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Ogata, Yudai; Chudo, Hiroyuki; Gu, B.; Kobayashi, Nobukiyo*; Ono, Masao; Harii, Kazuya; Matsuo, Mamoru; Saito, Eiji; Maekawa, Sadamichi
Journal of Magnetism and Magnetic Materials, 442, p.329 - 331, 2017/11
Times Cited Count：8 Percentile：66.67(Materials Science, Multidisciplinary)Sato, Hiroyuki; Terada, Atsuhiko; Hayashida, Hitoshi; Kamiji, Yu; Kobayashi, Jun; Yamagishi, Isao; Morita, Keisuke; Kato, Chiaki
JAEA-Research 2013-042, 25 Pages, 2014/03
JAEA-Research-2013-042.pdf:5.13MB
Spent zeolite adsorption vessels in the Fukushima No.1 nuclear power plant are kept for long-term with washing out with fresh water for prevention of corrosion remaining salt component in vessel. However, corrosion result is concerned by residual concentration of salt component, washing out experiment is carried out using actual and unspent adsorption vessel (KURION). KURION adsorption vessel is filled with 1,650 ppm of sodium chloride (1,000 ppm of chloride ion) and washed out with pure water for estimating washing effect in this experiment. Pure water is streamed with volume flow rate 4.5 m
/h, chloride concentration in vessel is measured with drainage sample water. 1,000 ppm of chloride concentration is decreased till 0.5 ppm and below by washing out with about double pure water volume of adsorbing material filling volume in vessel, washing out is more effective in KURION adsorption vessel.
Kojima, Atsushi; Hanada, Masaya; Hilmi, A.*; Inoue, Takashi; Watanabe, Kazuhiro; Taniguchi, Masaki; Kashiwagi, Mieko; Umeda, Naotaka; Tobari, Hiroyuki; Kobayashi, Shinichi*; et al.
Review of Scientific Instruments, 83(2), p.02B117_1 - 02B117_5, 2012/02
Times Cited Count：17 Percentile：60.33(Instruments & Instrumentation)Production of 500 keV, 3 A beams has been successfully achieved in the JT-60 negative by overcoming the low voltage holding of the accelerator. Toward the design of next ion source, database for the voltage holding capability based on experimental results is required and obtained. As a result, the voltage holding capability was found to vary with 67 N power of -0.15 and with 31.7 S power of -0.125 where N is the aperture number and S is the anode surface area. When N = 1100 and S = 2 m
are applied to the design of JT-60SA ion source, the factors C are estimated to be 23 and 29, respectively. Therefore, the influence of the local electric field around the apertures is stronger than that of the surface area.
Nishimura, Masahiro; Kamide, Hideki; Ohshima, Hiroyuki; Kobayashi, Jun; Sato, Hiroyuki
Proceedings of 19th International Conference on Nuclear Engineering (ICONE-19) (CD-ROM), 8 Pages, 2011/10
A sodium cooled fast reactor is designed to attain a high burn-up of core fuel in commercialized fast reactor cycle systems. In high burn-up fuel subassemblies, deformation of fuel pin due to the swelling and thermal bowing may decrease local flow velocity via change of flow area in the subassembly and influence the heat removal capability. Therefore, it is important to obtain the detail of flow velocity distribution in a wire wrapped pin bundle. In this study, water experiments were carried out to investigate the detailed velocity distribution in a subchannel of nominal pin geometry as the first step. These basic data are not only useful for understanding of pin bundle thermal hydraulics but also a code validation. A wire-wrapped 3-pin bundle water model was applied to investigate the detailed velocity distribution in the subchannel which is surrounded by 3 pins with wrapping wire.
Kojima, Atsushi; Hanada, Masaya; Tanaka, Yutaka*; Taniguchi, Masaki; Kashiwagi, Mieko; Inoue, Takashi; Umeda, Naotaka; Watanabe, Kazuhiro; Tobari, Hiroyuki; Kobayashi, Shinichi*; et al.
AIP Conference Proceedings 1390, p.466 - 475, 2011/09
Times Cited Count：2 Percentile：53.22(Physics, Atomic, Molecular & Chemical)Voltage holding tests by using JT-60 negative ion source and small electrodes was carried out because JT-60 negative ion source had a critical problem about low voltage holding capability for long time. As a result, the voltage holding capability is decreased with the increase of area where local electric field is generated, as well as the surface area according to existing scaling low about surface area. Therefore, in order to improve the voltage holding without changing the existing accelerator, the voltage holding test was carried out by extending gap lengths of the negative ion source. In order to improve the voltage holding, beam radiation shield needs to be optimized additionally. As a result, the voltage holding has been improved to 500 kV and stabilized. By using this modified ion source, negative ion beams of 500 keV up to 3A has been successfully produced.
Kojima, Atsushi; Hanada, Masaya; Tanaka, Yutaka*; Kawai, Mikito*; Akino, Noboru; Kazawa, Minoru; Komata, Masao; Mogaki, Kazuhiko; Usui, Katsutomi; Sasaki, Shunichi; et al.
Nuclear Fusion, 51(8), p.083049_1 - 083049_8, 2011/08
Times Cited Count：51 Percentile：88.18(Physics, Fluids & Plasmas)Hydrogen negative ion beams of 490 keV, 3 A and 510 keV, 1 A have been successfully produced in the JT-60 negative ion source with three acceleration stages. These successful productions of the high-energy beams at high current have been achieved by overcoming the most critical issue, i.e., a poor voltage holding of the large negative ion sources with the grids of 2 m for JT-60SA and ITER. To improve voltage holding capability, the breakdown voltages for the large grids was examined for the first time. It was found that a vacuum insulation distance for the large grids was 6-7 times longer than that for the small-area grid (0.02 m). From this result, the gap lengths between the grids were tuned in the JT-60 negative ion source. The modification of the ion source also realized a significant stabilization of voltage holding and a short conditioning time. These results suggest a practical use of the large negative ion sources in JT-60SA and ITER.
Kojima, Atsushi; Hanada, Masaya; Tanaka, Yutaka*; Kawai, Mikito*; Akino, Noboru; Kazawa, Minoru; Komata, Masao; Mogaki, Kazuhiko; Usui, Katsutomi; Sasaki, Shunichi; et al.
Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03
Hydrogen negative ion beams of 490keV, 3A and 510 keV, 1A have been successfully produced in the JT-60 negative ion source with three acceleration stages. These successful productions of the high-energy beams at high current have been achieved by overcoming the most critical issue, i.e., a poor voltage holding of the large negative ion sources with the grids of 
2 m for JT-60SA and ITER. To improve voltage holding capability, the breakdown voltages for the large grids was examined for the first time. It was found that a vacuum insulation distance for the large grids was 6-7 times longer than that for the small-area grid (0.02 m). From this result, the gap lengths between the grids were tuned in the JT-60 negative ion source. The modification of the ion source also realized a significant stabilization of voltage holding and a short conditioning time. These results suggest a practical use of the large negative ion sources in JT-60 SA and ITER.
Kikuzawa, Nobuhiro; Suzuki, Takahiro; Ito, Yuichi; Miura, Akihiko; Fukuta, Shimpei; Ikegami, Masanori*; Sako, Hiroyuki; Kobayashi, Tetsuya; Suzuki, Hiroyuki; Hasegawa, Kazuo
Proceedings of 7th Annual Meeting of Particle Accelerator Society of Japan (DVD-ROM), p.677 - 679, 2010/08
To avoid heat damage and radioactivation by beam loss of the J-PARC accelerator, Machine Protection System (MPS) has been developed. Actually, high responsibility and high reliability have been achieved in J-PARC. Beam-stop method in addition to a way of RFQ OFF has been requested in order to avoid damage to the RFQ. Therefore, we have been developing a fast beam-stop system by using a RF chopper. The fast beam-stop system, including beam test, is described in this paper.
Miura, Akihiko; Kobayashi, Tetsuya; Hasegawa, Kazuo; Sako, Hiroyuki; Ikegami, Masanori*
Proceedings of 7th Annual Meeting of Particle Accelerator Society of Japan (DVD-ROM), p.939 - 941, 2010/08
MEBT-Chopper tuning procedure was proposed using a downstream wire scanner monitor and this has been employed for the beam commissioning of the J-PARC Linac. This paper introduces the results obtained by several tuning experiences and its tendencies. Finally, tolerance depending on the tank level of RFQ (Radio-Frequency Quadrupole Linac) is introduced.
Fang, Z.*; Michizono, Shinichiro*; Anami, Shozo*; Yamaguchi, Seiya*; Naito, Fujio*; Fukui, Yuji*; Kawamura, Masato*; Kubota, Chikashi*; Nammo, Kesao*; Kobayashi, Tetsuya; et al.
Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.1434 - 1436, 2010/05
The output energy of the J-PARC proton linac will be upgraded from 181 to 400 MeV in the next two years by adding high-b acceleration sections. The upgrade of the FPGA-based digital LLRF controller for the 400 MeV linac will be presented in this paper. This new LLRF controller works for both the 324-MHz low-b and 972-MHz high-b sections. Many functions have been added into the LLRF controller, such as (1) working for different RF systems, (2) gradually increasing the feedback gains in the feedback loop instead of fixed ones, (3) automatic chopped beam compensation, (4) automatically switching the beam loading compensation in accordance with different beam operation mode, (5) input RF-frequency tuning to match the RF cavities during RF start-up, and (6) auto-tuning of the RF cavity tuner by detecting the phase curve of the RF cavity during the field decay instead of the phase difference between the cavity input and output signals.
Kojima, Atsushi; Kobayashi, Takayuki; Tobari, Hiroyuki
Purazuma, Kaku Yugo Gakkai-Shi, 86(5), P. 297, 2010/05
The 13th Young Scientist Workshop was held at Naka Fusion Institute and organized by Division of Advanced Plasma Research and Tokamak System Technology. 52 young scientists participated in the workshop, and 6 overview talks and 23 oral talks were given about plasma heating and control techniques. Because the participants had both of oral and poster presentations, the participants understood the study of each other and the discussion lasted during the workshop. On the last day of the workshop, the participants visited the ITER gyrotrons, ITER remote handling and the control room of JT-60.
Sato, Susumu; Miura, Akihiko; Igarashi, Zenei*; Ikegami, Masanori*; Ueno, Akira; Sako, Hiroyuki; Morishita, Takatoshi; Yoshikawa, Hiroshi; Hasegawa, Kazuo; Kobayashi, Tetsuya
Proceedings of 6th Annual Meeting of Particle Accelerator Society of Japan (CD-ROM), p.298 - 300, 2010/03
no abstracts in English
Sato, Hiroyuki; Kobayashi, Jun; Miyakoshi, Hiroyuki; Kamide, Hideki
Proceedings of 13th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-13) (CD-ROM), 13 Pages, 2009/09
A sodium cooled fast reactor is designed to attain a high burn-up core in a feasibility study on commercialized fast reactor cycle systems. It is of importance to obtain the flow velocity distribution in a wire wrapped pin bundle for the high burn-up core. A 2.5 times enlarged 7-pin bundle water model was applied to investigate the detailed velocity distribution in an inner subchannel surrounded by 3 pins with wrapping wire. The velocity distribution in an inner subchannel with the wrapping wire was measured by Particle Image Velocimetry. In the vertical velocity distribution in a narrow space between the pins, the wrapping wire decreased the velocity downstream of the wire and asymmetrical flow distribution was formed between the pin and wire. In the horizontal velocity distribution, swirl flow around the wrapping wire was obviously observed.
Tomimoto, Hiroshi; Kato, Yasushi; Owada, Hiroyuki; Sato, Nao; Shimazaki, Yosuke; Kozawa, Takayuki; Shinohara, Masanori; Hamamoto, Shimpei; Tochio, Daisuke; Nojiri, Naoki; et al.
JAEA-Technology 2009-025, 29 Pages, 2009/06
JAEA-Technology-2009-025.pdf:21.78MB
The first driver fuel of the HTTR (High Temperature Engineering test Reactor) was loaded in 1998 and the HTTR reached first criticality state in the same year. The HTTR has been operated using the first driver fuel for a decade. In Fuel elements assembling, 4770 of fuel rods which consist of 12 kinds of enrichment uranium are loaded into 150 fuel graphite blocks for HTTR second driver fuel elements. Measures of prevention of fuel rod miss loading, are employed in fuel design. Additionally, precaution of fuel handling on assembling are considered. Reception of fuel rods, assembling of fuel elements and storage of second driver fuels in the fresh fuel storage rack in the HTTR were started since June, 2008. Assembling, storage and pre-service inspection were divided into three parts. The second driver fuel assembling was completed in September, 2008. This report describes concerns of fuel handling on assembling and storage work for the HTTR fuel elements.
Ito, Kenji*; Oka, Toshitaka*; Kobayashi, Yoshinori*; Shirai, Yasuharu*; Wada, Kenichiro*; Matsumoto, Masataka*; Fujinami, Masanori*; Hirade, Tetsuya; Honda, Yoshihide*; Hosomi, Hiroyuki*; et al.
Materials Science Forum, 607, p.248 - 250, 2009/00
So far no standard procedure for the positron annihilation lifetime (PAL) technique has been established. A lack of the standards has led to difficulty in ensuring the equivalency and reliability of data from different laboratories. As a first, we conducted an interlaboratory comparison of PAL measurements for metal, polymer and silica glass with agreed procedures for data recording and analysis. The PAL data recorded at different laboratories were analyzed with a single lifetime component for the metal sample and with three components for the others, respectively. Based on the results of the reported positron and ortho-positronium lifetimes, the possible sources of the uncertainties in the PAL measurements are discussed. To reduce the effect of scattered 
rays, a lead shield was placed between the detectors. The uncertainty was significantly decreased, signifying that placing lead shields between the detectors effectively reduced the false signals due to the scattered rays.
Hasegawa, Kazuo; Asano, Hiroyuki; Chishiro, Etsuji; Hori, Toshihiko; Ito, Takashi; Kobayashi, Tetsuya; Kondo, Yasuhiro; Namekawa, Yuya; Oguri, Hidetomo; Okoshi, Kiyonori; et al.
Proceedings of 24th International Linear Accelerator Conference (LINAC 2008) (CD-ROM), p.55 - 57, 2009/00
The beam commissioning of the J-PARC linac started in November 2006 and 181 MeV acceleration was successfully achieved in January 2007. The linac has delivered beams to the 3 GeV Rapid Cycling Synchrotron for its commissioning, and then, the subsequent Main Ring Synchrotron and the neutron target commissioning. The linac uses a Cs-free LaB
-driven ion source and 20 units of 324 MHz klystrons. As of June 2008, the operation times are about 3,000 and 6,000 hours for the ion source and the RF source, respectively. The operating experience of the linac is described.
Ito, Kenji*; Oka, Toshitaka*; Kobayashi, Yoshinori*; Shirai, Yasuharu*; Wada, Kenichiro*; Matsumoto, Masataka*; Fujinami, Masanori*; Hirade, Tetsuya; Honda, Yoshihide*; Hosomi, Hiroyuki*; et al.
Journal of Applied Physics, 104(2), p.026102_1 - 026102_3, 2008/07
Times Cited Count：48 Percentile：83.42(Physics, Applied)Interlaboratory comparison of positron annihilation lifetime measurements using synthetic fused silica and polycarbonate was conducted with the participation of 12 laboratories. By regulating procedures for the measurement and data analysis the uncertainties of the positron lifetimes obtained at different laboratories were significantly reduced in comparison with those reported in the past.
Sato, Hiroyuki; Kobayashi, Jun; Miyakoshi, Hiroyuki; Kamide, Hideki
Proceedings of 16th International Conference on Nuclear Engineering (ICONE-16) (CD-ROM), 9 Pages, 2008/05
A sodium cooled fast reactor is designed to attain a high burn-up core in a feasibility study on commercialized fast reactor cycle systems. In high burn-up fuel subassemblies, deformation of fuel pin due to the swelling and thermal bowing may decrease flow rate via change of flow area in the sub-assembly and influence the heat removal capability. A 2.5 times enlarged 7-pin bundle water model was applied to investigate the influence of pin bowing and wrapping wire. The test section consisted of a hexagonal acrylic duct tube and fluorinated resin pins which had the refractive index nearly the same with water and high light transmission rate. This enabled to visualize around the central pin through the outer pins. Velocity distribution was measured by using PIV in sub-channels around the central pin in reference and deformation condition. Velocity distribution around the wrapping wire was measured and the wire influenced to the velocity and RMS in the wide region near the pin surface.
Kobayashi, Jun; Sato, Hiroyuki; Hayashi, Kenji; Kamide, Hideki
JAEA-Technology 2008-026, 30 Pages, 2008/03
JAEA-Technology-2008-026.pdf:8.59MB
High burn-up core in a sodium cooled fast reactor may result in fuel pin deformation due to irradiation, e.g., swelling and bowing. Such deformation will influence thermal hydraulics in a core fuel subassembly, i.e., the highest temperature. Thus it is significant to estimate pin deformation effects. A water experiment was carried out to measure velocity field in a deformed pin bundle by using transparent resin and refractive index matching technique. In the experiment, the deformed pin geometry should be measured as a boundary condition. Here an optical measurement technique of pin bundle geometry was developed. An image of a horizontal cross section of the pin bundle was captured by a camera set on an inclined line to the pin bundle axis. This image was converted to a straight image to the pin bundle axis by taking accounts of refraction at the wall. The positions of deformed pins were well estimated by this method.
Hirano, Koichiro; Ao, Hiroyuki; Morishita, Takatoshi; Asano, Hiroyuki; Hori, Toshihiko; Yamazaki, Masayoshi; Kobayashi, Tetsuya; Kubota, Chikashi*; Yamazaki, Yoshishige
Proceedings of 5th Annual Meeting of Particle Accelerator Society of Japan and 33rd Linear Accelerator Meeting in Japan (CD-ROM), p.497 - 499, 2008/00
An ACS (Annular Coupled Structure) module has been developing for the 190-MeV to 400-MeV part of the J-PARC Linac. We have conducted the high power test of the first ACS module which consists of two accelerating tanks with 17 cells and a bridge tank with 9 cells. This paper describes results of the high power RF tests. The module achieved an average axial accelerating gradient of E0 = 4.5 MV/m at 1.8 MW RF input power, 0.6 ms pulse width, and 50 Hz repetition rate.
