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Hiratsuka, Shinya; Asamori, Koichi; Saiga, Atsushi
JAEA-Research 2022-002, 38 Pages, 2022/06
JAEA-Research-2022-002.pdf:4.49MB
Deep groundwater originates from dehydration of Pacific and Philippine Sea slab subducting beneath Japanese islands, which has characteristics of high temperature and is rich in carbonate species. In this respect, it is very important for geological disposal of high-level radioactive waste to estimate reservoir and migration pathway of deep groundwater. The region where cracks are densely distributed can be regarded as the migration pathway of slab-derived fluid. It is highly probable that the region has strong anisotropy. Shear wave propagating through anisotropic media splits into two mutually orthogonally polarized waves due to shear wave polarization anisotropy. In this report, we applied shear wave splitting analysis to Hongu area of Tanabe City, Wakayama Prefecture and estimated the spatial distribution of leading shear wave polarization direction (LSPD) and arrival time difference between leading and lagging shear waves (dt). Based on comparison with helium isotope ratio of ground water and bubbling gas samples and two-dimensional resistivity structure estimated by previous study, we attempt to estimate migration pathway of slab-derived fluid in Hongu area of Tanabe City, Wakayama Prefecture. The main results are summarized as follows. When helium isotope ratio of groundwater and bubbling gas samples is high, dt value tends to be large. Shear wave propagating through high and low resistivity anomaly zone show small and large dt values, respectively. Previous study suggested that slab-derived fluid migrates from deeper part of western side of Hongu area and wells out in Yunomine and Kawayu hot springs. This is consistent with spatial distribution of dt values estimated by this study.
Goto, Akira; Sasaki, Akimichi*; Komatsu, Tetsuya; Miwa, Atsushi*; Terusawa, Shuji*; Kagohara, Kyoko*; Shimada, Koji
JAEA-Research 2020-013, 88 Pages, 2020/11
JAEA-Research-2020-013.pdf:22.86MB
JAEA-Research-2020-013-appendix(CD-ROM).zip:0.18MB
Improvement of the investigation techniques to identify active faults is important for the implementation of geological disposal projects from the viewpoint of avoiding locations where permeability increases due to fault displacement. Generally, the existence of active faults is confirmed by aerial photography interpretation of fault displacement topography, which is a topographical trace of fault movement, and on-site geological surveys. However, the investigation method for cases where the topographical traces are unclear is not sufficiently developed. Therefore, to improve existing topographical methods, this study deciphered lineaments up to the rank of poorly defined features, which are almost neglected in general active fault research. The investigation area is one of the geodetic strain concentration zone, called the southern Kyushu shear zone, where the seismogenic faults of the 1997 Kagoshima northwest earthquakes are concealed. We conducted aerial photography interpretation of 62 sheets of 1/25,000 topographic maps, and obtained 1,327 lineaments. Distribution density, direction and length of lineaments were also investigated with topographic and geologic information. As a result, it was clarified that the east-west lineaments in the south Kyushu shear zone predominate in the western part, and the lineaments are densely distributed in the aftershock distribution area of the Kagoshima northwest earthquake. Along with these results, we have compiled a catalog of typical 13 lineaments based on combinations of clarity, direction, length and geomorphic characters of lineaments.
Kondo, Hiroo*; Kanemura, Takuji*; Park, C. H.*; Oyaizu, Makoto*; Hirakawa, Yasushi; Furukawa, Tomohiro
Fusion Engineering and Design, 146(Part A), p.285 - 288, 2019/09
Times Cited Count：1 Percentile：10.81(Nuclear Science & Technology)Herein, the wall shear stress in a double contraction nozzle has been evaluated experimentally to produce a liquid lithium (Li) target as a beam target for intense fusion neutron sources such as the International Fusion Materials Irradiation Facility (IFMIF), the Advanced Fusion Neutron Source (A-FNS), and the DEMO Oriented Neutron Source (DONES). The boundary layer thickness and wall shear stress are essential physical parameters to understand erosion-corrosion by the high-speed liquid Li flow in the nozzle, which is the key component in producing a stable Li target. Therefore, these parameters were experimentally evaluated using an acrylic mock-up of the target assembly. The velocity distribution in the nozzle was measured by a laser-doppler velocimeter and the momentum thickness along the nozzle wall was calculated using an empirical prediction method. The resulting momentum thickness was used to estimate the variation of the wall shear stress along the nozzle wall. Consequently, the wall shear stress was at the maximum in the second convergent section in front of the nozzle exit.
Tsusaka, Kimikazu*; Inagaki, Daisuke*; Niunoya, Sumio*; Jo, Mayumi*
Proceedings of 8th Asian Rock Mechanics Symposium (ARMS-8) (USB Flash Drive), 9 Pages, 2014/10
Miyato, Naoaki; Kishimoto, Yasuaki; Li, J.*
Journal of Plasma Physics, 72(6), p.821 - 824, 2006/12
Times Cited Count：0 Percentile：0.01(Physics, Fluids & Plasmas)Zonal flow behaviour and its effect on turbulent transport in reversed shear tokamaks are investigated by global nonlinear simulation of ion temperature gradient driven turbulence. When safety factor 
is reduced, zonal flows in a minimum region change from oscillatory ones to stationary ones and suppress the turbulent transport effectively. This result indicates that the change of zonal flow behaviour in the minimum region may trigger the formation of ion transport barriers.
Hayashi, Nobuhiko; Takizuka, Tomonori; Sakamoto, Yoshiteru; Fujita, Takaaki; Kamada, Yutaka; Ide, Shunsuke; Koide, Yoshihiko
Plasma Physics and Controlled Fusion, 48(5A), p.A55 - A61, 2006/05
Times Cited Count：7 Percentile：24.63(Physics, Fluids & Plasmas)no abstracts in English
Idomura, Yasuhiro; Tokuda, Shinji; Kishimoto, Yasuaki
Nuclear Fusion, 45(12), p.1571 - 1581, 2005/12
Times Cited Count：39 Percentile：74.86(Physics, Fluids & Plasmas)Using a global gyrokinetic toroidal particle code, the toroidal electron temperature gradient driven (ETG) turbulence is studied in positive and reversed shear tokamaks. In the nolinear turbulent state, the ETG turbulence in the positive and reversed shear configurations show quite different structure formations. In the positive shear configuration, the ETG turbulence is dominated by streamers which have a ballooning type structure, and the electron temperature 
profile is quickly relaxed to the marginally stable state in a turbulent time scale. In the reversed shear configuration, quasi-steady zonal flows are produced in the regative shear region, while the positive shear region is characterized by streamers. Accordingly, the electron thermal diffusivity 
has a gap structure across the 
surface, and the gradinet is sustained above the marginal value for a long time in the quasi-steady phase. The results suggest a stiffness of the profile in positive shear tokamaks, and a possibility of the Te transport barrier in reversed shear tokamaks.
Hayashi, Nobuhiko; Takizuka, Tomonori; Ozeki, Takahisa
Nuclear Fusion, 45(8), p.933 - 941, 2005/08
Times Cited Count：13 Percentile：41.32(Physics, Fluids & Plasmas)We have investigated profile formation and sustainment of current hole (CH) plasma by 1.5D transport simulations with current limit model inside CH based on Axisymmetric Tri-Magnetic-Islands equilibrium. Sharp reduction of anomalous transport in RS region can reproduce JT-60U experiments. The transport becomes neoclassical-level in RS region, which results in autonomous profile formation of ITB and CH through large bootstrap current. ITB width determined by neoclassical-level transport agrees with that in JT-60U. Energy confinement inside ITB agrees with JT-60U scaling. The scaling means that core plasma inside ITB is governed by MHD equilibrium limit, i.e., autonomous limitation of energy confinement. The plasma with large CH is sustained with full current drive by bootstrap current. The plasma with small CH and small bootstrap current fraction shrinks due to penetration of inductive current. This shrink is prevented and CH size can be controlled by appropriate external CD. CH plasma is found to respond autonomically to external CD. Application of CH plasma to reactor is discussed.
Hayashi, Nobuhiko; Takizuka, Tomonori; Ozeki, Takahisa
Proceedings of 20th IAEA Fusion Energy Conference (FEC 2004) (CD-ROM), 8 Pages, 2004/11
Profile formation and sustainment of tokamak plasmas with current hole (CH) have been investigated by using 1.5D transport simulations. A current limit model inside CH based on the Axisymmetric Tri-Magnetic-Islands equilibrium is introduced. We found that the sharp reduction of anomalous transport in the reversed-shear (RS) region can reproduce JT-60U experiment. The transport becomes neoclassical-level in RS region, which results in the autonomous formation of internal transport barrier (ITB) and CH through large bootstrap current. ITB width determined by neoclassical-level transport agrees with that in JT-60U. Energy confinement inside ITB agrees with JT-60U scaling, which means autonomous limitation of energy confinement. The plasma with large CH is sustained with the full current drive by bootstrap current. The plasma with small CH and small bootstrap current fraction shrinks due to inductive current penetration. This shrink is prevented and the CH size can be controlled by appropriate external current drive (CD). The CH plasma is found to respond autonomically to external CD.
-values in the ITB events in JT-60U reverse shear plasmasNeudatchin, S. V.*; Takizuka, Tomonori; Hayashi, Nobuhiko; Isayama, Akihiko; Shirai, Hiroshi; Fujita, Takaaki; Kamada, Yutaka; Koide, Yoshihiko; Suzuki, Takahiro
Nuclear Fusion, 44(9), p.945 - 953, 2004/09
The formation of internal transport barriers (ITBs) near q=3 surfaces in normal shear (NrS) discharges of JT-60U is known. In reverse shear (RS) JT-60U plasmas, the role of q minimum (qmin) equal to 3.5,3,2.5,2 was not obvious for ITB formation. ITB-events (non-local confinement bifurcations inside and around ITB) are found in various NrS and RS plasmas. Under sufficient heating power, ITB-events are seen at rational and not rational values of qmin. The space-time evolution of Te and Ti is similar, suggesting the same mechanism of Te and Ti transport. The temporal formation of strong ITB under passing of qmin=3 (after periodical improvements and degradations via ITB-events) in RS mode is presented. Under smaller power, ITB-events are observed only at rational values of qmin. In a weak RS shot, abrupt rise of Te is seen at qmin=3.5, while more cases of Ti rise are observed. The difference of Te and Ti evolutions seen regularly under the low power, suggests decoupling of Te and Ti transport.
-values in the ITB events in JT-60U reverse shear plasmasNeudatchin, S. V.*; Takizuka, Tomonori; Hayashi, Nobuhiko; Isayama, Akihiko; Shirai, Hiroshi; Fujita, Takaaki; Kamada, Yutaka; Koide, Yoshihiko; Suzuki, Takahiro
Nuclear Fusion, 44(9), p.945 - 953, 2004/09
Times Cited Count：18 Percentile：51.13(Physics, Fluids & Plasmas)The formation of internal transport barriers (ITBs) near =2,3 surfaces in normal shear (NrS) discharges of JT-60U and JET is known. In reverse shear (RS) JT-60U plasmas, the role of minimum (
) equal to 3.5,3,2.5,2 is not obvious for ITB formation. In this paper, the effect of low rational values on ITB-events in JT-60U NrS and RS plasmas is investigated. Under sufficient neutral beam power (
8MW for 1.2-1.5MA/3.8T pulses), ITB-events are seen at rational and non-rational values of . The space-time evolutions of 
and 
are similar, suggesting the same mechanism for and transports. The temporal formation of stronger ITB under passing =3 (after periodical improvements and degradations via ITB-events) in RS H-mode with =8MW is presented. Under smaller power, ITB-events are observed only at rational values. In a weak RS shot with =4MW, the abrupt rise of is seen at =3.5, while more cases of rise are observed. The difference between the and evolutions for the low power suggests the decoupling of and transports.
n eigenmodesKonovalov, S. V.; Mikhailovskii, A. B.*; Shirokov, M. S.*; Kovalishen, E. A.*; Ozeki, Takahisa
Physics of Plasmas, 11(9), p.4531 - 4534, 2004/09
Times Cited Count：19 Percentile：53.19(Physics, Fluids & Plasmas)no abstracts in English
Takase, Kazuyuki; Yoshida, Hiroyuki; Ose, Yasuo*; Tamai, Hidesada
JSME International Journal, Series B, 47(2), p.323 - 331, 2004/05
no abstracts in English
Li, J.; Kishimoto, Yasuaki
Physics of Plasmas, 11(4), p.1493 - 1510, 2004/04
Times Cited Count：59 Percentile：85.15(Physics, Fluids & Plasmas)The electron temperature gradient (ETG) driven turbulence in tokamak core plasmas is numerically investigated based on three-dimensional gyrofluid model with adiabatic ion response. Attentions are focused on the zonal flow dynamics in ETG fluctuations and the resultant electron heat transport. A high electron energy confinement mode is found in the weak magnetic shear regime, which is closely relevant with self-organization behavior of turbulence through the enhanced zonal flow dynamics rather than the weak shear stabilization of ETG fluctuations. It is demonstrated that the weak shear is favorable for the enhancement of zonal flows in ETG turbulence.
Konovalov, S. V.; Mikhailovskii, A.*; Kovalishen, E.*; Ozeki, Takahisa; Takizuka, Tomonori; Shirokov, M. S.*
Proceedings of 20th IAEA Fusion Energy Conference (FEC 2004) (CD-ROM), 8 Pages, 2004/00
Alfven eigenmodes in tokamaks with reversed magnetic shear are studied theoretically by incorporating into the mode description the effects known theories of Global, Kinetic and Toroidal Alfven Eigenmodes. In particular mode forming effect due to thermal plasma density gradient is examined. Criteria of the fast ion density and its gradient on the existence of a localized solution of the eigenmode equation is softened by this effect. Effects of finite Larmor radius, continuum damping and fast ion density gradient are also studied.
Fujita, Takaaki; JT-60 Team
Nuclear Fusion, 43(12), p.1527 - 1539, 2003/12
Times Cited Count：32 Percentile：68.04(Physics, Fluids & Plasmas)Recent JT-60U results toward high integrated performance are reported with emphasis on the projection to the reactor-relevant regime. N-NB and EC power increased up to 6.2 MW and 3 MW, respectively. A high betap H-mode plasma with full non-inductive current drive has been obtained at 1.8 MA and the fusion triple product reached 3.1E20m
keVs. NTM suppression with EC was accomplished using a real-time feedback control system and improvement in betaN was obtained. A stable existence of current hole was observed. High DT-equivalent fusion gain of 0.8 was maintained for 0.55 s in a plasma with a current hole. The current profile control in high bootstrap current reversed shear plasmas was demonstrated using N-NB and LH. A new operation scenario has been established in which a plasma with high bootstrap current fraction and ITBs is produced without the use of OH coil. A new type of AE mode has been proposed and found to explain the observed frequency chirp quite well. Ar exhaust with EC heating was obtained in a high betap mode plasma.
Takizuka, Tomonori
Purazuma, Kaku Yugo Gakkai-Shi, 79(11), p.1123 - 1129, 2003/11
no abstracts in English
Miura, Yukitoshi; JT-60 Team
Physics of Plasmas, 10(5), p.1809 - 1815, 2003/05
Times Cited Count：10 Percentile：31.59(Physics, Fluids & Plasmas)no abstracts in English
Kubo, Hirotaka; Sakurai, Shinji; Higashijima, Satoru; Takenaga, Hidenobu; Itami, Kiyoshi; Konoshima, Shigeru; Nakano, Tomohide; Koide, Yoshihiko; Asakura, Nobuyuki; Shimizu, Katsuhiro; et al.
Journal of Nuclear Materials, 313-316(1-3), p.1197 - 1201, 2003/03
Times Cited Count：20 Percentile：75.71(Materials Science, Multidisciplinary)no abstracts in English
Takizuka, Tomonori
Purazuma, Kaku Yugo Gakkai-Shi, 78(12), p.1282 - 1284, 2002/12
An idea of a new equilibrium of a strongly-reversed-shear tokamak plasma with a current hole is proposed. This equilibrium configuration called "Axisymmetric Tri-Magnetic-Islands (ATMI) equilibrium" has three islands, a central-negative-current island and side-positive-current islands, along the R direction and two x-points along the Z direction. The equilibrium is stable with the elongation coils when the current in the ATMI region is limited small.
