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SiYamashita, Takuya*; Shimoyama, Yusuke*; Haga, Yoshinori; Matsuda, Tatsuma*; Yamamoto, Etsuji; Onuki, Yoshichika; Sumiyoshi, Hiroaki*; Fujimoto, Satoshi*; Levchenko, A.*; Shibauchi, Takasada*; et al.
Nature Physics, 11(1), p.17 - 20, 2015/01
Times Cited Count：51 Percentile：89.11(Physics, Multidisciplinary)Shimizu, Atsushi; Furusawa, Takayuki; Homma, Fumitaka; Inoi, Hiroyuki; Umeda, Masayuki; Kondo, Masaaki; Isozaki, Minoru; Fujimoto, Nozomu; Iyoku, Tatsuo
Journal of Nuclear Science and Technology, 51(11-12), p.1444 - 1451, 2014/11
Times Cited Count：1 Percentile：8.82(Nuclear Science & Technology)JAEA has kept up a data-base system of operation and maintenance experiences of the HTTR. The objective of this system is to share the information obtained operation and maintenance experiences and to make use of lessons learned and knowledge into a design, construction and operation managements of the future HTGR. More than one thousand records have been registered into the system between 1997 and 2012. This paper describes the status of the data-base system, and provides suggestions for improvement from four experiences: (1) performance degradation of helium compressors; (2) malfunction of reserved shutdown system in reactivity control system; (3) maintenance experiences of emergency gas turbine generators; and (4) experiences of the Great East Japan Earthquake. These experiences are extracted from the system as important lessons learned to be expected to apply for design, construction and operation managements of future HTGR.
Fujimoto, Kayoko; Nakano, Tomohide; Kubo, Hirotaka; Sawada, Keiji*; Takizuka, Tomonori; Kawashima, Hisato; Shimizu, Katsuhiro; Asakura, Nobuyuki
Plasma and Fusion Research (Internet), 4, p.025_1 - 025_7, 2009/08
The volume recombination in detached divertor plasmas is a key process to reduce the ion flux to the divertor plates. Two-dimensional measurement is one of the ways to investigate a spatial structure of the volume recombination. In this work, the deuterium Balmer-series lines from a detached divertor plasma were observed two-dimensionally with a spatial resolution of 1 cm and were reconstructed into two-dimensional emissivities with a tomography technique. The ratio of the D
to the D
emissivity was compared to that calculated by the collisional-radiative model. This ratio could not be explained only by the excitation of D by electron impact, indicating that the volume recombination contributed to the D emission. This is the case for the region above the inner strike point with 8 cm and 4 cm, respectively, in the r- and the z-direction on the poloidal cross-section.
Nakano, Tomohide; Kubo, Hirotaka; Asakura, Nobuyuki; Takenaga, Hidenobu; Oyama, Naoyuki; Kawashima, Hisato; Fujimoto, Kayoko
Nuclear Fusion, 48(8), p.085002_1 - 085002_8, 2008/08
Times Cited Count：13 Percentile：46.55(Physics, Fluids & Plasmas)Particle control is one of the key issues for steady-state operation in fusion reactors. In short discharges, the first wall absorbs hydrogen particles and it works as a pump (wall pumping). The wall pumping is effective to control the plasma density. However, in future tokamak devices, wall retention increases in a long discharge. Then, it is expected that the wall retention is saturated and the wall pumping does not work. Therefore, for steady-state operation, particle control by active divertor pumping without the wall pumping should be established. In JT-60U, long-pulse high-density H-mode plasmas have been sustained by divertor pumping under global wall saturation. The energy confinement and ELM activity can be sustained, while wall pumping does not work and even outgas appears. The outgas is attributed to increase in the divertor-plate temperature. On the other hand, wall pumping continues for longer than 20 s in high-density (ne 
0.8 nGW) discharges with an X-point MARFE and detached divertor plasma. X-point MARFEs have also been controlled by the divertor pumping. As a result, the electron density control by the divertor pumping and the gas puffing is effective under the wall saturation. However, it should be noted that the wall-pumping rate changes to maintain the electron density against the control. The change in the wall pumping suggests dynamic equilibrium between particle flux and desorption as an important wall-pumping mechanism.
in detached divertor plasmas of JT-60UNakano, Tomohide; Kubo, Hirotaka; Asakura, Nobuyuki; Shimizu, Katsuhiro; Konoshima, Shigeru; Fujimoto, Kayoko; Kawashima, Hisato; Higashijima, Satoru
Nuclear Fusion, 47(11), p.1458 - 1467, 2007/11
Times Cited Count：20 Percentile：57.53(Physics, Fluids & Plasmas)no abstracts in English
Fujimoto, Kayoko; Nakano, Tomohide; Kubo, Hirotaka; Sawada, Keiji*; Takizuka, Tomonori; Shimizu, Katsuhiro; Kawashima, Hisato; Asakura, Nobuyuki
Plasma and Fusion Research (Internet), 2, p.S1121_1 - S1121_4, 2007/11
Understanding deuterium particle behavior in the divertor plasma is necessary to study the ionizing and recombining plasmas. Two-dimensional spectroscopic measurement of deuterium emission is useful to understand deuterium particle behavior in divertor plasmas. The information of the ionization and recombination can be obtained by measurement of deuterium Balmer-series lines. A wide-spectral-band spectrometer with a CCD detector was used to observe deuterium Balmer-series lines with two-dimensional spatial distribution in the JT-60U divertor region. From the measurement, we can obtain a two-dimensional distribution of D and D
using a computer tomography technique. The D emission was strong above the strike point in the inner divertor and around the strike point in the outer divertor. The D emission was strong above the strike point in the inner divertor.
Kambe, Shinsaku; Sakai, Hironori; Kato, Harukazu*; Tokunaga, Yo; Fujimoto, Tatsuya*; Walstedt, R. E.*; Ikeda, Shugo; Maehira, Takahiro*; Haga, Yoshinori; Onuki, Yoshichika
Physical Review B, 76(2), p.024411_1 - 024411_6, 2007/07
Times Cited Count：6 Percentile：31.25(Materials Science, Multidisciplinary)We report NMR studies on a single crystal of UCoGa, which has the same tetragonal HoCoGa (115) structure as the
-wave high-
superconductor PuCoGa. The spin-lattice relaxation rate (
) in UCoGa issmall comparing with those of other actinide 115 compounds. This fact is consistent with a semi-metallic nature of UCoGa suggested by de Haas-van Alphen effect measurements and band calculations. From comparison of at crystallografically different Ga and Co sites and the static susceptibility, an existence of two bands with rather different characters is revealed.
P
probed by muon spin relaxationIto, Takashi; Higemoto, Wataru; Oishi, Kazuki; Fujimoto, Tatsuya*; Heffner, R. H.; Nishida, Nobuhiko*; Sato, Kazuhiko*; Sugawara, Hitoshi*; Aoki, Yuji*; Kikuchi, Daisuke*; et al.
Journal of the Physical Society of Japan, 76(5), p.053707_1 - 053707_4, 2007/05
Times Cited Count：27 Percentile：74.88(Physics, Multidisciplinary)A filled skutterudite compound SmRuP shows metal-insulatortransition at 
=16.5K with magnetic anomaly. A possibility of magnetic octupole ordering has been discussed on the basis of multipole degrees of freedom belonging to thecrystalline-electric-field ground state. We investigated local magnetic states in the ordered state by using the muon spin relaxation method. An increase of muon spin relaxation rate was detected in zeroapplied field just below , indicating time-reversal-symmetry breaking in the ordered state. This result suggests that the order parameter includes magnetic octupole and/ordipole. Magnitude of the internal field at the muon site monotonically increases with decreasing temperature, growing steeply below 
=3K. The longitudinal relaxation rate has a maximum at around , suggesting suppression of magnetic fluctuations. We discussed these experimental facts on the basis of the multipoledegrees of freedom.
Kubo, Hirotaka; Nakano, Tomohide; Asakura, Nobuyuki; Takenaga, Hidenobu; Tsuzuki, Kazuhiro; Oyama, Naoyuki; Kawashima, Hisato; Shimizu, Katsuhiro; Urano, Hajime; Fujimoto, Kayoko; et al.
Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 8 Pages, 2007/03
no abstracts in English
Nakano, Tomohide; Kubo, Hirotaka; Asakura, Nobuyuki; Shimizu, Katsuhiro; Konoshima, Shigeru; Fujimoto, Kayoko; Kawashima, Hisato; Higashijima, Satoru
Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 8 Pages, 2007/03
Volume recombination of C and 
into C
is observed for the first time in detached plasmas with MARFE. It is found that the recombination flux of C to C is comparable to the ionization flux of C to C, and that the recombination zone is above an X-point and beneath the ionization zone. This result suggests that this volume recombination predominantly produces C ions, which contribute 60-80 % to the total radiation power in the divertor plasma.
Sumita, Junya; Shibata, Taiju; Kikuchi, Takayuki; Ishihara, Masahiro; Iyoku, Tatsuo; Sawa, Kazuhiro; Fujimoto, Nozomu
JAEA-Data/Code 2007-001, 57 Pages, 2007/02
JAEA-Data-Code-2007-001.pdf:3.0MB
Visual inspection by a TV camera and material properties measurement by surveillance test on core support graphite structures are planned for the High Temperature Engineering Test Reactor (HTTR) to confirm their structural integrity and characteristics. The surveillance test is aimed to investigate the change of material and mechanical properties by aging effects such as fast neutron irradiation and oxidation. The obtained data will be used not only for evaluating the structural integrity of the core support graphite structure of the HTTR but also for design data to advanced Very High Temperature Reactor (VHTR) discussed at generation IV international forum. This report describes the material properties and installed position of surveillance specimens in the HTTR in order to carry out the surveillance test.
Fujimoto, Kayoko; Nakano, Tomohide; Kubo, Hirotaka; Kawashima, Hisato; Shimizu, Katsuhiro; Asakura, Nobuyuki
Fusion Science and Technology, 51(2T), p.247 - 249, 2007/02
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)no abstracts in English
Meguro, Yoshihiro; Tomioka, Osamu; Imai, Tomoki*; Fujimoto, Shigeyuki*; Nakashima, Mikio; Yoshida, Zenko; Honda, Tadashi*; Koya, Fumio*; Kitamura, Nobu*; Wada, Ryutaro*; et al.
Proceedings of International Waste Management Symposium 2004 (WM '04) (CD-ROM), 8 Pages, 2004/03
Supercritical CO
fluid leaching (SFL) method using supercritical CO fluid containing a complex of HNO
- tri-n-butyl phosphate (TBP) was applied to removal of uranium from radioactive solid wastes. Sea sands, incineration ashes and porous alumina bricks were employed as matrixes of simulated solid wastes. Real radioactive incineration ash wastes and firebrick wastes were also subjected to the SFL treatment. It was found that uranium could be efficiently removed from both of the simulated wastes and real wastes by the SFL method. The removal efficiency of uranium from the real waste was lower than that from the corresponding artificial waste. About 1 g and 35 mg of uranium were recovered from 10 g of the real ash waste and 37 g of the real firebrick waste, respectively.
Fujima, Kazumi*; Nishihara, Katsunobu*; Kawamura, Toru*; Furukawa, Hiroyuki*; Kagawa, Takashi*; Koike, Fumihiro*; More, R.*; Murakami, Masakatsu*; Nishikawa, Takeshi*; Sasaki, Akira; et al.
Emerging Lithographic Technologies VIII, Proceedings of SPIE Vol.5374, p.405 - 412, 2004/00
no abstracts in English
Nakano, Tomohide; Fujimoto, Takashi*; Goto, Motoshi*; Hatayama, Akiyoshi*; Kado, Shinichiro*; Kato, Takako*; Kimura, Mineo*; Kubo, Hirotaka; Murakami, Izumi*; Ono, Noriyasu*; et al.
Annual Report of National Institute for Fusion Science; April 2003 - March 2004, P. 414, 2003/10
no abstracts in English
Kim, J.*; Kim, D. E.*; Kawachi, Tetsuya; Hasegawa, Noboru; Sukegawa, Kota*; Iwamae, Atsushi*; Fujimoto, Takashi*
Journal of the Optical Society of Korea, 7(3), p.145 - 149, 2003/09
The anistropy of electron energy distribution in oxygen plasmas produced by a high intensinty laser was investigated by using polarization spectroscopy. An ultra-short pulsed laser with a pulse duration of 66.5 fs and a power density of 1
10
W/cm
was used. At this power density and pulse duration, the plasma was generated predominantly by optical field ionization. The degree of polarization of OVI 1s2p P-1s4d D
(J=1/2-3/2 and J=3/2-5/2) transition line at 129.92 
の1s 2pP-1s4sS (J=1/2-1/2 and J=3/2-1/2) transition line at 132.26 AA was used to calibrate the sensitivity of the optical system. The dependencies of the degree of polarization on the initial gas density and on the laser polarization were investigated. When the laser polarization was changed from a linear to a circlar polarization was decreased. When the initial gas density was increased, the degree of polarization was decreased.
interactionOtsuka, Takaharu*; Fujimoto, Rintaro*; Utsuno, Yutaka; Brown, B. A.*; Homma, Michio*; Mizusaki, Takahiro*
Physical Review Letters, 87(8), p.082502_1 - 082502_4, 2001/08
Times Cited Count：631 Percentile：99.4(Physics, Multidisciplinary)no abstracts in English
ray from fuel of High Temperature Engineering Test Reactor; Method of measurement and resultsFujimoto, Nozomu; Nojiri, Naoki; Takada, Eiji*; Yamashita, Kiyonobu; Kikuchi, Takayuki; Nakagawa, Shigeaki; Kojima, Takao; Umeta, Masayuki; Hoshino, Osamu; Kaneda, Makoto*; et al.
JAERI-Tech 2001-002, 64 Pages, 2001/02
JAERI-Tech-2001-002.pdf:3.64MB
no abstracts in English
*; *; *; *; *; *; *; *; *; *; et al.
JNC TJ7420 2001-004, 144 Pages, 1987/01
JNC-TJ7420-2001-004.pdf:10.57MB
no abstracts in English
