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Journal Articles

The Surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; Matsuoka, Moe*; et al.

Science, 364(6437), p.272 - 275, 2019/04

 Times Cited Count:99 Percentile:0.17(Multidisciplinary Sciences)

The near-Earth asteroid 162173 Ryugu, the target of Hayabusa2 sample return mission, is believed to be a primitive carbonaceous object. The Near Infrared Spectrometer (NIRS3) on Hayabusa2 acquired reflectance spectra of Ryugu's surface to provide direct measurements of the surface composition and geological context for the returned samples. A weak, narrow absorption feature centered at 2.72 micron was detected across the entire observed surface, indicating that hydroxyl (OH)-bearing minerals are ubiquitous there. The intensity of the OH feature and low albedo are similar to thermally- and/or shock-metamorphosed carbonaceous chondrite meteorites. There are few variations in the OH-band position, consistent with Ryugu being a compositionally homogeneous rubble-pile object generated from impact fragments of an undifferentiated aqueously altered parent body.

Journal Articles

Technical basis of accident tolerant fuel updated under a Japanese R&D project

Yamashita, Shinichiro; Nagase, Fumihisa; Kurata, Masaki; Nozawa, Takashi; Watanabe, Seiichi*; Kirimura, Kazuki*; Kakiuchi, Kazuo*; Kondo, Takao*; Sakamoto, Kan*; Kusagaya, Kazuyuki*; et al.

Proceedings of 2017 Water Reactor Fuel Performance Meeting (WRFPM 2017) (USB Flash Drive), 10 Pages, 2017/09

In Japan, the research and development (R&D) project on accident tolerant fuel and other components (ATFs) of light water reactors (LWRs) has been initiated in 2015 for establishing technical basis of ATFs. The Japan Atomic Energy Agency (JAEA) has coordinated and carried out this ATF R&D project in cooperation with power plant providers, fuel venders and universities for making the best use of the experiences, knowledges in commercial uses of zirconium-base alloys (Zircaloy) in LWRs. ATF candidate materials under consideration in the project are FeCrAl steel strengthened by dispersion of fine oxide particles(FeCrAl-ODS) and silicon carbide (SiC) composite, and are expecting to endure severe accident conditions in the reactor core for a longer period of time than the Zircaloy while maintaining or improving fuel performance during normal operations. In this paper, the progresses of the R&D project are reported.

Journal Articles

Progress report of Japanese simulation research projects using the high-performance computer system Helios in the International Fusion Energy Research Centre

Ishizawa, Akihiro*; Idomura, Yasuhiro; Imadera, Kenji*; Kasuya, Naohiro*; Kanno, Ryutaro*; Satake, Shinsuke*; Tatsuno, Tomoya*; Nakata, Motoki*; Nunami, Masanori*; Maeyama, Shinya*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 92(3), p.157 - 210, 2016/03

The high-performance computer system Helios which is located at The Computational Simulation Centre (CSC) in The International Fusion Energy Research Centre (IFERC) started its operation in January 2012 under the Broader Approach (BA) agreement between Japan and the EU. The Helios system has been used for magnetised fusion related simulation studies in the EU and Japan and has kept high average usage rate. As a result, the Helios system has contributed to many research products in a wide range of research areas from core plasma physics to reactor material and reactor engineering. This project review gives a short catalogue of domestic simulation research projects. First, we outline the IFERC-CSC project. After that, shown are objectives of the research projects, numerical schemes used in simulation codes, obtained results and necessary computations in future.

Journal Articles

Trends of nitrogen oxide release during thermal decomposition of nitrates in highly active liquid waste

Amano, Yuki; Watanabe, Koji; Tashiro, Shinsuke; Yamane, Yuichi; Ishikawa, Jun; Yoshida, Kazuo; Uchiyama, Gunzo; Abe, Hitoshi

Nippon Genshiryoku Gakkai Wabun Rombunshi, 14(2), p.86 - 94, 2015/06

Radioactive materials could be released into air due to the accidental boiling of high active liquid waste (HALW) in reprocessing plants. Volatile radioactive nuclides, such as ruthenium, are released from the tanks into the atmosphere. Nitrogen oxides (NOx) are also released due to the thermal decomposition of metal nitrates in HALW. The released NOx transport volatile ruthenium and cause redox reactions associated with the composition or decomposition of volatile ruthenium. In this study, NOx release data were obtained by heating simulated HALW up to 600$$^{circ}$$C. As a result, the release of NOx from the simulated HALW was observed from 200$$^{circ}$$C to 600$$^{circ}$$C, and the main release of NOx was observed at about 340$$^{circ}$$C. All the lanthanide nitrates were found to decompose in the simulated HALW, and the thermal decomposition temperature of the lanthanide nitrates decreased after the addition of ruthenium dioxide to the mixed lanthanide nitrates solution.

Journal Articles

Three-dimensional and multienergy $$gamma$$-ray simultaneous imaging by using a Si/CdTe Compton camera

Suzuki, Yoshiyuki*; Yamaguchi, Mitsutaka; Odaka, Hirokazu*; Shimada, Hirofumi*; Yoshida, Yukari*; Torikai, Kota*; Sato, Takahiro; Arakawa, Kazuo*; Kawachi, Naoki; Watanabe, Shigeki; et al.

Radiology, 267(3), p.941 - 947, 2013/06

 Times Cited Count:10 Percentile:54.38(Radiology, Nuclear Medicine & Medical Imaging)

Journal Articles

An Evaluation of three-dimensional imaging by use of Si/CdTe Compton cameras

Yamaguchi, Mitsutaka; Nagao, Yuto; Kawachi, Naoki; Fujimaki, Shu; Kamiya, Tomihiro; Odaka, Hirokazu*; Kokubun, Motohide*; Takeda, Shinichiro*; Watanabe, Shin*; Takahashi, Tadayuki*; et al.

Proceedings of 2013 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC), 3 Pages, 2013/00

Journal Articles

A New method for monitoring beam range by measuring low energy photons

Yamaguchi, Mitsutaka; Torikai, Kota*; Kawachi, Naoki; Shimada, Hirofumi*; Sato, Takahiro; Nagao, Yuto; Fujimaki, Shu; Kokubun, Motohide*; Watanabe, Shin*; Takahashi, Tadayuki*; et al.

Proceedings of 2013 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC), 2 Pages, 2013/00

Journal Articles

Beam range estimation by measuring bremsstrahlung

Yamaguchi, Mitsutaka; Torikai, Kota*; Kawachi, Naoki; Shimada, Hirofumi*; Sato, Takahiro; Nagao, Yuto; Fujimaki, Shu; Kokubun, Motohide*; Watanabe, Shin*; Takahashi, Tadayuki*; et al.

Physics in Medicine & Biology, 57(10), p.2843 - 2856, 2012/05

 Times Cited Count:18 Percentile:39.31(Engineering, Biomedical)

Journal Articles

Three-dimensional imaging test for a head module of a Si/CdTe Compton camera for medical application

Yamaguchi, Mitsutaka; Kawachi, Naoki; Kamiya, Tomihiro; Sato, Takahiro; Suzui, Nobuo; Fujimaki, Shu; Odaka, Hirokazu*; Ishikawa, Shinnosuke*; Kokubun, Motohide*; Watanabe, Shin*; et al.

JAEA-Review 2011-043, JAEA Takasaki Annual Report 2010, P. 145, 2012/01

no abstracts in English

Journal Articles

Flux pinning properties of correlated pinning at low temperatures in ErBCO films with inclined columnar defects

Awaji, Satoshi*; Namba, Masashi*; Watanabe, Kazuo*; Kai, Hideki*; Mukaida, Masashi*; Okayasu, Satoru

Journal of Applied Physics, 111(1), p.013914_1 - 013914_4, 2012/01

 Times Cited Count:18 Percentile:34.06(Physics, Applied)

The effect of $$c$$-axis correlated pinning on the critical current density $$J$$$$_{c}$$ at low temperatures under high magnetic fields was investigated on the basis of the transport measurements of $$J$$$$_{c}$$ and irreversibility field B$$_{irr}$$ properties of an ErBa$$_{2}$$Cu$$_{3}$$O$$_{y}$$ film with inclined columnar defects. The contribution of correlated pinning on $$J$$$$_{c}$$ decreased drastically with decreasing temperature under high magnetic fields above the matching field. At low temperatures, the presence of a matching field limited the pinning force for correlated pinning, while the ratio of the maximum pinning force of the correlated pinning to the random one was proportional to the inverse of B$$_{irr}$$. In order to improve the critical current properties at low temperatures under high magnetic fields, an increase in the matching field and/or the introduction of strong random pinning are effective.

Journal Articles

Conceptual design study of JSFR, 2; Reactor system

Eto, Masao*; Kamishima, Yoshio*; Okamura, Shigeki*; Watanabe, Osamu*; Oyama, Kazuhiro*; Negishi, Kazuo; Kotake, Shoji*; Sakamoto, Yoshihiko; Kamide, Hideki

Proceedings of International Conference on Fast Reactors and Related Fuel Cycles (FR 2009) (CD-ROM), 10 Pages, 2012/00

In the JSFR design, the diameter of the Reactor Vessel (RV) shall be minimized and the reactor internal structures shall be simplified for reduction in construction cost. The reduction in the RV diameter is achieved by adopting an advanced refueling system and the hot RV with high temperature wall. The flow velocity in the reactor upper plenum increases because the diameter of the RV is decreased. As the result, the coolant flow field in reactor upper plenum is severe. The optimization of the coolant flow field in the reactor upper plenum was carried out for prevention the cover gas entrainment and the vortex cavitations at the hot leg intake. In addition, structural integrities for seismic loadings and thermal loadings were evaluated because the design seismic loading was highly increased and the vessel wall is directly exposed to the thermal transients of the upper plenum. This paper describes the characteristics and the results of the design study of the reactor system.

Journal Articles

Development of head module for multi-head Si/CdTe Compton camera for medical applications

Yamaguchi, Mitsutaka; Kawachi, Naoki; Suzui, Nobuo; Fujimaki, Shu; Kamiya, Tomihiro; Odaka, Hirokazu*; Ishikawa, Shinnosuke*; Kokubun, Motohide*; Watanabe, Shin*; Takahashi, Tadayuki*; et al.

Nuclear Instruments and Methods in Physics Research A, 648(Suppl.1), p.S2 - S7, 2011/08

 Times Cited Count:1 Percentile:86.98(Instruments & Instrumentation)

We are constructing a three-dimensional imaging system for medical and biological applications. The system will allow simultaneous imaging at high spatial and energy resolutions across a wide energy range, from several tens of keV to a few MeV. In this work, one prototype head module have been developed for a multi-head Si/CdTe Compton camera system. The performance of the prototype was evaluated with a sealed Ba-133 radiation source. The experiments confirmed that the imaging results were consistent with actual source position. In addition to the resolution for the parallel directions to the detector surface, the position resolution was evaluated for the depth direction at a point in near region of the head-module. These position resolutions were well reproduced by Monte Carlo simulation results.

Journal Articles

Cooperative behavior of the random and correlated pinning in Er123 films with columnar defects

Awaji, Satoshi*; Namba, Masashi*; Watanabe, Kazuo*; Ito, Shun*; Aoyagi, Eiji*; Kai, Hideki*; Mukaida, Masashi*; Okayasu, Satoru

IEEE Transactions on Applied Superconductivity, 21(3), p.3192 - 3195, 2011/06

 Times Cited Count:5 Percentile:67.77(Engineering, Electrical & Electronic)

The flux pinning behaviors for the heavy ion irradiated Er123 films are investigated based on the detailed $$J$$$$_{rm c}$$ ($$B$$, $$T$$, $$theta$$) properties. The double peaks of $$F$$$$_{rm p}$$ curves for $$B$$//c appear in case of the matching field of 0.3 T along $$c$$-axis and 1.7 T tilted from $$c$$-axis. In addition, the peaks on $$J$$$$_{rm c}$$ ($$theta$$) at $$theta$$ = 0$$^{circ}$$ (B//c), which originate from the columnar defects, decrease with increasing magnetic field but increase again near the irreversibility field. We found that the cooperation model of the $$c$$-axis correlated and random pinning centers can describe the observed double peak behavior of $$F$$$$_{rm p}$$(B) and the angular dependence of $$J$$$$_{rm c}$$ related to the correlated pinning.

Journal Articles

Counting rate performance measurement of newly developed Si/CdTe Compton camera for biological and medical applications

Yamaguchi, Mitsutaka; Kawachi, Naoki; Kamiya, Tomihiro; Suzui, Nobuo; Fujimaki, Shu; Odaka, Hirokazu*; Ishikawa, Shinnosuke*; Kokubun, Motohide*; Watanabe, Shin*; Takahashi, Tadayuki*; et al.

2010 IEEE Nuclear Science Symposium Conference Record (CD-ROM), p.2004 - 2007, 2010/10

Journal Articles

Radioactive certified reference materials

Watanabe, Kazuo

Bunseki, 2010(7), p.349 - 350, 2010/07

Outline of radioactive certified reference materials (CRM) for the analysis of nuclear materials and radioactive nuclides were described. The nuclear fuel CRMs are supplied by the three institutes: NBL in the US, CETAMA in France and IRMM in Belgium. For the RI CRMs, the Japan Radioisotope Association is engaged in activities concerning supply. The natural-matrix CRMs for the analysis of trace levels of radio-nuclides are prepared and supplied by NIST in the US and the IAEA.

Journal Articles

29th report of ITPA topical group meeting

Isayama, Akihiko; Sakakibara, Satoru*; Furukawa, Masaru*; Matsunaga, Go; Yamazaki, Kozo*; Watanabe, Kiyomasa*; Idomura, Yasuhiro; Sakamoto, Yoshiteru; Tanaka, Kenji*; Tamura, Naoki*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 86(6), p.374 - 377, 2010/06

no abstracts in English

Journal Articles

Development and basic study for lesion size measuring system on an endoscopic image

Oka, Kiyoshi; Seki, Takeshi*; Naito, Takehito*; Watanabe, Shinya*; Wakabayashi, Takao*; Naganawa, Akihiro*; Inui, Kazuo*; Yoshino, Junji*

Nippon Gazo Igaku Zasshi, 28(1), p.12 - 24, 2010/05

Focusing on the measurement function loaded on our rigid-typed endoscope for the fetal surgery treatment, we proposed that its combination with a generally used digestive endoscope enabled calibration of lesion size in stomach. While adding the function, with which the target size is to be easily measured, on the endoscope, we simplified the system structure as much as possible. We also tried to minimize the total cost by using the generally used endoscope, instead of making it from scratch. Combining another development, the composite-type optical fiberscope with diameter of 1.1mm, with a generally used endoscope, we proposed the following as the features: (1)acquisition of fiberscope image, (2)laser irradiation for treatments, (3)applying the real time measurement function of distance and blood flow by semiconductor laser to the generally used endoscope. We have operated the clinical study to the gastric wall of person with no health problem, using this system and confirmed it was available for practical use.

Journal Articles

27th report of ITPA topical group meeting

Osakabe, Masaki*; Shinohara, Koji; Toi, Kazuo*; Todo, Yasushi*; Hamamatsu, Kiyotaka; Murakami, Sadayoshi*; Yamamoto, Satoshi*; Idomura, Yasuhiro; Sakamoto, Yoshiteru; Tanaka, Kenji*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 85(12), p.839 - 842, 2009/12

no abstracts in English

JAEA Reports

Root cause analysis method applied to accidents and troubles of nuclear research facilities

Sato, Takeshi; Watanabe, Norio; Yoshida, Kazuo

JAEA-Technology 2009-028, 29 Pages, 2009/05


The importance to make use of lessons learned and knowledge from accidents and troubles in safety management of nuclear research facilities is recognized widely. By the root cause analysis of accidents and troubles, lessons learned and knowledge have been arrived about safety management of facilities. The root cause analysis has been performed for accidents and troubles generated at nuclear research facilities in Japan Atomic Energy Agency (JAEA) from about 1990. Because the analysis is performed for various facilities, anyone have been used the analysis method of possible of utilize. On this account the analysis method has been developed and adopted an existing analysis method. This report introduces the analysis method that has been used for the root cause analysis of these accidents and troubles. Furthermore, this report apply a generally well known JCO Criticality Accident to each analysis method as an example and explain on the direction for uses.

Journal Articles

Ablation-initiated isotope-selective atomic absorption spectroscopy of lanthanide elements

Miyabe, Masabumi; Oba, Masaki; Iimura, Hideki; Akaoka, Katsuaki; Maruyama, Yoichiro; Wakaida, Ikuo; Watanabe, Kazuo

AIP Conference Proceedings 1104, p.30 - 35, 2009/03

no abstracts in English

186 (Records 1-20 displayed on this page)