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Journal Articles

Gapless spin liquid in a square-kagome lattice antiferromagnet

Fujihara, Masayoshi*; Morita, Katsuhiro*; Mole, R.*; Mitsuda, Setsuo*; Toyama, Takami*; Yano, Shinichiro*; Yu, D.*; Sota, Shigetoshi*; Kuwai, Tomohiko*; Koda, Akihiro*; et al.

Nature Communications (Internet), 11(1), p.3429_1 - 3429_7, 2020/07

 Times Cited Count:8 Percentile:81.73(Multidisciplinary Sciences)

Journal Articles

The Effects of plutonium content and self-irradiation on thermal conductivity of mixed oxide fuel

Ikusawa, Yoshihisa; Morimoto, Kyoichi; Kato, Masato; Saito, Kosuke; Uno, Masayoshi*

Nuclear Technology, 205(3), p.474 - 485, 2019/03

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

This study evaluated the effects of plutonium content and self-irradiation on the thermal conductivity of mixed-oxide (MOX) fuel. Samples of UO$$_{2}$$ fuel and various MOX fuels were tested. The MOX fuels had a range of plutonium contents, and some samples were stored for 20 years. The thermal conductivity of these samples was determined from thermal diffusivity measurements taken via laser flash analysis. Although the thermal conductivity decreased with increasing plutonium content, this effect was slight. The effect of self-irradiation was investigated using the stored samples. The reduction in thermal conductivity caused by self-irradiation depended on the plutonium content, its isotopic composition, and storage time. The reduction in thermal conductivity over 20 years' storage can be predicted from the change of lattice parameter. In addition, the decrease in thermal conductivity caused by self-irradiation was recovered with heat treatment, and recovered almost completely at temperatures over 1200 K. From these evaluation results, we formulated an equation for thermal conductivity that is based on the classical phonon-transport model. This equation can predict the thermal conductivity of MOX fuel thermal conductivity by accounting for the influences of plutonium content and self-irradiation.

Journal Articles

Improvement of plant reliability based on combining of prediction and inspection of crack growth due to intergranular stress corrosion cracking

Uchida, Shunsuke; Chimi, Yasuhiro; Kasahara, Shigeki; Hanawa, Satoshi; Okada, Hidetoshi*; Naito, Masanori*; Kojima, Masayoshi*; Kikura, Hiroshige*; Lister, D. H.*

Nuclear Engineering and Design, 341, p.112 - 123, 2019/01

 Times Cited Count:2 Percentile:42.44(Nuclear Science & Technology)

Improvement of plant reliability based on reliability-centered-maintenance (RCM) is going to be undertaken in NPPs. RCM is supported by risk-based maintenance (RBM). The combination of prediction and inspection is one of the key issues to promote RBM. Early prediction of IGSCC occurrence and its propagation should be confirmed throughout the entire plant systems which should be accomplished by inspections at the target locations followed by timely application of suitable countermeasures. From the inspections, accumulated data will be applied to confirm the accuracy of the code, to tune some uncertainties of the key data for prediction, and then, to increase their accuracy. The synergetic effects of prediction and inspection on application of effective and suitable countermeasures are expected. In the paper, the procedures for the combination of prediction and inspection are introduced.

Journal Articles

${it In-situ}$ observation of dislocation evolution in ferritic and austenitic stainless steels under tensile deformation by using neutron diffraction

Sato, Shigeo*; Kuroda, Asumi*; Sato, Kozue*; Kumagai, Masayoshi*; Harjo, S.; Tomota, Yo*; Saito, Yoichi*; Todoroki, Hidekazu*; Onuki, Yusuke*; Suzuki, Shigeru*

Tetsu To Hagane, 104(4), p.201 - 207, 2018/00

 Times Cited Count:5 Percentile:43.06(Metallurgy & Metallurgical Engineering)

Journal Articles

Status of development of Lithium Target Facility in IFMIF/EVEDA project

Wakai, Eiichi; Kondo, Hiroo; Kanemura, Takuji; Hirakawa, Yasushi; Furukawa, Tomohiro; Hoashi, Eiji*; Fukada, Satoshi*; Suzuki, Akihiro*; Yagi, Juro*; Tsuji, Yoshiyuki*; et al.

Proceedings of Plasma Conference 2014 (PLASMA 2014) (CD-ROM), 2 Pages, 2014/11

In the IFMIF/EVEDA (International Fusion Materials Irradiation Facility/ Engineering Validation and Engineering Design Activity), the validation tests of the EVEDA lithium test loop with the world's highest flow rate of 3000 L/min was succeeded in generating a 100 mm-wide and 25 mm-thick free-surface lithium flow steadily under the IFMIF operation condition of a high-speed of 15 m/s at 250$$^{circ}$$C in a vacuum of 10 $$^{-3}$$ Pa. Some excellent results of the recent engineering validations including lithium purification, lithium safety, and remote handling technique were obtained, and the engineering design of lithium facility was also evaluated. These results will advance greatly the development of an accelerator-based neutron source to simulate the fusion reactor materials irradiation environment as an important key technology for the development of fusion reactor materials.

Journal Articles

Engineering validation and engineering design of lithium target facility in IFMIF/EVEDA project

Wakai, Eiichi; Kondo, Hiroo; Kanemura, Takuji; Furukawa, Tomohiro; Hirakawa, Yasushi; Watanabe, Kazuyoshi; Ida, Mizuho*; Ito, Yuzuru; Niitsuma, Shigeto; Edao, Yuki; et al.

Fusion Science and Technology, 66(1), p.46 - 56, 2014/07

 Times Cited Count:4 Percentile:36.81(Nuclear Science & Technology)

Journal Articles

Bend-fatigue properties of JPCA and Alloy800H specimens irradiated in a spallation environment

Saito, Shigeru; Kikuchi, Kenji*; Hamaguchi, Dai; Endo, Shinya; Sakuraba, Naotoshi; Miyai, Hiromitsu; Kawai, Masayoshi*; Dai, Y.*

Journal of Nuclear Materials, 450(1-3), p.27 - 31, 2014/07

 Times Cited Count:0 Percentile:0.01(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Present status of klystron power supply systems for J-PARC linac 2013

Kawamura, Masato*; Chishiro, Etsuji; Hori, Toshihiko; Shinozaki, Shinichi; Sato, Fumiaki; Fukui, Yuji*; Futatsukawa, Kenta*; Yamazaki, Masayoshi*; Sagawa, Ryu*; Miyajima, Noriyuki*; et al.

Proceedings of 10th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.605 - 607, 2014/06

This report describes the present status of the klystron power supply systems for the J-PARC linac. The systems for the 181 MeV linac were operated from September to May. A few breakdowns were occurred, and are described in this report. The new systems for the upgrade of the linac from 181MeV to 400 MeV have been installed until now, and the 3 HVDCPSs and the 3 anode modulators of the new systems have been operated. All the systems for 400 MeV linac will be operated in this autumn.

Journal Articles

Magnetic Compton scattering studies of magneto-dielectric Ba(Co$$_{0.85}$$Mn$$_{0.15}$$)O$$_{3-delta}$$

Shinoda, Ryoichi*; Ito, Masayoshi*; Sakurai, Yoshiharu*; Yamamoto, Hiroyuki; Hirao, Norie; Baba, Yuji; Iwase, Akihiro*; Matsui, Toshiyuki*

Journal of Applied Physics, 113(17), p.17E307_1 - 17E307_3, 2013/05

 Times Cited Count:8 Percentile:38.93(Physics, Applied)

We revealed that the Ba(Co$$_{0.85}$$Mn$$_{0.15}$$)O$$_{3-delta}$$ (BCMO) ceramic samples exhibited ferromagnetic-dielectric behavior below the magnetic transition temperature of about 35 K. The origin of their magnetic ordering was expected to super-exchange coupling of Co$$^{4+}$$($$d^5$$)-O$$^{2-}$$-Mn$$^{4+}$$ ($$d^3$$) with bonding angle of 180$$^{circ}$$. and/or Mn$$^{4+}$$($$d^3$$)-O$$^{2-}$$-Mn$$^{4+}$$ ($$d^3$$) with bonding angle of 90$$^{circ}$$. The magnetic spin momentum estimated by the magnetic Compton profiles (MCP) of the samples had similar temperature dependence as that determined by the SQUID measurement, which meant that the observed magnetic moments could be ascribed to the spin moment. The shapes of the MCPs of the samples were completely same regardless of the temperature measured. This result indicates that there are no changes of the momentum space distribution of spin density between ferromagnetic and paramagnetic states. So, this magnetic transition is simply caused by a thermal fluctuation of the spin.

Journal Articles

Development of small specimen test techniques for the IFMIF test cell

Wakai, Eiichi; Kim, B. J.; Nozawa, Takashi; Kikuchi, Takayuki; Hirano, Michiko*; Kimura, Akihiko*; Kasada, Ryuta*; Yokomine, Takehiko*; Yoshida, Takahide*; Nogami, Shuhei*; et al.

Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 6 Pages, 2013/03

Journal Articles

Local structure analysis of SmFe$$_2$$ and TbFe$$_2$$

Yoneda, Yasuhiro; Kohara, Shinji*; Ito, Masayoshi*; Abe, Hiroshi; Takeuchi, Mitsuaki*; Uchida, Hirohisa*; Matsumura, Yoshihito*

Transactions of the Materials Research Society of Japan, 38(1), p.109 - 112, 2013/03

We performed local structure analysis of SmFe$$_2$$ and TbFe$$_2$$ in the crystallization process from amorphous by using synchrotron X-ray pair-distribution function (PDF) method. The giant mangetostrictive materials of these compounds can be controlled its property by ion irradiation. In amorphous TbFe$$_2$$ and SmFe$$_2$$, the mosaic block size was small and the short-range order structure owing to Fe-Fe network maintained. In crystalline SmFe$$_2$$, a rigid long-range order structure of Fe-Fe and Sm-Sm network coexisted and it had a large mosaic block size. On the other hand, in crystalline TbFe$$_2$$, Fe-Fe network degraded by Tb-Tb network owing to its lattice tolerance.

Journal Articles

Tensile mechanical properties of a stainless steel irradiated up to 19 dpa in the Swiss spallation neutron source

Saito, Shigeru; Kikuchi, Kenji*; Hamaguchi, Dai; Usami, Koji; Endo, Shinya; Ono, Katsuto; Matsui, Hiroki; Kawai, Masayoshi*; Dai, Y.*

Journal of Nuclear Materials, 431(1-3), p.44 - 51, 2012/12

 Times Cited Count:2 Percentile:20.56(Materials Science, Multidisciplinary)

To evaluate the lifetime of the beam window of an accelerator-driven transmutation system (ADS), post irradiation examination (PIE) of the STIP (SINQ target irradiation program, SINQ; Swiss spallation neutron source) specimens was carried out. The specimens tested in this study were made from the austenitic steel JPCA (Japan primary candidate alloy). The specimens were irradiated at SINQ Target 4 (STIP-II) with high-energy protons and spallation neutrons. The irradiation conditions were as follows: the proton energy was 580 MeV, irradiation temperatures ranged from 100 to 430$$^{circ}$$C, and displacement damage levels ranged from 7.1 to 19.5 dpa. Tensile tests were performed in air at room temperature (R.T.), 250$$^{circ}$$C and 350$$^{circ}$$C. Fracture surface observation after the tests was done by SEM (Scanning electron microscope). Results of the tensile tests performed at R.T. showed the extra hardening of JPCA at higher dose compared to the fission neutron irradiated data. At the higher temperatures, 250$$^{circ}$$C and 350$$^{circ}$$C, the extra hardening was not observed. Degradation of ductility bottomed around 10 dpa, and specimens kept their ductility until 19.5 dpa. All specimens fractured in ductile manner. The result from a microstructure observation on a specimen irradiated to 19.3 dpa at 420$$^{circ}$$C indicates that some agglomeration of bubbles on grain boundaries was observed in the specimen irradiated to 19.3 dpa at 420$$^{circ}$$C. However the tensile specimen irradiated up to 18.4 dpa at 425$$^{circ}$$C still exhibited little loss of ductility. Since He/dpa was very high on SINQ target irradiations, the formation of highly dense small bubbles in the matrix consequently avoided the accumulation of He on grain boundaries, which might have resulted in avoiding grain boundary embrittlement.

Journal Articles

Development of lithium target system in engineering validation and engineering design activity of the International Fusion Materials Irradiation Facility (IFMIF/EVEDA)

Wakai, Eiichi; Kondo, Hiroo; Sugimoto, Masayoshi; Fukada, Satoshi*; Yagi, Juro*; Ida, Mizuho; Kanemura, Takuji; Furukawa, Tomohiro; Hirakawa, Yasushi; Watanabe, Kazuyoshi; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 88(12), p.691 - 705, 2012/12

no abstracts in English

Journal Articles

Dosimetry for 110 keV electron beam processing

Seito, Hajime; Matsui, Shinjiro*; Hakoda, Teruyuki; Ishikawa, Masayoshi*; Haruyama, Yasuyuki; Kaneko, Hirohisa; Kimura, Jun*; Kojima, Takuji

Zairyo Gijutsu, 30(1), p.10 - 16, 2012/01

The dosimetry of a 110 keV electron beam (EB) irradiation field is studied using a calorimeter, film dosimeter, and Monte Carlo simulation. This is important base for dose control in practical processing to guarantee the process reproducibility and product reliability. The simulation results are validated on the measurement of the energy fluence obtained by the calorimeter at one position in the air plane at different distances from a beam exit window. The spatial dose distribution obtained from the simulation is compared to that obtained by the film dosimeter. They show good agreement within $$pm$$5.0%. The precision of $$pm$$5.0% is sufficient to control the surface modification of polymers and the development of semiconductor devices in practical radiation processing. These results suggest that film dosimetry results at just one position in the air plane are sufficient to determine the irradiation characteristics of the low energy EB, and to provide a base of quality control measures in practical radiation processing.

Journal Articles

New frontier for studying magnetism by magnetic Compton scattering; Study of perpendicular magnetic anisotropy films

Sakurai, Hiroshi*; Ito, Masayoshi*; Agui, Akane

Magune, 6(5), p.270 - 276, 2011/10

no abstracts in English

Journal Articles

Microscopic magnetization process in Tb$$_{43}$$Co$$_{57}$$ film by magnetic Compton scattering

Agui, Akane; Matsumoto, Sayaka*; Sakurai, Hiroshi*; Tsuji, Naruki*; Homma, Satoshi*; Sakurai, Yoshiharu*; Ito, Masayoshi*

Applied Physics Express, 4(8), p.083002_1 - 083002_3, 2011/08

 Times Cited Count:14 Percentile:55.3(Physics, Applied)

We have succeeded in measuring microscopic magnetic hysteresis loop of amorphous Tb$$_{43}$$Co$$_{57}$$ film. Spin selective magnetic hysteresis (SSMH) loop was measured by magnetic Compton scattering at synchrotron radiation facility SPring-8 and obtaining orbital selective magnetic hysteresis (OSMH) loop was firstly obtained by combining with result of macroscopic magnetic hysteresis loop.

Journal Articles

Present status of RF source in J-PARC linac; Recovery from earthquake disaster and energy upgrade

Kawamura, Masato*; Chishiro, Etsuji; Shinozaki, Shinichi; Fang, Z.*; Fukui, Yuji*; Naito, Fujio*; Yamazaki, Masayoshi*; Tsubota, Naoaki; Futatsukawa, Kenta; Sato, Fumiaki; et al.

Proceedings of 8th Annual Meeting of Particle Accelerator Society of Japan (Internet), 3 Pages, 2011/08

We will report about status of linac 400 MeV upgrade program and northeast Japan earthquake restoration. On March 11, the linac suffered serious damage as consequence of the earthquake, and was shuttled down for long term. Linac RF group restores the facilities and is accomplishing 400 MeV upgrade at the same time.

Journal Articles

Study on ion-irradiation-induced ferromagnetism in FeRh intermetallic compound by means of magnetic Compton scattering

Kosugi, Shinya*; Matsui, Toshiyuki*; Ishikawa, Norito; Ito, Masayoshi*; Sakurai, Yoshiharu*; Aiko, Kazuma*; Shimizu, Hirotaka*; Tahara, Yuki*; Hori, Fuminobu*; Iwase, Akihiro*

Journal of Applied Physics, 109(7), p.07B737_1 - 07B737_3, 2011/04

 Times Cited Count:7 Percentile:33.93(Physics, Applied)

The magnetic Compton profiles of FeRh intermetallic compound were measured to study the ferromagnetism induced by 200 MeV Xe ion irradiation. The magnetic effect at 50 K increases with increasing the ion-fluence. The analysis of the experimental result revealed that the values of spin moment induced by the irradiation were close to the values of magnetization obtained by a superconducting quantum interference device magnetometer, suggesting that the ion irradiation mainly induces the spin magnetic moment.

Journal Articles

Power supply system for klystron in J-PARC linac

Kawamura, Masato*; Fukui, Yuji*; Naito, Fujio*; Chishiro, Etsuji; Yamazaki, Masayoshi*; Suzuki, Hiroyuki*; Shinozaki, Shinichi; Hasegawa, Kazuo

Proceedings of 25th International Linear Accelerator Conference (LINAC 2010) (CD-ROM), p.887 - 889, 2010/09

This paper describes the present status, technical specifications, operating experience, and upgrade plane for the power supply system (PS system) for the klystrons in the J-PARC. The PS systems include both the high voltage DC power supplies (DCPSs), which drives one or four modulating-anode klystron each, and the anode-modulators, one per klystron. Currently, the energy output of the J-PARC linac is 181 MeV, which includes the energy necessary to run twenty 324 MHz klystrons. In 2012, the linac will add twenty-five 972 MHz klystrons and upgrade the energy output to 400 MeV.

Journal Articles

Investigation of nano porous SiC based fibers synthesized by precursor method

Kita, Kenichiro; Narisawa, Masaki*; Nakahira, Atsushi*; Mabuchi, Hiroshi*; Ito, Masayoshi*; Sugimoto, Masaki; Yoshikawa, Masahito

Advances in Polymer Derived Ceramics and Composites; Ceramic Transactions, Vol.213, p.45 - 50, 2010/06

105 (Records 1-20 displayed on this page)