium dioxide, contribution of lattice vibration to thermal properties was investigated.
Suzuki, Masahiro; Ishii, Katsunori; Yamamoto, Takuma; Kihara, Yoshiyuki; Kato, Yoshiyuki; Kurita, Tsutomu; Yoshimoto, Katsunobu; Fujii, Kanichi
Proceedings of Global Congress on Microwave Energy Applications (GCMEA 2008/MAJIC 1st), p.501 - 504, 2008/08
The natural resources, oil and uranium, would dry up around the midway of this century. FBR cycle most probably rescues this difficult situation. Mass production of MOX fuel for FBR, therefore, is the supreme subject to Japanese energy strategy. For this subject, we are attacking with Microwave heating technology. Up to present, we have succeeded to produce excellent PuO/UO bulk, 2 kgMOX/batch, advancing toward the mass production target, 5 kgU/h for one batch.
Asakura, Koichi; Kato, Yoshiyuki; Furuya, Hirotaka
Nuclear Technology, 162(3), p.265 - 275, 2008/06
Times Cited Count：9 Percentile：52.81(Nuclear Science & Technology)UO, PuO and MOX (mixed oxide of U and Pu) powders were prepared by the MH (microwave heating de-nitration), ADU (Ammonia diuranate) and OX (oxalate) methods. The BET specific surface area, avarage particle size by air permiation method, bulk density, tap density, angle of repose, angle of spatula and cohesiveness of these powders were measured. The degree of surface roughness was evaluated from the ratio of BET surface area to the one calculated from average particle size and then flowability was evaluated on the basis of Carr's theory. These results were compared for the different powders and preperation methods as a parameter of calcination temperature. The degree of surface roughness in MH-MOX powder was larger than in ADU-UO powder and smaller in OX-PuO powder. These results could be understood using the concpt of H
ttig and Tamman temperatures commonly cited in ceramics materials. As already reported for the general papers, the flowabilities of MH-MOX and ADU-UO powders also decreased with increase of compressibility, and their absolute values were below 50 points. According to Carr's theory, the brderline between free-flowing and non-free-flowing powders is from 60 to 69 points. It is, therefore, necessary for the mixed powder of MH-MOX powder, ADU-UO powder and dry recycled MOX scrap powder to be granulated to provide a free flowing feed to the pelletizing press in the MOX pellet fabrication process.
Makino, Takayoshi; Okita, Takatoshi; Kato, Yoshiyuki; Kurita, Tsutomu; Takahashi, Yoshiharu; Aono, Shigenori
Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 5 Pages, 2005/10
A simplified MOX pellet fabrication process, called short process, has been developed to drastically reduce fuel fabrication cost.The MH powder has characteristic of fine particle and low flowability. It is difficult to pelletize the MH powder directly without granulation into smaller size FR pellet compared with LWR fuel. Therefore, small-scale hot tests to improve the flowability of the MH powder has been carried out using two kinds of methods, and quality of the pellet was evaluated.
Kato, Yoshiyuki; Kurita, Tsutomu; Abe, Tomoyuki
Journal of Nuclear Science and Technology, 41(8), p.857 - 862, 2004/00
Times Cited Count：12 Percentile：61.53(Nuclear Science & Technology)The application of the fluoride volatility process in the reprocessing of fuel from the fast breeder reactor is regarded as one of the economical methods. Plutonium hexafluoride (PuF
), however, reacting with fluorine (F2) and plutonium dioxide (PuO) as the raw material, is in an unstable condition and tends to remain as a solid compound in the process after decomposing into plutonium tetrafluoride (PuF
). Suitable conditions should be established for the practical use of this process. One of them is to enhance the stability of PuF. The behaviour of plutonium fluorination and relevant chemical reactions were investigated by referring to sundry literature and by thermodynamic calculation. It was then compared with recent data from laboratory scale experiments for this paper. Results from the theoretical analysis agreed with experimental observation that PuF could be formed stably under a high temperature condition (approx.1000 K) with over supply of figher concentration of F2.
Sato, Yoshihiko; Koyama, Tomozo; Miura, Akihiko; ; ; Shigetome, Yoshiaki
Proceedings of 2nd International Conference on Safewaste 2000, 0 Pages, 2000/10
On march 11,1997, bituminization demonstration facility(BDF) in Tokai Reprocessing Plant (TRP) of power reactor and nuclear fuel development corporation (PNC) made fire and explosion incident. Investigation of the cause of the fire and explosion incident at BDF was carefully conducted. The main cause of the fire is clarified to have been physical heating inside the extruder that provided unusual high temperature of bituminized product at filling. Physical feating is considered to be derived from decrease of feed rate of liquid waste to the extruder. The causes of the explosion are accumulation offlammable gas generated from insufficiently extinguished bituminized product inside the filling room of which the ventilation system was shut doen. The gas was ignited by another ignition of the heated drum.
Shigetome, Yoshiaki; ;
JNC TN8410 99-035, 62 Pages, 1999/12
The bituminization demonstration facility (BDF) of Tokai reprocessing plant had a fire and explosion incident. Thermal analysis of simulated bituminized products was conducted to investigate the chemical behavior of them. This analysis detected no activating factors which enhance chemical heat reactions. According to the operators' observation, filling temperature of the bituminization product rose to an unusually high temperature before the incident. The overheating effect on the bituminized product was investigated by 'keeping high temperature' test. Hollows and brittle material were generated in the products after the heating. This state is similar to the actual state of the products processed in the BDF from 28 to 29 batch.
Koyama, Tomozo; ; Omori, Eiichi; ; ; Shibata, Atsuhiro; Shigetome, Yoshiaki
JNC TN8410 99-027, 423 Pages, 1999/12
The bituminization demonstration facility of Tokai Reprocessig Plant had a fire and explosion incident. The cause of the incident was investigated. Also, the facility condition and release of radioactive materials were evaluated. The cause of the fire and subsequent explosion was determined in a two year investigation. The main cause of the fire was that the temperature of the bituminized product rose to an unusually high temperature by a physical heating phenomena inside the extruder, which was caused by the lowering the feed rate of liquid waste. A moderate chemical reaction in the bituminized product continued and consequently the bituminized product overheated and ignited. The cause of the explosion was the accumulation of flammable gases generated from insufficiently extinguished bituminized product in the filling room in which the ventilation system had been shut down. The flammable gas was ignited by another bituminized product that overheated to the flash point temperature. This report details the condition of the facility before and after the incident, cause of the incident, and an evaluated amount of released radioactive materials.
; ; Omori, Eiichi
JNC TN8410 99-038, 76 Pages, 1999/09
This report describes the observation results of facility damages caused by the fire and explosion that occurred in March 11, 1997 at Bituminization Development Facility of Tokai Reprocessing Plant, JNC. Following to the recently published report ; "Facility damages by the explosion" PNC TN8410 98-013, this report focused on the other red cells than the filling room (R152) and extruder room (R151), and detail of the extruder and inside the filling room that can be observed in accordance with the facility clearing after September 1997. There were little damage in the other cells except the filling room and extruder room, those were only covered with the soot that may be transfered through the ventiration ducts. There was no damage in the body of the extruder except some damages on the discharge nozzle that may be caused by the blown off shielding panel. The detailed damages were also observed inside the filling room. Also the explosion pressure was estimated through the measurement of compressed drum, the results was almost same as the recent estimation.
;
JNC TN8410 99-036, 113 Pages, 1999/09
The fire and explosion incident occurred at Bituminization Demonstration Facility of PNC Tokai Works on March 11, 1997. In order to ascertain the cause of incident, the investigation has been pushed forward. For the investigation, we prepared simulated bituminized product for measurement of heat generation in low temperature region less than 200 C. We used calvet Calorimeter MS80 for the heat generation measurement. Result of measurement, We were able to catch the feeble heat generation from bituminized product. The maximum calorific value that was able to detect it in isothermal measurement was approximately 1 mW /g in 160 C. It was approximately 2 mW /g in 200 C. And, as the another measurement, the measurement condition went heat rate by 0.01 C/minute, the highest temperature 190 C. As a result, the maximum generation of heat value that was able to detect it was approximately 0.5 mW /g. I changed simulated bituminized products and measured these. A difference of condition is salt particle size, salt content rate (45%, 60%), addition of the simulated precipitate. But there was not a difference in the generation of heat characteristic detected.
