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Journal Articles

Comparison between simulations using the PHITS code and activated material analysis

Sukegawa, Atsuhiko; Okuno, Koichi*

IEEE Transactions on Plasma Science, 43(11), p.3916 - 3920, 2015/11

 Times Cited Count:0 Percentile:100(Physics, Fluids & Plasmas)

In the present study a comparison between simulations using the PHITS code and activated material analysis of JT-60U has been performed. Neutron transport have been simulated using the Monte Carlo methods PHITS to determine the neutron fluency at the irradiation position. The Activated analysis has been complemented by the foil-activation technique. The preliminary result of these PHITS simulations has been confirmed by comparing the reaction rates of gold, cobalt, and nickel foils activation. The simulation results by PHITS consisted with the measured reaction rate of each foils near the device.

Journal Articles

Estimation of the lifetime of resin insulators against baking temperature for JT-60SA in-vessel coils

Sukegawa, Atsuhiko; Murakami, Haruyuki; Matsunaga, Go; Sakurai, Shinji; Takechi, Manabu; Yoshida, Kiyoshi; Ikeda, Yoshitaka

Fusion Engineering and Design, 98-99, p.2076 - 2079, 2015/10

 Times Cited Count:1 Percentile:86.4(Nuclear Science & Technology)

The JT-60SA project is a EU - JA satellite tokamak under Broader Approach in support of the ITER project. In-vessel coils are designed and assembled by JA. The resin-insulator is required to have a heat resistance against the baking temperature of vacuum vessel of $$sim$$200$$^{circ}$$C (40000 hour). Thus the assessment of the heat load is fundamental for the design of the coils. However, the estimation of the lifetime of resin-insulator under the high-temperature region has not been examined. In the present study, the estimation of the lifetime of seven candidate resin-insulators such as epoxy resin and cyanate-ester resin under the $$sim$$220$$^{circ}$$C temperature region have been performed for the current coils design. Weight reduction of the seven candidate insulators was measured at different heating times under 180$$^{circ}$$C, 200$$^{circ}$$C and 220$$^{circ}$$C environment using three thermostatic ovens, respectively. The reduction of the insulators has been used as input for Weibull-analysis towards Arrhenius-plot. Lifetime of the resins has been estimated for the first time at the high temperature region by the plot. Lifetime of the resin-insulators have been evaluated and discussed as well as the available temperature of the in-vessel coils.

Journal Articles

Activation, Radiation shielding materials

Sukegawa, Atsuhiko; Iida, Hiromasa*; Itoga, Toshio*; Okumura, Keisuke; Kai, Tetsuya; Konno, Chikara; Nakashima, Hiroshi; Nakamura, Takashi*; Ban, Shuichi*; Yashima, Hiroshi*; et al.

Hoshasen Shahei Handobukku; Kisohen, p.299 - 356, 2015/03

no abstracts in English

Journal Articles

Dismantlement of large fusion experimental device JT-60U

Ikeda, Yoshitaka; Okano, Fuminori; Sakasai, Akira; Hanada, Masaya; Akino, Noboru; Ichige, Hisashi; Kaminaga, Atsushi; Kiyono, Kimihiro; Kubo, Hirotaka; Kobayashi, Kazuhiro; et al.

Nippon Genshiryoku Gakkai Wabun Rombunshi, 13(4), p.167 - 178, 2014/12

The JT-60U torus was disassembled so as to newly install the superconducting tokamak JT-60SA torus. The JT-60U used the deuterium for 18 years, so the disassembly project of the JT-60U was the first disassembly experience of a fusion device with radioactivation in Japan. All disassembly components were stored with recording the data such as dose rate, weight and kind of material, so as to apply the clearance level regulation in future. The lessons learned from the disassembly project indicated that the cutting technologies and storage management of disassembly components were the key factors to conduct the disassembly project in an efficient way. After completing the disassembly project, efforts have been made to analyze the data for characterizing disassembly activities, so as to contribute the estimation of manpower needs and the radioactivation of the disassembly components on other fusion devices.

Journal Articles

Evaluation of two-stage system for neutron measurement aiming at increase in count rate at Japan Atomic Energy Agency - Fusion Neutronics Source

Shinohara, Koji; Ishii, Keiichi*; Ochiai, Kentaro; Baba, Mamoru*; Sukegawa, Atsuhiko; Sasao, Mamiko*; Kitajima, Sumio*

Review of Scientific Instruments, 85(11), p.11E823_1 - 11E823_4, 2014/11

 Times Cited Count:0 Percentile:100(Instruments & Instrumentation)

Journal Articles

Safe disassembly and storage of radioactive components of JT-60U torus

Ikeda, Yoshitaka; Okano, Fuminori; Hanada, Masaya; Sakasai, Akira; Kubo, Hirotaka; Akino, Noboru; Chiba, Shinichi; Ichige, Hisashi; Kaminaga, Atsushi; Kiyono, Kimihiro; et al.

Fusion Engineering and Design, 89(9-10), p.2018 - 2023, 2014/10

 Times Cited Count:2 Percentile:77.88(Nuclear Science & Technology)

Disassembly of the JT-60U torus was started in 2009 after 18-years D$$_{2}$$ operations, and was completed in October 2012. The JT-60U torus was featured by the complicated and welded structure against the strong electromagnetic force, and by the radioactivation due to D-D reactions. Since this work is the first experience of disassembling a large radioactive fusion device in Japan, careful disassembly activities have been made. About 13,000 components cut into pieces with measuring the dose rates were removed from the torus hall and stored safely in storage facilities by using a total wokers of 41,000 person-days during 3 years. The total weight of the disassembly components reached up to 5,400 tons. Most of the disassembly components will be treated as non-radioactive ones after the clearance verification under the Japanese regulation in future. The assembly of JT-60SA has started in January 2013 after this disassembly of JT-60U torus.

JAEA Reports

Investigation for application and improvement of the PHITS code to nuclear fusion facilities (Contract research)

Sukegawa, Atsuhiko; Niita, Koji*

JAEA-Data/Code 2014-013, 61 Pages, 2014/08

JAEA-Data-Code-2014-013.pdf:34.06MB

The accuracy and efficiency of the PHITS code has been investigated towards the application to the fusion facilities by making comparison between PHITS and MCNP calculation for a simplified cylindrical model, for a 3D detailed model of tokamak fusion device, and for experimental assembly models of accelerator for fusion facilities. It was clarified that the results of neutron and photon spectrum obtained by the PHITS code agree with those of MCNP within statistical errors as far as they use the same cross section library, the same model and the same neutron source for the calculation. Moreover, the results of both codes are consistent each other within statistical errors for the case with the same weight window method as a variance reduction technique.

Journal Articles

Flexible heat-resistant neutron and $$gamma$$-ray shielding resins

Sukegawa, Atsuhiko; Anayama, Yoshimasa*

Progress in Nuclear Science and Technology (Internet), 4, p.627 - 630, 2014/04

Flexible heat-resistant neutron and $$gamma$$-ray shielding resins have been developed, which consists of polymer resin with boron powder or FeW powder. The resins were manufactured by a newly agitation technique of only by chemical reaction to Low-Cost radiation shielding resin. The neutron resin will be applied around ports of a vacuum vessel of superconducting tokamak device as an additional shielding material and decreased in an effect on neutron streaming of the device. The $$gamma$$-ray resin will be suitable for a collimator to plasma diagnostics.

JAEA Reports

Storage management of disassembled and radioactive components of JT-60 tokamak device; Storage of radioactive components by containers

Nishiyama, Tomokazu; Miyo, Yasuhiko; Okano, Fuminori; Sasajima, Tadayuki; Ichige, Hisashi; Kaminaga, Atsushi; Miya, Naoyuki; Sukegawa, Atsuhiko; Ikeda, Yoshitaka; Sakasai, Akira

JAEA-Technology 2014-006, 30 Pages, 2014/03

JAEA-Technology-2014-006.pdf:4.87MB

JT-60 tokamak device and the peripheral equipment were disassembled so as to be upgraded to the superconducting tokamak JT-60SA. The disassembled components were stored into storage and airtight containers at the radioactive control area. The total weight and the total number of those components are about 1,100 tons and about 11,500 except for large components. Radiation measurements and records of the radioactive components were required one by one under the law of Act on Prevention of Radiation Disease Due to Radioisotopes, etc. for the control of transport and storage from the radioactive control area to the other area. The storage management of the radioactive components was implemented by establishing the work procedure and the component management system by barcode tags. The radioactive components as many as 11,500 were surely and effectively stored under the law. The report gives the outline of the storage of JT-60 radioactive components by the storage containers.

Journal Articles

Radiation control in the JT-60 facilities; Radiation measurement for Tokamak fusion device operation under neutron environment

Sukegawa, Atsuhiko

Purazuma, Kaku Yugo Gakkai-Shi, 89(11), p.805 - 809, 2013/11

no abstracts in English

Journal Articles

Flexible heat resistant neutron shielding resin

Sukegawa, Atsuhiko; Anayama, Yoshimasa*; Okuno, Koichi*; Sakurai, Shinji; Kaminaga, Atsushi

Journal of Nuclear Materials, 417(1-3), p.850 - 853, 2011/10

 Times Cited Count:16 Percentile:18.15(Materials Science, Multidisciplinary)

A flexible heat resistant neutron shielding material has been developed, which consists of polymer resin with 1 weight % boron. The neutron shielding performance of the developed resin, examined by the $$^{252}$$Cf neutron source is almost the same as that of the polyethylene. The outgas of H$$_{2}$$, H$$_{2}$$O, CO and CO$$_{2}$$ from the resin have been measured at 250 $$^{circ}$$C environment. The resin will be applied around the port of the vacuum vessel as an additional shielding material and prevented the effects on the neutron streaming of the superconducting tokamak device such as JT-60SA.

Journal Articles

Management of radioactive materials for the disassembly of JT-60U fusion tokamak device

Sukegawa, Atsuhiko; Miya, Naoyuki; Oikawa, Akira

Proceedings of 19th International Conference on Nuclear Engineering (ICONE-19) (CD-ROM), 8 Pages, 2011/10

The radioactivities on the materials of JT-60U fusion device, which decommissioning is underway toward the upgraded superconducting tokamak machine, have been evaluated by calculation and measurements on the specimens of the structure materials and the components. In the induced activities on those materials, the highest activation on the material was stainless steel. The essential nuclide was $$^{60}$$Co in the stainless steels. The stainless steel 316 of about 35 tons constitutes the base of interiorities as a first wall on the vacuum vessel in JT-60U. For the management of radioactive materials, the evaluation for the steels with the activated nuclides is important. The activated structure materials are kept in the controlled area in the JT-60 facilities, according to the criteria for handling activated materials by the defined domestic government.

Journal Articles

Conceptual radiation shielding design of superconducting tokamak fusion device by PHITS

Sukegawa, Atsuhiko; Kawasaki, Hiromitsu*; Okuno, Koichi*

Progress in Nuclear Science and Technology (Internet), 2, p.375 - 381, 2011/10

A complete 3D neutrons and photons transport analysis by Monte Carlo transport code system PHITS (Particle and Heavy Ion Transport code System) have been performed for superconducting tokamak fusion device such as JT-60 Super Advanced (JT-60SA). It is possible to make use of PHITS in the port streaming analysis around the devices for the tokamak fusion device, the duct streaming analysis in the building where the device is installed, and the sky shine analysis for the site boundary. The neutron transport analysis by PHITS makes it clear that the shielding performance of the superconducting tokamak fusion device with the cryostat is improved by the graphical results. From the standpoint of the port streaming and the duct streaming, it is necessary to calculate by 3D codes for the neutronics analysis of superconducting tokamak fusion device.

Journal Articles

Applicability of the PHITS code to a tokamak fusion device

Sukegawa, Atsuhiko; Okuno, Koichi*; Kawasaki, Hiromitsu*

RIST News, (51), p.20 - 29, 2011/07

no abstracts in English

Journal Articles

Development of flexible neutron-shielding resin as an additional shielding material

Sukegawa, Atsuhiko; Anayama, Yoshimasa*; Onishi, Seiki; Sakurai, Shinji; Kaminaga, Atsushi; Okuno, Koichi*

Journal of Nuclear Science and Technology, 48(4), p.585 - 590, 2011/04

Soft-type neutron shielding resin has been developed by improving an existing hard-type neutron shielding material by the epoxy-based resin as the additional shielding material. A flexible heat resistant neutron shielding material has been developed, which consists of newly polymer-based resin with boron. The neutron shielding performance of the developed flexible heat resistant resin by the $$^{252}$$Cf neutron source is almost the same as that of the polyethylene. The outgas of H, H$$_{2}$$, NH$$_{4}$$, H$$_{2}$$O, CO, O$$_{2}$$, C$$_{4}$$H$$_{10}$$ and CO$$_{2}$$ from the developed resin have been measured at high temperature environment (250$$^{circ}$$C) by thermal desorption spectroscopy methods. The soft-type resin and the newly developed heat resistant resin will be applied to prevent the effects of the neutron streaming and to control the movement of vibrated pipe as the seal material around the plumbing in the future fast reactor and the innovative fission reactor.

Journal Articles

Neutronic analysis of fusion tokamak devices by PHITS

Sukegawa, Atsuhiko; Takiyoshi, Koji*; Amano, Toshio*; Kawasaki, Hiromitsu*; Okuno, Koichi*

Progress in Nuclear Science and Technology (Internet), 1, p.36 - 39, 2011/02

A complete 3D radiation shielding analysis by PHITS has been performed for the JT-60U and JT-60 superconducting tokamak device (JT-60SA) in the present study. The PHITS has been developed for high energy particles physics in Japan. The neutron and photon transport analysis less than 20 MeV with the general cross section library is the same algorism of MCNP-4C code. The monoenergetic neutron (E$$_{rm n}$$ = 2.45 MeV) of the DD fusion devices are used for the neutron source in the analysis. The neutron source distribution are available a toroidally symmetric source for the analysis. The toroidal source has a poloidal distribution, so that a source routine in the PHITS has been replaced a newly developed source routine. The visual nuclear responses such as the neutron flux distribution, the photon flux distribution, the nuclear heating of the coils and the dose rate around the devices has been calculated by the PHITS for the fusion tokamak devices. Initial results by the PHITS have been demonstrated.

Journal Articles

High-heat-resistant neutron shielding resin

Sukegawa, Atsuhiko; Okuno, Koichi*; Sakurai, Shinji

Nuclear Technology, 168(2), p.553 - 558, 2009/11

 Times Cited Count:2 Percentile:80.2(Nuclear Science & Technology)

The resin as a neutron shielding material with flexibility in shape and lightness is expected to be set up near the fusion tokamak devices and as the collimator of the diagnostics. KRAFTON-HB4 is epoxy-based resin that contains boron. It has been developed for future FBR shielding materials. The heat resistant temperature is $$<$$ 150$$^{circ}$$C. EPONITE is neutron shielding material based on Colemanite and epoxy-based resin that contains boric acid. It has been developed for a PET shielding materials. The heat resistant temperature is $$<$$ 200$$^{circ}$$C. The boron-loaded resin with the heat resistance applicable to 300$$^{circ}$$C has been newly developed. The developed resin is made of phenol-based resin that has improved heatproof. The weight percent of hydrogen and boron are the developed resin (H: 1.94, B: 6.1), KRAFTON-HB4 (H: 10.5, B: 2.0), and EPONITE (H: 3.8, B: 30.4). Neutron attenuation experiments of these resins were carried out using $$^{252}$$Cf neutron source. In the experiments, neutron dose attenuation were measured by a REM counter. The tenth layer of Polyethylene, the developed resin, KRAFTON-HB4 and EPONITE are 0.14 m, 0.14 m, 0.15 m and 0.09 m, respectively.

Journal Articles

Status of JT-60SA tokamak under the EU-JA broader approach agreement

Matsukawa, Makoto; Kikuchi, Mitsuru; Fujii, Tsuneyuki; Fujita, Takaaki; Hayashi, Takao; Higashijima, Satoru; Hosogane, Nobuyuki; Ikeda, Yoshitaka; Ide, Shunsuke; Ishida, Shinichi; et al.

Fusion Engineering and Design, 83(7-9), p.795 - 803, 2008/12

 Times Cited Count:15 Percentile:25.93(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Conceptual design of JT-60SA cryostat

Shibama, Yusuke; Sakurai, Shinji; Masaki, Kei; Sukegawa, Atsuhiko; Kaminaga, Atsushi; Sakasai, Akira; Matsukawa, Makoto

Fusion Engineering and Design, 83(10-12), p.1605 - 1609, 2008/12

 Times Cited Count:5 Percentile:60.95(Nuclear Science & Technology)

The conceptual design of JT-60SA cryostat is summarized. JT-60SA is designed to be a fully superconducting device and assumed deuterium operation, therefore a cryostat is introduced to secure three functions, which are thermal insulation for entire superconducting magnets, bio-shielding, and gravity support for the entire tokamak device. The cryostat is required to cover up the tokamak devices, which are 15 m of total height and 7 m of radius, and to support the total devices weight of 2550 tons. The cryostat consists of vessel body, gravity support and auxiliary facilities, such as 80 K thermal shield and exhaust system. Each of them is outlined with JT-60SA design conditions, and the operational condition of auxiliary system is clarified, especially, capacity of the exhaust system, which is related to the 80 K thermal shield design.

Journal Articles

Absolute calibration of microfission chamber in JT-60U

Hayashi, Takao; Nishitani, Takeo; Sukegawa, Atsuhiko; Ishikawa, Masao; Shinohara, Koji

Review of Scientific Instruments, 79(10), p.10E506_1 - 10E506_3, 2008/10

 Times Cited Count:4 Percentile:73.94(Instruments & Instrumentation)

In D-D or D-T operation fusion devices, the fusion neutron yield is the most important parameter to estimate the fusion power. We have conducted calibrations of a microfission chamber, 14 mm in diameter and 200 mm in length, by both Cf-252 neutron source and real plasmas in JT-60U. The detector employs both pulse counting and Campbelling modes in the electronics to cover 10$$^{7}$$ dynamic range of the neutron source strength. The efficiencies were influenced by the various components. The point efficiencies can be integrated and averaged with angle to provide toroidal line efficiencies. The line efficiencies of microfission chamber and the nearest neutron monitor of U-235 fission chamber was 5.38 $$times$$ 10$$^{-9}$$ and 1.77 $$times$$ 10$$^{-8}$$, respectively. Then the calibration using real plasma was also performed. The detection efficiency in Campbelling mode was about three-tenth of the nearest neutron monitor, which is consistent with the calibration result using Cf-252 neutron source.

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