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Journal Articles

Development of magnetic sensors for JT-60SA

Takechi, Manabu; Matsunaga, Go; Sakurai, Shinji; Sasajima, Tadayuki; Yagyu, Junichi; Hoshi, Ryo*; Kawamata, Yoichi; Kurihara, Kenichi; JT-60SA Team; Nishikawa, T.*; et al.

Fusion Engineering and Design, 96-97, p.985 - 988, 2015/10

 Times Cited Count:5 Percentile:45.73(Nuclear Science & Technology)

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

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:77.62(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

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.

JAEA Reports

Disassembly of JT-60 tokamak device and ancillary facilities for JT-60 tokamak

Okano, Fuminori; Ichige, Hisashi; Miyo, Yasuhiko; Kaminaga, Atsushi; Sasajima, Tadayuki; Nishiyama, Tomokazu; Yagyu, Junichi; Ishige, Yoichi; Suzuki, Hiroaki; Komuro, Kenichi; et al.

JAEA-Technology 2014-003, 125 Pages, 2014/03

JAEA-Technology-2014-003.pdf:13.32MB

The disassembly of JT-60 tokamak device and its peripheral equipments, where the total weight was about 5400 tons, started in 2009 and accomplished in October 2012. This disassembly was required process for JT-60SA project, which is the Satellite Tokamak project under Japan-EU international corroboration to modify the JT-60 to the superconducting tokamak. This work was the first experience of disassembling a large radioactive fusion device based on Radiation Hazard Prevention Act in Japan. The cutting was one of the main problems in this disassembly, such as to cut the wielded parts together with toroidal field coils, and to cut the vacuum vessel into two. After solving these problems, the disassembly completed without disaster and accident. This report presents the outline of the JT-60 disassembly, especially tokamak device and ancillary facilities for tokamak device.

JAEA Reports

Disassembly of JT-60 tokamak device

Okano, Fuminori; Ikeda, Yoshitaka; Sakasai, Akira; Hanada, Masaya; Ichige, Hisashi; Miyo, Yasuhiko; Kaminaga, Atsushi; Sasajima, Tadayuki; Nishiyama, Tomokazu; Yagyu, Junichi; et al.

JAEA-Technology 2013-031, 42 Pages, 2013/11

JAEA-Technology-2013-031.pdf:18.1MB

The disassembly of JT-60 tokamak device and its peripheral equipments, where the total weight was about 6200 tons, started in 2009 and accomplished in October 2012. This disassembly was required process for JT-60SA project, which is the Satellite Tokamak project under Japan-EU international corroboration to modify the JT-60 to the superconducting tokamak. This work was the first experience of disassembling a large radioactive fusion device based on Radiation Hazard Prevention Act in Japan. The cutting was one of the main problems in this disassembly, such as to cut the wielded parts together with toroidal field coils, and to cut the vacuum vessel into two. After solving these problems, the disassembly completed without disaster and accident. This report presents the outline of the JT-60 disassembly, especially tokamak device.

Journal Articles

Report of detaching of internal tile according to dismantlement of JT-60

Yagyu, Junichi; Miyo, Yasuhiko; Sasajima, Tadayuki; Sakasai, Akira; Shibanuma, Kiyoshi

Heisei-22-Nendo Kumamoto Daigaku Sogo Gijutsu Kenkyukai Hokokushu (CD-ROM), 4 Pages, 2011/03

no abstracts in English

Journal Articles

Storage and safety management of radioactive components for disassembly of JT-60 tokamak device

Nishiyama, Tomokazu; Okano, Fuminori; Miyo, Yasuhiko; Kubo, Hirotaka; Miya, Naoyuki; Oikawa, Akira; Sasajima, Tadayuki; Sakasai, Akira

Heisei-22-Nendo Kumamoto Daigaku Sogo Gijutsu Kenkyukai Hokokushu (CD-ROM), 5 Pages, 2011/03

no abstracts in English

Journal Articles

Fuelling characteristics of supersonic molecular beam injection in JT-60U

Takenaga, Hidenobu; Miyo, Yasuhiko; Bucalossi, J.*; Marty, V.*; Urano, Hajime; Asakura, Nobuyuki; Nishiyama, Tomokazu; Sasajima, Tadayuki; Masaki, Kei; Kaminaga, Atsushi

Nuclear Fusion, 50(11), p.115003_1 - 115003_10, 2010/11

 Times Cited Count:15 Percentile:42.34(Physics, Fluids & Plasmas)

The supersonic molecular beam injection (SMBI) was successfully operated in JT-60U. Frequent density jumps were clearly observed in the main plasma against the SMBI pulses with the background gas pressure ($$P$$$$_{rm BK}$$) of 2-6 bar. Fuelling efficiency exhibited weak dependence on $$P$$$$_{rm BK}$$ and the injection direction (high- and low-field-side injections). The amount of the fuelling necessary for achieving the same density level is much smaller for the SMBI than for the gas-puffing. It is comparable for the SMBI and the pellet injection even with shallower penetration of the SMBI as discussed below. The SMBI ionization area was estimated based on emission measured using the fast TV camera with a time resolution of 0.167 ms. The estimations indicated similar penetration position for $$P$$$$_{rm BK}$$ = 6 and 2 bar, although the ionization area was larger for 6 bar. This result supports the weak $$P$$$$_{rm BK}$$ dependence of the fuelling efficiency. The front of the ionization area moved between first and second frames of the fast TV camera and it reached just inside the separatrix in the second frame. The ionization area was significantly expanded from the expected SMB size and the expansion was also enhanced between two frames. These relatively slow changes between two frames suggest that interaction between SMB and plasma significantly influences the fuelling characteristics.

Journal Articles

The Characteristics of the internal transport barrier under reactor relevant conditions in JT-60U weak shear plasmas

Takenaga, Hidenobu; Oyama, Naoyuki; Urano, Hajime; Sakamoto, Yoshiteru; Asakura, Nobuyuki; Kamiya, Kensaku; Miyo, Yasuhiko; Nishiyama, Tomokazu; Sasajima, Tadayuki; Masaki, Kei; et al.

Nuclear Fusion, 49(7), p.075012_1 - 075012_11, 2009/07

 Times Cited Count:8 Percentile:65.01(Physics, Fluids & Plasmas)

Characteristics of internal transport barrier (ITB) have been investigated under reactor relevant condition with edge fuelling and electron heating in JT-60U weak shear plasmas. High confinement was sustained at high density with edge fuelling by shallow pellet injection or supersonic molecular beam injection (SMBI). The ion temperature (T$$_{i}$$) in the central region inside the ITB decreased due to cold pulse propagation even with edge fuelling. By optimizing the injection frequency and the penetration depth, the decreased central T$$_{i}$$ was recovered and good ITB was sustained with enhanced pedestal pressure. The T$$_{i}$$-ITB also degraded significantly with electron cyclotron heating (ECH), when stiffness feature was strong in the electron temperature (T$$_{e}$$) profile. The ion thermal diffusivity in the ITB region increased with the electron thermal diffusivity, indicating existence of clear relation between ion and electron thermal transport. On the other hand, T$$_{i}$$-ITB unchanged or even grew, when stiffness feature was weak in the T$$_{e}$$ profile. Density fluctuation level at ITB seemed to be unchanged during ECH, however, correlation length became longer in the T$$_{i}$$-ITB degradation case and shorter in the T$$_{i}$$-ITB unchanging case.

Journal Articles

Characteristics of internal transport barrier under reactor relevant condition in JT-60U weak shear plasmas

Takenaga, Hidenobu; Oyama, Naoyuki; Urano, Hajime; Sakamoto, Yoshiteru; Kamiya, Kensaku; Miyo, Yasuhiko; Nishiyama, Tomokazu; Sasajima, Tadayuki; Masaki, Kei; Kaminaga, Atsushi; et al.

Proceedings of 22nd IAEA Fusion Energy Conference (FEC 2008) (CD-ROM), 8 Pages, 2008/10

Characteristics of internal transport barrier (ITB) have been investigated under reactor relevant condition with edge fuelling and electron heating in JT-60U weak shear plasmas. High confinement was sustained at high density with edge fuelling by shallow pellet injection or supersonic molecular beam injection (SMBI). The ion temperature ($$T_{i}$$) in the central region decreased even with edge fuelling. The $${it T}_{i}$$ decrease with edge fuelling was larger inside the ITB than that outside the ITB, which can be described by cold pulse propagation using the ion thermal diffusivity ($$chi_{i}$$) estimated from power balance analysis in the SMBI case. By optimizing the injection frequency and the penetration depth, the decreased $$T_{i}$$ was recovered and good ITB was sustained with enhanced pedestal pressure. The $$T_{i}$$-ITB also degraded significantly when stiffness feature was strong in the electron temperature ($$T_{e}$$) profile against electron cyclotron heating (ECH). The value of $$chi_{i}$$ in the ITB region increased with the electron thermal diffusivity ($${it chi}_{e}$$), indicating existence of clear relation between ion and electron thermal transport. On the other hand, $$T_{i}$$-ITB unchanged or even grew, when stiffness feature was weak in the $$T_{e}$$ profile. Density fluctuation level seemed to be unchanged during ECH, however, correlation length became longer in the $${it T}_{i}$$-ITB degradation case and shorter in the $$T_{i}$$-ITB unchanging case.

Journal Articles

Tokamak machine monitoring and control system for JT-60

Miyo, Yasuhiko; Yagyu, Junichi; Nishiyama, Tomokazu; Honda, Masao; Ichige, Hisashi; Kaminaga, Atsushi; Sasajima, Tadayuki; Arai, Takashi; Sakasai, Akira

Fusion Engineering and Design, 83(2-3), p.337 - 340, 2008/04

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

Development of magnetic probe; Application and result of AT-probes to JT-60U (Joint research)

Yagyu, Junichi; Sasajima, Tadayuki; Miyo, Yasuhiko; Sakakibara, Satoru*; Kawamata, Yoichi

JAEA-Technology 2007-015, 27 Pages, 2007/03

JAEA-Technology-2007-015.pdf:2.94MB

The feedback control of the plasma position and shape based on signals of magnetic probes is performed on JT-60. The fabrication cost of these magnetic probes is very high. Therefore, the cost reduction is required for the use in a next device. On the other hand, the magnetic field measurement in three axial directions with the advanced technology (AT) probes is simultaneously made on LHD of NIFS. The AT-probe has been developed at a low fabrication cost and in compact size and light weight. The possibility of application of the AT-probe in a Tokamak device (JT-60U) has been investigated in collaboration between JAEA and NIFS. We designed and fabricated the casing and interface for the AT-probe, and installed it under the first wall of JT-60U. A comparison of output signals between the installed AT-probe and a existing magnetic probe was made. Tests have been carried out to evaluate the vibration resistance and the radioactive resistance through about two thousand shots with high performance plasmas including one hundred disruption shots in JT-60U. As a result, the AT-probe has a good performance and an enough usable prospect in environment of the Tokamak device.

Journal Articles

Pulsed supersonic gas injection installation for JT-60

Miyo, Yasuhiko; Nishiyama, Tomokazu; Takenaga, Hidenobu; Kaminaga, Atsushi; Sasajima, Tadayuki; Masaki, Kei

Heisei-18-Nendo Nagoya Daigaku Sogo Gijutsu Kenkyukai Sochi Gijutsu Kenkyukai Hokokushu, p.124 - 127, 2007/03

no abstracts in English

Journal Articles

Design and installation of ferritic steel tiles for ripple reduction of toroidal magnetic field in JT-60U

Sasajima, Tadayuki; Masaki, Kei; Sakurai, Shinji; Shibama, Yusuke; Hayashi, Takao; Suzuki, Yutaka; Takahashi, Ryukichi

Heisei-18-Nendo Nagoya Daigaku Sogo Gijutsu Kenkyukai Sochi Gijutsu Kenkyukai Hokokushu, p.148 - 151, 2007/03

no abstracts in English

Journal Articles

Fabrication of 8Cr-2W ferritic steel tile for reduction in toroidal magnetic field ripple on JT-60U

Kudo, Yusuke; Sawai, Tomotsugu; Sakurai, Shinji; Masaki, Kei; Suzuki, Yutaka; Sasajima, Tadayuki; Hayashi, Takao; Takahashi, Ryukichi*; Honda, Masao; Jitsukawa, Shiro; et al.

Journal of the Korean Physical Society, 49(96), p.S297 - S301, 2006/12

Installation of ferritic steel tiles was proposed in JT-60U to reduce the toroidal magnetic field ripple and to improve the fast ion loss, which degrades heating efficiency and increases heat load on plasma facing component under large volume plasma operations. We selected a 8Cr-2W-0.2V ferritic steel with the cost-effectiveness, in which concentration limits of activation elements in F82H were relaxed because of the less number of neutron generations from deuterium operations on JT-60U. The fabricated ferritic steel has clear tempered martensitic microstructure, and sufficient magnetic and mechanical properties. The saturated magnetization was estimated to 1.7 Tesla at 573 K, lower than expected, but effectiveness in JT-60U was confirmed by numerical analyses. To research the effect of material conditions, such as microstructure and heat treatment, on saturated magnetization of the ferritic steel based on 8-9Cr is important for the future fusion reactors which will be planned to install the ferritic steel as the in-vessel components.

Journal Articles

Impacts of particle fuelling on confinement and pedestal parameter in JT-60U

Takenaga, Hidenobu; Oyama, Naoyuki; Urano, Hajime; Kamiya, Kensaku; Miyo, Yasuhiko; Nishiyama, Tomokazu; Sasajima, Tadayuki; Masaki, Kei; Hiratsuka, Hajime; Ichige, Hisashi; et al.

Europhysics Conference Abstracts (CD-ROM), 30I, 4 Pages, 2006/00

no abstracts in English

Journal Articles

In-out asymmetry of low-$$Z$$ impurity deposition on the JT-60 divertor tiles

Masaki, Kei; Yagyu, Junichi; Miyo, Yasuhiko; Goto, Yoshitaka*; Arai, Takashi; Hayashi, Takao; Kodama, Kozo; Sasajima, Tadayuki; Kaminaga, Atsushi; Tanabe, Tetsuo*; et al.

Journal of Nuclear Materials, 329-333(Part1), p.845 - 848, 2004/08

 Times Cited Count:0 Percentile:100(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Installation of a advanced technology probe in JT-60U

Sasajima, Tadayuki; Yagyu, Junichi; Miyo, Yasuhiko; Miya, Naoyuki; Sakakibara, Satoru*

KEK Proceedings 2003-16 (CD-ROM), 4 Pages, 2004/02

no abstracts in English

Journal Articles

Advanced fusion technologies developed for JT-60 superconducting Tokamak

Sakasai, Akira; Ishida, Shinichi; Matsukawa, Makoto; Akino, Noboru; Ando, Toshinari*; Arai, Takashi; Ezato, Koichiro; Hamada, Kazuya; Ichige, Hisashi; Isono, Takaaki; et al.

Nuclear Fusion, 44(2), p.329 - 334, 2004/02

no abstracts in English

36 (Records 1-20 displayed on this page)