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Suekuni, Koichiro*; Lee, C. H.*; Tanaka, Hiromi*; Nishibori, Eiji*; Nakamura, Atsushi*; Kasai, Hidetaka*; Mori, Hitoshi*; Usui, Hidetomo*; Ochi, Masayuki*; Hasegawa, Takumi*; et al.
Advanced Materials, 30(13), p.1706230_1 - 1706230_6, 2018/03
Times Cited Count：51 Percentile：89.35(Chemistry, Multidisciplinary)Thermoelectric materials for highly efficient devices must satisfy conflicting requirements of high electrical conductivity and low thermal conductivity. In this paper, we studied the crystal structure and phonon dynamics of tetrahedrites (Cu,Zn)
(Sb,As)
S
. The results revealed that the Cu atoms in a planar coordination are rattling, which effectively scatter phonons. These findings provide a new strategy for the development of highly efficient thermoelectric materials with planar coordination.
Kobayashi, Takayuki; Isayama, Akihiko; Hasegawa, Koichi; Suzuki, Sadaaki; Hiranai, Shinichi; Sato, Fumiaki; Wada, Kenji; Yokokura, Kenji; Shimono, Mitsugu; Sawahata, Masayuki; et al.
Fusion Engineering and Design, 86(6-8), p.763 - 767, 2011/10
Times Cited Count：6 Percentile：44.28(Nuclear Science & Technology)Progress of antenna development of the Electron Cyclotron Range of Frequency system for JT-60 SA is presented. Capability of pulse length of 100 s, which requires active cooling for mirrors, and flexibility of beam injection angles in both poloidal and toroidal directions are required for the antenna with high reliability. Mechanical and structural design works of the launcher (antenna and its support with steering structure) based on a linear motion antenna concept are in progress. The key component is a long-stroke bellows which enables to alter poloidal injection angle and a bellows which enables to alter toroidal injection angle. Using a newly fabricated mock-up of the steering structure, it was confirmed that the antenna was mechanically realized for poloidal and toroidal injection angle ranges of -10 to +45
and -15 to +15, respectively. Those angles are consistent with angles required in JT-60SA. The results of thermal and structural analyses are also presented.
Kobayashi, Takayuki; Isayama, Akihiko; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; Sato, Fumiaki; et al.
Nuclear Fusion, 51(10), p.103037_1 - 103037_10, 2011/10
Times Cited Count：19 Percentile：62.41(Physics, Fluids & Plasmas)A new gyrotron operation technique to increase oscillation efficiency was developed on the JT 60 ECRF system. The electron pitch factor was optimized by controlling anode voltage within 0.1 s after the start of the operation. By applying this technique, the gyrotron output power of 1.5 MW for 4 s was recorded, for the first time. The reduced collector heat load at 1.5 MW operations was reduced by 20% and it will be acceptable for longer pulse operation. A new gyrotron with an improved mode converter was developed in order to demonstrate reduction of the stray radiation which had limited the pulse length. The stray radiation was reduced to 1/3 of that of the original gyrotron. A conditioning operation of the improved gyrotron is proceeding up to 31 s at 1 MW. These progresses significantly contribute to enhancing the high power and long pulse capability of the ECRF system toward JT 60SA.
Kobayashi, Takayuki; Isayama, Akihiko; Fasel, D.*; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; et al.
Journal of Plasma and Fusion Research SERIES, Vol.9, p.363 - 368, 2010/08
Improvements are required for expanding the pulse length of the JT-60 ECRF system (5s) for JT-60SA (100s). Newly developed power supplies will be fabricated and installed by EU. The conditioning operation of an improved gyrotron equipping a newly designed mode convertor has been started. The mode convertor will reduce heat flux on the internal components and therefore expected to enable long pulse operation at 1 MW. Pre-programmed and/or feedback control of the heater current and anode voltage, which was successfully demonstrated in JT-60U, will be key techniques because the beam current decreases during a shot. The evacuated transmission lines have a capability of 1 MW per line. Since maintenance of the components in the vacuum vessel is difficult, a linear motion antenna concept was proposed to reduce risks of water leakage and fault of the driving mechanism in the vacuum vessel. The detailed design and the low power test of a mock-up antenna have been started.
Kobayashi, Takayuki; Terakado, Masayuki; Sato, Fumiaki; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Hiranai, Shinichi; Igarashi, Koichi; et al.
Plasma and Fusion Research (Internet), 4, p.037_1 - 037_10, 2009/08
Electron cyclotron (EC) heating and current drive (CD) are key tools to control fusion plasma especially for effective electron heating and for suppression of neoclassical tearing mode (NTM). Recently, developments of a high power gyrotron and a power modulation technique have been successfully achieved on JT-60U ECRF system in order to enhance the system performance. Stable gyrotron oscillation with oscillation power of 1.5 MW for 1 s was demonstrated in 2007, for the first time. Then temperature rise of cavity and collector has been investigated. It has been shown that the longer pulse operation with 1.5 MW by an improved 110 GHz gyrotron is possible. In addition, modulated ECCD in synchronized with NTM rotation has been performed with the oscillation power of 0.8 MW and the frequency around 5 kHz. The synchronizing system has worked very well and it has played an essential role in NTM suppression experiments on JT-60U.
Moriyama, Shinichi; Kobayashi, Takayuki; Isayama, Akihiko; Terakado, Masayuki; Sawahata, Masayuki; Suzuki, Sadaaki; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Hiranai, Shinichi; et al.
Nuclear Fusion, 49(8), p.085001_1 - 085001_7, 2009/07
Times Cited Count：21 Percentile：61.72(Physics, Fluids & Plasmas)In the gyrotron development in JT-60U ECRF system, output power of 1.5 MW for 1 s has been achieved at 110 GHz. It is the world highest power oscillation 
1 s. In addition to the carefully designed cavity and collector in view of thermal stress, an RF shield for the adjustment bellows, and a low-dielectric-loss DC break enabled this achievement. Power modulation technique by anode voltage control was improved to obtain high modulation frequency and 5 kHz has been achieved for NTM stabilizing experiments. Long pulse demonstration of 0.4 MW, 30 s injection to the plasma has been achieved with real time control of anode/cathode-heater. It has been confirmed that the temperature of cooled components were saturated and no evidence of damage were found. An innovative antenna having wide range of beam steering capability with linearly-moving-mirror concept has been designed for long pulse. Beam profile and mechanical strength analyses shows the feasibility of the antenna.
hort (cv. White Aga)Kondo, Masayoshi*; Koike, Yosuke*; Okuhara, Hiroyuki*; Oda, Masayuki*; Hase, Yoshihiro; Yoshihara, Ryohei; Kobayashi, Hitoshi*
JAEA-Review 2008-055, JAEA Takasaki Annual Report 2007, P. 67, 2008/11
no abstracts in English
Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; Igarashi, Koichi; Sato, Fumiaki; Wada, Kenji; et al.
JAEA-Technology 2008-065, 98 Pages, 2008/10
JAEA-Technology-2008-065.pdf:38.83MB
Construction of the JT-60SA (super advanced) is planned as an upgrade of JT-60U as the satellite tokamak in ITER broader approach and as the national centralized tokamak facility program in Japan. The present JT-60U will be disassembled and the JT-60SA will be constructed at the same location in the JT-60 tours hall. The disassembly work will be planned in the period from 2009 to 2011. In this report, disassembly of the radio frequency heating system of JT-60U in the amplifier rooms and heating power supply building is studied on (1) object for disassembly, (2) work plan, (3) estimation of materials amount, (4) procedure.
Moriyama, Shinichi; Kobayashi, Takayuki; Isayama, Akihiko; Terakado, Masayuki; Sawahata, Masayuki; Suzuki, Sadaaki; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Hiranai, Shinichi; et al.
Proceedings of 22nd IAEA Fusion Energy Conference (FEC 2008) (CD-ROM), 8 Pages, 2008/10
In the gyrotron development in JT-60U ECRF system, output power of 1.5 MW for 1 s has been achieved at 110 GHz. It is the world highest power oscillation 1 s. In addition to the carefully designed cavity and collector in view of thermal stress, an RF shield for the adjustment bellows, and a low-dielectric-loss DC break enabled this achievement. Power modulation technique by anode voltage control was improved to obtain high modulation frequency and 5 kHz has been achieved for NTM stabilizing experiments. Long pulse demonstration of 0.4 MW, 30 s injection to the plasma has been achieved with real time control of anode/cathode-heater. It has been confirmed that the temperature of cooled components were saturated and no evidence of damage were found. An innovative antenna having wide range of beam steering capability with linearly-moving-mirror concept has been designed for long pulse. Beam profile and mechanical strength analyses shows the feasibility of the antenna.
Chinone, Shumpei*; Ishizawa, Akito*; Tokuhiro, Koji*; Nakatsubo, Koichi*; Amano, Masayuki*; Hase, Yoshihiro; Narumi, Issei; Tanaka, Atsushi
JAEA-Review 2007-060, JAEA Takasaki Annual Report 2006, P. 83, 2008/03
no abstracts in English
Isobe, Nobuhiro*; Sukekawa, Masayuki*; Nakayama, Yasunari*; Date, Shingo*; Otani, Tomomi*; Takahashi, Yukio*; Kasahara, Naoto; Shibamoto, Hiroshi*; Nagashima, Hideaki*; Inoue, Kazuhiko*
Nuclear Engineering and Design, 238(2), p.347 - 352, 2008/02
Times Cited Count：21 Percentile：78.82(Nuclear Science & Technology)The effect of ratcheting on fatigue strength was investigated in order to rationalize the strain limit as a design criterion of commercialized fast reactor systems. Ratcheting fatigue tests were conducted at 550C. Duration of the ratchet straining was set for a certain number of strain cycles taking the loading condition of fast reactors into account, and the number of cycles for strain accumulation was defined as the ratchet-expired cycle. Fatigue lives decrease as the accumulated strain by ratcheting increases. Fatigue life reduction was negligible when the maximum mean stress was less than 25 MPa, corresponding to an accumulated strain of 2.2 percent. Accumulated strain is limited to 2 percent in the present design guidelines and this strain limit is considered effective to avoid reducing fatigue life by ratcheting. Micro-crack growth behaviors were also investigated in these tests in order to discuss the life reduction mechanisms in ratcheting conditions.
Nishida, Akemi; Matsubara, Hitoshi; Tian, R.; Hazama, Osamu; Suzuki, Yoshio; Araya, Fumimasa; Nakajima, Norihiro; Tani, Masayuki; Kondo, Makoto
Nihon Genshiryoku Gakkai Wabun Rombunshi, 6(3), p.376 - 382, 2007/09
Unexpected accidents such as oil-tank fires caused by the earthquake and breakage of pipes of nuclear plants have occurred over the past several years. Higher reliability is thus now increasingly expected to maintain the safety of infrastructures. We have been intensely focused on the construction of an analysis system called the "three-dimensional virtual vibration testbed," which is a numerical simulation system for a nuclear plant which considers the interconnection of machines, pipes, buildings, and their foundations under real operating conditions. In this paper, the "part-wise analysis method" is proposed in which each structural component is treated independently and analyzed as an assembly structure. Further, the system configurations in a parallel distribution environment are described. This study shows one of the successful examples of the application of this method to a nuclear-plant cooling system that has tens of millions of degrees of freedom.
Tani, Masayuki; Nakajima, Norihiro; Nishida, Akemi; Suzuki, Yoshio; Matsubara, Hitoshi; Araya, Fumimasa; Kushida, Noriyuki; Hazama, Osamu; Kondo, Makoto; Kawasaki, Kozo
Proceedings of Joint International Topical Meeting on Mathematics & Computations and Supercomputing in Nuclear Applications (M&C+SNA 2007) (CD-ROM), 12 Pages, 2007/04
Chinone, Shumpei*; Hanaoka, Yasushi*; Tokuhiro, Koji*; Nakatsubo, Koichi*; Amano, Masayuki*; Hase, Yoshihiro; Tanaka, Atsushi; Narumi, Issei
JAEA-Review 2006-042, JAEA Takasaki Annual Report 2005, P. 90, 2007/02
no abstracts in English
Suzuki, Yoshio; Aoyagi, Tetsuo; Tani, Masayuki; Nakajima, Norihiro; Hirayama, Toshio
Genshiryoku eye, 52(10), p.35 - 39, 2006/10
no abstracts in English
Suzuki, Yoshio; Matsumoto, Nobuko; Idomura, Yasuhiro; Tani, Masayuki
Kashika Joho Gakkai-Shi, 26(Suppl.1), p.49 - 52, 2006/07
no abstracts in English
Suzuki, Yoshio; Minami, Takahiro; Tani, Masayuki; Nakajima, Norihiro; Keller, R.*; Beisel, T.*
Proceedings of 7th International Meeting on High Performance Computing for Computational Science (VECPAR '06)/Workshop on Computational Grids and Clusters (WCGC '06) (CD-ROM), 9 Pages, 2006/07
The interoperability among different science grid systems is indispensable to worldwide use of a large-scale experimental facility as well as a large-scale supercomputer. One of the simplest ways to achieve the interoperability is to convert messages among different science grid systems without modifying themselves. Under such consideration, the interoperability between UNICORE and ITBL (IT-Based Laboratory) has been achieved with hardly modifying these grid systems by adopting a connection server which works as a mediator. Until international standardization is established, the method of message conversion among different science grid systems is promising as a way to establish the interoperability.
Hazama, Osamu; Suzuki, Yoshio; Matsubara, Hitoshi; Tian, R.; Nishida, Akemi; Tani, Masayuki; Nakajima, Norihiro
Proceedings of 7th MpCCI User Forum, p.132 - 136, 2006/00
Nuclear power plants are large in scale and functionally very complex structures. For safety precautions, they are maintained under very strict rules. Yet, no controlled experiments are possible to deal with full-scale nuclear reactors and its cooling systems in its entirety. In order to maintain the safety of these nuclear power plants against extra-large earthquakes and aging, Japan Atomic Energy Agency (JAEA) is currently constructing a fully three-dimensional virtual earthquake testbed on the ITBL Grid infrastructure. Currently, we have developed a high-performance finite element elastostatic simulation system based on component and part-wise assembly. Using the program, we were able to construct a finite element model of an experimental high-temperature gas reactor (HTGR) called HTTR, or High Temperature engineering Test Reactor.
Seki, Masami; Moriyama, Shinichi; Shinozaki, Shinichi; Hasegawa, Koichi; Hiranai, Shinichi; Yokokura, Kenji; Shimono, Mitsugu; Terakado, Masayuki; Fujii, Tsuneyuki
Fusion Engineering and Design, 74(1-4), p.273 - 277, 2005/11
Times Cited Count：3 Percentile：24.22(Nuclear Science & Technology)no abstracts in English
Fujii, Tsuneyuki; Seki, Masami; Moriyama, Shinichi; Terakado, Masayuki; Shinozaki, Shinichi; Hiranai, Shinichi; Shimono, Mitsugu; Hasegawa, Koichi; Yokokura, Kenji; JT-60 Team
Journal of Physics; Conference Series, 25, p.45 - 50, 2005/00
The JT-60U electron cyclotron range of frequency (ECRF) is utilized to realize high performance plasma. Its output power is 4 MW at 110 GHz. By controlling the anode voltage of the gyrotron used in the JT-60U ECRF heating system, the gyrotoron output can be controlled. Then, the anode voltage controller was developed to modulate the injected power into plasmas. This low cost controller achieved the modulation frequency 12 - 500 Hz at 0.7 MW. This controller also extended the pulse width from 5s to 16 s at 0.5 MW. For these long pulses, temperature rise of the DC break made of Alumina ceramics is estimated. Its maximum temperature becomes 
140 deg. From the analysis of this temperature rise, DC break materials should be changed to low loss materials for the objective pulse width of 30 s. The stabilization of neoclassical tearing mode (NTM) was demonstrated by ECRF heating using the real-time system in which the ECRF beams are injected to the NTM location predicted from ECE measurement every 10 ms.
