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Journal Articles

Ion beam induced luminescence analysis of europium complexes in styrene-divinylbenzene copolymer-coated spherical silica by proton and argon ion beams irradiation

Nakahara, Masaumi; Watanabe, So; Takeuchi, Masayuki; Yuyama, Takahiro*; Ishizaka, Tomohisa*; Ishii, Yasuyuki*; Yamagata, Ryohei*; Yamada, Naoto*; Koka, Masashi*; Kada, Wataru*; et al.

Nuclear Instruments and Methods in Physics Research B, 542, p.144 - 150, 2023/09

The structures of Eu complexes in the adsorbents prepared with various extractants were evaluated by ion beam induced luminescence analysis in an extraction chromatography for minor actinides recovery. The luminescence of Eu was measured with a proton beam obtained from the single-ended accelerator and an argon ion beam obtained from the azimuthally varying field cyclotron in Takasaki Ion Accelerators for Advanced Radiation Application in National Institutes for Quantum Science and Technology. In this study, it was confirmed that the spectral shape of Eu complexes in the adsorbents varied depending on the kinds of extractants, and the correlation between the change in the spectra and the structures of Eu complexes was investigated.

Journal Articles

Soil dust and bioaerosols as potential sources for resuspended $$^{137}$$Cs occurring near the Fukushima Dai-ichi Nuclear Power Plant

Ota, Masakazu; Takahara, Shogo; Yoshimura, Kazuya; Nagakubo, Azusa; Hirouchi, Jun; Hayashi, Naho; Abe, Tomohisa; Funaki, Hironori; Nagai, Haruyasu

Journal of Environmental Radioactivity, 264, p.107198_1 - 107198_15, 2023/08

 Times Cited Count:0 Percentile:0(Environmental Sciences)

One of the current major radiation exposure pathways from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident-fallout is inhalation of the re-suspended $$^{137}$$Cs occurring in air. While wind-induced soil particle resuspension has been recognized as a primary mechanism of $$^{137}$$Cs resuspension, studies following the FDNPP accident suggested that fungal spores can be a significant source of the atmospheric $$^{137}$$Cs particularly in the rural areas such as difficult-to-return zone (DRZ). To elucidate the relative importance of the two resuspension phenomena, we propose a model simulating resuspension of $$^{137}$$Cs as soil particles and fungal spores, and applied it to DRZ. Our model's calculation showed that soil particle resuspension was responsible for the surface-air $$^{137}$$Cs observed during winter-spring, but could not account for the higher $$^{137}$$Cs concentrations observed in summer-autumn. The higher concentrations in the summer-autumn were in general reproduced by implementing fungal spore $$^{137}$$Cs emission, that replenished low soil particle $$^{137}$$Cs resuspension in that period. According to our model's concept, $$^{137}$$Cs accumulation in fungal spores and high spore emission rate characterized by the rural environment were likely responsible for the abundance of spore $$^{137}$$Cs in the air. It was inferred that the influence of the fungal spores on the atmospheric $$^{137}$$Cs would last longer since un-decontaminated forests still exist in DRZ.

JAEA Reports

Research on atmospheric radioactivity concentration in the specified reconstruction and revitalization base (FY2018-FY2021)

Abe, Tomohisa; Funaki, Hironori; Yoshimura, Kazuya; Shiribiki, Natsu*; Sanada, Yukihisa

JAEA-Data/Code 2023-001, 38 Pages, 2023/05

JAEA-Data-Code-2023-001.pdf:3.04MB
JAEA-Data-Code-2023-001-appendix(CD-ROM).zip:32.02MB

In this study, commissioned by the Cabinet Office, we conducted a survey on radioactive materials in atmospheric dust in three municipalities (Futaba Town, Okuma Town, and Tomioka Town) in Fukushima Prefecture to contribute to the assessment of internal exposure in the Specified Reconstruction and Revitalization Base (SRRB). Air dust samplers were installed in the targeted municipalities to investigate the atmospheric $$^{137}$$Cs concentrations and to evaluate internal exposure doses based on measured value. This report summarizes the results of measurements between 2018 and 2021. A database of information on internal exposure dose assessment results based on atmospheric radioactivity concentrations and actual measurements, and meteorological observation data was compiled.

Journal Articles

Evaluation of external dose exposure of workers during house demolition and dose reduction work in a difficult-to-return zone

Sanada, Yukihisa; Tokiyoshi, Masanori*; Nishiyama, Kyohei*; Sato, Rina; Yoshimura, Kazuya; Funaki, Hironori; Abe, Tomohisa; Ishida, Mutsushi*; Nagamine, Haruo*; Fujisaka, Motoyuki*

Nihon Genshiryoku Gakkai Wabun Rombunshi (Internet), 22(2), p.87 - 96, 2023/04

Since the accident at the Fukushima Daiichi Nuclear Power Plant, many decontamination works have been carried out, but it is difficult to say that much data on workers' exposure has necessarily been analyzed in detail. In this paper, based on the GPS location information carried by the workers together with their personal dosimeters, the air dose rate in the work area and the characteristics of each type of work were analyzed. The results showed that more than 50% of the measured actual doses were more than twice the median planned dose calculated from the air dose rate and actual working hours. Furthermore, as a result of the analysis by work type, it was found that the exposure doses of demolition workers tended to be high, and that this was due to the fact that most of the work was carried out before the work was carried out to reduce the dose at the work site. In addition, when the conversion from air dose to effective dose was taken into account, there were many cases of underestimation where the planned values were lower than the measured values, and it is considered important for management to set appropriate working factor.

Journal Articles

Ion beam induced luminescence spectra of europium complexes in silica-based adsorbent

Nakahara, Masaumi; Watanabe, So; Ishii, Yasuyuki*; Yamagata, Ryohei*; Yamada, Naoto*; Koka, Masashi*; Yuyama, Takahiro*; Ishizaka, Tomohisa*; Kada, Wataru*; Hagura, Naoto*

QST-M-39; QST Takasaki Annual Report 2021, P. 62, 2023/02

In an extraction chromatography method for minor actinides recovery, analysis for the structure of complex in a silica-based adsorbent has been studied to separate minor actinides efficiently. In this study, Eu was used as simulated material of minor actinides, and silica-based adsorbents containing Eu complex were prepared. The ion beam induced luminescence spectra of Eu complexes in silica-based adsorbents were measured, and the basic data for the structures of Eu complexes were obtained.

Journal Articles

Basic study on tritium monitor using plastic scintillator for treated water discharge at Fukushima Daiichi Nuclear Power Plant

Sanada, Yukihisa; Abe, Tomohisa; Sasaki, Miyuki; Kanno, Marina*; Yamada, Tsutomu*; Nakasone, Takamasa*; Miyazaki, Nobuyuki*; Oshikiri, Keisuke*; Watabe, Hiroshi*

Journal of Nuclear Science and Technology, 10 Pages, 2023/00

The "treated water" from which the main radioactive materials were removed contains tritium, and stakeholders in Japan have been debating how to treat it. The amount of treated water stored in the facility has reached its limit, and the Japanese government has decided that the treatment method will be to discharge the water into the ocean by FY 2023 (FY: Fiscal Year). The present research developed a simple and practical tritium monitor for the Fukushima Daiichi Nuclear Power Station (FDNPS) tritiated water release. A simple and practical tritium monitor was developed for FDNPS tritiated water release based on thin plastic scintillator sheets. The developed devices were calibrated using standard tritium solutions and a method for calculating the minimum detectable activity. Fifteen 0.25 mm-thick scintillators can be placed in the 0.26 L flow cell where the sample water is fed, yielding an active surface area of 3,200 mm$$^{2}$$. The efficiency of tritiated water with full water is 0.000035 cps Bq$$^{-1}$$. The minimum detectable activity under simple shielding conditions was 7,800 Bq L$$^{-1}$$ (Measurement time was 3,600 s).

Journal Articles

Temporal change in atmospheric radiocesium during the first seven years after the Fukushima Dai-ich Nuclear Power Plant accident

Abe, Tomohisa; Yoshimura, Kazuya; Sanada, Yukihisa

Aerosol and Air Quality Research, 21(7), p.200636_1 -  200636_11, 2021/07

 Times Cited Count:4 Percentile:29.46(Environmental Sciences)

Journal Articles

Radiation monitoring and evaluation of exposure doses to lift the evacuation orders for the zones designated for reconstruction and recovery

Sanada, Yukihisa; Kurikami, Hiroshi; Funaki, Hironori; Yoshimura, Kazuya; Abe, Tomohisa; Ishida, Mutsushi*; Tanimori, Soichiro*; Sato, Rina

Nihon Genshiryoku Gakkai Wabun Rombunshi, 20(2), p.62 - 73, 2021/06

Japanese government starts to consider radiation protection in the "specific reconstruction reproduction base area" of which evacuation order will be lifted by 2023. It is essential to grab the present situations of radiation contamination and evaluate exposure dose in the area to realize the plan. Many surveys have evaluated the distributions of air dose rate and exposure dose has been estimated based on the results since the Fukushima Daiichi Nuclear Power Plant accident. Nevertheless, more detailed information on exposure is needed for the areas because its radiation level is relatively high. That is also to help make prudent evaluation plan. This study aimed to evaluate the detailed contamination situation there and estimate exposure dose with considering areal circumstances. Investigations were carried out for (1) airborne survey of air dose rate using an unmanned helicopter (2) evaluation of airborne radiocesium and (3) estimation of external/internal effective doses for typical activity patterns assumed.

JAEA Reports

The Data-base of the radiation monitoring in Fukushima based on the comprehensive radiation monitoring plan

Abe, Tomohisa; Ogiya, Takashi*; Shibata, Katsuya*; Hanawa, Tatsuaki*; Sanada, Yukihisa

JAEA-Data/Code 2020-004, 280 Pages, 2020/08

JAEA-Data-Code-2020-004.pdf:3.91MB

After the accidents at Fukushima Daiichi Nuclear Power Station (FDNPS), Japan Atomic Energy Agency has carried on survey for distribution situation of radiation materials under the direction of the Ministry of Education, Culture, Sports, Science and Technology (later the Nuclear Regulatory Agency) from June 2011 to FY2019. This report is mainly summarized as data-base of air dose rate, integrated dose and radionuclide concentration of some types of environmental sample (airborne dust, soil, pine needles) in the radiation monitoring in Fukushima Prefecture (20 km far from FDNPS). The results of radiation monitoring were analyzed for temporal change at each measurement site under the unification format. Furthermore, the effective half-life and the dispersion at each location and sample were evaluated based on these big data.

Journal Articles

Study on optimizing microwave heating denitration method and powder characteristics of uranium trioxide

Segawa, Tomoomi; Kawaguchi, Koichi; Kato, Yoshiyuki; Ishii, Katsunori; Suzuki, Masahiro; Fujita, Shunya*; Kobayashi, Shohei*; Abe, Yutaka*; Kaneko, Akiko*; Yuasa, Tomohisa*

Proceedings of 2019 International Congress on Advances in Nuclear Power Plants (ICAPP 2019) (Internet), 9 Pages, 2019/05

A solution of plutonium nitrate and uranyl nitrate is converted into a mixed oxide by microwave heating denitration method. In the present study, for improving the efficiency of microwave heating and achieving high-temperature uniformity to produce homogeneous UO$$_{3}$$ powder, the microwave heating test of potassium chloride and uranyl nitrate solution, and numerical simulation analysis were conducted. The potassium chloride agar was adjusted to the dielectric loss, which is close to that of the uranyl nitrate solution and the optimum support table height was estimated to be 50 mm for denitration of the uranyl nitrate solution by microwave heating. The adiabator improved the efficiency of microwave heating denitration. Moreover, the powder yield was improved by using the adiabator owing to ease of scraping of the denitration product from the bottom of the denitration vessel.

Journal Articles

Micro-PIXE analysis study of ferrite products synthesized from simulated radioactive liquid waste containing chemical hazardous elements

Abe, Tomohisa; Shimazaki, Takejiro; Osugi, Takeshi; Nakazawa, Osamu; Yamada, Naoto*; Yuri, Yosuke*; Sato, Takahiro*

QST-M-16; QST Takasaki Annual Report 2017, P. 140, 2019/03

no abstracts in English

Journal Articles

Mechanism of flashing phenomena by microwave heating and influence of high dielectric constant solution

Fujita, Shunya*; Abe, Yutaka*; Kaneko, Akiko*; Yuasa, Tomohisa*; Segawa, Tomoomi; Kato, Yoshiyuki; Kawaguchi, Koichi; Ishii, Katsunori

Proceedings of 11th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-11) (Internet), 7 Pages, 2018/11

Mixed uranium oxide and plutonium oxide powder is produced from uranyl nitrate and plutonium nitrate mixed solution by the microwave heating denitration method in the spent fuel reprocessing process. Since the microwave heating method is accompanied by a boiling phenomenon, it is necessary to fully grasp the operating conditions in order to avoid flashing and spilling in the mass production of denitrification technology for the future. In this research, it was clarified that the heat transfer coefficient became lower as the dielectric constant increased. The dominant factor of the blowing up phenomena is supposed to be generation of the innumerable bubble rather than bubble's growth.

Journal Articles

Mechanism of flashing phenomena induced by microwave heating

Fujita, Shunya*; Abe, Yutaka*; Kaneko, Akiko*; Yuasa, Tomohisa*; Segawa, Tomoomi; Yamada, Yoshikazu; Kato, Yoshiyuki; Ishii, Katsunori

Proceedings of 26th International Conference on Nuclear Engineering (ICONE-26) (Internet), 8 Pages, 2018/07

Mixed uranium oxide and plutonium oxide powder is produced from uranyl nitrate and plutonium nitrate mixed solution by the microwave heating denitration method in the spent fuel reprocessing process. Since the microwave heating method is accompanied by a boiling phenomenon, it is necessary to fully grasp the operating conditions in order to avoid flashing and spilling in the mass production of denitrification technology for the future. In this research, it was confirmed that a potassium chloride aqueous solution as a simulant of uranyl nitrate aqueous solution with high dielectric loss cause loss of microwave at the solution surface as the dielectric loss increased with the increase of KCl concentration by experimental and electromagnetic field analysis, and revealed that the change in the heating condition affects the generation of flushing.

Journal Articles

Application of ferrite process to radioactive waste; Study of ferrite product stability by micro-PIXE analysis

Abe, Tomohisa; Shimazaki, Takejiro; Osugi, Takeshi; Yamada, Naoto*; Yuri, Yosuke*; Sato, Takahiro*

QST-M-8; QST Takasaki Annual Report 2016, P. 61, 2018/03

no abstracts in English

Journal Articles

Flushing phenomena and flow structure by microwave heating

Fujita, Shunya*; Abe, Yutaka*; Kaneko, Akiko*; Chonan, Fuminori*; Yuasa, Tomohisa*; Yamaki, Tatsunori*; Segawa, Tomoomi; Yamada, Yoshikazu

Proceedings of 25th International Conference on Nuclear Engineering (ICONE-25) (CD-ROM), 8 Pages, 2017/07

From the observation results, in the process of flushing, the behaviors leading to flushing were classified divided into three types. First type is that first generation bubble from heating leads to flushing. Second type is that nucleate boiling continues during heating and stop, finally single bubble generates and leads to flushing. Third type is defined that gradual evaporation occurs without bubbles. It was revealed that the total quantities of heat released by flushing are approximately equal when assuming the flushing mechanism, it can be triggered that a large amount of micro bubbles are instantaneously generated and grew.

Journal Articles

Element distribution measurement in incineration ash using micro-PIXE analysis

Abe, Tomohisa; Shimazaki, Takejiro; Nakayama, Takuya; Osone, Osamu; Osugi, Takeshi; Nakazawa, Osamu; Yuri, Yosuke*; Yamada, Naoto*; Sato, Takahiro*

QST-M-2; QST Takasaki Annual Report 2015, P. 83, 2017/03

no abstracts in English

Journal Articles

Report on the weekend basic course for Division of Nuclear Fuel Cycle and Environment in fiscal year 2015

Taniguchi, Takumi; Abe, Tomohisa

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 23(1), p.73 - 74, 2016/06

The weekend basic course for Division of Nuclear Fuel Cycle and Environment was held on November 7 (Sat) and 8 (Sun) on 2015 at Tohoku University Aobayama Campus in Sendai City. Twenty-eight people from universities and companies attended the course, and seven lectures and group discussions were held. I will report the outline of this course and the contents of the group discussion.

Journal Articles

Formation of a uniform ion beam using multipole magnets

Yuri, Yosuke; Ishizaka, Tomohisa; Yuyama, Takahiro; Okumura, Susumu; Ishibori, Ikuo; Yokota, Wataru; Watanabe, Shinichi*; Kubono, Shigeru*; Oshiro, Yukimitsu*

Proceedings of 2009 Particle Accelerator Conference (PAC '09) (DVD-ROM), p.3895 - 3897, 2009/05

Journal Articles

Comprehensive cost estimation method for decommissioning

Kudo, Kenji; Kawatsuma, Shinji; Rindo, Hiroshi; Watabe, Kozo; Tomii, Hiroyuki; Shiraishi, Kunio; Yagi, Naoto; Fukushima, Tadashi; Zaitsu, Tomohisa

Proceedings of 14th International Conference on Nuclear Engineering (ICONE-14) (CD-ROM), 8 Pages, 2006/07

Japan Atomic Energy Research Institute (JAERI) played a leading role in basic research in the field of atomic energy research and development, while Japan Nuclear Cycle Development Institute (JNC) did a major role in FBR cycle development and high level waste disposal. Following the Government's decision in December 2001, JAERI and JNC was merged as of October 1st, 2005. The new organization, Japan Atomic Energy Agency (JAEA), is an institute for comprehensive R&D for atomic energy, and is the largest research and development institute among Governmental R&D organizations. Its missions are basic research on atomic energy, R&D for nuclear fuel cycle, decommissioning of own facilities and disposal of waste, contribution to safety and non-proliferation, etc. The JAEA owns a number of nuclear facilities: research reactors such as JRR-2 and Joyo, prototype reactors such as ATR "Fugen" and FBR "Monju", fuel cycle plants such as Uranium Enrichment Demonstration Plant at Ningyo-Toge, MOX fuel plants at Tokai, Reprocessing Plant at Tokai, and Hot Laboratories such as JRTF and FMF. As a part of preparation of the mergence, JNC and JAERI have jointly developed a comprehensive cost estimation method for decommissioning, based on decommissioning and refurbishing experiences of JAERI and JNC. This method involves more estimation parameters from typical decommissioning activities than before, so as to make it more reliable. JAERI and JNC have estimated the total cost for decommissioning by using this method, and concluded that the cost would be 600 billion yen (approx. 5 billion USD).

Journal Articles

Cost estimation method for decommissioning of nuclear facilities

Tomii, Hiroyuki; Matsuo, Kiyoshi*; Shiraishi, Kunio; Watabe, Kozo; Saiki, Hideo*; Kawatsuma, Shinji*; Rindo, Hiroshi*; Zaitsu, Tomohisa*

Dekomisshoningu Giho, (31), p.11 - 20, 2005/03

no abstracts in English

58 (Records 1-20 displayed on this page)