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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:86 Percentile:0.14(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

An Evaluation method of reflectance spectra to be obtained by Hayabusa2 Near-Infrared Spectrometer (NIRS3) based on laboratory measurements of carbonaceous chondrites

Matsuoka, Moe*; Nakamura, Tomoki*; Osawa, Takahito; Iwata, Takahiro*; Kitazato, Kohei*; Abe, Masanao*; Nakauchi, Yusuke*; Arai, Takehiko*; Komatsu, Mutsumi*; Hiroi, Takahiro*; et al.

Earth, Planets and Space (Internet), 69(1), p.120_1 - 120_12, 2017/09

AA2017-0327.pdf:1.53MB

 Times Cited Count:2 Percentile:83.59(Geosciences, Multidisciplinary)

We have conducted ground-based performance evaluation tests of the Near-Infrared Spectrometer (NIRS3) onboard Hayabusa2 spacecraft and established a method for evaluating its measured reflectance spectra. Reflectance spectra of nine powdered carbonaceous chondrite samples were measured by both NIRS3 and a FT-IR spectrometer. Since raw data obtained by NIRS3 had considerable spectral distortion caused by systematic offsets in sensitivity of individual pixels, we have established two methods for correcting the NIRS3 data by comparing them with the corresponding FT-IR data. In order to characterize the absorption bands in NIRS3 spectra, the depth of each band component D$$lambda$$ is defined for each wavelength $$lambda$$ ($$mu$$m). Reflectance spectra of asteroid Ryugu, the target asteroid of Hayabusa2, to be recorded by the NIRS3 are expected to reveal the characteristics of the surface materials by using the evaluation technique.

Journal Articles

NIRS3; The Near Infrared Spectrometer on Hayabusa2

Iwata, Takahiro*; Kitazato, Kohei*; Abe, Masanao*; Otake, Makiko*; Arai, Takehiko*; Arai, Tomoko*; Hirata, Naru*; Hiroi, Takahiro*; Honda, Chikatoshi*; Imae, Naoya*; et al.

Space Science Reviews, 208(1-4), p.317 - 337, 2017/07

 Times Cited Count:20 Percentile:34.5(Astronomy & Astrophysics)

NIRS3: The Near Infrared Spectrometer is installed on the Hayabusa2 spacecraft to observe the target C-type asteroid 162173 Ryugu at near infrared wavelengths of 1.8 to 3.2 micrometer. It aims to obtain reflectance spectra in order to detect absorption bands of hydrated and hydroxide minerals in the 3 micrometer-band. We adopted a linear-image sensor with indium arsenide (InAs) photo diodes and a cooling system with a passive radiator to achieve an optics temperature of 188 K, which enables to retaining sufficient sensitivity and noise level in the 3 micrometer wavelength region. We conducted ground performance tests for the NIRS3 flight model (FM) to confirm its baseline specifications. The results imply that the properties such as the signal-to-noise ratio (SNR) conform to scientific requirements to determine the degree of aqueous alteration, such as CM or CI chondrite, and the stage of thermal metamorphism on the asteroid surface.

Journal Articles

2016 Professional Engineer (PE) test preparation course "Nuclear and Radiation Technical Disciplines"

Takahashi, Naoki; Yoshinaka, Kazuyuki; Harada, Akio; Yamanaka, Atsushi; Ueno, Takashi; Kurihara, Ryoichi; Suzuki, Soju; Takamatsu, Misao; Maeda, Shigetaka; Iseki, Atsushi; et al.

Nippon Genshiryoku Gakkai Homu Peji (Internet), 64 Pages, 2016/00

no abstracts in English

JAEA Reports

Assessment report of research and development on "Nuclear Safety Research" in FY2014 (Post- and pre-review report)

Kudo, Tamotsu; Onizawa, Kunio*; Nakamura, Takehiko

JAEA-Evaluation 2015-011, 209 Pages, 2015/11

JAEA-Evaluation-2015-011.pdf:10.36MB

Japan Atomic Energy Agency (JAEA) consulted an assessment committee, "Evaluation Committee of Research and Development (R&D) Activities for Nuclear Safety", for post- and pre-review assessment of R&D on nuclear safety research. In response to JAEA's request, the Committee assessed mainly the progress of the R&D project according to guidelines, which addressed the rationale behind the R&D project, the relevance of the project outcome and the efficiency of the project implementation during the period of the current and next plan. As a result, the Committee concluded that the progress of the R&D project is satisfactory. This report describes the results of evaluation by the Committee. In addition, the appendix of this report contains presentations used for the evaluation, and responses from JAEA on the comments from the member of the Committee.

Journal Articles

Review of five investigation committees' reports on the Fukushima Dai-ichi Nuclear Power Plant severe accident; Focusing on accident progression and causes

Watanabe, Norio; Yonomoto, Taisuke; Tamaki, Hitoshi; Nakamura, Takehiko; Maruyama, Yu

Journal of Nuclear Science and Technology, 52(1), p.41 - 56, 2015/01

 Times Cited Count:5 Percentile:46.24(Nuclear Science & Technology)

On March 11, 2011, the Tohoku District-off the Pacific Ocean Earthquake and the subsequent tsunami resulted in the severe core damage at TEPCO's Fukushima Dai-ichi Nuclear Power Plant Units 1-3, involving hydrogen explosions at Units 1, 3, and 4 and the large release of radioactive materials to the environment. Four independent committees were established by the Japanese government, the Diet of Japan, the Rebuild Japan Initiative Foundation, and TEPCO to investigate the accident and published their respective reports. Also, the Nuclear and Industrial Safety Agency carried out an analysis of accident causes to obtain the lessons learned from the accident and made its report public. This article reviews the reports and clarifies the differences in their positions, from the technological point of view, focusing on the accident progression and causes. Moreover, the undiscussed issues are identified to provide insights useful for the near-term regulatory activities including accident investigation by the Nuclear Regulation Authority.

Journal Articles

Six-axis multi-anvil press for high-pressure, high-temperature neutron diffraction experiments

Sano, Asami; Hattori, Takanori; Arima, Hiroshi*; Yamada, Akihiro*; Tabata, Satoshi*; Kondo, Masahiro*; Nakamura, Akihiro*; Kagi, Hiroyuki*; Yagi, Takehiko*

Review of Scientific Instruments, 85(11), p.113905_1 - 113905_8, 2014/11

 Times Cited Count:23 Percentile:21.21(Instruments & Instrumentation)

We developed a six-axis multi-anvil press, ATSUHIME, for high-pressure and high-temperature in situ time-of-flight neutron powder diffraction experiments. The press has six orthogonally oriented hydraulic rams that operate individually to compress a cubic sample assembly. Experiments indicate that the press can generate pressures up to 9.3 GPa and temperatures up to 2000 K using a 6-6-type cell assembly, with available sample volume of about 50 mm $$^{3}$$. Using a 6-8-type cell assembly, the available conditions expand to 16 GPa and 1273 K. Combination of the six-axis press and the collimation devices realized high-quality diffraction pattern with no contamination from the heater or the sample container surrounding the sample. This press constitutes a new tool for using neutron diffraction to study the structures of crystals and liquids under high pressures and temperatures.

JAEA Reports

Assessment report of research and development on "Nuclear Safety Research" (Interim report)

Kudo, Tamotsu; Onizawa, Kunio; Nakamura, Takehiko

JAEA-Evaluation 2013-003, 253 Pages, 2014/02

JAEA-Evaluation-2013-003.pdf:30.6MB

JAEA consulted an assessment committee, "Evaluation Committee of Research and Development (R&D) Activities for Nuclear Safety", for interim assessment of R&D on nuclear safety research in accordance with "General Guideline for Evaluation of Government R&D Activities" by Cabinet Office, Government of Japan, "Guideline for Evaluation of R&D in MEXT" and so on. In response to JAEA's request, the Committee assessed mainly the progress of the R&D project according to guidelines, which addressed the rationale behind the R&D project, the relevance of the project outcome and the efficiency of the project implementation during the period of the current midterm plan. As a result, the Committee concluded that the progress of the R&D project is satisfactory. This report describes the results of evaluation by the Committee. In addition, the appendix of this report contains presentations used for the evaluation, and responses from JAEA on the comments from the member of the Committee.

Journal Articles

Determination of electrochemical corrosion potential along the JMTR in-pile loop, 1; Evaluation of ECP of stainless steel in high-temperature water as a function of oxidant concentrations and exposure time

Uchida, Shunsuke; Hanawa, Satoshi; Nishiyama, Yutaka; Nakamura, Takehiko; Sato, Tomonori; Tsukada, Takashi; Kysela, J.*

Nuclear Technology, 183(1), p.119 - 135, 2013/07

 Times Cited Count:3 Percentile:68.05(Nuclear Science & Technology)

In-pile loop experiments are one of the key technologies which can provide an understanding of corrosion behaviors of structural materials in nuclear power plants (NPPs). The experiments should be supported not only by reliable measurement tools to confirm corrosive conditions under neutron and $$gamma$$ ray irradiations but also by theoretical models for extrapolating the measured data to predict corrosion behaviors in NPPs. The relationships among electrochemical corrosion potential (ECP), metal surface conditions, exposure time and other environmental conditions have been determined from in situ measurements of corrosion behaviors of stainless steel specimens exposed to H$$_{2}$$O$$_{2}$$ and O$$_{2}$$ in high temperature water. Based on the relationships, a model to evaluate ECP of stainless steel was developed by coupling an electrochemical model and a double oxide layer model. Major conclusions obtained from the evaluation model are as follows. (1) The difference in ECP behaviors of the specimens exposed to H$$_{2}$$O$$_{2}$$ and O$$_{2}$$ were mainly from the thickness and developing rate of the inner oxide layers. (2) Calculated ECP behaviors, e.g., the different responses to H$$_{2}$$O$$_{2}$$ and O$$_{2}$$ and hysteresis and memory effects, agreed with the measured ones. (3) Neutron exposure might decrease ECP due to radiation-induced diffusion in the oxide layer. The ECP evaluation model will be applied to evaluation of corrosive conditions in the JMTR in-pile loop.

Journal Articles

Determination of electrochemical corrosion potential along the JMTR in-pile loop, 2; Validation of ECP electrodes and the extrapolation of measured ECP data

Hanawa, Satoshi; Nakamura, Takehiko; Uchida, Shunsuke; Kus, P.*; Vsolak, R.*; Kysela, J.*; Sakai, Masanori*

Nuclear Technology, 183(1), p.136 - 148, 2013/07

 Times Cited Count:2 Percentile:77.33(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Review of five investigation committees' reports on the Fukushima Dai-ichi Nuclear Power Plant severe accident; Focusing on accident progression and causes

Watanabe, Norio; Yonomoto, Taisuke; Tamaki, Hitoshi; Nakamura, Takehiko; Maruyama, Yu

Nippon Genshiryoku Gakkai Wabun Rombunshi, 12(2), p.113 - 127, 2013/06

On March 11, 2011, the Tohoku District - off the Pacific Ocean Earthquake and the subsequent tsunami resulted in the severe core damage at the TEPCO's Fukushima Dai-ichi Nuclear Power Station Units 1-3, involving hydrogen explosions at Units 1, 3, and 4 and the large release of radioactive materials to the environment. The four independent committees were established by the Government, the Diet of Japan and the Rebuild Japan Initiative Foundation as well as TEPCO to investigate the accident and published their respective reports. Also, the Nuclear and Industrial Safety Agency carried out the analysis of accident causes to obtain the lessons learned from the accident and made its report public. This article reviews the reports and clarifies the differences in their positions, from the technological point of view, focusing on the accident progression and causes. As well, the undiscussed issues are identified to provide insights useful for the near-term regulatory activities including accident investigation by the Nuclear Regulation Authority.

Journal Articles

Irradiation capability of Japanese materials test reactor for water chemistry experiments

Hanawa, Satoshi; Hata, Kuniki; Chimi, Yasuhiro; Nishiyama, Yutaka; Nakamura, Takehiko

Proceedings of 2012 Nuclear Plant Chemistry Conference (NPC 2012) (CD-ROM), 9 Pages, 2012/09

no abstracts in English

Journal Articles

Status of Japanese design and validation activities of test facilities in IFMIF/EVEDA

Wakai, Eiichi; Kikuchi, Takayuki; Kogawara, Takafumi; Kimura, Haruyuki; Yokomine, Takehiko*; Kimura, Akihiko*; Nogami, Shuhei*; Kurishita, Hiroaki*; Saito, Masahiro*; Nishimura, Arata*; et al.

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 6 Pages, 2011/03

Japanese activities of test facilities in IFMIF-EVEDA (International Fusion Materials Irradiation Facility-Engineering Validation and Engineering Design Activities) project have three subjects of engineering design of post irradiation examination (PIE) facilities, small specimen test technique (SSTT), and engineering design of high flux test module (HFTM), and this paper is summarized about present status. Functional analysis and design of 2-D and 3-D models of PIE facility were performed. In HFTM, as materials of heater, W-3Re alloy and/or SiC/SiC composite were selected in the points of high temperature materials, fabrication technology and some suitable properties such as resistance of thermal shock, high temperature re-crystallization, ductility, resistance of irradiation degradation, and low-activation. In SSTT, a test machine of fracture toughness was designed and developed for small specimens with 10 mm square, and it had high accuracy controllability for stress and displacement.

Journal Articles

ECP measurements under neutron and $$gamma$$ ray in in-pile loop and their data evaluation by water radiolysis calculations

Hanawa, Satoshi; Nakamura, Takehiko; Uchida, Shunsuke; Kus, P.*; Vsolak, R.*; Kysela, J.*

Proceedings of 2010 Nuclear Plant Chemistry Conference (NPC 2010)/8th International Radiolysis, Electrochemistry & Materials Performance Workshop (CD-ROM), 10 Pages, 2010/10

In order to establish reliable electrochemical corrosion potential (ECP) sensors for applying in reactor core peripherals of power plants, performance tests of sensors under irradiation were carried out in the in-pile loop of the experimental reactor, LVR-15, at the Nuclear Research Institute (NRI) in Czech Republic. Responses of different kinds of sensors under neutron and $$gamma$$ irradiation conditions have been compared each other. Corrosive conditions along the in-pile loop were calculated by water radiolysis calculation code, WRAC-J and calculated corrosive conditions were compared with the measured results. As a result of the evaluation, it was confirmed that the ECP sensors could be applied to irradiation conditions of reactor peripherals, while the water radiolysis model could be also applied for evaluation of corrosive conditions of reactor peripherals.

Journal Articles

ECP evaluation by water radiolysis and ECP model calculations

Hanawa, Satoshi; Nakamura, Takehiko; Uchida, Shunsuke; Kus, P.*; Vsolak, R.*; Kysela, J.*

Proceedings of 2010 Nuclear Plant Chemistry Conference (NPC 2010)/8th International Radiolysis, Electrochemistry & Materials Performance Workshop (CD-ROM), 10 Pages, 2010/10

In-pile ECP measurements data was evaluated by water radiolysis calculations. The data was obtained by using in-pile loop in an experimental reactor, LVR-15, at the Nuclear Research Institute (NRI) in Czech Republic. Three types of ECP sensors, a Pt electrode, an Ag/AgCl sensor and a zirconia membrane sensor containing Ag/Ag$$_{2}$$O were used at several levels of the irradiation rig at various neutron flux and $$gamma$$ rates. Concentration of chemical species along the water flow was calculated by a radiolysis code, WRAC-J. The radiolysis calculation results were transferred to an ECP model. In the model, anodic and cathodic current densities were calculated with combination of an electrochemistry model and an oxide film growth model. The measured ECP data were compared with the radiolysis/ECP calculation results, and applicability of radiolysis model was confirmed.

Journal Articles

Fuels and materials irradiation test plan at JMTR

Ise, Hideo; Ogiyanagi, Jin; Nakamura, Jinichi; Sasajima, Hideo; Takasa, Akira; Hanawa, Satoshi; Kawaguchi, Yoshihiko; Chimi, Yasuhiro; Nishiyama, Yutaka; Nakamura, Takehiko

FAPIG, (180), p.22 - 25, 2010/02

Refurbishment of Japan Materials Testing Reactor (JMTR) is conducted in Japan Atomic Energy Agency (JAEA) in order to solve irradiation related issues for safe long-term operation of current light water reactors (LWRs) and development of advanced LWRs. JMTR will restart its operation in FY 2011. Manufacturing and installation of the irradiation test facilities on safety research of fuels and materials are also in progress. The outline of the fuels and materials irradiation test plan is described in this report.

Journal Articles

Identification of radical position of fission gas release in high-burnup fuel pellets under RIA conditions

Sasajima, Hideo; Sugiyama, Tomoyuki; Chuto, Toshinori; Nagase, Fumihisa; Nakamura, Takehiko; Fuketa, Toyoshi

Journal of Nuclear Science and Technology, 47(2), p.202 - 210, 2010/02

 Times Cited Count:3 Percentile:72.46(Nuclear Science & Technology)

Fission gas release positions in high burnup fuel pellets were examined after the pulse-irradiations which simulated reactivity initiated accident (RIA) conditions in the Nuclear Safety Research Reactor (NSRR). The ratio of xenon to krypton ((Xe/Kr) ratio) in the released gas showed that fission gas was released from the entire region of the pellets of the examined PWR fuels during the pulse-irradiations. On the other hand, most fission gas was released from the center and/or intermediate regions of the examined BWR fuel pellets. Consequently, it is likely that fission gas is not released selectively from the rim structure at the pellet periphery under RIA conditions.

Journal Articles

Terminal solid solubility of hydrogen in hafnium

Ogiyanagi, Jin; Chimi, Yasuhiro; Shimada, Sachio*; Nakamura, Takehiko; Abe, Katsuhiro*

Journal of Nuclear Science and Technology, 47(2), p.197 - 201, 2010/02

 Times Cited Count:1 Percentile:88.49(Nuclear Science & Technology)

The terminal solid solubility (TSS) of hydrogen during hydride dissolution/precipitation is determined by the differential scanning calorimetry technique for non-irradiated hafnium (Hf) that is used as control rods of light water reactors. The hydrogen concentration in hydrogenated Hf samples ranged from 27 to 300 wt ppm. The reliability of the TSS data obtained for Hf was confirmed by those for Zircaloy-2 (Zry-2) obtained in this study with the literature data, and best-fit equations for the obtained TSS curves for Hf are derived. The TSS for Hf at 573 K, which corresponds to an operational temperature of control rods in boiling water reactors, is in the range of 10-15 wt ppm, and is found to be 1/5-1/7 of the TSS for Zry-2.

Journal Articles

Water chemistry test at the Japan Materials Testing Reactor

Hanawa, Satoshi; Chimi, Yasuhiro; Nishiyama, Yutaka; Nakamura, Takehiko

Proceedings of Symposium on Water Chemistry and Corrosion in Nuclear Power Plants in Asia 2009, p.221 - 225, 2009/10

Water chemistry in reactor core environment is of great interest in structural materials integrity evaluation, because it plays an important role in corrosion behaviours of the materials. In order to provide significant information on stress corrosion crack growth behaviours, water chemistry tests under well quantified corrosive condition will be performed. In order to perform the tests, a new test facility is being constructed in the Japan Material Testing Reactor (JMTR). The tests will be performed under various conditions by changing water chemistry of feeding water, dose rate and flow rate at the irradiation test section etc. parametrically. The construction of the test facility will be finished in 2012 to start the tests.

Journal Articles

Newly-designed capsules for fuel ramp tests in the JMTR

Hanawa, Satoshi; Ogiyanagi, Jin; Inaba, Yoshitomo; Sasajima, Hideo; Nakamura, Jinichi; Nakamura, Takehiko

Proceedings of Top Fuel 2009 (DVD-ROM), p.350 - 356, 2009/09

In order to perform power transient tests of new design LWR's fuels, new power transient test capsules, the natural convection capsule and the forced convection capsule, are being developed. The natural convection capsule has relatively simple structure, and the test fuel rod is cooled by the natural convection of the coolant. The basic technologies for the natural convection capsule have already been established and the power transient tests will be started by using this capsule. The forced convection capsule has relatively complicated structure for circulating the cooling water and controlling the cooling water temperature. By performing several mock-up test, we confirmed that the target linear heat rate is achievable by the capsules, and elemental technologies to realize the forced convection capsule is feasible.

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