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Xu, X.*; Odaira, Takumi*; Xu, S.*; Hirata, Kenji*; Omori, Toshihiro*; Ueki, Kosuke*; Ueda, Kyosuke*; Narushima, Takayuki*; Nagasako, Makoto*; Kainuma, Ryosuke*; et al.
Advanced Materials & Processes, 180(7), p.35 - 37, 2022/10
Odaira, Takumi*; Xu, S.*; Hirata, Kenji*; Xu, X.*; Omori, Toshihiro*; Ueki, Kosuke*; Ueda, Kyosuke*; Narushima, Takayuki*; Nagasako, Makoto*; Harjo, S.; et al.
Advanced Materials, 34(27), p.2202305_1 - 2202305_11, 2022/07
Times Cited Count:12 Percentile:87.73(Chemistry, Multidisciplinary)Matsuya, Yusuke; Kusumoto, Tamon*; Yachi, Yoshie*; Hirata, Yuho; Miwa, Misako*; Ishikawa, Masayori*; Date, Hiroyuki*; Iwamoto, Yosuke; Matsuyama, Shigeo*; Fukunaga, Hisanori*
AIP Advances (Internet), 12(2), p.025013_1 - 025013_9, 2022/02
Times Cited Count:4 Percentile:59.24(Nanoscience & Nanotechnology)Boron Neutron Capture Therapy (BNCT) is a radiation therapy, which can selectively eradicate solid tumors by -particles and Li ions generated through the nuclear reaction between thermal neutron and B in tumor cells. With the development of accelerator-based neutron sources that can be installed in medical institutions, accelerator-based boron neutron capture therapy is expected to become available at several medical institutes around the world in the near future. Lithium is one of the targets that can produce thermal neutrons from the Li(p,n)Be near-threshold reaction. Particle and Heavy Ion Transport code System (PHITS) is a general-purpose Monte Carlo code, which can simulate a variety of diverse particle types and nuclear reactions. The latest PHITS code enables simulating the generation of neutrons from the Li(p,n)Be reactions by using Japanese Evaluated Nuclear Data Library (JENDL-4.0/HE). In this study, we evaluated the neutron fluence using the PHITS code by comparing it to reference data. The subsequent neutron transport simulations were also performed to evaluate the boron trifluoride (BF) detector responses and the recoiled proton fluence detected by a CR-39 plastic detector. As a result, these comparative studies confirmed that the PHITS code can accurately simulate neutrons generated from an accelerator using a Li target. The PHITS code has a significant potential for contributing to more precise evaluating accelerator-based neutron fields and understandings of therapeutic effects of BNCT.
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.
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.
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:54 Percentile:71.62(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.
Nakashima, Yosuke*; Takeda, Hisahito*; Ichimura, Kazuya*; Hosoi, Katsuhiro*; Oki, Kensuke*; Sakamoto, Mizuki*; Hirata, Mafumi*; Ichimura, Makoto*; Ikezoe, Ryuya*; Imai, Tsuyoshi*; et al.
Journal of Nuclear Materials, 463, p.537 - 540, 2015/08
Times Cited Count:19 Percentile:82.55(Materials Science, Multidisciplinary)Nakashima, Yosuke*; Sakamoto, Mizuki*; Yoshikawa, Masayuki*; Oki, Kensuke*; Takeda, Hisahito*; Ichimura, Kazuya*; Hosoi, Katsuhiro*; Hirata, Mafumi*; Ichimura, Makoto*; Ikezoe, Ryuya*; et al.
Proceedings of 25th IAEA Fusion Energy Conference (FEC 2014) (CD-ROM), 8 Pages, 2014/10
Tsuchida, Hidetsugu*; Majima, Takuya*; Tomita, Shigeo*; Sasa, Kimikazu*; Narumi, Kazumasa; Saito, Yuichi; Chiba, Atsuya; Yamada, Keisuke; Hirata, Koichi*; Shibata, Hiromi*; et al.
Nuclear Instruments and Methods in Physics Research B, 315, p.336 - 340, 2013/11
Times Cited Count:3 Percentile:26.71(Instruments & Instrumentation)Kato, Atsushi; Chikazawa, Yoshitaka; Uto, Nariaki; Hirata, Shingo; Obata, Hiroyuki*
Proceedings of International Conference on Fast Reactors and Related Fuel Cycles (FR 2009) (CD-ROM), 12 Pages, 2012/00
A basic feasibility of the helium gas cask has been evaluated by thermal analyses. There have been conducted two analyses: whole cask and detail inside subassembly analyses. The detail inside subassembly analysis has shown that the temperature distribution is mainly governed by thermal conductivity and natural convection of coolant helium hardly contributes heat removal. In the case of a cask with five subassemblies with 2.2 kW decay heat per each, the maximum cladding temperature is evaluated to be 361 C satisfying cladding temperature limit of 395 C. Those results have shown the basic feasibility of the helium gas fresh fuel shipping cask.
Hirata, Shingo; Chikazawa, Yoshitaka; Kato, Atsushi; Uto, Nariaki; Obata, Hiroyuki*; Kotake, Shoji*
Proceedings of International Conference on Fast Reactors and Related Fuel Cycles (FR 2009) (CD-ROM), 10 Pages, 2012/00
In Fast Reactor Cycle Technology Development (FaCT) project, Japan Sodium-cooled Fast Reactor (JSFR) is going to adopt an advanced fuel handling system. As for ex-vessel spent fuel handling, a pot which contains two fuel subassemblies simultaneously and is applicable size to compact reactor vessel, has been developing so as to shorten a refueling period leading to an improvement of plant availability. The pot is required to provide sufficient cooling capability even in case of transportation malfunction during transportation of spent fuel subassemblies with high decay heat. In the present study, experimental and analytical studies to evaluate the cooling capacity of the pot are summarized.
Kato, Atsushi; Hirata, Shingo; Chikazawa, Yoshitaka; Uto, Nariaki; Obata, Hiroyuki*; Kotake, Shoji*; Uzawa, Masayuki*
Proceedings of 2010 International Congress on Advances in Nuclear Power Plants (ICAPP '10) (CD-ROM), p.692 - 699, 2010/06
In the JSFR design, a single rotating plug and an upper inner structure (UIS) with a vertically penetrating slit are proposed, so that the fuel handling machine (FHM) can access any subassembly by horizontal movement of the FHM arm in the slit space. As a result of a full-scale mockup test, excellent performance in normal operation has been shown. In this study, from the viewpoint of achieving reliability of the pantograph type FHM, behavior of the FHM mockup have been investigated under abnormal conditions.
Kato, Atsushi; Hirata, Shingo; Chikazawa, Yoshitaka; Uto, Nariaki; Obata, Hiroyuki; Kotake, Shoji
Proceedings of 2009 International Congress on Advances in Nuclear Power Plants (ICAPP '09) (CD-ROM), p.9281_1 - 9281_6, 2009/05
One of the most important challenges to commercialize a Fast Reactor is to increase economic competitiveness. For that purpose, Japan Sodium cooled Fast Reactor (hereafter JSFR) aims to simplify the plant system and reduce the raw and processed material by adopting innovative technologies. In the JSFR design, a single rotating plug and a reactor upper inner structure (hereafter UIS) with a vertically penetrating slit are proposed, so that the fuel handling machine (hereafter FHM) can access any subassembly by horizontal movement of the FHM arm in the slit space. The feature of this FHM enables no need for the UIS removal when the rotational plug moves round above the core, which can achieve a compact reactor vessel to enhance the economic competitiveness. We fabricated the full scale FHM test equipment to perform comprehensive tests in the air for demonstrating the feasibility of the key characteristics of this FHM concept.
Hayashi, Takumi; Konishi, Satoshi; Ohira, Shigeru; Nakamura, Hirofumi; Inoue, Masahiko*; Watanabe, Tetsuo*; Hirata, Kazuhiro*; Naruse, Yuji; Okuno, Kenji; Barnes, J. W.*; et al.
JAERI-M 93-094, 54 Pages, 1993/03
no abstracts in English
Hayashi, Takumi; Konishi, Satoshi; Nakamura, Hirofumi; Inoue, Masahiko*; Hirata, Kazuhiro*; Okuno, Kenji; Naruse, Yuji; Barnes, J. W.*; W.Harbin*; Anderson, J. L.*; et al.
JAERI-M 93-084, 32 Pages, 1993/03
no abstracts in English
Hayashi, Takumi; Nakamura, Hirofumi; Konishi, Satoshi; Inoue, Masahiko*; Hirata, Kazuhiro*; Okuno, Kenji; Naruse, Yuji; Anderson, J. L.*; Sherman, R. H.*; Willms, R. S.*; et al.
JAERI-M 93-083, 54 Pages, 1993/03
no abstracts in English
Hayashi, Takumi; Nakamura, Hirofumi; Konishi, Satoshi; Inoue, Masahiko*; Hirata, Kazuhiro*; Okuno, Kenji; Naruse, Yuji; Barnes, J. W.*; W.Harbin*; Bartlit, J. R.*; et al.
JAERI-M 93-082, 32 Pages, 1993/03
no abstracts in English
Hayashi, Takumi; Nakamura, Hirofumi; Konishi, Satoshi; Yamanishi, Toshihiko; Inoue, Masahiko*; Hirata, Kazuhiro*; Okuno, Kenji; Naruse, Yuji; Anderson, J. L.*; Barnes, J. W.*; et al.
JAERI-M 93-081, 35 Pages, 1993/03
no abstracts in English
Konishi, Satoshi; Hayashi, Takumi; Inoue, Masahiko*; Hirata, Kazuhiro*; Okuno, Kenji; Naruse, Yuji; Barnes, J. W.*; W.Harbin*; Bartlit, J. R.*; Anderson, J. L.*
JAERI-M 93-080, 29 Pages, 1993/03
no abstracts in English
Hirata, Kazuhiro*; Matsumoto, A.*; Yamanishi, Toshihiko; Okuno, Kenji; Naruse, Yuji; Yamamoto, Ichiro*
Fusion Technology, 21(2P2), p.937 - 941, 1992/03
Times Cited Count:26 Percentile:88.97(Nuclear Science & Technology)no abstracts in English