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Onishi, Hiroaki; Miyashita, Seiji*
JPS Conference Proceedings (Internet), 38, p.011157_1 - 011157_6, 2023/05
Onishi, Hiroaki; Miyashita, Seiji*
Physical Review B, 106(13), p.134436_1 - 134436_13, 2022/10
Times Cited Count:0 Percentile:0(Materials Science, Multidisciplinary)Funaki, Hironori; Tsuji, Hideki*; Nakanishi, Takahiro; Yoshimura, Kazuya; Sakuma, Kazuyuki; Hayashi, Seiji*
Science of the Total Environment, 812, p.152534_1 - 152534_10, 2022/03
Times Cited Count:13 Percentile:68.64(Environmental Sciences)Reservoir sediments generally act as a sink for radionuclides derived from nuclear accidents, but under anaerobic conditions, several radionuclides remobilise in bioavailable form from sediment to water columns, which may contribute to a long-term contamination in aquatic products. This study systematically investigated the Cs activities between sediment and pore water, which is a direct evidence of the remobilisation of bioavailable Cs from sediments, in two highly contaminated reservoirs affected by the Fukushima Dai-ichi Nuclear Power Plant accident. Our results strongly indicate a competitive ion exchange process between Cs and NH via a highly selective interaction with the frayed edges sites of phyllosilicate minerals to be the major reason for the variability of the Kd values between sediment and pore water, even in the Fukushima case.
Tsuji, Hideki*; Ishii, Yumiko*; Shin, M.*; Taniguchi, Keisuke*; Arai, Hirotsugu*; Kurihara, Momo*; Yasutaka, Tetsuo*; Kuramoto, Takayuki*; Nakanishi, Takahiro; Lee, S*; et al.
Science of the Total Environment, 697, p.134093_1 - 134093_11, 2019/12
Times Cited Count:18 Percentile:58.6(Environmental Sciences)To investigate the main factors that control the dissolved radiocesium concentration in river water in the area affected by the Fukushima Daiichi Nuclear Power Plant accident, the correlations between the dissolved Cs concentrations at 66 sites normalized to the average Cs inventories for the watersheds with the land use, soil components, topography, and water quality factors were assessed. We found that the topographic wetness index is significantly and positively correlated with the normalized dissolved Cs concentration. Similar positive correlations have been found for European rivers because wetland areas with boggy organic soils that weakly retain Cs are mainly found on plains. However, for small Japanese river watersheds, the building area ratio in the watershed strongly affected the dissolved Cs concentration.
Kurihara, Momo*; Yasutaka, Tetsuo*; Aono, Tatsuo*; Ashikawa, Nobuo*; Ebina, Hiroyuki*; Iijima, Takeshi*; Ishimaru, Kei*; Kanai, Ramon*; Karube, Jinichi*; Konnai, Yae*; et al.
Journal of Radioanalytical and Nuclear Chemistry, 322(2), p.477 - 485, 2019/11
Times Cited Count:4 Percentile:21.22(Chemistry, Analytical)We assessed the repeatability and reproducibility of methods for determining low dissolved radiocesium concentrations in freshwater in Fukushima. Twenty-one laboratories pre-concentrated three of 10 L samples by five different pre-concentration methods (prussian-blue-impregnated filter cartridges, coprecipitation with ammonium phosphomolybdate, evaporation, solid-phase extraction disks, and ion-exchange resin columns), and activity of radiocesium was measured. The z-scores for all of the Cs results were within 2, indicating that the methods were accurate. The relative standard deviations (RSDs) indicating the variability in the results from different laboratories were larger than the RSDs indicating the variability in the results from each separate laboratory.
Nakanishi, Takahiro; Sato, Seiji; Matsumoto, Takumi*
Radiation Protection Dosimetry, 184(3-4), p.311 - 314, 2019/10
Times Cited Count:8 Percentile:65.94(Environmental Sciences)There has been significant concern about an increase of exposure dose in living sphere due to the accumulation of radiocesium discharged from contaminated mountainous forest in Fukushima. In this study, we investigated the history of radiocesium deposition on some floodplains in Fukushima. Radiocesium concentrations of river suspended particles and air dose rates at floodplains were also observed continuously. In many situations, annual sediment accumulation at floodplains was only several kg m and its radiocesium concentration was gradually decreasing in line with that of suspended particle. Simultaneously, air dose rates on floodplains were decreasing with time. In 2015 with heavy flood discharge, several hundred kg m of sediment accumulation and sharply decrease of air dose rate was observed at rivers without reservoir. Conversely, radiocesium accumulation at floodplain was significant reduced due to deposition on upstream reservoir.
Tsuruta, Tadahiko; Niizato, Tadafumi; Nakanishi, Takahiro; Dohi, Terumi; Nakama, Shigeo; Funaki, Hironori; Misono, Toshiharu; Oyama, Takuya; Kurikami, Hiroshi; Hayashi, Seiji*; et al.
JAEA-Review 2017-018, 86 Pages, 2017/10
Since the accidents at Fukushima Daiichi Nuclear Power Plant following the Tohoku Region Pacific Coast Earthquake on March 11th, 2011, Fukushima Environmental Safety Center has carried out research on natural mobilization of radionuclide (especially radiocesium) and future forecast from forest to water system and surrounding residential areas. The report summarizes the latest results that have been accumulated from each study field, of our agency together with the other related research organizations. The contents of the report is to be used as evidence-based information for the QA-styled pages in the website of JAEA Sector of Fukushima Research and Development at the time of next renewal.
Onishi, Hiroaki; Miyashita, Seiji*
Physical Review B, 90(22), p.224426_1 - 224426_11, 2014/12
Times Cited Count:1 Percentile:4.64(Materials Science, Multidisciplinary)Uchida, Masaki*; Maekawa, Takashi*; Tanaka, Hitoshi*; Ide, Shunsuke; Takase, Yuichi*; Watanabe, Fumitake*; Nishi, Seiji*
Nuclear Fusion, 51(6), p.063031_1 - 063031_9, 2011/06
Times Cited Count:11 Percentile:43.96(Physics, Fluids & Plasmas)Hojo, Ikuko*; Matsumoto, Yoshihiro; Maruyama, Takashi*; Nagamatsu, Shinichi*; Entani, Shiro; Sakai, Seiji; Konishi, Takehisa*; Fujikawa, Takashi*
Photon Factory News, 29(1), p.20 - 25, 2011/05
no abstracts in English
Konishi, Tomoya*; Nishiwaki, Nagatoshi*; Tojo, Takashi*; Ishikawa, Takuma*; Teraoka, Teruki*; Ueta, Yukiko*; Kihara, Yoshifumi*; Moritoki, Hideji*; Tono, Tatsuo*; Musashi, Mio*; et al.
Physica Status Solidi (C), 8(2), p.405 - 407, 2011/02
Times Cited Count:3 Percentile:74.76(Engineering, Electrical & Electronic)Uchida, Masaki*; Maekawa, Takashi*; Tanaka, Hitoshi*; Ide, Shunsuke; Takase, Yuichi*; Watanabe, Fumitake*; Nishi, Seiji*
Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2010/10
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.
Tobita, Kenji; Nishio, Satoshi; Enoeda, Mikio; Kawashima, Hisato; Kurita, Genichi; Tanigawa, Hiroyasu; Nakamura, Hirofumi; Honda, Mitsuru; Saito, Ai*; Sato, Satoshi; et al.
Nuclear Fusion, 49(7), p.075029_1 - 075029_10, 2009/07
Times Cited Count:139 Percentile:97.7(Physics, Fluids & Plasmas)Recent design study on SlimCS focused mainly on the torus configuration including blanket, divertor, materials and maintenance scheme. For vertical stability of elongated plasma and high beta access, a sector-wide conducting shell is arranged in between replaceable and permanent blanket. The reactor adopts pressurized-water-cooled solid breeding blanket. Compared with the previous advanced concept with supercritical water, the design options satisfying tritium self-sufficiency are relatively scarce. Considered divertor technology and materials, an allowable heat load to the divertor plate should be 8 MW/m or lower, which can be a critical constraint for determining a handling power of DEMO (a combination of alpha heating power and external input power for current drive).
Akiba, Masato; Enoeda, Mikio; Tsuru, Daigo; Tanigawa, Hisashi; Hirose, Takanori; Mori, Kensuke*; Seki, Yohji; Ezato, Koichiro; Suzuki, Satoshi; Nishi, Hiroshi; et al.
Fusion Engineering and Design, 84(2-6), p.329 - 332, 2009/02
Times Cited Count:16 Percentile:70.85(Nuclear Science & Technology)One of the most important missions of ITER is to provide a test bed for breeding blanket modules, which are called as Test Blanket Module (TBM). JAEA has been extensively developing a Water-Cooled Solid Breeder Test Blanket Module (WCSB TBM) for ITER. This paper describes results of recent R&D activities on WCSB TBM in JAEA. JAEA developed fabrication technology of F82H rectangular cooling tubes, and has successfully fabricated the near-full scale first wall mock-up of WCSB TBM by Hot Isostatic Press (HIP) technique, which is fully made of F82H. The mock-up has been high-heat flux tested in the DATS facility in JAEA, which is an ion beam test facility. The inlet temperature of the cooling water is about 280 C with 15 MPa, which is almost the same as the WCSB TBM design conditions. The mock-up has endured a heat load of 0.5 MW/m, 30 s for 80 thermal cycles. Neither hot spots nor thermal degradation have been observed.
Shiroya, Seiji*; Misawa, Tsuyoshi*; Unesaki, Hironobu*; Ichihara, Chihiro*; Kobayashi, Keiji*; Nakamura, Hiroshi*; Shin, Kazuo*; Imanishi, Nobutsugu*; Kanazawa, Satoshi*; Mori, Takamasa
JAERI-Tech 2004-025, 93 Pages, 2004/03
In view of the future plan of Research Reactor Institute, Kyoto University, the present study consisted of (1) the transmission experiments of high energy neutrons through materials, (2) experimental simulation of ADSR using the Kyoto University Critical Assembly(KUCA), and (3) conceptual neutronics design study on KUR type ADSR using the MCNP-X code. Through the present study, valuable knowledge on the basic nuclear characteristics of ADSR, which is indispensable to promote the study on ADSR, was obtained both theoretically and experimentally. For the realization of ADSR, it is considered to be necessary to accumulate results of research steadily. For this purpose, it is inevitable (1) to compile the more precise nuclear data for the wide energy range, (2) to establish experimental techniques for reactor physics study on ADSR including subcriticality measurement and absolute neutron flux measurement, and (3) to develop neutronics calculation tools which take into account the neutron generation process by the spallation reaction and the delayed neutron behavior.
Onishi, Hiroaki; Miyashita, Seiji*
Physica B; Condensed Matter, 329-333(2), p.874 - 875, 2003/05
Times Cited Count:0 Percentile:0(Physics, Condensed Matter)We investigate a one-dimensional antiferromagnetic Heisenberg model coupled to quantum lattice vibration by a quantum Monte Carlo method. For heavy mass, the lattice fluctuation can be regarded to be adiabatic and the system dimerizes at low temperature. On the other hand, for light mass, the lattice takes a uniform configuration on the thermal average and magnetic properties coincide with those of the uniform lattice system. These phenomena can be understood from the difference of the time scale of the motion between the spin and the lattice.
Onishi, Hiroaki; Miyashita, Seiji*
Journal of the Physical Society of Japan, 72(2), p.392 - 398, 2003/02
Times Cited Count:5 Percentile:38.82(Physics, Multidisciplinary)We investigate a one-dimensional antiferromagnetic Heisenberg model coupled to quantum lattice vibration using a quantum Monte Carlo method. We study the ground-state lattice fluctuation where the system shows a characteristic structure factor. We also study the mass dependence of magnetic properties such as the magnetic susceptibility and the magnetic excitation spectrum. For heavy mass, the system shows the same behavior as the case of classical lattice vibration. On the other hand, for light mass, magnetic properties coincide with those of the static uniform chain. We investigate the physical mechanism of this behavior and propose the picture of quantum narrowing.
Kakuta, Toshiya*; Hirata, Shingo*; Mori, Seiji*; Konishi, Satoshi; Kawamura, Yoshinori; Nishi, Masataka; Ohara, Yoshihiro
Fusion Science and Technology, 41(3), p.1069 - 1073, 2002/05
Research-and-development of the supercritical water-cooled prototype fusion reactor which has cost competitiveness has been performed in Japan Atomic Energy Research Institute (JAERI). It is necessary to establish immediately the design concept of the blanket tritium recovery system which collects tritium continuously and safely from the supercritical water-cooled blanket because fuel self-sufficiency is inevitable in the prototype reactor. The candidate systems are; 1) batch-processing cryogenic molecular sheave bed recovery system with cryogenic temperature operation, 2) continuous processing Pd membrane penetration recovery system with high vacuum operation. In the present study, however, the third candidate system, the hydrogen pump system with protonic conductors, was investigated. As a result of the study, it was made clear that the system with minimized energy consumption and minimized accidental tritium release could be realized by using the hydrogen pump for the blanket tritium recovery system of the prototype fusion reactor.
Niitaka, Seiji*; Yoshimura, Kazuyoshi*; Kosuge, K.*; Nishi, Masakazu*; Kakurai, Kazuhisa
Physical Review Letters, 87(17), p.177202_1 - 177202_4, 2001/10
Times Cited Count:97 Percentile:91.57(Physics, Multidisciplinary)no abstracts in English