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Journal Articles

Study on optimizing microwave heating denitration method and powder characteristics of uranium trioxide

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$$_{3}$$ 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.

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

Field test around Fukushima Daiichi Nuclear Power Plant site using improved Ce:Gd$$_{3}$$(Al,Ga)$$_{5}$$O$$_{12}$$ scintillator Compton camera mounted on an unmanned helicopter

Shikaze, Yoshiaki; Nishizawa, Yukiyasu; Sanada, Yukihisa; Torii, Tatsuo; Jiang, J.*; Shimazoe, Kenji*; Takahashi, Hiroyuki*; Yoshino, Masao*; Ito, Shigeki*; Endo, Takanori*; et al.

Journal of Nuclear Science and Technology, 53(12), p.1907 - 1918, 2016/12

 Times Cited Count:11 Percentile:6.81(Nuclear Science & Technology)

The Compton camera was improved for use with the unmanned helicopter. Increase of the scintillator array from 4$$times$$4 to 8$$times$$8 and expanse of the distance between the two layers contributed to the improvements of detection efficiency and angular resolution, respectively. Measurements were performed over the riverbed of the Ukedo river of Namie town in Fukushima Prefecture. By programming of flight path and speed, the areas of 65 m $$times$$ 60 m and 65 m $$times$$ 180 m were measured during about 20 and 30 minutes, respectively. By the analysis the air dose rate maps at 1 m height were obtained precisely with the angular resolution corresponding to the position resolution of about 10 m from 10 m height. Hovering flights were executed over the hot spot areas for 10-20 minutes at 5-20 m height. By using the reconstruction software the $$gamma$$-ray images including the hot spots were obtained with the angular resolution same as that evaluated in the laboratory (about 10$$^{circ}$$).

Journal Articles

Hydrogen behavior in primary precipitate of F82H steel; Atomistic calculation based on the density functional theory

Watanabe, Yoshiyuki; Iwakiri, Hirotomo*; Murayoshi, Norihiko*; Kato, Daiji*; Tanigawa, Hiroyasu

Plasma and Fusion Research (Internet), 10, p.1205086_1 - 1205086_2, 2015/12

In this paper, formation energy of isolated hydrogen atom in Cr$$_{23}$$C$$_{6}$$ has been theoretically investigated with atomistic calculation based on the density functional theory. The lowest calculated formation energy of a hydrogen atom is -0.48 eV with a trigonal bipyramidal configuration surrounded by five regular Cr lattice atoms. A comparison of the formation energy of hydrogen atom in bcc-iron may indicate that hydrogen atoms in F82H steel are more energetically favorable in Cr$$_{23}$$C$$_{6}$$-based precipitate rather than Fe-based matrix, leading to an increase of the tritium retention in the precipitate.

Journal Articles

Neutron irradiation effect of high-density MoO$$_{3}$$ pellets for Mo-99 production, 2

Nishikata, Kaori; Ishida, Takuya; Yonekawa, Minoru; Kato, Yoshiaki; Kurosawa, Makoto; Kimura, Akihiro; Matsui, Yoshinori; Tsuchiya, Kunihiko; Sano, Tadafumi*; Fujihara, Yasuyuki*; et al.

KURRI Progress Report 2014, P. 109, 2015/07

As one of effective applications of the Japan Materials Testing Reactor (JMTR), JAEA has a plan to produce $$^{99}$$Mo by (n,$$gamma$$) method ((n,$$gamma$$)$$^{99}$$Mo production), a parent nuclide of $$^{99m}$$Tc. In this study, preliminary irradiation test was carried out with the high-density molybdenum trioxide (MoO$$_{3}$$) pellets in the hydraulic conveyer (HYD) of the Kyoto University Research Reactor (KUR) and the $$^{99m}$$Tc solution extracted from $$^{99}$$Mo was evaluated. After the irradiation test of the high-density MoO$$_{3}$$ pellets in the KUR, $$^{99m}$$Tc was extracted from the Mo solution and the recovery rate of $$^{99m}$$Tc achieved the target values. The $$^{99m}$$Tc solution also got the value that satisfied the standard value for $$^{99m}$$Tc radiopharmaceutical products by the solvent extraction method.

Journal Articles

Development of solubility improvement technology for nitric acid of plutonium dioxide in scrap MOX powder

Kato, Yoshiyuki

Nippon 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.

Journal Articles

Development of failure evaluation method for BWR lower head in severe accident, 2; Applicability evaluation of the FEM using uni-axial material data for multi-axial deformation analysis

Nemoto, Yoshiyuki; Kato, Hitoshi; Kaji, Yoshiyuki; Yoshida, Hiroyuki

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 5 Pages, 2015/05

For the evaluation of reactor pressure vessel (RPV) lower head rupture probably occurred during the severe accident in Fukushima Daiichi Nuclear Power Plants, JAEA is conducting the thermal-hydraulics / mechanical coupling analysis. In the mechanical analysis based on the finite element method (FEM), material property data previously obtained from uni-axial material tests are applied. The lower head of BWR such as Fukushima NPP, has complicated structure compared to PWR, with control rod guide tubes, stub tubes, etc., therefore the mechanical analyses need to treat multi-axial deformation of the materials. To perform such mechanical analysis, the applicability of the analytical model using uni-axial data for multi-axial deformation analysis must be validated. In this study, the internal pressure creep tests were performed because which can realize the multi-axial deformation condition. In addition, mechanical analyses were conducted and the analytical results were compared with the experimental data.

Journal Articles

Heating efficiency of microwave heating direct denitration of a mixture of uranyl nitrate and plutonium nitrate

Kato, Yoshiyuki

Nippon 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.

Journal Articles

Effects of temperature on stress corrosion cracking behavior of stainless steel and outer oxide distribution in cracks due to exposure to high-temperature water containing hydrogen peroxide

Nakano, Junichi; Sato, Tomonori; Kato, Chiaki; Yamamoto, Masahiro; Tsukada, Takashi; Kaji, Yoshiyuki

Journal of Nuclear Materials, 444(1-3), p.454 - 461, 2014/01

 Percentile:100(Materials Science, Multidisciplinary)

Cracking growth tests were conducted in high-temperature water containing hydrogen peroxide (H$$_{2}$$O$$_{2}$$) at 561 to 423 K to evaluate the effects of H$$_{2}$$O$$_{2}$$ on stress corrosion cracking (SCC) of stainless steel (SS) at temperature lower than the boiling water reactor (BWR) operating temperature. Small compact tension (CT) specimens were prepared from thermally sensitized type 304 SS. Despite the observation of only a small portion intergranular SCC (IGSCC) near the side groove of the CT specimen at 561 K in high-temperature water containing 100 ppb of H$$_{2}$$O$$_{2}$$, the IGSCC area expanded to the central region of the CT specimens at 423 and 453 K. Effects of H$$_{2}$$O$$_{2}$$ on SCC appeared intensely at temperature lower than the BWR operating temperature. To estimate the environment in the cracks, outer oxide distribution on the fracture surface and fatigue pre-crack were examined by laser Raman spectroscopy and thermal equilibrium calculation was performed.

Journal Articles

Morphology of stress corrosion cracking due to exposure to high-temperature water containing hydrogen peroxide in stainless steel specimens with different crevice lengths

Nakano, Junichi; Sato, Tomonori; Kato, Chiaki; Yamamoto, Masahiro; Tsukada, Takashi; Kaji, Yoshiyuki

Journal of Nuclear Materials, 441(1-3), p.348 - 356, 2013/10

 Times Cited Count:2 Percentile:72.96(Materials Science, Multidisciplinary)

Crack growth tests were performed in high-temperature water containing hydrogen peroxide (H$$_{2}$$O$$_{2}$$) to evaluate the relationships between the crevice structure and H$$_{2}$$O$$_{2}$$ on stress corrosion cracking (SCC) growth morphology of stainless steel (SS). Small compact tension (CT) specimens with different fatigue pre-crack lengths were prepared. 20$$sim$$300 ppb H$$_{2}$$O$$_{2}$$ was injected into the high-temperature water at 561 K. Intergranular SCC (IGSCC) was observed only near the side grooves of the CT specimens. Owing to pre-crack shortening, the IGSCC area expanded to the central region of the CT specimens. The effects of H$$_{2}$$O$$_{2}$$ on SS appeared intensely near the surfaces exposed to high levels of H$$_{2}$$O$$_{2}$$. The calculations for the percentage of H$$_{2}$$O$$_{2}$$ remaining showed that the effects of H$$_{2}$$O$$_{2}$$ flowed from both sides of the crack were more obvious than those flowed from the crack mouth.

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, 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.

Journal Articles

Wet granulation of mixed oxide powders de-nitrated by the microwave heating

Kato, Yoshiyuki

Journal of Nuclear Science and Technology, 49(10), p.999 - 1009, 2012/10

AA2012-0237.pdf:1.28MB

 Times Cited Count:2 Percentile:74.11(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 $$mu$$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.

Journal Articles

Effects of temperature on SCC propagation in high temperature water injected with hydrogen peroxide

Nakano, Junichi; Sato, Tomonori; Kato, Chiaki; Kaji, Yoshiyuki; Yamamoto, Masahiro; Tsukada, Takashi

Proceedings of 2012 Nuclear Plant Chemistry Conference (NPC 2012) (CD-ROM), 9 Pages, 2012/09

It has been reported that the corrosion behavior of stainless steels in high temperature water with hydrogen peroxide (H$$_{2}$$O$$_{2}$$) was different from those with O$$_{2}$$. To evaluate the effect of H$$_{2}$$O$$_{2}$$ on stress corrosion cracking (SCC), SCC growth tests were conducted in high temperature water injected with H$$_{2}$$O$$_{2}$$. In 100 ppb H$$_{2}$$O$$_{2}$$ at 561 K, an intergranular SCC (IGSCC) was observed only small portion of area near the side grooves of the CT specimen. In 100 ppb H$$_{2}$$O$$_{2}$$ at 453 K, however, IGSCC extended to the central region of the CT specimen. Effects of H$$_{2}$$O$$_{2}$$ on SCC growth behavior appeared stronger at lower temperature due to a reduction of the thermal decomposition of H$$_{2}$$O$$_{2}$$. Moreover, outer oxide layer of oxide film formed on the crack of the CT specimen was examined to estimate environmental situations in the cracks and a thermal equilibrium calculation was performed.

JAEA Reports

Evaluating techniques and phenomena of Stress Corrosion Cracking (SCC) in Light Water Reactors (LWRs); SCC evaluating techniques for predicting core internal and pipe aging of LWRs, technical data collection (Contract research)

Yamamoto, Masahiro; Kato, Chiaki; Sato, Tomonori; Nakano, Junichi; Ugachi, Hirokazu; Tsukada, Takashi; Kaji, Yoshiyuki; Tsujikawa, Shigeo*; Hattori, Shigeo*; Yoshii, Tsuguyasu*; et al.

JAEA-Review 2012-007, 404 Pages, 2012/03

JAEA-Review-2012-007.pdf:36.72MB

There are many LWRs which have been operated for more than 20 years in Japan and it is expected that technique corresponding to aging plants are necessary established for safety operation in LWRs. A lot of troubles related to SCC are reported and many investigations are concerned with SCC mechanism and technical evaluation. In this paper, those research data were collected as possible widely and reviewed systematically. Current circumstances concerned with SCC in LWRs were reviewed specifically as follows: SCC incidents, SCC evaluation methods for crack initiation and propagation, the investigations concerned with SCC mechanism and monitoring technique for corrosive environment. Influences with reactor types (BWR, PWR), materials (stainless steels, Ni alloys) and SCC evaluating methods (laboratories and actual plants) were summarized as graphs and tables easy to understand in common/difference points concerned with SCC. From these arranged results, future themes were considered and remarked SCC phenomenon was summarized in actual plants. As for SCC evaluations under the accelerate conditions in the laboratory test, it was suggested that a computational prediction and modeling including statistical technique and microscopic analysis in crack initiation were important. Furthermore it was suggested that monitoring techniques predicting SCC initiation and grasping plant circumstance in operation and feasibility in actual plants were important.

Journal Articles

Evaluation of the relative biological effectiveness of carbon ion beams in the cerebellum using the rat organotypic slice culture system

Yoshida, Yukari*; Suzuki, Yoshiyuki*; Al-Jahdari, W. S.*; Hamada, Nobuyuki*; Funayama, Tomoo; Shirai, Katsuyuki*; Kato, Hiroyuki*; Sakashita, Tetsuya; Kobayashi, Yasuhiko; Nakano, Takashi*

Journal of Radiation Research, 53(1), p.87 - 92, 2012/02

 Times Cited Count:6 Percentile:51.97(Biology)

Journal Articles

Development of pressing machine with a die wall lubrication system for the simplified MOX pellet fabrication method in the FaCT project

Sudo, Katsuo; Takano, Tatsuo; Takeuchi, Kentaro; Kihara, Yoshiyuki; Kato, Masato

Proceedings of International Conference on Toward and Over the Fukushima Daiichi Accident (GLOBAL 2011) (CD-ROM), 5 Pages, 2011/12

Japan Atomic Energy Agency has been contracted to advance the Fast Reactor Cycle Technology Development project. As one part of the project, a simplified MOX pellet fabrication method has been developed for fast reactor fuels. In previous reports, feasibility of a simplified MOX pellet fabrication method was confirmed through hot and cold laboratory-scale experiments. The die wall lubrication pressing technology was one of the important technologies included in the development of the simplified MOX pellet fabrication method. In the work described here, a pressing machine with a die wall lubrication system was developed, and MOX pellet fabrication experiments were carried out on the kilogram MOX scale.

Journal Articles

Development of oxygen-to-metal ratio of MOX pellet adjustment technology for the simplified MOX pellet fabrication method in the FaCT project

Takano, Tatsuo; Sudo, Katsuo; Takeuchi, Kentaro; Kihara, Yoshiyuki; Kato, Masato

Proceedings of International Conference on Toward and Over the Fukushima Daiichi Accident (GLOBAL 2011) (CD-ROM), 7 Pages, 2011/12

Development of high burn-up fuels is essential to improve economy of the fast reactor fuel cycle. Increase of fuel burn-up is known to cause fuel-cladding chemical interaction (FCCI) and it mainly determines a lifetime of fuel pin. In order to extend a lifetime of fuel pin by mitigating FCCI, development of low oxygen-to-metal (O/M) MOX fuel has been carried out in plutonium fuel development center of JAEA. MOX fuel needs adjustment of the O/M ratio to less than 1.97 for high burn-up of 150 GWd/t. Therefore, O/M adjustment technology is one of the main subjects in development of a simplified MOX pellet fabrication method which has been advanced in the FaCT (Fast reactor Cycle Technology development) project. In previous work, changes in O/M ratio of MOX pellet during heat treatment were calculated from measurement results of oxygen potentials. On the basis of above calculation, heating tests were carried out to prepare low O/M ratio MOX pellets on a laboratory scale. The O/M ratios obtained in the heating tests were well consistent with calculation results. In the present study, a kilogram MOX scale furnace to adjust O/M ratio of MOX pellets for targeted value has been developed as next step.

Journal Articles

Stress corrosion cracking behavior of type 304 stainless steel irradiated under different neutron dose rates at JMTR

Kaji, Yoshiyuki; Kondo, Keietsu; Aoyagi, Yoshiteru; Kato, Yoshiaki; Taguchi, Taketoshi; Takada, Fumiki; Nakano, Junichi; Ugachi, Hirokazu; Tsukada, Takashi; Takakura, Kenichi*; et al.

Proceedings of 15th International Conference on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors (CD-ROM), p.1203 - 1216, 2011/08

In order to investigate the effect of neutron dose rate on tensile property and irradiation assisted stress corrosion cracking (IASCC) growth behavior, the crack growth rate (CGR) test, tensile test and microstructure observation have been conducted with type 304 stainless steel specimens. The specimens were irradiated in high temperature water simulating the temperature of boiling water reactor (BWR) up to about 1dpa with two different dose rates at the Japan Materials Testing Reactor (JMTR). The radiation hardening increased with the dose rate, but there was little effect on CGR. Increase of the yield strength of specimens irradiated with the low dose rate condition was caused by the increase of number density of frank loops. Little difference of radiation-induced segregation at grain boundaries was observed in specimens irradiated by different dose rates. Furthermore, there was little effect on local plastic deformation behavior near crack tip in the crystal plasticity simulation.

Journal Articles

High temperature oxidation of FBR structural materials in carbon dioxide and in air

Furukawa, Tomohiro; Kato, Shoichi; Inagaki, Yoshiyuki; Aritomi, Masanori*

Proceedings of 19th International Conference on Nuclear Engineering (ICONE-19) (CD-ROM), 5 Pages, 2011/05

A key problem in the application of a supercritical carbon dioxide (CO$$_{2}$$) turbine cycle to a fast breeder reactor is the corrosion of structural materials brought about by supercritical CO$$_{2}$$ at high temperatures. In this study, high-temperature oxidation tests on the structural materials were performed in carbon dioxide pressurized at 0.2 and 1 MPa, and in air, and the oxidation behavior were compared. Results of investigating the effect of CO$$_{2}$$ pressure including the previous reports tested at 10 MPa and at 20 MPa, the effect was hardly observed for all steels. In air environment, weight gain caused by high temperature oxidation was much lower than that in CO$$_{2}$$.

131 (Records 1-20 displayed on this page)