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Journal Articles

Development of a radiation survey device for a multipurpose unmanned surface vehicle

Sanada, Yukihisa; Miyamoto, Kenji*; Momma, Hiroyasu*; Miyazaki, Nobuyuki*; Nakasone, Takamasa*; Tahara, Junichiro*; Baba, Shoichiro*; Furuyama, Hiroki*

Marine Technology Society Journal, 55(5), p.222 - 230, 2021/09

Large quantities of volatile radionuclides were released into the atmosphere following the Fukushima Daiichi Nuclear Power Station (FDNPS) accident in March 2011. To evaluate their effect on aquatic organisms and radiocesium behavior in the environment, the monitoring of radioactive cesium in the waterbed soil is important. We developed a dedicated radiation survey device that can both directly measure and collect some sediment samples. A comprehensive test was conducted using this device, which was installed in an unmanned surface vehicle at Fukushima offshore contaminated by radiocesium that resulted from the FDNPS accident. Consequently, the effectiveness of this device was confirmed because the measurement results of the sediment-core sample and in-situ radiation survey results show a good correlation. A successful application of this device in the time of post-nuclear facility accident is expected.

JAEA Reports

Survey on the radioactive substance in the coastal areas near Fukushima Prefecture in FY2019 (Contract research)

Misono, Toshiharu; Tsuruta, Tadahiko; Nakanishi, Takahiro; Sanada, Yukihisa; Shiribiki, Takehiko; Miyamoto, Kenji*; Urabe, Yoshimi*

JAEA-Research 2020-008, 166 Pages, 2020/10


After the accident at TEPCO Fukushima Daiichi Nuclear Power Station (1F), marine monitoring survey on radioactive substances have been conducted with financially supported by the Nuclear Regulatory Agency from FY2019. Results obtain in the project in FY2019 are presented in this report. Based on scientific grounds, the concept necessary for "progress of sea area monitoring" was arranged for the future medium- to long-term investigation of radiocesium concentrations. As basic information of survey frequency revise, a seabed topography and sediment distribution survey was conducted, and an attempt was made to understand the relationship between the seabed topography and the grain size distribution of bottom sediment. A columnar core sample was collected in the coastal area and analyzed for radioactive cesium concentration. In order to understand the dynamics of radioactive cesium contained in suspended matter flowing in from a river, suspended solids was collected using a sediment trap and the concentration of radioactive cesium was measured. We re-analyzed the towed monitoring data that had been implemented since 2013, and tried to improve the accuracy of the radioactive cesium distribution estimation map in the coastal area.

Journal Articles

Development of the unmanned surface vehicle for radiation monitoring at seabed; Observation of temporal change of radiocesium concentration in the sea bottom sediment at coastal zone of Fukushima

Sanada, Yukihisa; Miyamoto, Kenji*; Ochi, Kotaro; Matsuzaki, Koji*; Ogawa, Toshihiro*; Senga, Yasuhiro*

Kaiyo Riko Gakkai-Shi, 24(2), p.9 - 18, 2018/12

Seven years passed since Fukushima Dai-ichi Nuclear Power Station accident which was caused large amount of radionuclide release to the sea. Elucidation of behavior mechanism of radiocesium in the seabed is required for restarting fishing industry. We developed radiation detection system using the unmanned surface vehicle for in-situ measurement of radiocesium concentration in seabed sediment. This system is able to automatically navigate to measurement point and obtain the radiation data on the bottom sediment. The detector was calibrated by comparing the actual sediment samples. The periodical measurement off-shore the Fukushima Prefecture was performed using developed this system. As these results, distribution of radiocesium concentration was changed due to oceanographic condition. However, radiocesium inventory was tendency to decrease according to radiocesium half-life in measurement area. This system is effective for elucidation of behavior mechanism of radiocesium because it can easily measure the radiocesium concentration in the bottom sediment.

JAEA Reports

Radiation monitoring using manned helicopter around the Nuclear Power Station in the fiscal year 2015 (Contract research)

Sanada, Yukihisa; Munakata, Masahiro; Mori, Airi; Ishizaki, Azusa; Shimada, Kazumasa; Hirouchi, Jun; Nishizawa, Yukiyasu; Urabe, Yoshimi; Nakanishi, Chika*; Yamada, Tsutomu*; et al.

JAEA-Research 2016-016, 131 Pages, 2016/10


By the nuclear disaster of Fukushima Daiichi Nuclear Power Station (FDNPS), Tokyo Electric Power Company (TEPCO), caused by the East Japan earthquake and the following tsunami occurred on March 11, 2011, a large amount of radioactive materials was released from the NPS. After the nuclear disaster, airborne radiation monitoring using manned helicopter was conducted around FDNPS. In addition, background dose rate monitoring was conducted around Sendai Nuclear Power Station. These results of the aerial radiation monitoring using the manned helicopter in the fiscal 2015 were summarized in the report.

Journal Articles

Measurement of heat load density profile on acceleration grid in MeV-class negative ion accelerator

Hiratsuka, Junichi; Hanada, Masaya; Kojima, Atsushi; Umeda, Naotaka; Kashiwagi, Mieko; Miyamoto, Kenji*; Yoshida, Masafumi; Nishikiori, Ryo; Ichikawa, Masahiro; Watanabe, Kazuhiro; et al.

Review of Scientific Instruments, 87(2), p.02B137_1 - 02B137_3, 2016/02

 Times Cited Count:1 Percentile:7.86(Instruments & Instrumentation)

To understand the physics of the negative ion extraction/acceleration, the heat load density profile on the acceleration grid has been firstly measured in the ITER prototype accelerator where the negative ions are accelerated to 1 MeV with five acceleration stages. In order to clarify the profile, the peripheries around the apertures on the acceleration grid were separated into thermally insulated 34 blocks with thermocouples. The spatial resolution is as low as 3 mm and small enough to measure the tail of the beam profile with a beam diameter of 16 mm. It was found that there were two peaks of heat load density around the aperture. These two peaks were also clarified to be caused by the intercepted negative ions and secondary electrons from detailed investigation by changing the beam optics and gas density profile. This is the first experimental result, which is useful to understand the trajectories of these particles.

Journal Articles

Current status of R&D activities and future plan and role of JAEA's two generic URLs

Koide, Kaoru; Osawa, Hideaki; Ito, Hiroaki; Tanai, Kenji; Semba, Takeshi; Naito, Morimasa; Sugihara, Kozo; Miyamoto, Yoichi

Annual Waste Management Symposium (WM 2015), Vol.5, p.3631 - 3645, 2015/00

JAEA has promoted R&D on HLW geological disposal technology. JAEA launched the Mizunami and the Horonobe URL Projects to cover the diversity of geological environments in Japan. The Mizunami URL Project is a geoscientific research project in the crystalline rock environment. The Horonobe URL Project consists of geoscientific studies and R&D on geological disposal technology in the sedimentary rock environment. Both URL projects have been planned to proceed in three overlapping phases, Surface-based investigation Phase, Construction Phase and Operation Phase. Currently, the construction of research galleries in both of the Mizunami and the Horonobe URLs has been completed to 500 m and 350 m depths, respectively. JAEA will promote R&D activities in Phase III including study of the long-term evolution of the geological environment, and contribute to international cooperation, development of human resources and communication amongst stakeholders through both URL projects.

Journal Articles

Study of negative hydrogen ion beam optics using the 2D PIC method

Miyamoto, Kenji*; Okuda, Shin*; Hatayama, Akiyoshi*; Hanada, Masaya; Kojima, Atsushi

AIP Conference Proceedings 1515, p.22 - 30, 2013/02

 Times Cited Count:8 Percentile:94.55

We have developed the integrated 2D PIC code for the analysis of the negative ion beam optics, in which an overall region from the source plasma to the accelerator is modeled. Thus, the negative ion trajectory can be solved self-consistently without any assumption of the plasma meniscus form initially. This code can reproduce the negative ion beam halo observed in an actual negative ion beam. It is confirmed that the surface produced negative ions which are extracted near the edge of the meniscus can be one of the reasons for the beam halo: these negative ions are over-focused due to the curvature of the meniscus. The negative ions are not focused by the electrostatic lens, and consequently become the beam halo.

Journal Articles

Study of plasma meniscus formation and beam halo in negative hydrogen ion sources

Okuda, Shin*; Miyamoto, Kenji*; Fukuyama, Toshishige*; Nishioka, Shu*; Hatayama, Akiyoshi*; Fukano, Azusa*; Hanada, Masaya; Kojima, Atsushi

AIP Conference Proceedings 1515, p.107 - 113, 2013/02

 Times Cited Count:9 Percentile:95.47

A meniscus of plasma-beam boundary in H$$^{-}$$ ion sources largely affects the extracted H$$^{-}$$ ion beam optics. Recently it is shown that the beam halo is mainly caused by the meniscus, i.e. ion emissive surface, close to the plasma grid (PG) where its curvature is large. The purpose of this study is to clarify the effect of H$$^{-}$$ surface production rate on plasma meniscus and beam halo formation with PIC (particle-in-cell) modeling. It is shown that the plasma meniscus and beam halo formation is strongly dependent on the amount of surface produced H$$^{-}$$ ions.

Journal Articles

Study of beam optics and beam halo by integrated modeling of negative ion beams from plasma meniscus formation to beam acceleration

Miyamoto, Kenji*; Okuda, Shin*; Hatayama, Akiyoshi*; Hanada, Masaya; Kojima, Atsushi

Applied Physics Letters, 102(2), p.023512_1 - 023512_4, 2013/01

 Times Cited Count:19 Percentile:67.04(Physics, Applied)

To understand the physical mechanism of the beam halo formation in negative ion beams, a two-dimensional particle-in-cell code for simulating the trajectories of negative ions created via surface production has been developed. The simulation code reproduces a beam halo observed in an actual negative ion beam. The negative ions extracted from the periphery of the plasma meniscus (an electro-static lens in a source plasma) are over-focused in the extractor due to large curvature of the meniscus.

Journal Articles

Numerical analysis of surface produced H$$^{-}$$ ions by using two-dimensional particle-in-cell method

Miyamoto, Kenji*; Okuda, Shin*; Hatayama, Akiyoshi*; Hanada, Masaya

Review of Scientific Instruments, 83(2), p.02A723_1 - 02A723_4, 2012/02

 Times Cited Count:8 Percentile:41.82(Instruments & Instrumentation)

The modeling and analysis of a negative ion source is proceeding by using a 2D particle-in-cell simulation. The effect of the H$$^{-}$$ ion production on the plasma grid (PG) surface is investigated. It is shown that with the increase of H$$^{-}$$ ions per time step, the H$$^{-}$$ ion current density is enhanced, while the electron current density decreases with increasing the H$$^{-}$$ production rate on the PG surface. Theseresults agree well with the experimental results observed in typical negative ion sources. Moreover, it is found that plasma quasi-neutrality is held mainly by both H$$^{+}$$ and H$$^{-}$$ ions in the bulk plasma.

JAEA Reports

Establishment of advanced integration technology for site characterization of deep geological repository; Development of information synthesis and interpretation system; Annual report 2007 (Contract research)

Osawa, Hideaki; Ota, Kunio; Hama, Katsuhiro; Sawada, Atsushi; Takeuchi, Shinji; Amano, Kenji; Saegusa, Hiromitsu; Matsuoka, Toshiyuki; Miyamoto, Tetsuo; Toyoda, Gakuji; et al.

JAEA-Research 2008-085, 742 Pages, 2008/11


This report shows the results the project for the establishment of comprehensive site characterization technology, entrusted from Natural Resources and Energy Agency, Ministry of Economy, Trade and Industry Natural Resources and Energy Agency in 2007.

Journal Articles

Effects of irradiation on mechanical properties of HIP-bonded reduced-activation ferritic/martensitic steel F82H first wall

Furuya, Kazuyuki; Wakai, Eiichi; Miyamoto, Kenji*; Akiba, Masato; Sugimoto, Masayoshi

Journal of Nuclear Materials, 367-370(1), p.494 - 499, 2007/08

 Times Cited Count:0 Percentile:0.01(Materials Science, Multidisciplinary)

A partial mock-up of a breeding blanket structure made of F82H steel has been successfully fabricated. In this study, microstructural observation and EDX analysis of the HIP interfaces were performed, and effects of irradiation on mechanical properties of the HIP-bonded region were also examined. Neutron irradiation was performed up to about 2 dpa at about 523 K. After the irradiation, tensile test was performed at temperatures of 295 and 523 K. The HIP interfaces possessed many precipitates, and enriched peak spectrum of chromium was detected from the precipitates. In addition, aspect of the spectrum was qualitatively equivalent to that of M$$_{23}$$C$$_{6}$$ in grain boundaries of F82H steel. In result, the HIP boundary has many M$$_{23}$$C$$_{6}$$ which were generally seen in grain boundaries of F82H steel. Rupture did not occur in the HIP interface. In result, it can be mentioned that bondability is maintained under the irradiation and testing conditions. The strength and elongation of the HIP-bonded region decreased somewhat in comparison with the results of an IEA standard steel.

Journal Articles

Reports on the ITPA (International Tokamak Physics Activity) Meeting on "MHD, Disruption and Plasma Control" and "Energetic Particles, Heating and Steady-State Operation"

Iio, Shunji*; Ide, Shunsuke; Ozeki, Takahisa; Sugihara, Masayoshi; Takase, Yuichi*; Takeji, Satoru*; Tobita, Kenji; Fukuyama, Atsushi*; Miyamoto, Kenro*

Purazuma, Kaku Yugo Gakkai-Shi, 78(6), P. 601, 2002/06

no abstracts in English

Journal Articles

Spatial uniformity of negative ion production in volume negative ion source

Morishita, Takatoshi; Miyamoto, Kenji*; Fujiwara, Yukio*; Hanada, Masaya; Kitagawa, Tadashi*; Kashiwagi, Mieko; Okumura, Yoshikazu; Watanabe, Kazuhiro

Review of Scientific Instruments, 73(2), p.1064 - 1066, 2002/02

 Times Cited Count:2 Percentile:19.85(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Recent ITER physics R&D expert group activities

Ogawa, Yuichi*; Takizuka, Tomonori; Miura, Yukitoshi; Toi, Kazuo*; Fukuda, Takeshi; Wakatani, Masahiro*; Ide, Shunsuke; Takase, Yuichi*; Tobita, Kenji; Fukuyama, Atsushi*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 77(10), p.1042 - 1048, 2001/10

no abstracts in English

JAEA Reports

Steering of H$$^{-}$$ ion beamlet by aperture displacement

Inoue, Takashi; Suzuki, Yasuo*; Miyamoto, Kenji; Okumura, Yoshikazu

JAERI-Tech 2000-051, 16 Pages, 2000/09


no abstracts in English

JAEA Reports

Steering of high energy negative ion beam and design of beam focusing/deflection compensation for JT-60U large negative ion source

Inoue, Takashi; Miyamoto, Kenji; Nagase, Akihito*; Okumura, Yoshikazu; Watanabe, Kazuhiro

JAERI-Tech 2000-023, p.27 - 0, 2000/03


no abstracts in English

Journal Articles

Negative hydrogen ion source for tokamak neutral beam injector

Okumura, Yoshikazu; Fujiwara, Yukio; Kashiwagi, Mieko; Kitagawa, Tadashi*; Miyamoto, Kenji; Morishita, Takatoshi; Hanada, Masaya; Takayanagi, Tomohiro; Taniguchi, Masaki; Watanabe, Kazuhiro

Review of Scientific Instruments, 71(2), p.1219 - 1224, 2000/02

 Times Cited Count:34 Percentile:84.07(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Hydrogen negative ion beam acceleration in a multiaperture five-stage electrostatic accelerator

Watanabe, Kazuhiro; Fujiwara, Yukio; Hanada, Masaya; Kashiwagi, Mieko; Kitagawa, Tadashi*; Miyamoto, Kenji; Morishita, Takatoshi; Okumura, Yoshikazu; Takayanagi, Tomohiro; Taniguchi, Masaki

Review of Scientific Instruments, 71(2), p.1231 - 1233, 2000/02

 Times Cited Count:9 Percentile:53.79(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Neutral beams for the International Thermonuclear Experimental Reactor

Inoue, Takashi; Di Pietro, E.*; Mondino, P. L.*; Bayetti, P.*; Hemsworth, R. S.*; Massmann, P.*; Fujiwara, Yukio; Hanada, Masaya; Miyamoto, Kenji; Okumura, Yoshikazu; et al.

Review of Scientific Instruments, 71(2), p.744 - 746, 2000/02

 Times Cited Count:17 Percentile:69.07(Instruments & Instrumentation)

no abstracts in English

51 (Records 1-20 displayed on this page)