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Journal Articles

New design of vacuum chambers for radiation shield installation at beam injection area of J-PARC RCS

Kamiya, Junichiro; Kotoku, Hirofumi; Shobuda, Yoshihiro; Takayanagi, Tomohiro; Yamamoto, Kazami; Yanagibashi, Toru*; Horino, Koki*; Miki, Nobuharu*

Journal of Physics; Conference Series, 1350, p.012172_1 - 012172_7, 2019/12

 Times Cited Count:0 Percentile:0.07

One of the issues in the J-PARC 3 GeV rapid cycling synchrotron is the high residual radiation dose around the beam injection point. A radiation shield is necessary to reduce radiation exposure of workers when maintenance is performed there. A space to install the radiation shield should be secured by newly designing a structure of the vacuum chamber at the injection point and the alumina ceramics beam pipes for the shift bump magnets. To make the space for the shield, the chamber is lengthened along the beam line and the cross-sectional shape is changed from circle to rectangle. The displacement and inner stress of the vacuum chamber due to atmospheric pressure were evaluated to be enough small by the calculation. For the ceramics beam pipe's rf-shield, the damping resistor was effective to reduce the induced modulation voltages by the pulsed magnetic field.

Journal Articles

Activation in injection area of J-PARC 3-GeV rapid cycling synchrotron and its countermeasures

Yamamoto, Kazami; Yamakawa, Emi*; Takayanagi, Tomohiro; Miki, Nobuharu*; Kamiya, Junichiro; Saha, P. K.; Yoshimoto, Masahiro; Yanagibashi, Toru*; Horino, Koki*; Nakanoya, Takamitsu; et al.

ANS RPSD 2018; 20th Topical Meeting of the Radiation Protection and Shielding Division of ANS (CD-ROM), 9 Pages, 2018/08

The existing beam power of the J-PARC Rapid Cycling Synchrotron is up to 500 kW, and higher radiation doses are concentrated in the injection area. These activations are caused by the interaction between the foil and the beam. To reduce dose exposure to workers near the injection point, we study a new design of the injection scheme. Experience has shown that eddy currents are generated in the metal flange near the magnet owing to the pulsed magnetic field, and the temperature exceeds 100 degrees C. The shield installed in the new injection system needs to have a layer structure, in which an insulator is inserted between iron shields to reduce the eddy current. From the results of the shielding calculation, even if 1 mm of polyethylene was inserted between two 9-mm-thick SUS 316 plates, which serve as shielding material, the shielding performance was reduced only about 5%, and we confirmed that it would function well.

Journal Articles

Upgrade of vacuum chamber at RCS beam injection area aimed at lower radiation and maintainability increase

Kamiya, Junichiro; Yamamoto, Kazami; Yanagibashi, Toru*; Sato, Atsushi*; Miki, Nobuharu*

Proceedings of 15th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.645 - 648, 2018/08

Surround of the beam injection point in the J-PARC 3 GeV Rapid Cycling Synchrotron is the area where the residual radioactive dose is higher than other areas due to the beam scattering by the charge stripping foil. However, there is very little space to install radiation shields around the vacuum chamber in the beam injection point. Furthermore, the vacuum leak has often occurred due to the heat expansion of the chamber flange due to the induced current by the nearby pulse magnet. To solve such problems for minimizing the radiation exposure of maintenance workers, the vacuum chamber rin the beam injection point was newly designed. The space for the radiation shields was created by lengthening and the changing the cross-sectional shape. The titanium alloy with high mechanical strength was used for the flange material so that the flange was able to be fastened with higher tightening torque.

Journal Articles

New injection system design of the J-PARC rapid cycling synchrotron

Yamamoto, Kazami; Kamiya, Junichiro; Saha, P. K.; Takayanagi, Tomohiro; Yoshimoto, Masahiro; Hotchi, Hideaki; Harada, Hiroyuki; Takeda, Osamu*; Miki, Nobuharu*

Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.374 - 378, 2017/12

The 3-GeV Rapid Cycling Synchrotron (RCS) of Japan Proton Accelerator Research Complex (J-PARC) aims to deliver 1-MW proton beam to the neutron target and Main Ring synchrotron. Present beam power of the Rapid Cycling Synchrotron is up to 500-kW and the higher radiation doses were concentrated in the injection area. These activations were caused by the interaction between the foil and the beam. To reduce the worker dose near the injection point, we have studied a new design of the injection scheme to secure enough space for radiation shielding and bellows. In the new system, two of four injection pulse bump magnets are replaced and we are able to ensure the additional space around the injection foil chamber. So far, new injection system seems not impossible. However, preliminary study result indicated that temperature of the duct and shielding metals would be slightly higher. The eddy current due to the shift bump magnet field generates heat. Thus we have to study details of above effect.

Journal Articles

New injection scheme of J-PARC rapid cycling synchrotron

Yamamoto, Kazami; Kamiya, Junichiro; Saha, P. K.; Takayanagi, Tomohiro; Yoshimoto, Masahiro; Hotchi, Hideaki; Harada, Hiroyuki; Takeda, Osamu*; Miki, Nobuharu*

Proceedings of 8th International Particle Accelerator Conference (IPAC '17) (Internet), p.579 - 581, 2017/05

The 3-GeV Rapid Cycling Synchrotron of Japan Proton Accelerator Research Complex aims to deliver 1-MW proton beam to the neutron target and Main Ring synchrotron. Present beam power of the Rapid Cycling Synchrotron is up to 500-kW and the higher radiation doses were concentrated in the injection area. These activations were caused by the interaction between the foil and the beam. To reduce the worker dose near the injection point, we have studied a new design of the injection scheme to secure enough space for radiation shielding and bellows. In the new system, two of four injection pulse bump magnets are replaced and we are able to ensure the additional space around the injection foil chamber. So far, new injection system seems not impossible. However, preliminary study result indicated that temperature of the duct and shielding metals would be slightly higher. The eddy current due to the shift bump magnet field generates heat. Thus we have to study details of above effect.

Journal Articles

Degassing of kicker magnet by in-situ bake-out method

Kamiya, Junichiro; Ogiwara, Norio; Hikichi, Yusuke; Kinsho, Michikazu; Miki, Nobuharu*; Yanagibashi, Toru*

Proceedings of 6th International Particle Accelerator Conference (IPAC '15) (Internet), p.2911 - 2913, 2015/06

New method of in-situ degassing of the kicker magnet in the beam line has been developed. The heater and heat shielding panels are installed in the vacuum chamber in this method. The heater was designed considering the maintainability. The graphite was selected as the heater and the high melting point metals were used as the reflectors just near the heater. The thermal analysis and the temperature measurement with the designed heater was performed. The ideal temperature distribution for the kicker degassing was obtained. The outgassing of the graphite during rising the temperature was measured. The result showed that the outgassing was extremely suppressed by the first heating. This means the outgassing of the graphite heater was negligible as long as it is used in the beam line without exposure to the air.

Journal Articles

ITER nuclear components, preparing for the construction and R&D results

Ioki, Kimihiro*; Akiba, Masato; Barabaschi, P.*; Barabash, V.*; Chiocchio, S.*; Daenner, W.*; Elio, F.*; Enoeda, Mikio; Ezato, Koichiro; Federici, G.*; et al.

Journal of Nuclear Materials, 329-333(1), p.31 - 38, 2004/08

 Times Cited Count:13 Percentile:66.18(Materials Science, Multidisciplinary)

The preparation of the procurement specifications is being progressed for key components. Progress has been made in the preparation of the procurement specifications for key nuclear components of ITER. Detailed design of the vacuum vessel (VV) and in-vessel components is being performed to consider fabrication methods and non-destructive tests (NDT). R&D activities are being carried out on vacuum vessel UT inspection with waves launched at an angle of 20 or 30 degree, on flow distribution tests of a two-channel model, on fabrication and testing of FW mockups and panels, on the blanket flexible support as a complete system including the housing, on the blanket co-axial pipe connection with guard vacuum for leak detection, and on divertor vertical target prototypes. The results give confidence in the validity of the design and identify possibilities of attractive alternate fabrication methods.

Journal Articles

Design and technology development of solid breeder blanket cooled by supercritical water in Japan

Enoeda, Mikio; Kosaku, Yasuo; Hatano, Toshihisa; Kuroda, Toshimasa*; Miki, Nobuharu*; Homma, Takashi; Akiba, Masato; Konishi, Satoshi; Nakamura, Hirofumi; Kawamura, Yoshinori; et al.

Nuclear Fusion, 43(12), p.1837 - 1844, 2003/12

 Times Cited Count:98 Percentile:94.12(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Examinations on plasma behaviour during disruptions on existing tokamaks and extrapolation to ITER

Sugihara, Masayoshi; Lukash, V.*; Kawano, Yasunori; Yoshino, Ryuji; Gribov, Y.*; Khayrutdinov, R.*; Miki, Nobuharu*; Omori, Junji*; Shimada, Michiya

Proceedings of 30th EPS Conference on Controlled Fusion and Plasma Physics (CD-ROM), 4 Pages, 2003/07

We examine plasma behaviours during plasma disruptions in detail in JT-60U and other tokamaks to derive appropriate physics guidelines for the behaviours. Their interpretations and their extrapolations to ITER are incorporated into the DINA code, which solves plasma transport and 2D free boundary plasma equilibrium simultaneously with circuit equations for the vacuum vessel and the PF coils. Sensitivity of the plasma behaviours and their impact on the EM force during disruptions due to the range of variation and uncertainty of the experimental data are examined.

Journal Articles

Wave form of current quench during disruptions in Tokamaks

Sugihara, Masayoshi; Lukash, V.*; Kawano, Yasunori; Yoshino, Ryuji; Gribov, Y.*; Khayrutdinov, R.*; Miki, Nobuharu*; Omori, Junji*; Shimada, Michiya

Purazuma, Kaku Yugo Gakkai-Shi, 79(7), p.706 - 712, 2003/07

The time dependence of the current decay during the current quench phase of disruptions, which can significantly influence the electro-magnetic force on the in-vessel components due to the induced eddy currents, is investigated using data obtained in JT-60U experiments in order to derive a relevant physics guideline for the predictive simulations of disruptions in ITER. It is shown that an exponential decay can fit the time dependence of current quench for discharges with large quench rate (fast current quench). On the other hand, for discharges with smaller quench rate (slow current quench), a linear decay can fit the time dependence of current quench better than exponential.

JAEA Reports

Nuclear, thermo-mechanical and tritium release analysis of ITER breeding blanket

Kosaku, Yasuo; Kuroda, Toshimasa*; Enoeda, Mikio; Hatano, Toshihisa; Sato, Satoshi; Sato, Shinichi*; Osaki, Toshio*; Miki, Nobuharu*; Akiba, Masato

JAERI-Tech 2003-058, 69 Pages, 2003/06

JAERI-Tech-2003-058.pdf:5.86MB

The design of the breeding blanket in ITER applies pebble bed breeder in tube (BIT) surrounded by multiplier pebble bed. It is assumed to use the same module support mechanism and coolant manifolds and coolant system as the shielding blankets. This work focuses on the verification of the design of the breeding blanket, from the viewpoints which is especially unique to the pebble bed type breeding blanket, such as, tritium breeding performance, tritium inventory and release behavior and thermo-mechanical performance of the ITER breeding blanket.

JAEA Reports

Japanese contribution to the design of primary module of shielding blanket in ITER-FEAT

Kuroda, Toshimasa*; Hatano, Toshihisa; Miki, Nobuharu*; Hiroki, Seiji; Enoeda, Mikio; Omori, Junji*; Sato, Shinichi*; Akiba, Masato

JAERI-Tech 2002-098, 136 Pages, 2003/02

JAERI-Tech-2002-098.pdf:24.33MB

no abstracts in English

Journal Articles

Progress on design and R&D of ITER FW/blanket

Ioki, Kimihiro*; Akiba, Masato; Cardella, A.*; Daenner, W.*; Elio, F.*; Enoeda, Mikio; Lorenzetto, P.*; Miki, Nobuharu*; Osaki, Toshio*; Rozov, V.*; et al.

Fusion Engineering and Design, 61-62, p.399 - 405, 2002/11

 Times Cited Count:11 Percentile:60.05(Nuclear Science & Technology)

We report progress on the ITER-FEAT Blanket design and R&D during 2001-2002. Four major sub-components (FW, shield body, flexible support and electrical connection) have been highlighted. Regarding the FW, design on a separate FW panel concept has progressed, and heat load tests on a small-scale mock-up have been successfully performed with 0.7 MW/m$$^{2}$$, 13000 cycles. Full-scale separate FW panels (dimensions: 0.9$$times$$0.25$$times$$0.07 m) have been fabricated by HIPing and brazing. Regarding the shield body, a radial flow cooling design has been developed, and full-scale partial mock-ups have been fabricated by using water-jet cutting. A separate FW panel was assembled with one the shield body mock-ups. Regarding the flexible support, mill-annealed Ti (easier fabricability) alloy has been selected, and the remote assembly has been considered in the design. In mechanical tests, the requires buckling strength and mechanical fatigue characteristics have been confirmed. Regarding the electrical connection, one-body structure design without welding joints has been developed. Mechanical fatigue tests in the 3 directions, have been carried out, and thermal fatigue tests and electrical tests in a solenoidal magnetic field have been performed. Feasibility of the design has been confirmed. Through progress on design and R&D of the blanket, cost reduction has been achieved, and feasibility of design and fabricability of the components have been confirmed.

JAEA Reports

Fabrication of the full scale separable first wall of ITER shielding blanket

Kosaku, Yasuo; Kuroda, Toshimasa*; Hatano, Toshihisa; Enoeda, Mikio; Miki, Nobuharu*; Akiba, Masato

JAERI-Tech 2002-078, 58 Pages, 2002/10

JAERI-Tech-2002-078.pdf:19.38MB

Shielding blanket for ITER-FEAT applies the unique first wall structure which is separable from the shield block for the purpose of radio-active waste reduction in the maintenance work and cost reduction in fabrication process. Also, it is required to have various types of slots in both of the first wall and the shield block, to reduce the eddy current for reduction of electro-magnetic force in disruption events. This report summarizes the achievement of such R&Ds as, slit grooving techniques for Be/DSCu/SS first wall panel and SS shield block, demonstration of Be armor joining to the real scal first wall panel, and demonstration of full scale first wall panel.

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