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Journal Articles

Numerical evaluation of the light transport properties of alternative He-3 neutron detectors using ceramic scintillators

Ozu, Akira; Takase, Misao*; Haruyama, Mitsuo; Kurata, Noritaka*; Kobayashi, Nozomi*; Kureta, Masatoshi; Nakamura, Tatsuya; To, Kentaro; Sakasai, Kaoru; Suzuki, Hiroyuki; et al.

Nuclear Instruments and Methods in Physics Research A, 798, p.62 - 69, 2015/10

 Times Cited Count:2 Percentile:22.25(Instruments & Instrumentation)

The light transport properties of scintillator light inside alternative He-3 neutron detector modules using scintillator sheets have been investigated by a ray-tracing simulation code. The detector module consists of a light-reflecting tube, a thin rectangular ceramic scintillator sheet laminated on a glass plate, and two photo-multiplier tubes (PMTs) mounted at both ends of the detector tube. The light induced on the surface of the scintillator sheet via nuclear interaction between the scintillator and neutrons are detected by the two PMTs. The light output of various detector modules in which the scintillator sheets are installed with several different arrangements were examined and evaluated in comparison with experimental results. The results derived from the simulation reveal that the light transport property is strongly dependent on the arrangement of the scintillator sheet inside the tube and the shape of the tube.

Journal Articles

Development and demonstration of a Pu NDA system using ZnS/$$^{10}$$B$$_{2}$$O$$_{3}$$ ceramic scintillator detectors

Nakamura, Hironobu; Ozu, Akira; Kobayashi, Nozomi*; Mukai, Yasunobu; Sakasai, Kaoru; Nakamura, Tatsuya; Soyama, Kazuhiko; Kureta, Masatoshi; Kurita, Tsutomu; Seya, Michio

Proceedings of INMM 55th Annual Meeting (Internet), 9 Pages, 2014/07

To establish an alternative technique of He-3 neutron detector that is used for nuclear material accountancy and safeguards, we have started an R&D project to develop a new type of neutron detector (Pu NDA system) using ZnS/$$^{10}$$B$$_{2}$$O$$_{3}$$ ceramic scintillator with support of Japanese government. The design of the alternative system (ASAS: Alternative Sample Assay System) is basically referenced from INVS (INVentory Sample assay system) which is passive neutron assay system of plutonium and has total 18 He-3 tubes (about 42% of counting efficiency), and the small amount of Pu in the MOX powder or Pu nitrate solution in a vial can be measured. In order to establish the technology and performance after the fabrication of the new detector progresses, we are planning to conduct demonstration activity in the early 2015 experimentally. The demonstration activity implements the confirmation of reproducibility about sample positioning, optimization of detector parameters, counting statistical uncertainty, stability (temperature and $$gamma$$-ray change) check and figure of merit (FOM) using check source and actual MOX powder. In addition to that, performance comparison between current INVS and the ASAS are also conducted. In this paper, we present some analytical study results using a Monte-Carlo simulation code (MCNP), entire ASAS design and demonstration plan to prove technology and performance.

Journal Articles

Evaluation of light transport property in alternative He-3 neutron detectors using ceramic scintillators by a ray-tracing simulation

Ozu, Akira; Takase, Misao*; Kurata, Noritaka*; Kobayashi, Nozomi*; Tobita, Hiroshi; Haruyama, Mitsuo; Kureta, Masatoshi; Nakamura, Tatsuya; Suzuki, Hiroyuki; To, Kentaro; et al.

Proceedings of 2014 IEEE Nuclear Science Symposium and Medical Imaging Conference; 21st International Symposium on Room-Temperature Semiconductor X-ray and $$gamma$$-ray detectors (NSS/MIC 2014), 5 Pages, 2014/00

In Japan Atomic Energy Agency, the helium-3 alternative neutron detector using ceramic scintillators for nuclear safeguards is under development with the support of the government. The alternative detector module consists of four components: an aluminum regular square tube, a light reflecting foil put on the inner surface of the square tube, a rectangular scintillator sheet sintered on a glass plate, and two PMTs provided at both ends of the tube. The scintillator sheet is fit on the diagonal inside the square tube. The light transport property of scintillator lights inside the tube influences on the fundamental performance of the alternative detector. Therefore, the properties of the lights emitted on the surface of the scintillator sheet and scintillation lights passing through the glass plate to the PMTs in several arrangements of the scintillator in the tubes were investigated with a ray-tracing simulation. The results are described in comparison with the experimental results.

Journal Articles

Development of an alternative plutonium canister assay system (APCA) using He-3 alternative neutron detector

Ozu, Akira; Kureta, Masatoshi; Haruyama, Mitsuo; Takase, Misao; Kurata, Noritaka; Kobayashi, Nozomi; Soyama, Kazuhiko; Nakamura, Tatsuya; Sakasai, Kaoru; To, Kentaro; et al.

Kaku Busshitsu Kanri Gakkai (INMM) Nihon Shibu Dai-34-Kai Nenji Taikai Rombunshu (Internet), 9 Pages, 2013/10

no abstracts in English

Journal Articles

Basic concept of JT-60SA tokamak assembly

Shibanuma, Kiyoshi; Arai, Takashi; Kawashima, Hisato; Hoshino, Katsumichi; Hoshi, Ryo; Kobayashi, Kaoru; Sawai, Hiroaki; Masaki, Kei; Sakurai, Shinji; Shibama, Yusuke; et al.

Journal of Plasma and Fusion Research SERIES, Vol.9, p.276 - 281, 2010/08

The JT-60 SA project is a combined project of JA-EU satellite tokamak program under the Broader Approach (BA) agreement and JA domestic program. Major components of JT-60SA for assembly are vacuum vessel (VV), superconducting coils (TF coils, EF coils and CS coil), in-vessel components such as divertor, thermal shield and cryostat. An assembly frame (with the dedicated cranes), which is located around the tokamak, is adopted to carry out effectively the assembly of tokamak components in the tokamak hall, independently of the facility cranes in the building. The assembly frame also provides assembly tools and jigs with jacks to support temporarily the components as well as to adjust the components at right positions. In this paper, the assembly scenario and scequence of the major components such as VV and TFC and the concept of the assembly frame including special jigs and fixtures are discussed.

Journal Articles

Development of negative ion based neutral beam injector toward JT-60SA

Tanaka, Yutaka; Hanada, Masaya; Kobayashi, Kaoru; Kamada, Masaki; Kisaki, Masashi

Journal of Plasma and Fusion Research SERIES, Vol.8, p.1547 - 1550, 2009/09

This paper reports recent R&D results on negative ion-based NBI system for JT-60 Super Advanced where 10 MW neutral beams is designed to be injected for 100 seconds. There are major two issues to realize such as a high-power and long-pulse injection, i.e., the improvement of voltage holding capability and the reduction of the grid power loading of the JT-60U negative ion source with three acceleration stages. As the first step for improving voltage holding capability, the breakdown location has been examined on site of JT-60U by measuring the lights emitted from spark gaps that are installed outside of the ion source in parallel with acceleration stages. To reduce the grid power to an allowable level, outward deflection of outmost beamlets, due to space charge of the inner beamlets, was suppressed by distorting the acceleration electric field at the edge of the grids. This allowed to reduce the highest grid power loading to acceptable level of 5 %.

Journal Articles

Energy spectra of bremsstrahlung X-rays emitted from an FRP insulator

Tanaka, Yutaka; Ikeda, Yoshitaka; Hanada, Masaya; Kobayashi, Kaoru; Kamada, Masaki; Kisaki, Masashi; Akino, Noboru; Yamano, Yasushi*; Kobayashi, Shinichi*; Grisham, L. R.*

IEEE Transactions on Plasma Science, 37(8), p.1495 - 1498, 2009/08

 Times Cited Count:1 Percentile:4.64(Physics, Fluids & Plasmas)

Voltage holding capability of the JT-60 negative ion source is limited by surface flashover on the FRP insulator. To improve the voltage holding capability of the ion source, the understanding of the surface flashover is required. In this study, electron energy is estimated by measuring the bremsstrahlung X-ray emitted from an FRP insulator. Energy spectra of X-ray were measured for 3 different positions and compared with those of the vacuum gap between electrodes. Near the anode, X-ray spectrum was dominated by the monoenergetic electron. Near the cathode, spectrum peak shifted to low energy compared with that near the anode. This result showed that a large amount of low energy electrons was generated on the surface of the FRP insulator near the cathode.

Journal Articles

Characteristics of voltage holding capability in multi-stage large electrostatic accelerator for fusion application

Kobayashi, Kaoru; Hanada, Masaya; Akino, Noboru; Sasaki, Shunichi; Ikeda, Yoshitaka; Takahashi, Masahiro*; Yamano, Yasushi*; Kobayashi, Shinichi*; Grisham, L. R.*

IEEE Transactions on Dielectrics and Electrical Insulation, 16(3), p.871 - 875, 2009/06

 Times Cited Count:1 Percentile:12.71(Engineering, Electrical & Electronic)

Voltage holding capability of a 500kV, 22A three-stage electrostatic accelerator, where large-area grids of 0.28 m$$^{2}$$ and large FRP insulators of 1.8 m in diameter are used, was examined. High voltage was independently applied to each acceleration stage, where the voltage holding capabilities of 130 kV were obtained. To identify whether the breakdowns occur in the gaps between the grids or the FRP insulators, high voltages were applied to the accelerator with and without the grids. Breakdown voltages without grids, i.e., the FRP insulator itself reached 170 kV of design value for each stage. These results show that the breakdown voltage of the accelerator was mainly determined by the gaps between the large-area grids. In this paper, the influence of non-uniform electric field and multi-stage grids on the voltage holding capabilities was also discussed.

Journal Articles

Electrons in the negative-ion-based NBI on JT-60U

Kisaki, Masashi; Hanada, Masaya; Kamada, Masaki; Tanaka, Yutaka; Kobayashi, Kaoru; Sasao, Mamiko*

AIP Conference Proceedings 1097, p.344 - 352, 2009/03

The stripped electron trajectories in a large negative ion accelerator with multi-apertures and three acceleration stages, where non-uniform stray magnetic field is horizontally created, are calculated in the JT-60 negative ion source by the 3-D numerical code. The horizontal non-uniform stray field results in a significant power loss of the stripped electrons in the outmost acceleration channel on the grounded grid (GRG). The power loss in the outmost acceleration channel is more than twice higher than that in the central channel due to the weaker stray field although the total power loading on the GRG is by 25% larger than that by assuming a uniform stray field.

Journal Articles

A New method for separating the $$D$$$$_{3}$$ and $$C$$$$_{2v}$$ isomers of C$$_{78}$$

Han, A. H.*; Wakahara, Takatsugu*; Maeda, Yutaka*; Akasaka, Takeshi*; Fujitsuka, Mamoru*; Ito, Osamu*; Yamamoto, Kazunori; Kako, Masahiro*; Kobayashi, Kaoru*; Nagase, Shigeru*

New Journal of Chemistry, 33(3), p.497 - 500, 2009/03

 Times Cited Count:7 Percentile:34.36(Chemistry, Multidisciplinary)

A new chemical method can be applied to isolate the isomers of C$$_{78}$$. The photochemical cycloaddition of a mixture of C$$_{78}$$($$D$$$$_{3}$$) and C$$_{78}$$($$C$$$$_{2v}$$) with disilirane affords only the mono-adduct of the $$C$$$$_{2v}$$ isomer of C$$_{78}$$. The counter part (C$$_{78}$$($$D$$$$_{3}$$)) does not give the mono-adduct with disilirane. The $$D$$$$_{3}$$ isomer itself and the adduct of the $$C$$$$_{2v}$$ isomer of C$$_{78}$$ with disilirane was easily separated by a HPLC procedure. A facile oxidative desilylation of the adduct took place, resulting in the formation of pristine C$$_{78}$$($$C$$$$_{2v}$$). In this context, the separation and the isolation of two isomers of C$$_{78}$$($$C$$$$_{2v}$$) and C$$_{78}$$($$D$$$$_{3}$$) were successfully accomplished by using a silylation-oxidative desilylation process.

Journal Articles

Recent R&D activities of negative-ion-based ion source for JT-60SA

Ikeda, Yoshitaka; Hanada, Masaya; Kamada, Masaki; Kobayashi, Kaoru; Umeda, Naotaka; Akino, Noboru; Ebisawa, Noboru; Inoue, Takashi; Honda, Atsushi; Kawai, Mikito; et al.

IEEE Transactions on Plasma Science, 36(4), p.1519 - 1529, 2008/08

 Times Cited Count:8 Percentile:34.65(Physics, Fluids & Plasmas)

The JT-60SA N-NBI system is required to inject 10 MW for 100 s at 500 keV. Three key issues should be solved for the JT-60SA N-NBI ion source. One is to improve the voltage holding capability. Recent R&D tests suggested that the accelerator with a large area of grids may need a high margin in the design of electric field and a long time for conditioning. The second issue is to reduce the grid power loading. It was found that some beamlets were strongly deflected due to beamlet-beamlet interaction and strike on the grounded grid. The grids are to be designed by taking account of beamlet-beamlet interaction in three-dimensional simulation. Third is to maintain the D- production for 100 s. A simple cooling structure is proposed for the active cooled plasma grid, where a key is the temperature gradient on the plasma grid for uniform D- production. The modified N-NBI ion source will start on JT-60SA in 2015.

JAEA Reports

Breakdown location without beam acceleration in the JT-60U negative ion source

Kobayashi, Kaoru; Hanada, Masaya; Kamada, Masaki; Akino, Noboru; Sasaki, Shunichi; Ikeda, Yoshitaka

JAEA-Technology 2008-042, 25 Pages, 2008/06


Breakdown locations of a JT-60U negative ion source were investigated to improve the voltage holding capability. The accelerator is characterized by three acceleration stages with large grids 0.45 m $$times$$ 1.1 m and large FRP insulators 1.8 m in inner diameter. High voltages were applied to each acceleration stage independently. Voltage holding capabilities of each stage were almost the same, $$sim$$ 120-130 kV, which was lower than the design acceleration voltage of 167 kV. Then, in order to identify whether the breakdowns occur in the gaps between grids or on the surface of the FRP insulators, high voltages were also applied to the accelerator with the grids and their support flanges removed. The voltage holding capabilities of three FRP insulators rapidly achieved 167 kV. These results indicate that the breakdowns mainly occur in the gaps between the acceleration grids and/or their support flanges.

Journal Articles

Role of DNA-PKcs in the bystander effect after low- or high-LET irradiation

Kanasugi, Yuichi*; Hamada, Nobuyuki*; Wada, Seiichi*; Funayama, Tomoo; Sakashita, Tetsuya; Kakizaki, Takehiko; Kobayashi, Yasuhiko; Takakura, Kaoru*

International Journal of Radiation Biology, 83(2), p.73 - 80, 2007/02

 Times Cited Count:30 Percentile:89.28(Biology)

no abstracts in English

Journal Articles

Chromosomal aberrations by medium-mediated bystander effects induced by high-LET radiations

Takakura, Kaoru*; Kanasugi, Yuichi*; Hamada, Nobuyuki*; Wada, Seiichi*; Funayama, Tomoo; Sakashita, Tetsuya; Kakizaki, Takehiko; Kobayashi, Yasuhiko

JAEA-Review 2006-042, JAEA Takasaki Annual Report 2005, P. 112, 2007/02

no abstracts in English

JAEA Reports

Investigation of safety concept of spallation neutron source

Kobayashi, Kaoru*; Kaminaga, Masanori; Haga, Katsuhiro; Kinoshita, Hidetaka; Aso, Tomokazu; Hino, Ryutaro

JAERI-Review 2002-010, 52 Pages, 2002/05


no abstracts in English

JAEA Reports

Estimation of thermochemical behavior of spallation products in mercury target

Kobayashi, Kaoru*; Kaminaga, Masanori; Haga, Katsuhiro; Kinoshita, Hidetaka; Aso, Tomokazu; Teshigawara, Makoto; Hino, Ryutaro

JAERI-Tech 2002-005, 118 Pages, 2002/02


In order to examine the radiation safety of a spallation mercury target system, it is necessary to clarify the chemical forms of spallation products generated by spallation reaction with proton beam. As for the chemical forms of spallation products in mercury that involves large amounts of spallation products, these forms were estimated by using the binary phase diagrams and the thermochemical equilibrium calculation based on the amounts of spallation product. Calculation results showed that the mercury would dissolve Al, As, B, Be, Bi, C, Co, Cr, Fe, Ga, Ge, Ir, Mo, Nb, Os, Re, Ru, Sb, Si, Ta, Tc, V and W in the element state, and Ag, Au, Ba, Br, Ca, Cd, Ce, Cl, Cs, Cu, Dy, Er, Eu, F, Gd, Hf, Ho, I, In, K, La, Li, Lu, Mg, Mn, Na, Nd, Ni, O, Pb, Pd, Pr, Pt, Rb, Rh, S, Sc, Se, Sm, Sn, Sr, Tb, Te, Ti, Tl, Tm, Y, Yb, Zn and Zr in the form of inorganic mercury compounds.

Journal Articles

Present status of spallation neutron source development; JAERI/KEK joint project in Japan

Kaminaga, Masanori; Haga, Katsuhiro; Aso, Tomokazu; Kinoshita, Hidetaka; Kogawa, Hiroyuki; Ishikura, Shuichi*; Terada, Atsuhiko*; Kobayashi, Kaoru*; Adachi, Junichi*; Teraoku, Takuji*; et al.

Proceedings of American Nuclear Society Conference "Nuclear Applications in the New Millennium" (AccApp-ADTTA '01) (CD-ROM), 9 Pages, 2002/00

no abstracts in English

JAEA Reports

Physical and thermochemical properties for inorganic mercury compounds

Kobayashi, Kaoru*; Kaminaga, Masanori; Haga, Katsuhiro; Kinoshita, Hidetaka; Aso, Tomokazu; Kogawa, Hiroyuki; Hino, Ryutaro

JAERI-Data/Code 2000-037, 69 Pages, 2000/12


no abstracts in English

JAEA Reports

Proposal of source term methodologies for mercury target system

Kobayashi, Kaoru*; Kaminaga, Masanori; Haga, Katsuhiro; Kinoshita, Hidetaka; Aso, Tomokazu; Kogawa, Hiroyuki; Hino, Ryutaro

JAERI-Tech 2000-050, 43 Pages, 2000/08


no abstracts in English

JAEA Reports

Design of the solid target structure and the study on the coolant flow distribution in the solid target using the 2-dimensional flow analysis

Haga, Katsuhiro; Susuki, Akira*; Terada, Atsuhiko*; Ishikura, Shuichi*; Teshigawara, Makoto; Kinoshita, Hidetaka; Kobayashi, Kaoru*; Kaminaga, Masanori; Hino, Ryutaro

JAERI-Tech 99-081, p.43 - 0, 1999/11


no abstracts in English

44 (Records 1-20 displayed on this page)