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Okagaki, Yuria; Shibamoto, Yasuteru; Wada, Yuki; Abe, Satoshi; Hibiki, Takashi*
Journal of Nuclear Science and Technology, 60(8), p.955 - 968, 2023/08
Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)Yoneda, Yasuhiro; Kim, S.*; Mori, Shigeo*; Wada, Satoshi*
Japanese Journal of Applied Physics, 61(SN), p.SN1022_1 - SN1022_10, 2022/11
Times Cited Count:1 Percentile:17.38(Physics, Applied)Local structural analysis of the (1-) BiFeO-BaTiO solid solution was performed by PDF analysis of the data obtained in the synchrotron radiation high-energy X-ray diffraction experiment. First, when XAFS experiments were performed and sample screening was performed, it was found that structural fluctuations were large in the BiFeO-rich composition. Therefore, PDF analysis of a sample with BiFeO-rich composition was performed. As a result, it was found that although the average structure is a cubic structure, the local structure can be reproduced with a rhombohedral crystal structure, and there is a displacement that breaks the symmetry of the rhombohedral structure in a composition with a large fluctuation.
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
Times Cited Count:43 Percentile:96.93(Astronomy & Astrophysics)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.
Kumada, Takayuki; Oba, Yojiro; Motokawa, Ryuhei; Morooka, Satoshi; Tominaga, Aki; Tanida, Hajime; Shobu, Takahisa; Konno, Azusa; Owada, Kenji*; Ono, Naoko*; et al.
Journal of Nuclear Materials, 528, p.151890_1 - 151890_7, 2020/01
Times Cited Count:1 Percentile:12.16(Materials Science, Multidisciplinary)We have developed an anomalous small-angle X-ray scattering (ASAXS) diffractometer in SPring-8 to investigate irradiation-induced nanostructural change in ion-beam irradiated stainless steel. A thermally-aged MA956 stainless steel sample displays power-law scattering that follows the Porod law at the magnitude of scattering vector, Q, below 0.5 nm and an overlapped shoulder around 0.7 nm. After the ion-beam irradiation, the intensity of the shoulder remained unchanged, whereas that of the power-law scattering nearly doubled. This result indicates that none of the structural parameters of the Cr-rich nanoprecipitates, such as the number density, size, and interface roughness, were changed by the irradiation.
Yoneda, Yasuhiro; Kunisada, Ryoichi*; Chikada, Tsukasa*; Ueno, Shintaro*; Fujii, Ichiro*; Nagata, Hajime*; Ohara, Koji*; Wada, Satoshi*
Japanese Journal of Applied Physics, 58(SL), p.SLLA03_1 - SLLA03_7, 2019/11
Times Cited Count:4 Percentile:21.91(Physics, Applied)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:259 Percentile:99.73(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.
Owada, Kenji*; Tsukada, Shinya*; Fukuda, Tatsuo; Tsutsui, Satoshi*; Baron, A. Q. R.*; Mizuki, Junichiro*; Owa, Hidehiro*; Yasuda, Naohiko*; Terauchi, Hikaru*
Physical Review B, 98(5), p.054106_1 - 054106_10, 2018/08
Times Cited Count:3 Percentile:15.56(Materials Science, Multidisciplinary)Ito, Yuta*; Schury, P.*; Wada, Michiharu*; Arai, Fumiya*; Haba, Hiromitsu*; Hirayama, Yoshikazu*; Ishizawa, Satoshi*; Kaji, Daiya*; Kimura, Sota*; Koura, Hiroyuki; et al.
Physical Review Letters, 120(15), p.152501_1 - 152501_6, 2018/04
Times Cited Count:60 Percentile:93.36(Physics, Multidisciplinary)Masses of Es, Fm and the transfermium nuclei Md, and No, produced by hot- and cold-fusion reactions, in the vicinity of the deformed neutron shell closure, have been directly measured using a multi-reflection time-of-flight mass spectrograph. The masses of Es and Md were measured for the first time. Using the masses of Md as anchor points for decay chains, the masses of heavier nuclei, up to Bh and Mt, were determined. These new masses were compared with theoretical global mass models and demonstrated to be in good agreement with macroscopic-microscopic models in this region. The empirical shell gap parameter derived from three isotopic masses was updated with the new masses and corroborate the existence of the deformed neutron shell closure for Md and Lr.
Yoneda, Yasuhiro; Kunisada, Ryoichi*; Chikada, Tsukasa*; Ueno, Shintaro*; Ohara, Koji*; Wada, Satoshi*
Transactions of the Materials Research Society of Japan, 43(2), p.93 - 96, 2018/04
KNbO nanocrystals were grown by solvothermal technique assisted by a microwave treatment. We performed high-energy X-ray diffraction to extract average and local structural parameters. The particle size can be evaluated by the Scherrer's equation. The unit cell size was reduced as the particle size increased. The local structure was found to be a rhombohedral structure, which was similar to that of the bulk KNbO.
Ebisuzaki, Toshikazu*; Wada, Satoshi*; Saito, Norihito*; Fujii, Takashi*; Nishimura, Akihiko
Reza Kenkyu, 45(10), p.664 - 665, 2017/10
no abstracts in English
Ouchi, Satoshi; Kurumada, Osamu; Kamiishi, Eigo; Sato, Masayuki; Ikekame, Yoshinori; Wada, Shigeru
JAEA-Technology 2016-015, 42 Pages, 2016/06
The purpose of the control rod drive mechanism seating position detector for JRR-3 is one of a method for confirming the shutdown condition of the reactor. The detector has been utilizing more than 25 years with maintenance regularly. However, it is occurred some trouble recently. Moreover, the detector has already been end of manufacture, and even in the successor detector, it unsuitable for the control rod drive mechanism of JRR-3 was confirmed. Therefore, it was necessary to select the adequate detector to the control rod drive mechanism of JRR-3. Accordingly, we built a test device with the aim of verify several detectors for integrity and function. At the time of the test for performance confirmation, it was occurred unexpected problems. Nevertheless, we devise improvement of the problems and took measures. Thus we were able to collect adequate detector for JRR-3 and replace to enhanced detector. This paper reports the Enhanced of Control rod drive mechanism seat position detector.
Kurumada, Osamu; Ikekame, Yoshinori; Ouchi, Satoshi; Sato, Masayuki; Kamiishi, Eigo; Wada, Shigeru
JAEA-Technology 2015-056, 35 Pages, 2016/03
The power supply for reactor control rod magnet of JRR-3 has been utilized for generating electromagnetic power of control rod coil and that was using more than 25 years. The power supply was required for provide to stabilize DC current. Therefore, we adopted series regulator method. Although, the power supply generate a high heat. Then, we decided to create switching regulator method in order to improve the aging and heat generation of the series regulator method. This paper reports the replacement of switching regulator method.
Yoneda, Yasuhiro; Kohara, Shinji*; Nakashima, Koichi*; Nagata, Hajime*; Wada, Satoshi*
Japanese Journal of Applied Physics, 54(10S), p.10NC01_1 - 10NC01_6, 2015/10
Times Cited Count:4 Percentile:18.63(Physics, Applied)The atomic-scale structure of KNbO nanopowder synthesized by solvothermal method has been studied using high-energy X-ray diffraction, Rietveld refinement, and the atomic pair-distribution function (PDF) technique. It was found that the local structure of KNbO nanoparticles deviates from the average structure. The local structure was found to be rhombohedral structure though the average structure was tetragonal structure. The rhombohedral distortion of NbO octahedra was maintained in the annealed sample.
Yoneda, Yasuhiro; Kohara, Shinji*; Kumada, Nobuhiro*; Wada, Satoshi*
Japanese Journal of Applied Physics, 53(9S), p.09PD01_1 - 09PD01_5, 2014/09
Times Cited Count:3 Percentile:13.42(Physics, Applied)The atomic-scale structure of solid solution of BaTiO (BT) and KNbO (KN) has been studied using high-energy X-ray diffraction, X-ray absorption fine structure, and atomic pair-distribution function analysis techniques. We prepared BT-KN solid solution through KNbTiO, in which Ti and Nb atoms are arranged randomly. The average structure of BT-KN solid solution was cubic structure and the local strcuture is also reproduced by the cubic structure. It is rare that a solid solution synthesized from ferroelectric materials has a local strcuture of a paraelectric material. Since the original correlation of BT or KN was lost, ferroelectricity disappeared in the BT-KN solid solution.
Sawada, Shinichi; Yamaguchi, Daisuke; Putra, A.; Koizumi, Satoshi*; Maekawa, Yasunari
Polymer Journal, 45(8), p.797 - 801, 2013/08
Times Cited Count:10 Percentile:32.2(Polymer Science)The nanoscale structures of graft-type polymer electrolyte membranes based on poly(ethylene-co-tetrafluoroethylene) (ETFE) films were investigated using a small-angle neutron scattering (SANS) technique. For comparison, SANS measurements were also performed on two precursor materials, the original ETFE film and polystyrene (PS)-grafted films. The SANS profiles of the grafted films showed shoulder peaks at a d-spacing of approximately 30 nm, which were attributed to the PS grafts introduced into the amorphous phases between the ETFE lamellar crystals. In the ETFE PEMs, the spacing of the polystyrene sulfonic acid (PSSA) grafts and ETFE crystals increased because the graft regions were enlarged by the volume of the attached sulfonic acid groups. Interestingly, the graft / crystal stack spacing in the PEMs did not increase from the dry- to fully-hydrated states. This finding implies restricted water absorption in the PSSA grafts between the ETFE lamellar crystals.
Iwase, Hiroki*; Sawada, Shinichi; Yamaki, Tetsuya; Koizumi, Satoshi; Onuma, Masato*; Maekawa, Yasunari
Macromolecules, 45(22), p.9121 - 9127, 2012/11
Times Cited Count:19 Percentile:50.58(Polymer Science)Fundamental understanding of the structure-property relationship of polymer electrolyte membranes (PEM) is prerequisite for a material design satisfying PEM performance requirement. Small-angle scattering in a wide- range was observed by focusing small-angle neutron scattering (FSANS), small-angle neutron scattering (SANS), and small-angle X-ray scattering (SAXS). The hierarchical structure of the PEM was characterized as being composed of conducting layers (graft domains) in lamellar stacks with 48-57 nm spacing on the surfaces of 480 nm diameter crystallites and ultra-small structures with a 1.7 nm correlation distance of the sulfonic acid groups in the conducting layers. From the change in the SAXS profiles as a function of grafting degrees, it was revealed that the graft domains around the crystallites were connected with the adjoining domains and thus, the PEMs with a higher degree of grafting had conductivity higher than that of Nafion.
Wada, Ken*; Hyodo, Toshio*; Yagishita, Akira*; Ikeda, Mitsuo*; Osawa, Satoshi*; Shidara, Tetsuo*; Michishio, Koji*; Tachibana, Takayuki*; Nagashima, Yasuyuki*; Fukaya, Yuki; et al.
European Physical Journal D, 66(2), p.37 - 40, 2012/02
Times Cited Count:38 Percentile:85.29(Optics)no abstracts in English
Imaizumi, Tomomi; Miyauchi, Masaru; Ito, Masayasu; Watahiki, Shunsuke; Nagata, Hiroshi; Hanakawa, Hiroki; Naka, Michihiro; Kawamata, Kazuo; Yamaura, Takayuki; Ide, Hiroshi; et al.
JAEA-Technology 2011-031, 123 Pages, 2012/01
The number of research reactors in the world is decreasing because of their aging. However, the planning to introduce the nuclear power plants is increasing in Asian countries. In these Asian countries, the key issue is the human resource development for operation and management of nuclear power plants after constructed them, and also the necessity of research reactor, which is used for lifetime extension of LWRs, progress of the science and technology, expansion of industry use, human resources training and so on, is increasing. From above backgrounds, the Neutron Irradiation and Testing Reactor Center began to discuss basic concept of a multipurpose low-power research reactor for education and training, etc. This design study is expected to contribute not only to design tool improvement and human resources development in the Neutron Irradiation and Testing Reactor Center but also to maintain and upgrade the technology on research reactors in nuclear power-related companies. This report treats the activities of the working group from July 2010 to June 2011 on the multipurpose low-power research reactor in the Neutron Irradiation and Testing Reactor Center and nuclear power-related companies.
Konno, Chikara; Wada, Masayuki*; Kondo, Keitaro; Onishi, Seiki; Takakura, Kosuke; Ochiai, Kentaro; Sato, Satoshi
Fusion Engineering and Design, 86(9-11), p.2682 - 2685, 2011/10
Times Cited Count:4 Percentile:32.59(Nuclear Science & Technology)JENDL-4, the major revised version of Japanese Evaluated Nuclear Data Library (JENDL), was released in spring, 2010. We analyzed the fusion neutronics benchmark experiments on iron at JAEA/FNS with JENDL-4.0 and MCNP4C as the detail benchmark test of JENDL-4.0 iron data. As a result, it is found out that the problems of iron data in JENDL-3.3 are adequately revised in JENDL-4.0 iron data; e.g. the first inelastic scattering cross section data of Fe and angular distribution of elastic scattering of Fe. The iron data in JENDL-4.0 are comparable to and are partly better than those in ENDF/B-VII.0 and JEFF-3.1.
Konno, Chikara; Takakura, Kosuke; Wada, Masayuki*; Kondo, Keitaro; Onishi, Seiki*; Ochiai, Kentaro; Sato, Satoshi
Progress in Nuclear Science and Technology (Internet), 2, p.346 - 357, 2011/10
The major revised version of Japanese Evaluated Nuclear Data Library (JENDL), JENDL-4, was released in 2010 spring. As the benchmark test of JENDL-4.0 in the shielding and fusion neutronics fields, we analyzed many integral benchmark experiments (in-situ and Time-of-Flight (TOF) experiments) with DT neutrons at JAEA/FNS with the MCNP code and JENDL-4.0. The experiments with assemblies including beryllium, carbon, silicon, vanadium, copper, tungsten and lead, nuclear data of which were revised in JENDL-4.0, were selected for this benchmark test. As a result, it is found that JENDL-4 improved some problems pointed out in JENDL-3.3 and that it is comparable to ENDF/B-VII.0 and JEFF-3.1.