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Hashimoto, Shoji*; Tanaka, Taku*; Komatsu, Masabumi*; Gonze, M.-A.*; Sakashita, Wataru*; Kurikami, Hiroshi; Nishina, Kazuya*; Ota, Masakazu; Ohashi, Shinta*; Calmon, P.*; et al.
Journal of Environmental Radioactivity, 238-239, p.106721_1 - 106721_10, 2021/11
Times Cited Count：14 Percentile：52.93(Environmental Sciences)This study was aimed at analysing performance of models for radiocesium migration mainly in evergreen coniferous forest in Fukushima, by inter-comparison between models of several research teams. The exercise included two scenarios of countermeasures against the contamination, namely removal of soil surface litter and forest renewal, and a specific konara oak forest scenario in addition to the evergreen forest scenario. All the models reproduced trend of time evolution of radiocesium inventories and concentrations in each of the components in forest such as leaf and organic soil layer. However, the variations between models enlarged in long-term predictions over 50 years after the fallout, meaning continuous field monitoring and model verification/validation is necessary.
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：54 Percentile：96.05(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.
Cs and 
Cs radioactivity measurementsMalins, A.; Imamura, Naohiro*; Niizato, Tadafumi; Takahashi, Junko*; Kim, M.; Sakuma, Kazuyuki; Shinomiya, Yoshiki*; Miura, Satoru*; Machida, Masahiko
Journal of Environmental Radioactivity, 226, p.106456_1 - 106456_12, 2021/01
Times Cited Count：7 Percentile：33.50(Environmental Sciences)Shirai, Nobutoshi; Miura, Yasushi; Tachibana, Ikuya; Omori, Satoru; Wake, Junichi; Fukuda, Kazuhito; Nakano, Takafumi; Nagasato, Yoshihiko
JAEA-Technology 2016-007, 951 Pages, 2016/07
JAEA-Technology-2016-007-01.pdf:11.93MBJAEA-Technology-2016-007-02.pdf:4.7MB
The periodic safety review of TRP is to confirm the safety activities and get effective additional measures the facility safety and its reliability. We implemented 4 items; for (1) evaluation of safety activity implementation, we confirmed we are adequately expanding its safety activities by the necessary documents and schemes. For (2) evaluation of status of safety activities reflecting the latest technical knowledges, we confirmed we reflect latest knowledges for improvement of safety and reliability. For (3) technical evaluation about aging degradation, we can keep the safety of the facilities important to safety and the sea discharge line, under assumption of the present maintenance, because of "focuses for aging degradation". For (4) planning measures about a 10-years-plan that the operator shall implement to keep the facility condition, by the technical evaluation, we found no additional safety plans into maintenance strategies.
Ishiyama, Toru; Kawasaki, Ichio; Miura, Hirohito*
Nihon Hozen Gakkai Dai-11-Kai Gakujutsu Koenkai Yoshishu, p.33 - 36, 2014/07
There are 4-boiler systems in NCL. These boilers have been operated in the long term over 20 years. One of them, the leakage of boiler water was found at one of the generating tubes, and 2 adjoining generating tubes were corroded in Dec, 2011. These generating tubes were investigated by immersion ultrasonic testing (UT) for measure thickness of the tube. As a result, thinner tube was found in a part of a bend and near the water drum. These parts are covered with sulfide deposit, it seems that the generating tubes were corroded by sulfide.
Miura, Tatsuya*; Nishikata, Atsushi*; Tsuru, Toru*; Yamamoto, Masahiro; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*
Fushoku Boshoku Kyokai Dai-58-Kai Zairyo To Kankyo Toronkai Koenshu, p.15 - 16, 2011/09
There exist some equipments made of Ti or Ti-5Ta alloy in the spent nuclear fuel reprocessing plant. These equipments are investigated for failure by hydrogen embrittlement. To evaluate the stabilities of hydrogen in the solutions using at the reprocessing plant, channel-flow-ellectrode (CFE) method was utilized. The method to determine the dissolved hydrogen concentration was considered from the results of anodic polarization curves.
Nagao, Keisuke*; Okazaki, Ryuji*; Nakamura, Tomoki*; Miura, Yayoi*; Osawa, Takahito; Bajo, Kenichi*; Matsuda, Shintaro*; Ebihara, Mitsuru*; Ireland, T.*; Kitajima, Fumio*; et al.
Science, 333(6046), p.1128 - 1131, 2011/08
Times Cited Count：135 Percentile：94.74(Multidisciplinary Sciences)A steroid surface materials record regolith processes and a history of cosmic-ray irradiation. Noble gas isotopes in three rocky grains from Itokawa have been determined. High concentrations of solar He, Ne, and Ar, as high as those in lunar soils, are released at variable temperatures from each sample. The isotopic compositions are essentially identical to those of solar wind but distinguishable in He relative abundance. These noble gas characteristics can be explained by repeated implantation and preferential loss of solar He by removal of weathered He-rich rim on the grain surface through friction among regolith grains on Itokawa. Residence time of regolith materials on Itokawa is alculated to be shorter than 10 Myr, suggesting that regolith materials of small asteroids would escape easily to space.
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.
Koarashi, Jun; Atarashi-Andoh, Mariko; Ishizuka, Shigehiro*; Miura, Satoru*; Saito, Takeshi*; Hirai, Keizo*
Global Change Biology, 15(3), p.631 - 642, 2009/03
Times Cited Count：46 Percentile：74.64(Biodiversity Conservation)Although it is well documented the possibility that global warming can lead to an acceleration of microbial decomposition of soil organic carbon (SOC), the magnitude and timing of this effect remains highly uncertain. The main reason is a lack of quantitative aspect of the heterogeneity in SOC biodegradability. To quantify the heterogeneity, we collected the soil and litter samples within a cool-temperate deciduous forest in Japan, separated chemically the samples into SOC fractions, determined their mean residence times (MRTs) based on the radiocarbon (
C) measurements, and finally represented the soil as a complex of six SOC pools with different range of MRTs. Predicted response of the SOC pools to warming demonstrates that the rate of SOC loss from the fast-cycling SOC pool diminishes quickly because of the substrate availability; in contrast, the warming continues to accelerate SOC loss from slow-cycling pools with MRTs of 20-200 year over the next century.
Sakanaka, Shogo*; Ago, Tomonori*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; Harada, Kentaro*; Hiramatsu, Shigenori*; Honda, Toru*; et al.
Proceedings of 11th European Particle Accelerator Conference (EPAC '08) (CD-ROM), p.205 - 207, 2008/06
Future synchrotron light sources based on the energy-recovery linacs (ERLs) are expected to be capable of producing super-brilliant and/or ultra-short pulses of synchrotron radiation. Our Japanese collaboration team is making efforts for realizing an ERL-based hard X-ray source. We report recent progress in our R&D efforts.
Koarashi, Jun; Atarashi-Andoh, Mariko; Ishizuka, Shigehiro*; Saito, Takeshi*; Hirai, Keizo*; Miura, Satoru*
Proceedings of International Symposium on Application of a Closed Experimental System to Modeling of C Transfer in the Environment, p.72 - 76, 2008/00
Recent debate has emphasized that our capacity to predict the response of soil organic carbon (SOC) to climate change depends on a clear understanding of the heterogeneity in SOC biodegradability. We collected soil samples from the Appi forest meteorology research site dominated by Japanese beech, separated the soil samples into three SOC fractions with a chemical method, and determined their radiocarbon isotope ratios using an accelerator mass spectrometry. The radiocarbon signatures allow us to estimate their turnover times (TTs), quantifying the rates of SOC decomposition. According to the estimated TTs, the SOC was distinguished into six SOC pools with distinct TTs of several years to 
1000 years. The annual SOC decomposition rate was summed up to 0.47 kgC m
y
, about a half of which was from the fastest-cycling pool (litter). Approximately 5% of SOC gave the over-millennium TTs, suggesting that this pool plays a role of a long-term carbon sequestration in the carbon cycle.
Ninomiya, Hiromasa; Akiba, Masato; Fujii, Tsuneyuki; Fujita, Takaaki; Fujiwara, Masami*; Hamamatsu, Kiyotaka; Hayashi, Nobuhiko; Hosogane, Nobuyuki; Ikeda, Yoshitaka; Inoue, Nobuyuki; et al.
Journal of the Korean Physical Society, 49, p.S428 - S432, 2006/12
To contribute DEMO and ITER, the design to modify the present JT-60U into superconducting coil machine, named National Centralized Tokamak (NCT), is being progressed under nationwide collaborations in Japan. Mission, design and strategy of this NCT program is summarized.
Nakano, Tomohide; Asakura, Nobuyuki; Takenaga, Hidenobu; Kubo, Hirotaka; Miura, Yukitoshi; Shimizu, Katsuhiro; Konoshima, Shigeru; Masaki, Kei; Higashijima, Satoru; JT-60 Team
Nuclear Fusion, 46(5), p.626 - 634, 2006/05
Times Cited Count：21 Percentile：56.18(Physics, Fluids & Plasmas)In order to understand plasma-wall interactions in a long time scale, the discharge pulse length has been extended from 15 s to 65 s, with the NB-heating duration extended to 30 s. Nearly-saturation of the divertor plates was observed in the latter half of long pulse ELMy H-mode discharges. Particle sink into the divertor plates gradually decreased, and subsequently, wall-pumping efficiency became zero. This wall saturation resulted in a rise of the main plasma density without any auxiliary particle supply besides NB with divertor-pumping. Even when the total injected energy reached up to 
350 MJ in a discharge, neither sudden increase of carbon generation such as carbon bloom nor increase of the dilution of the main plasma was observed.
Kikuchi, Mitsuru; Tamai, Hiroshi; Matsukawa, Makoto; Fujita, Takaaki; Takase, Yuichi*; Sakurai, Shinji; Kizu, Kaname; Tsuchiya, Katsuhiko; Kurita, Genichi; Morioka, Atsuhiko; et al.
Nuclear Fusion, 46(3), p.S29 - S38, 2006/03
Times Cited Count：13 Percentile：40.72(Physics, Fluids & Plasmas)The National Centralized Tokamak (NCT) facility program is a domestic research program for advanced tokamak research to succeed JT-60U incorporating Japanese university accomplishments. The mission of NCT is to establish high beta steady-state operation for DEMO and to contribute to ITER. The machine flexibility and mobility is pursued in aspect ratio and shape controllability, feedback control of resistive wall modes, wide current and pressure profile control capability for the demonstration of the high-b steady state.
Tsuchiya, Katsuhiko; Akiba, Masato; Azechi, Hiroshi*; Fujii, Tsuneyuki; Fujita, Takaaki; Fujiwara, Masami*; Hamamatsu, Kiyotaka; Hashizume, Hidetoshi*; Hayashi, Nobuhiko; Horiike, Hiroshi*; et al.
Fusion Engineering and Design, 81(8-14), p.1599 - 1605, 2006/02
Times Cited Count：1 Percentile：9.69(Nuclear Science & Technology)no abstracts in English
-edge of perpendicular magnetic Dy
Co
filmsAgui, Akane; Mizumaki, Masaichiro*; Asahi, Toru*; Sayama, Junichi*; Matsumoto, Koji*; Morikawa, Tsuyoshi*; Matsushita, Tomohiro*; Osaka, Tetsuya*; Miura, Yoshimasa*
Journal of Alloys and Compounds, 408-412, p.741 - 745, 2006/02
Times Cited Count：7 Percentile：45.51(Chemistry, Physical)no abstracts in English
plasma operationTamai, Hiroshi; Akiba, Masato; Azechi, Hiroshi*; Fujita, Takaaki; Hamamatsu, Kiyotaka; Hashizume, Hidetoshi*; Hayashi, Nobuhiko; Horiike, Hiroshi*; Hosogane, Nobuyuki; Ichimura, Makoto*; et al.
Nuclear Fusion, 45(12), p.1676 - 1683, 2005/12
Times Cited Count：15 Percentile：44.69(Physics, Fluids & Plasmas)Design studies are shown on the National Centralized Tokamak facility. The machine design is carried out to investigate the capability for the flexibility in aspect ratio and shape controllability for the demonstration of the high-beta steady state operation with nation-wide collaboration, in parallel with ITER towards DEMO. Two designs are proposed and assessed with respect to the physics requirements such as confinement, stability, current drive, divertor, and energetic particle confinement. The operation range in the aspect ratio and the plasma shape is widely enhanced in consistent with the sufficient divertor pumping. Evaluations of the plasma performance towards the determination of machine design are presented.
Takenaga, Hidenobu; Asakura, Nobuyuki; Kubo, Hirotaka; Higashijima, Satoru; Konoshima, Shigeru; Nakano, Tomohide; Oyama, Naoyuki; Porter, G. D.*; Rognlien, T. D.*; Rensink, M. E.*; et al.
Nuclear Fusion, 45(12), p.1618 - 1627, 2005/12
Times Cited Count：20 Percentile：53.78(Physics, Fluids & Plasmas)no abstracts in English
Takenaga, Hidenobu; Asakura, Nobuyuki; Higashijima, Satoru; Nakano, Tomohide; Kubo, Hirotaka; Konoshima, Shigeru; Oyama, Naoyuki; Isayama, Akihiko; Ide, Shunsuke; Fujita, Takaaki; et al.
Journal of Nuclear Materials, 337-339, p.802 - 807, 2005/03
Times Cited Count：14 Percentile：66.75(Materials Science, Multidisciplinary)no abstracts in English
Takenaga, Hidenobu; Asakura, Nobuyuki; Kubo, Hirotaka; Higashijima, Satoru; Konoshima, Shigeru; Nakano, Tomohide; Oyama, Naoyuki; Porter, G. D.*; Rognlien, T. D.*; Rensink, M. E.*; et al.
Proceedings of 20th IAEA Fusion Energy Conference (FEC 2004) (CD-ROM), 8 Pages, 2004/11
no abstracts in English
