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Hirata, Sakiko*; Kusaka, Ryoji; Meiji, Shogo*; Tamekuni, Seita*; Okudera, Kosuke*; Hamada, Shoken*; Sakamoto, Chihiro*; Honda, Takumi*; Matsushita, Kosuke*; Muramatsu, Satoru*; et al.
Inorganic Chemistry, 62(1), p.474 - 486, 2023/01
Times Cited Count：0 Percentile：0.01(Chemistry, Inorganic & Nuclear)Shimada, Kazumasa; Iijima, Masashi*; Watanabe, Masatoshi*; Takahara, Shogo
Proceedings of Asian Symposium on Risk Assessment and Management 2021 (ASRAM 2021) (Internet), 17 Pages, 2021/10
The radiation doses received by the off-site responders in the Fukushima Daiichi Nuclear Power Station accident were assessed. Atmospheric dispersion simulation was conducted with the source term of the previous research to calculate the atmospheric concentration and ground surface deposition in the municipalities where off-site responders actives. The external exposure dose from cloudshine and groundshine, the internal exposure dose due to inhalation of radioactive plume and resuspended radio nuclei, and the temporal and spatial distribution within each municipality were assessed. As a result of comparing the assessed values of the external exposure dose with the measured values of the personal dosimeter, the measured values were within the assessed range. As a result of our assessment with internal dose exposure, if the exposures occurred without protective measures, the potential daily effective dose in the period between 12 and 31 March 2011 were several tens mSv per day or more in the relatively high dose area. Therefore, to keep the doses received by the responders below the reference level of 20 mSv recommended by the ICRP, it is necessary to ensure that the protective measures for internal exposures such as masks are taken, and to manage the time spent for their activity at least daily.
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.
Takahara, Shogo; Iijima, Masashi*; Watanabe, Masatoshi*
Health Physics, 118(6), p.664 - 677, 2020/06
Times Cited Count：9 Percentile：71.58(Environmental Sciences)Assessment model of radiation doses from external exposures was developed based on the actual measurement of individual doses and ambient dose equivalent rate inside and outside of a house in Fukushima city. The survey on behavioral pattern was also carried out under the same purpose. In addition to the actual measurement and survey by ourselves, we also took into account the latest insights from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. Comparisons between the assessed results and the measured ones revealed that the time dependences of doses obtained using the developed models were in good agreement with the results of actual measurements. In addition, we were able to reproduce the distribution of doses for indoor and outdoor workers. Therefore, our probabilistic approach was validated. According to our assessment and actual measurement, no participants received 1 mSv/y or higher in Fukushima city in eight years after the FDNPP accident.
Takahara, Shogo; Watanabe, Masatoshi*
Proceedings of Asian Symposium on Risk Assessment and Management 2019 (ASRAM 2019) (USB Flash Drive), 9 Pages, 2019/09
Internal exposure from ingestion pathway is one of most concerned contributor to the received doses to the public after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. In the present study, we developed the dose prediction model taking into account the ecological half-lives of radionuclides in foodstuffs and the reduction effects on concentration of radionuclides in cooking-process based on the experiences and the latest insights of the FDNPP accident. From comparison of the retrospective assessment results in Fukushima city between our models and the previous models (market bascket, duplicate, sewer sludge method), no contradictions were observed. In addition, it was found that the potential annual effective doses, which were assessed using the developed model, is several tens micro Sieverts in the first year after the FDNPP accident, and subsequent years the doses is also not exceeding several micro Sv for the future in Fukushima city.
Takahara, Shogo; Watanabe, Masatoshi*; Hirouchi, Jun; Iijima, Masashi*; Munakata, Masahiro
Health Physics, 114(1), p.64 - 72, 2018/01
Times Cited Count：2 Percentile：20.93(Environmental Sciences)Hirouchi, Jun; Takahara, Shogo; Komagamine, Hiroshi*; Watanabe, Masatoshi*; Munakata, Masahiro
Proceedings of Asian Symposium on Risk Assessment and Management 2017 (ASRAM 2017) (USB Flash Drive), 11 Pages, 2017/11
no abstracts in English
Hirouchi, Jun; Takahara, Shogo; Iijima, Masashi; Watanabe, Masatoshi; Munakata, Masahiro
Radiation Physics and Chemistry, 140, p.127 - 131, 2017/11
Times Cited Count：3 Percentile：28.82(Chemistry, Physical)Takahara, Shogo; Watanabe, Masatoshi; Oguri, Tomomi; Kimura, Masanori; Hirouchi, Jun; Munakata, Masahiro; Homma, Toshimitsu
JAEA-Data/Code 2016-016, 65 Pages, 2017/02
JAEA-Data-Code-2016-016.pdf:2.32MB
We surveyed on structural and material data on 22 facilities which are listed in local disaster management plan in Matsue city. These facilities can be divided into educational facilities, communal facilities and gymnastic hall. Height and floor-area of rooms, as well as window-area were collected as the structural data. We also collected information on constructional materials, and density of those. In addition, mass-thicknesses of the constructional materials were evaluated based on our surveys, and compared to the previous studies which were made in Japan, U.S., and European countries. Consequently, it was found that there is no significant difference of mass-thickness of constructional materials between the results of our surveys and the previous studies. However, for gymnastic hall, since thin metal plates are used for roofs, we can point out that the mass-thickness of roofs are much lower than those for other concrete facilities and clay tile roofing wooden houses.
Sugimoto, Masaki; Idesaki, Akira; Yoshikawa, Masahito; Watanabe, Shogo*; Seki, Shu*
Advances in Polymer Derived Ceramics and Composites; Ceramic Transactions, Vol.213, p.105 - 110, 2010/06
We have succeeded in synthesizing ceramic nano fibers from precursor polymers using Single Particle Nanofabrication Technique (SPNT). A thin film of the precursor polymer was cross-linked by MeV-order heavy-ion beam irradiation along ion tracks of nano-size in radius through the whole thickness of the thin film. Nano fibers were developed on the surface of the substrate by dissolution and washing away of un-crosslinked polymer. Subsequent pyrolysis converted polymeric into ceramic nano fibers. The radius, length and number density of nano fibers are controlled by liner energy transfer (LET) of ion beam, thickness of polymeric target and number of projected ions, respectively.
Sakanaka, Shogo*; Akemoto, Mitsuo*; Aoto, Tomohiro*; Arakawa, Dai*; Asaoka, Seiji*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; et al.
Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.2338 - 2340, 2010/05
Future synchrotron light source using a 5-GeV energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting R&D efforts for that. We are developing high-brightness DC photocathode guns, two types of cryomodules for both injector and main superconducting (SC) linacs, and 1.3 GHz high CW-power RF sources. We are also constructing the Compact ERL (cERL) for demonstrating the recirculation of low-emittance, high-current beams using above-mentioned critical technologies.
Sakai, Hiroshi*; Furuya, Takaaki*; Kako, Eiji*; Noguchi, Shuichi*; Sato, Masato*; Sakanaka, Shogo*; Shishido, Toshio*; Takahashi, Takeshi*; Umemori, Kensei*; Watanabe, Ken*; et al.
Proceedings of 45th Advanced ICFA Beam Dynamics Workshop on Energy Recovery Linacs (ERL '09) (Internet), p.57 - 62, 2010/05
Development of a SC Cavity Injector Cryomodule and Main linac Cryomodule for the compact ERL is being continued at KEK since 2006. Design of an injector cryomodule containing three 2-cell 1.3-GHz cavities for Injector Cryomodule and two 9-cell 1.3-GHz cavities for Main linac Cryomodule are almost completed. Status of R&D and design details are reported.
Takahara, Shogo; Watanabe, Norio
Nihon Genshiryoku Gakkai Wabun Rombunshi, 5(4), p.282 - 291, 2006/12
no abstracts in English
Watanabe, Norio; Takahara, Shogo
JAEA-Review 2006-027, 141 Pages, 2006/09
JAEA-Review-2006-027.pdf:24.85MB
Primary Water Stress Corrosion Cracking (PWSCC), which occurs on nickel-based alloy (Alloy 600) reactor coolant pressure boundary components, has been a safety concern at pressurized water reactors (PWRs). During the years from 2000 to 2002, in particular, circumferential cracks on reactor pressure vessel head penetrations and significant degradation of vessel head have been observed at U. S. PWR plants and thus, awareness of the safety significance of PWSCC was raised because circumferential cracking and leakage of RPV head nozzles and corrosion of the RPV head resulting from PWSCC may lead to pressure boundary failure if the conditions are not detected and repaired. In response to the recent experience, the Nuclear Regulatory Commission (NRC) issued the inspection Order EA-03-009 for PWR licensees to prepare and implement more effective inspections of the reactor vessel heads and associated penetration nozzles. This report provides the description on the historical NRC's responses to PWSCC issues and the review of the forty-five events, reported as licensee event reports, involving PWSCC on reactor coolant pressure boundary components at U. S. PWRs during the years from 1999 to 2005.
Yamada, Hirokazu*; Kawamura, Hiroshi; Tsuchiya, Kunihiko; Ishitsuka, Etsuo; Uchida, Munenori*; Akutsu, Yoichi; Motoki, Ryozo; Watanabe, Wataru; Hirata, Shogo*
JAERI-Tech 2004-036, 138 Pages, 2004/03
JAERI-Tech-2004-036.pdf:4.07MB
This document shows the model case concerned with the utilization of constructed facility for the construction of post irradiation examination facility for fusion blanket. In this report, the radioisotope application and development laboratory is considered as constructed facility for post irradiation examination facility and we planned to improve the radioisotope application and development laboratory to the facility of post irradiation examination for fusion material to reduce the construction fee for this facility and promotion of efficiency by concentration of any equipment for fusion material research.
Sugimoto, Masaki; Yoshikawa, Masahito; Watanabe, Shogo*; Seki, Shu*
no journal, ,
We have succeeded in synthesizing the self-standing silicon carbide (SiC) nano-fiber from Si-based polymers using Single Particle Nanofabrication Technique (SPNT) with multi angle ion beam irradiation. Si-based polymers were cross-linked by MeV-order heavy-ion along ion tracks of nano-size in radius through the whole thickness of the polymer thin film. Nano fibers were developed on the surface of the substrate by dissolution and washing away of un-crosslinked polymer by solvent. Subsequent pyrolysis converted polymeric into inorganic SiC nano fibers.
Sawamura, Masaru; Umemori, Kensei*; Sakanaka, Shogo*; Suwada, Tsuyoshi*; Takahashi, Takeshi*; Furuya, Takaaki*; Noguchi, Shuichi*; Kako, Eiji*; Shishido, Toshio*; Watanabe, Ken*; et al.
no journal, ,
Superconducting accelerator cavities are essential for the energy-recovery linac. The superconducting cavities are used in an injector and a main linac. A new model has been designed for the ERL. A center-single-cell cavity, an end-single-cell cavity and 9-cell cavity have been constructed. Vertical tests were performed for the center-single-cell cavity and the end-single cell cavity. A 2-cell cavity for the injector is under construction.
Sugimoto, Masaki; Yoshikawa, Masahito; Watanabe, Shogo*; Seki, Shu*
no journal, ,
We have succeeded in synthesizing metal folding ceramic (SiC) nano-fiber from Si-based precursor polymers using Single Particle Nanofabrication Technique (SPNT). Si-based polymers were cross-linked along ion tracks of nano-size in diameter through the whole thickness of polymer thin film. Nano-fiber was developed on the surface of the substrate by dissolution and washing away of uncross-linked polymer by solvent. Subsequent pyrolysis converted polymeric into inorganic SiC nano fibers. The diameter of nano fiber was depended on LET (liner energy transfer), molecular weight and cross-linking efficiency of polymers.
Hirouchi, Jun; Takahara, Shogo; Watanabe, Masatoshi; Munakata, Masahiro
no journal, ,
no abstracts in English
Watanabe, Masatoshi; Takahara, Shogo; Hirouchi, Jun; Munakata, Masahiro
no journal, ,
no abstracts in English
