Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.
Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03
Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.
Mori, Masanobu*; Sagara, Katsuya*; Arai, Kaori*; Nakatani, Nobutake*; Ohira, Shinichi*; Toda, Kei*; Itabashi, Hideyuki*; Kozaki, Daisuke*; Sugo, Yumi; Watanabe, Shigeki; et al.
Journal of Chromatography A, 1431, p.131 - 137, 2016/01
Tobari, Hiroyuki; Inoue, Takashi; Taniguchi, Masaki; Kashiwagi, Mieko; Umeda, Naotaka; Dairaku, Masayuki; Yamanaka, Haruhiko; Watanabe, Kazuhiro; Sakamoto, Keishi; Kuriyama, Masaaki*; et al.
Fusion Engineering and Design, 88(6-8), p.975 - 979, 2013/10
The HV bushing, one of the ITER NB components, which is to be procured by JADA, is a multi-conductor feed through composed of five-stage double-layered insulator columns with large brazed ceramic ring and fiber reinforced plastic (FRP) ring. The HV bushing is a bulk head between insulation gas at 0.6 MPa and vacuum. The FRP ring is required to sustain the pressure load, seismic load and dead weight. Brazing area of the ceramic ring with Kovar is required to maintain vacuum leak tightness and pressure tightness against the air filled at 0.6 MPa. To design the HV bushing satisfying the safety factor of 3.5, mechanical analyses were carried out. As for the FRP ring, it was confirmed that isotropic fiber cloth FRP rings should be used for sufficient strength against shear stress. Also, shape and fixation area of the Kovar sleeve were modified to lower the stress at the joint area. As a result, a design of the insulator for the HV bushing was established satisfying the requirement.
Sato, Satoshi; Ochiai, Kentaro; Konno, Chikara; Morota, Hidetsugu*; Nasif, H.*; Tanaka, Masanobu*; Polunovskiy, E.*; Loughlin, M.*
Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 8 Pages, 2013/03
Detailed nuclear analyses for the latest ITER NB system are required to ensure that NB design conforms to the nuclear regulations for the ITER building and licensing. A variety of nuclear analyses was started for ITER NB system including a tokamak building of 50m 35m 20m and outside the building by using a Monte Carlo code MCNP in 2009. MCNP geometry input data were successfully produced from simplified NB CAD data with the improved GEOMIT code, which automatically converts CAD data to MCNP geometry input data. We have performed calculations of the effective dose rates during DT operation and after shutdown, and activation of the NB components, etc.
Kashiwagi, Mieko; Taniguchi, Masaki; Umeda, Naotaka; Dairaku, Masayuki; Tobari, Hiroyuki; Yamanaka, Haruhiko; Watanabe, Kazuhiro; Inoue, Takashi; DeEsch, H. P. L.*; Grisham, L. R.*; et al.
AIP Conference Proceedings 1515, p.227 - 236, 2013/02
In a five stage multi-aperture multi-grid (MAMuG) accelerator for the ITER neutral beam injector (NBI), 1 MeV, 40 A D ion beam is required for 1 hour. However, beamlets are deflected due to (1) magnetic field for electron suppression and (2) space charge repulsion between beamlets, and consequently, cause excess grid heat load. A three dimensional beam analysis has been carried out to compensate the beamlet deflections. This paper shows that the beamlet deflections due to (1) and (2) are compensated by an aperture offset of only 0.6 mm applied to the aperture of 17 mm in diameter in the extractor and by a metal bar attached around aperture area beneath the extractor, respectively. When the metal bar is increased to 3 mm in thickness and installed 30 mm away from the aperture area, the beamlet is steered gently by the weaker electric field distortion. The beam optics was confirmed not deteriorated by those compensations. The presentation also discusses application of these compensation techniques to the ITER design.
Kashiwagi, Mieko; Taniguchi, Masaki; Umeda, Naotaka; DeEsch, H. P. L.*; Grisham, L. R.*; Boilson, D.*; Hemsworth, R. S.*; Tanaka, Masanobu*; Tobari, Hiroyuki; Watanabe, Kazuhiro; et al.
Review of Scientific Instruments, 83(2), p.02B119_1 - 02B119_3, 2012/02
In a multi-aperture multi-grid (MAMuG) accelerator of the ITER neutral beam injector (NBI), 1 MeV, 40 A D ion beam is required for 3600 s. Suppression of grid power loading by the direct interception of deflected beamlets is one of the critical issues to realize this accelerator. The beamlets are deflected due to space charge repulsion among beamlets/beam groups and magnetic field. Moreover, the beamlet deflection is influenced by electric field distortion generated by grid supports. To examine such complicated beamlet deflections and design the compensating methods, a three-dimensional beam analysis has been applied to the ITER accelerator. As the simulation model, a 1/4 accelerator model including step/edge of the grid supports is constructed. As results, compensation methods of the beamlet deflection, that it, a metal bar of 1 mm thick around the aperture area, and an aperture offset of 1 mm, were designed.
Tanaka, Masanobu*; Hemsworth, R. S.*; Kuriyama, Masaaki*; Svensson, L.*; Boilson, D.*; Inoue, Takashi; Tobari, Hiroyuki; Kashiwagi, Mieko; Taniguchi, Masaki; Umeda, Naotaka; et al.
IEEE Transactions on Plasma Science, 39(6), p.1379 - 1385, 2011/06
In the ITER neutral beam injector (NBI) for plasma heating and current drive, 40 A D ions are accelerated to 1 MeV with a five-stage electrostatic accelerator. Since the accelerator is immersed in vacuum, vacuum insulation of -1 MV is one of critical issues. In order to sustain high voltage of -1 MV, minimum gap length between the accelerator and the vacuum vessel at ground potential was designed to be more than 900 mm on the basis of previous experimental data. High voltage bushing (HVB) acting as an insulating feed-through supplying electric power and cooling water to the accelerator consists of five stack insulator and each stage is designed to withstand -200 kV. A full-scale and single-stage mockup bushing was manufactured and tested to demonstrate stable voltage holding. As a result, DC -203 kV was sustained stably for 5 hours and the insulation design of HVB has been confirmed.
Tobari, Hiroyuki; Inoue, Takashi; Hanada, Masaya; Dairaku, Masayuki; Watanabe, Kazuhiro; Umeda, Naotaka; Taniguchi, Masaki; Kashiwagi, Mieko; Yamanaka, Haruhiko; Takemoto, Jumpei; et al.
Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03
High voltage (HV) bushing in the ITER NBI is one of critical components, which acts as a feedthrough for electric power and cooling water from the -1 MV power supply in SF gas to beam source inside vacuum. JAEA has overcome a longstanding issue on manufacturing of a large bore ceramic ring with 1.56 m in diameter as the insulator of the five-stage HV bushing. Joining method of the ceramic and metal flange with thick Kovar plate to form vacuum boundary was also developed. By assembling components, a full-size mockup bushing simulating one stage of the HV bushing was successfully manufactured. In the voltage holding test, the high voltage of 240 kV including the margin of 20 % of a rated voltage was sustained for 3600 s without breakdown, and the voltage holding capability required in ITER was successfully verified.
Kashiwagi, Mieko; Taniguchi, Masaki; Kojima, Atsushi; Dairaku, Masayuki; Hanada, Masaya; Hemsworth, R. S.*; Mizuno, Takatoshi*; Takemoto, Jumpei; Tanaka, Masanobu*; Tanaka, Yutaka*; et al.
Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03
At JAEA, a multi-aperture multi-grid accelerator has been developed for the ITER neutral beam system. A target is H ion beam acceleration of 0.5 A (200 A/m) at 1 MeV. In real accelerators, it was found that the voltage holding was about a half of that obtained in an ideal small electrode. After applying necessary gap length and radii of edges of grid supports to lower local electric field concentrations, the accelerator succeeded in sustaining 1 MV for 4000 s. As a result, beam parameters were increased to 879 keV, 0.36 A (157 A/m) at perveance matched condition from 796 kV, 0.32 A (140 A/m) reported in FEC2008. In the beam acceleration, the beamlet deflections due to magnetic field and space charge repulsion caused direct interceptions, that resulted in limitations in the beam energy and current. Compensation of these beamlet deflections has been tested applying aperture offset and field shaping plate, which were examined in a three-dimensional beam analysis.
Tanaka, Naritake*; Kimura, Hitoshi*; Faried, A.*; Sakai, Makoto*; Sano, Takaaki*; Inose, Takanori*; Soda, Makoto*; Okada, Koji*; Nakajima, Masanobu*; Miyazaki, Tatsuya*; et al.
Cancer Science, 101(6), p.1487 - 1492, 2010/06
We examined the intracellular localization of cisplatin, a key chemotherapeutic agent, in esophageal cancer cell lines and determined their sensitivity to cisplatin using in-air micro-PIXE. Two human esophageal squamous cell carcinoma (ESCC) cell lines, TE-2 and TE-13, were examined for their response to cisplatin using MTT assay, flow cytometry and DNA fragmentation assays. Real-time reverse transcription-polymerase chain reaction was also used to evaluate the mRNA expression of multidrug resistance protein 2 (MRP2) in both cell lines. Platinum localizations of intracellular and intranuclear were measured using in-air micro-PIXE. TE-2 cells were more sensitive to cisplatin than TE-13 cells. The results of this study suggest that in-air micro-PIXE could be a useful quantitative method for evaluating the cisplatin sensitivity of individual cells. Finally, we speculate that MRP2 in the cell membrane may play an important role in regulating cisplatin sensitivity of ESCC cells.
Fujiwara, Kazushige*; Ito, Masanobu*; Sasanuma, Miwa*; Tanaka, Hideo*; Hirotani, Kiyoshi*; Onizawa, Kunio; Suzuki, Masahide; Amezawa, Hiroo*
Transactions of 20th International Conference on Structural Mechanics in Reactor Technology (SMiRT-20) (CD-ROM), 8 Pages, 2009/08
Concerns over aged nuclear power stations are mounting in Japan today. However, there exists only a small number of experimental studies regarding the effect of radiation exposure to concrete. We have consequently conducted an irradiation test at JMTR on concrete specimens to confirm the effect of radiation exposure on the basic material properties of concrete. Irradiation temperature was kept lower than 65C. The maximum fast neutron fluence reached 1210 n/cm (E 0.1 MeV), which is sufficiently exceeding total fast neutron fluence to be exposed to the concrete located at the exterior of a reactor pressure vessel in a typical BWR for 60-year operation. Compressive strength of the irradiated concrete specimens was roughly equivalent to that of concrete specimens cured for the same duration under the standard environment. By measuring chemically bound water content of irradiated specimens, no changes after irradiation were observed. It was confirmed that radiation exposure did not significantly affect the basic material properties of concrete within the range of radiation doses adopted in this study.
Jacquinot, J.*; Albajar, F.*; Beaumont, B.*; Becoulet, A.*; Bonicelli, T.*; Bora, D.*; Campbell, D.*; Chakraborty, A.*; Darbos, C.*; Decamps, H.*; et al.
Fusion Engineering and Design, 84(2-6), p.125 - 130, 2009/06
The electron cyclotron (EC), ion cyclotron (IC), neutral beam (NB) and, lower hybrid (LH) systems for ITER have been reviewed in 2007/2008 in light of progress of physics and technology. Although the overall specifications are unchanged, notable changes have been approved. Firstly, the full 73MW should be commissioned and available on a routine basis before the D/T phase. Secondly, the possibility to operate the NB at full power during the hydrogen phase requiring new shine through protection; IC with 2 antennas with increased robustness; 2 MW transmission systems to provide an easier upgrading of the EC power; the addition of a building dedicated to the RF power sources and to a testing facility for acceptance of diagnostics and heating port plugs. Thirdly, the need of a plan for developing, in time for the active phase, a CD system such as LH suitable for very long pulse operation of ITER was recognized.
Hemsworth, R. S.*; Decamps, H.*; Graceffa, J.*; Schunke, B.*; Tanaka, Masanobu*; Dremel, M.*; Tanga, A.*; DeEsch, H. P. L.*; Geli, F.*; Milnes, J.*; et al.
Nuclear Fusion, 49(4), p.045006_1 - 045006_15, 2009/04
The ITER neutral beam (NB) injectors are the first injectors that will be operated under conditions and constraints similar to those in a fusion reactor. These injectors will be operated in a radiation environment and they will be activated due to the neutron flux from ITER. The injectors uses a single large ion source and accelerator that will produce 40 A 1 MeV D beams for pulse lengths of up to 3600 s. Design changes have been made to the ITER NB injectors over the past 4 years as follows: (1) Modifications to allow installation and maintenance of the beamline components with an overhead crane. (2) The RF driven negative ion source has replaced the filamented ion source. (3) The ion source power supplies will be located in an air insulated high voltage (-1 MV) deck located outside the tokamak building instead of inside an SF6 insulated HV deck located above the injector. This paper describes the status of the design as of December 2008 including the above mentioned changes.
Yamaguchi, Tetsuji; Sakamoto, Yoshifumi; Akai, Masanobu; Takazawa, Mayumi; Iida, Yoshihisa; Tanaka, Tadao; Nakayama, Shinichi
Physics and Chemistry of the Earth, 32(1-7), p.298 - 310, 2007/00
Dissolution rate of montmorillonite, diffusivity of hydroxide ion and permeability coefficient in compacted sand-bentonite mixtures were experimentally determined and formulated. A coupled mass-transport/chemical-reaction code was developed to predict variation in permeability of engineered bentonite barrier with alkaline fluid by using the formulae.
Yamaguchi, Tetsuji; Sakamoto, Yoshifumi; Iida, Yoshihisa; Negishi, Kumi; Taki, Hiroshi; Akai, Masanobu; Jinno, Fumika; Kimura, Yuichiro; Ueda, Masato; Tanaka, Tadao; et al.
Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 6 Pages, 2005/10
no abstracts in English
Tanaka, Tadao; Sakamoto, Yoshifumi; Yamaguchi, Tetsuji; Takazawa, Mayumi; Akai, Masanobu; Negishi, Kumi; Iida, Yoshihisa; Nakayama, Shinichi
JAERI-Conf 2005-007, p.105 - 110, 2005/08
Highly alkaline environments induced by cementitious materials in radioactive waste repositories are likely to dissolve and to alter montmorillonite, the main constituent of bentonite buffer materials. For the prediction of the long-term variations in permeability of compacted sand-bentonite mixtures, long-term alteration of bentonite should be quantified based on information accumulated by using the compacted or powdered bentonite materials, with batch experiments or column experiments. In this study, we summarize distinctive information obtained from various experimental systems, and propose functional and effective integration of experimental approaches to prediction of bentonite alteration.
Takazawa, Mayumi; Negishi, Kumi; Sakamoto, Yoshifumi; Akai, Masanobu; Yamaguchi, Tetsuji; Iida, Yoshihisa; Tanaka, Tadao; Nakayama, Shinichi
JAERI-Conf 2005-007, p.236 - 241, 2005/08
no abstracts in English
Nakayama, Shinichi; Sakamoto, Yoshifumi; Yamaguchi, Tetsuji; Akai, Masanobu; Tanaka, Tadao; Sato, Tsutomu*; Iida, Yoshihisa
Applied Clay Science, 27(1-2), p.53 - 65, 2004/10
Alkaline environments induced by cement in radioactive waste repositories are likely to alter montmorillonite, the main constituent of bentonite buffer materials. Over long time periods, the alteration may cause the physical and/or chemical properties of the buffer to deteriorate. For the purpose of acquiring numerical data to quantify the effect of alteration on permeability of bentonite buffer, dissolution rates of montmorillonite and diffusivity of hydroxide ions in compacted sand-bentonite mixture specimens have been measured under highly alkaline, simulated groundwater conditions. The dissolution rate of montmorillonite was given by the linear dependence on time under the employed experimental conditions of pH 13 to 14 and temperatures of 90 to 170C. The diffusivity of hydroxide ions was obtained in through-diffusion experiments combined with a pore diffusion model. The experiments were performed under relatively low temperatures of 10 to 50C to minimize the effect of alteration of bentonite. The effective diffusivity was on the order of 10 to 10 m/s.
Takazawa, Mayumi; Yamaguchi, Tetsuji; Sakamoto, Yoshifumi; Akai, Masanobu; Tanaka, Tadao; Nakayama, Shinichi
NUMO-TR-04-05, p.A3_59 - A3_62, 2004/10
no abstracts in English
Akai, Masanobu; Ito, Nobuyuki*; Yamaguchi, Tetsuji; Tanaka, Tadao; Iida, Yoshihisa; Nakayama, Shinichi; Inagaki, Shingo*
JAERI-Tech 2004-058, 47 Pages, 2004/09
Geochemistry Research Equipment for TRU Waste Elements has been installed in Back-end Cycle Key Elements Research Facility (BECKY) of Nuclear Fuel Cycle Safety Engineering Research Facility (NUCEF). This equipment is designed to study geochemical behavior of TRU elements and other radionuclides contained in TRU waste (TRU waste elements) and to acquire data for safety assessments of radioactive wastes disposal. The equipment consists of anaerobic glove box systems, aerobic glove box systems equipped with built-in barrier performance testing apparatus, and analytical instruments. This report describes principles, structure, performance and safety designs of each component of the equipment, and results of research performed in the equipment.