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Journal Articles

Design and actual performance of J-PARC 3 GeV rapid cycling synchrotron for high-intensity operation

Yamamoto, Kazami; Kinsho, Michikazu; Hayashi, Naoki; Saha, P. K.; Tamura, Fumihiko; Yamamoto, Masanobu; Tani, Norio; Takayanagi, Tomohiro; Kamiya, Junichiro; Shobuda, Yoshihiro; et al.

Journal of Nuclear Science and Technology, 32 Pages, 2022/02

In the Japan Proton Accelerator Research Complex, the purpose of the 3 GeV rapid cycling synchrotron (RCS) is to accelerate a 1 MW, high-intensity proton beam. To achieve beam operation at a repetition rate of 25 Hz at high intensities, the RCS was elaborately designed. After starting the RCS operation, we carefully verified the validity of its design and made certain improvements to establish a reliable operation at higher power as possible. Consequently, we demonstrated beam operation at a high power, namely, 1 MW. We then summarized the design, actual performance, and improvements of the RCS to achieve a 1 MW beam.

Journal Articles

Fragmentation and cooling behavior of a simulated molten core material discharged into a sodium pool with limited depth and volume

Matsuba, Kenichi; Kato, Shinya; Kamiyama, Kenji; Akayev, A. S.*; Baklanov, V. V.*

Proceedings of 28th International Conference on Nuclear Engineering; Nuclear Energy the Future Zero Carbon Power (ICONE 28) (Internet), 4 Pages, 2021/08

In order to obtain experimental knowledge on fragmentation and cooling behavior of molten core material discharged into regions where the depth and volume of sodium are limited, a series of out-of-pile experiments using molten alumina as a simulant for molten core material was conducted. It was found that following mechanisms might be involved in the fragmentation and cooling behavior in a shallow sodium pool: (1) FCI which occurs at location of impingement of the molten jet on the bottom plate promotes fragmentation. (2) If there is a sufficient amount of sodium as a heat sink outside the region, heat exchange by sodium flow in and out due to vapor expansion and condensation suppresses the sodium temperature rise. (3) This temperature suppression contributes to effective cooling of molten core material. In the future study, in order to confirm the mechanisms which was clarified in this study, analytical evaluation of the experimental result will be carried out using a simulation tool.

Journal Articles

Validation of analysis models on relocation behavior of molten core materials in sodium-cooled fast reactors based on the melt discharge experiment

Igarashi, Kai*; Onuki, Ryoji*; Sakai, Takaaki*; Kato, Shinya; Matsuba, Kenichi; Kamiyama, Kenji

Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 6 Pages, 2020/08

Journal Articles

Study on the discharge behavior of molten-core through the control rod guide tube in the core disruptive accident of SFR

Kato, Shinya; Matsuba, Kenichi; Kamiyama, Kenji; Ganovichev, D. A.*; Baklanov, V. V.*

Proceedings of 2019 International Congress on Advances in Nuclear Power Plants (ICAPP 2019) (Internet), 9 Pages, 2019/05

In order to ensure In-Vessel Retention (IVR) of molten-core in Core Disruptive Accident (CDA), we are investigating the possibility of the molten-core discharge through the control rod guide tube (CRGT) to prevent energetics due to exceeding the prompt criticality. Internal structures of the CRGT, such as a sodium-flow regulator when the CRGT is connected to the high-pressure plenum, may disturb the discharge of molten-core from the core region. Based on above background, an experimental program to clarify characteristics of molten-core discharge through the CRGT has been commenced as one of subjects under a joint study with National Nuclear Center of the Republic of Kazakhstan (NNC-RK) named EAGLE-3 project. An experiment using molten-alumina as fuel simulant and sodium was conducted at the out-of-pile test facility owned by NNC-RK to investigate sodium cooling effect around the sodium flow regulator on its destruction. The experimental result represented that void development at the initiation of molten-alumina discharge eliminated liquid-phase sodium from the discharge path and this also eliminated sodium cooling effect around the sodium flow regulator. As a result, early destruction of the sodium flow regulator and massive discharge of molten alumina occurred in turn.

Journal Articles

A Failure investigation of the beam collimator system in the J-PARC 3 GeV rapid cycling synchrotron

Okabe, Kota; Yamamoto, Kazami; Kamiya, Junichiro; Takayanagi, Tomohiro; Yamamoto, Masanobu; Yoshimoto, Masahiro; Takeda, Osamu*; Horino, Koki*; Ueno, Tomoaki*; Yanagibashi, Toru*; et al.

Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.853 - 857, 2017/12

The most important issue is to reduce the uncontrolled beam loss in the high intensity hadron accelerator such as J-PARC proton accelerators. The J-PARC 3 GeV Synchrotron (RCS) has a collimator system which narrows a high intensity beam in the RCS. After startup of RCS in 2007, the collimator system of the RCS worked well. However, in April 2016, vacuum leakage at the collimator system occurred during the maintenance operation. To investigate a cause of the failure, we took apart iron shields of the collimator reducing exposed dose of operators. As a result of inspection, we succeeded to identify the cause of the vacuum leakage failure. In this presentation, we report the failure investigation of the beam collimator system in the RCS.

Journal Articles

Creep-fatigue tests of double-end notched bar made of Mod.9Cr-1Mo steel

Shimomura, Kenta; Kato, Shoichi; Wakai, Takashi; Ando, Masanori; Hirose, Yuichi*; Sato, Kenichiro*

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 9 Pages, 2015/05

This paper describes experimental and analytical works to confirm that the design standard for SFR components sufficiently covers possible failure mechanisms. Creep-fatigue damage evaluation method in JSME design standard for SFR components has been constructed based on experiments and/or numerical analyses of conventional austenitic stainless steels, such as 304SS. Since the material characteristics of Mod.9Cr-1Mo steel are substantially different from those of austenitic stainless steels, it is required to verify the applicability of the design standards to the SFR components made of Mod.9Cr-1Mo steel. A series of uni-axial creep-fatigue tests were conducted using double-ended notch bar specimens made of Mod.9Cr-1Mo steel under displacement controlled condition with 30 minute holding. The curvature radii of the specimens were 1.6mm, 11.2mm and 40.0mm. The specimen having 1.6mm notch and 11.2mm notch failed from outer surface but the specimen having 40.0mm notch showed obvious internal crack nucleation. In addition, though total duration time of the creep-fatigue test was only 2,000 hours, a lot of creep voids and inter granular crack growth were observed. To clarify the cause of such peculiar failure, some additional experiments were performed, as well as some numerical analyses. We could point out that such a peculiar failure aspect might result from corresponding stress distribution in the cross section. As a result of a series of investigations, possible causes of such peculiar failure could be narrowed down. A future investigation plan was proposed to clarify the most significant cause.

Journal Articles

Evidence of electronic polarization of the As ion in the superconducting phase of F-doped LaFeAsO

Kim, J.*; Fujiwara, Akihiko*; Sawada, Tomohiro*; Kim, Y.*; Sugimoto, Kunihisa*; Kato, Kenichi*; Tanaka, Hiroshi*; Ishikado, Motoyuki*; Shamoto, Shinichi; Takata, Masaki*

IUCrJ, 1(3), p.155 - 159, 2014/05

 Times Cited Count:2 Percentile:24.15(Chemistry, Multidisciplinary)

Using a charge density analysis based on synchrotron radiation X-ray powder diffraction data, we found that the charge carriers only accumulated in the iron layer of the superconducting phase of LaFeAsO$$_{1-x}$$F$$_{x}$$ at low temperatures. Analysis of the electrostatic potential distribution revealed the concerted enhancement of the electronic polarization of the As ions and the carrier redistribution.

Journal Articles

Trial synthesis of Li$$_{2}$$Be$$_{2}$$O$$_{3}$$ for high-functional tritium breeders

Hoshino, Tsuyoshi; Oikawa, Fumiaki; Natori, Yuri*; Kato, Kenichi*; Sakka, Tomoko*; Nakamura, Mutsumi*; Tatenuma, Katsuyoshi*

Fusion Engineering and Design, 88(9-10), p.2268 - 2271, 2013/10

 Times Cited Count:1 Percentile:12.53(Nuclear Science & Technology)

Lithium titanate with additional Li (Li$$_{2+x}$$TiO$$_{3+y}$$) and lithium orthosilicate (Li$$_{4}$$SiO$$_{4}$$) is one of the most promising candidates for use in a tritium breeder because of its good chemical and mechanical stabilities. Currently, mixtures of tritium breeder pebble and neutron multiplier (Be or Be$$_{12}$$Ti) pebble are being considered for use in increasing the tritium breeding ratio in a breeding blanket. However, lithium and beryllium are gradually reacted under practical operating conditions, and therefore a high-functional tritium breeder such as lithium beryllium oxide (Li$$_{2}$$Be$$_{2}$$O$$_{3}$$) needs to be developed to compensate for this reactive characteristic under high temperature use. In this study, methods of synthesizing Li$$_{2}$$Be$$_{2}$$O$$_{3}$$ have been extensively investigated by means of solid-phase reaction. The solid-phase reaction of LiOH(H$$_{2}$$O) and BeO is a suitable synthesis method for lithium beryllium oxide (Li$$_{2}$$Be$$_{2}$$O$$_{3}$$). It is expected that single-phase Li$$_{2}$$Be$$_{2}$$O$$_{3}$$ will be stable under the mixture conditions of a tritium breeder and neutron multiplier in the blanket region at high temperatures.

Journal Articles

A Study for proposal of welded joint strength reduction factors of modified 9Cr-1Mo steel for Japan sodium cooled fast reactor (JSFR)

Wakai, Takashi; Onizawa, Takashi; Kato, Takehiko*; Date, Shingo*; Kikuchi, Koichi*; Sato, Kenichiro*

Proceedings of 2013 ASME Pressure Vessels and Piping Conference (PVP 2013) (DVD-ROM), 8 Pages, 2013/07

Journal Articles

The Result of beam commissioning in J-PARC 3-GeV RCS

Harada, Hiroyuki; Hotchi, Hideaki; Saha, P. K.; Shobuda, Yoshihiro; Hayashi, Naoki; Yamamoto, Kazami; Yoshimoto, Masahiro; Tamura, Fumihiko; Yamamoto, Masanobu; Kinsho, Michikazu; et al.

Proceedings of 52nd ICFA Advanced Beam Dynamics Workshop on High-Intensity and High-Brightness Hadron Beams (HB 2012) (Internet), p.339 - 343, 2012/09

J-PARC 3-GeV RCS has started the beam commissioning since Oct. 2007. In the beam commissioning, the beam tuning for basic parameters and high-intensity operation has been continuously performed. This presentation will describe the results of the beam-loss reduction and minimization for high-intensity operation.

Journal Articles

Beam commissioning and operation of the Japan Proton Accelerator Research Complex 3-GeV rapid cycling synchrotron

Hotchi, Hideaki; Harada, Hiroyuki; Hayashi, Naoki; Kinsho, Michikazu; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Yamamoto, Kazami; Yamamoto, Masanobu; Yoshimoto, Masahiro; et al.

Progress of Theoretical and Experimental Physics (Internet), 2012(1), p.02B003_1 - 02B003_26, 2012/00

 Times Cited Count:13 Percentile:64.55(Physics, Multidisciplinary)

The J-PARC 3-GeV RCS is a high-power pulsed proton driver aiming at 1 MW output beam power. The RCS was beam commissioned in October 2007 and made available for user operation in December 2008 with an output beam power of 4 kW. Since then, the output beam power of the RCS has been steadily increasing as per progressions of beam tuning and hardware improvements. So far, the RCS has successfully achieved high-intensity beam trials of up to 420 kW at a low-level intensity loss of less than 1%, and the output beam power for the routine user program has been increased to 210 kW. The most important issues in increasing the output beam power are the control and minimization of beam loss to maintain machine activation within the permissible level. This paper presents the recent progress in the RCS beam power ramp-up scenario, with particular emphasis on our efforts for beam loss issues.

Journal Articles

Development of advanced tritium breeding material with added lithium for ITER-TBM

Hoshino, Tsuyoshi; Kato, Kenichi*; Natori, Yuri*; Oikawa, Fumiaki; Nakano, Natsuko*; Nakamura, Mutsumi*; Sasaki, Kazuya*; Suzuki, Akihiro*; Terai, Takayuki*; Tatenuma, Katsuyoshi*

Journal of Nuclear Materials, 417(1-3), p.684 - 687, 2011/10

 Times Cited Count:39 Percentile:95.49(Materials Science, Multidisciplinary)

Lithium titanate (Li$$_{2}$$TiO$$_{3}$$) is one of the most promising candidates among tritium breeding materials because of its good tritium release. Addition of H$$_{2}$$ to inert sweep gas has been proposed for enhancing the tritium release from tritium breeding materials. However, the mass of Li$$_{2}$$TiO$$_{3}$$ was decreased with time in the hydrogen atmosphere. It is assumed that the mass decrease indicates the loss of the oxygen contained in the sample caused by the change from Ti $$^{4+}$$ to Ti $$^{3+}$$, and that the partial pressures of Li-containing species were increased in the hydrogen atmosphere. In order to decrease the mass-change at high temperature, advanced tritium breeding material with added Li should be developed to improve the physical and chemical stability in hydrogen atmosphere. In the case of the Li$$_{2+x}$$TiO$$_{3+y}$$ samples used by the present study, LiOHH$$_{2}$$O and H$$_{2}$$TiO$$_{3}$$ were proportionally mixed with the molar ratio Li/Ti of either 2.0 and 2.2. These samples are designated as L20 (Li/Ti = 2.0) and L22 (Li/Ti = 2.2), respectively. The results of XRD measurement showed that the phases in advanced tritium breeding material were as follows. L22 existed as non-stoichiometric compound Li$$_{2+x}$$TiO$$_{3+y}$$.

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.

JAEA Reports

Annual report on the environmental radiation monitoring around the Tokai Reprocessing Plant FY2009

Sumiya, Shuichi; Matsuura, Kenichi; Watanabe, Hitoshi; Nakano, Masanao; Takeyasu, Masanori; Fujita, Hiroki; Isozaki, Tokuju; Morisawa, Masato; Mizutani, Tomoko; Kokubun, Yuji; et al.

JAEA-Review 2011-004, 161 Pages, 2011/03

JAEA-Review-2011-004.pdf:4.09MB

Environmental radiation monitoring around the Tokai Reprocessing Plant has been performed by the Nuclear Fuel Cycle Engineering Laboratories, based on "Safety Regulations for the Reprocessing Plant of Japan Atomic Energy Agency, Chapter IV - Environmental Monitoring". This annual report presents the results of the environmental monitoring and the dose estimation to the hypothetical inhabitant due to the radioactivity discharged from the plant to the atmosphere and the sea during April 2009 to March 2010. Appendices present comprehensive information, such as monitoring program, monitoring methods, monitoring results and their trends, meteorological data and discharged radioactive wastes.

Journal Articles

Dissolution techniques with microwave heating devices for radiochemical analysis of ash and cement-solidified product samples

Haraga, Tomoko; Ishimori, Kenichiro; Kato, Kenichi; Kameo, Yutaka; Takahashi, Kuniaki

Bunseki Kagaku, 60(1), p.87 - 90, 2011/01

 Times Cited Count:0 Percentile:0(Chemistry, Analytical)

In order to dissolve radioactive ash (fly ash and bottom ash) and cement-solidified product of radioactive liquid wastes, a dissolution method using microwave heating devices was developed. In present method, most metal elements in samples were extracted with HCl and HNO$$_{3}$$ to sample solution and a precipitate with silica as the main ingredient was decomposed with HF and HNO$$_{3}$$. As a result, fluoride residue was sufficiently reduced and more than 99% of radionuclides were recovered to sample solution. The ash and cement-solidified product samples were successfully dissolved in a shorter time as compared with a conventional method by external heating.

Journal Articles

Lower critical fields and the anisotropy in PrFeAsO$$_{1-y}$$ single crystals

Okazaki, Ryuji*; Konczykowski, M.*; Van der Beek, C. J.*; Kato, Tomonari*; Hashimoto, Kenichiro*; Shimozawa, Masaaki*; Shishido, Hiroaki*; Yamashita, Minoru*; Ishikado, Motoyuki; Kito, Hijiri*; et al.

Physica C, 470(Suppl.1), p.S485 - S486, 2010/12

 Times Cited Count:0 Percentile:0(Physics, Applied)

We report the lower critical fields $$H_{c1}$$ measurements on Fe-based oxipnictide PrFeAsO$$_{1-y}$$ single crystals for $$H$$ $$parallel$$ $$c$$ and $$H$$ $$parallel$$ $$ab$$-planes. To avoid the difficulty of $$H_{c1}$$ determinations due to the flux pinning, we developed a novel method using a miniature hall-sensor array which can evaluate the local magnetic induction ai each sensor position. The hall sensor which is placed on the edge of the crystal clearly resolves the first flux penetration from the Meissner state. The temperature dependence of $$H_{c1}$$ for $$H$$ $$parallel$$ $$c$$ is well scaled by the in-plane penetration depth and is consistent with a full-gap superconducting state. The anistropy of $$H_{c1}$$ at low temperatures is estimated to be $$sim$$ 3, which is much smaller than of $$H_{c2}$$. This indicates the multiband superconductivity, in which the active bands for superconductivity are more two-dimensional.

Journal Articles

Disorder and flux pinning in superconducting pnictide single crystals

Van der Beek, C. J.*; Rizza, G.*; Konczykowski, M.*; Fertey, P.*; Monnet, I.*; Okazaki, Ryuji*; Kato, Tomonari*; Hashimoto, Kenichiro*; Shimozawa, Masaaki*; Shishido, Hiroaki*; et al.

Physica C, 470(Suppl.1), p.S385 - S386, 2010/12

 Times Cited Count:1 Percentile:7.06(Physics, Applied)

Crystalline disorder in the pnictide superconductor PrFeAsO$$_{1-x}$$ is studied using magneto-optical visualisation of flux penetration, transmission electron microscopy, and X-ray diffraction using synchrotron radiation. Critical-state like flux distributions and the magnitude and temperature dependence of the critical current demonstrate bulk vortex pinning by oxygen vacancies at all temperatures.

Journal Articles

First neutron production utilizing J-PARC pulsed spallation neutron source JSNS and neutronic performance demonstrated

Maekawa, Fujio; Harada, Masahide; Oikawa, Kenichi; Teshigawara, Makoto; Kai, Tetsuya; Meigo, Shinichiro; Oi, Motoki; Sakamoto, Shinichi; Takada, Hiroshi; Futakawa, Masatoshi; et al.

Nuclear Instruments and Methods in Physics Research A, 620(2-3), p.159 - 165, 2010/08

 Times Cited Count:63 Percentile:97.68(Instruments & Instrumentation)

The J-PARC 1-MW pulsed spallation neutron source JSNS was successfully launched on 30th of May 2008. To demonstrate the unique features of the moderator design and the neutronic performance of JSNS the neutron spectral intensity, absolute neutron flux, and time structure of the neutron pulse shapes etc have been measured using several neutron instruments since then. The measured energy spectra clearly revealed the feature of the para-hydrogen, as expected when designing the moderator. The measured neutron flux below 0.4 eV agreed with the corresponding design value within $$pm$$20%, thus suggesting that the JSNS design calculations to have been reliable. World-class high-resolution diffraction data could be recorded due to the suitability of design of the moderators and the instruments. Another world-class high-intensity neutron flux was also capable of being demonstrated due to the unique design of the large cylindrical coupled moderator.

JAEA Reports

Annual report on the environmental radiation monitoring around the Tokai Reprocessing Plant FY2008

Takeishi, Minoru; Sumiya, Shuichi; Matsuura, Kenichi; Watanabe, Hitoshi; Nakano, Masanao; Takeyasu, Masanori; Isozaki, Hisaaki*; Isozaki, Tokuju; Morisawa, Masato; Fujita, Hiroki; et al.

JAEA-Review 2009-048, 177 Pages, 2009/12

JAEA-Review-2009-048.pdf:19.3MB
JAEA-Review-2009-048(errata).pdf:0.12MB

Environmental radiation monitoring around the Tokai Reprocessing Plant has been performed by the Nuclear Fuel Cycle Engineering Laboratories, based on "Safety Regulations for the Reprocessing Plant of Japan Atomic Energy Agency, Chapter IV; Environmental Monitoring". This annual report presents the results of the environmental monitoring and the dose estimation to the hypothetical inhabitant due to the radioactivity discharged from the plant to the atmosphere and the sea during April 2008 to March 2009. Appendices present comprehensive information, such as monitoring program, monitoring methods, monitoring results and their trends, meteorological data and discharged radioactive wastes.

Journal Articles

New synthesis method of advanced lithium titanate with Li$$_{4}$$TiO$$_{4}$$ additives for ITER-TBM

Hoshino, Tsuyoshi; Kato, Kenichi*; Natori, Yuri*; Nakamura, Mutsumi*; Sasaki, Kazuya*; Hayashi, Kimio; Terai, Takayuki*; Tatenuma, Katsuyoshi*

Fusion Engineering and Design, 84(2-6), p.956 - 959, 2009/06

 Times Cited Count:39 Percentile:93.81(Nuclear Science & Technology)

Li$$_{2}$$TiO$$_{3}$$ is one of the most promising candidates among the proposed solid breeder materials for fusion reactors. Addition of H$$_{2}$$ to inert sweep gas has been proposed for enhancing the release of bred tritium from breeder material. However, the mass of Li$$_{2}$$TiO$$_{3}$$ was found to decrease with time in the hydrogen atmosphere. This mass change indicates that the oxygen content of the sample decreased, suggesting the change from Ti$$^{4+}$$ to Ti$$^{3+}$$. In order to control the mass change at the time of high temperature use, the development of lithium titanate which has Li$$_{4}$$TiO$$_{4}$$ additive is expected to be effective.

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