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Journal Articles

Cs extraction from chloride media by calixarene crown-ethers

Simonnet, M.; Sittel, T.*; We${ss}$ling, P.*; Geist, A.*

Energies (Internet), 15(20), p.7724_1 - 7724_10, 2022/10

Journal Articles

Cesium-rich microparticles runoff during rainfall; A Case study in the Takase River

Tatsuno, Takahiro*; Waki, Hiromichi*; Kakuma, Minato*; Nihei, Naoto*; Wada, Toshihiro*; Yoshimura, Kazuya; Nakanishi, Takahiro; Ote, Nobuhito*

Radiation Protection Dosimetry, 198(13-15), p.1052 - 1057, 2022/09

 Times Cited Count:0 Percentile:0.02(Environmental Sciences)

JAEA Reports

Development of the sintering solidification method for spent zeolite to long-term stabilization (Contract research); FY2020 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Shibaura Institute of Technology*

JAEA-Review 2022-008, 116 Pages, 2022/06

JAEA-Review-2022-008.pdf:5.36MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2020. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2018, this report summarizes the research results of the "Development of the sintering solidification method for spent zeolite to long-term stabilization" conducted from FY2018 to FY2021 (this contract was extended to FY2021). Since the final year of this proposal was FY2021, the results for four fiscal years were summarized. The present study aims to develop a new sintering solidification method in which glass is added as a binder to spent zeolite which is adsorbed radionuclides such as Cs and the nuclides are immobilized by sintering them. In this project, the optimum conditions for sintering solidification and the basic performance of the sintered solidified body will be evaluated by cold tests, and they will be demonstrated by hot tests. In FY2020, the cold tests

Journal Articles

Contamination processes of tree components in Japanese forest ecosystems affected by the Fukushima Daiichi Nuclear Power Plant accident $$^{137}$$Cs fallout

Ota, Masakazu; Koarashi, Jun

Science of the Total Environment, 816, p.151587_1 - 151587_21, 2022/04

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

In forests affected by the Fukushima Daiichi Nuclear Power Plant accident, trees became contaminated with $$^{137}$$Cs. However, $$^{137}$$Cs transfer processes determining tree contamination (particularly for stem wood, which is a prominent commercial resource in Fukushima) remain insufficiently understood. This study proposes a model for simulating the dynamic behavior of $$^{137}$$Cs in a forest tree-litter-soil system and applied it to two contaminated forests (cedar plantation and natural oak stand) in Fukushima. The model-calculated results and inter-comparison of the results with measurements elucidated the relative impact of distinct $$^{137}$$Cs transfer processes determining tree contamination. The transfer of $$^{137}$$Cs to trees occurred mostly ($$>$$ 99%) through surface uptake of $$^{137}$$Cs directly trapped by leaves or needles and bark during the fallout. By contrast, root uptake of $$^{137}$$Cs from the soil was unsubstantial and several orders of magnitude lower than the surface uptake over a 50-year period following the accident. As a result, the internal contamination of the trees proceeded through an enduring recycling (translocation) of $$^{137}$$Cs absorbed on the tree surface at the time of the accident. A significant surface uptake of $$^{137}$$Cs at the bark was identified, contributing 100% (leafless oak tree) and 30% (foliated cedar tree; the remaining surface uptake occurred at the needles) of the total $$^{137}$$Cs uptake by trees. It was suggested that the trees growing at the study sites are currently (as of 2021) in a decontamination phase; the activity concentration of $$^{137}$$Cs in the stem wood decreases by 3% per year, mainly through radioactive decay of $$^{137}$$Cs and partly through a dilution effect from tree growth.

JAEA Reports

Result of measurement of the ambient dose equivalent rates by car-borne surveys using KURAMA-II from 2012 until 2019

Ando, Masaki; Saito, Kimiaki

JAEA-Technology 2021-032, 66 Pages, 2022/03

JAEA-Technology-2021-032.pdf:3.84MB

Since the occurrence of the accident at the TEPCO Fukushima Daiichi Nuclear Power Station, the Japan Atomic Energy Agency (JAEA) has been conducting a series of car-borne survey over a wide area in the eastern part of Japan using the monitoring system KURAMAII. In this report, outline of the car-borne surveys are summarized and the following characteristics of the temporal changes in each prefecture and region were investigated using the measured data obtained from 2012 to 2019; 1) Average and maximum values for each prefecture for the six years from 2014 to 2019, 2) Average values for each prefecture from 2012 to 2019, 3) Average values for each evacuation order area category, regional category, and northern Soso-area municipality in Fukushima Prefecture from 2012 to 2019, and 4) Average and maximum values for each municipality in each prefecture for four times (at almost two-year intervals) of the measurement results from 2012 to 2018.

Journal Articles

Cesium chemistry in the LWR severe accident and towards the decommissioning of Fukushima Daiichi Nuclear Power Station

Osaka, Masahiko; Gou$"e$llo, M.*; Nakajima, Kunihisa

Journal of Nuclear Science and Technology, 59(3), p.292 - 305, 2022/03

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

Research on the fission product chemistry made after the severe accident of the Fukushima Daiichi Nuclear Power Station were reviewed with focus on the Cesium chemistry in terms of two regimes, namely the accidental source term and the long-term source term via aqueous phase towards the decommissioning. For the accidental source term, Cs chemical interaction with Mo, B and Si were reviewed. Regarding the unique issue of long-term source term via aqueous phase, Cs penetration into concrete and fuel debris leaching were mentioned as the main sources of FPs. Efforts on the preparation of thermodynamic data for the Cs complex oxides were described. All these Cs chemical behaviors should be modelled and validated/verified through the analysis and evaluation of the actual samples including fuel debris that would be taken from the Fukushima Daiichi Nuclear Power Station in near future.

Journal Articles

Radiation monitoring in the residential environment; Time dependencies of air dose rate and $$^{137}$$Cs inventory

Yoshimura, Kazuya; Nakama, Shigeo; Fujiwara, Kenso

Journal of Radiation Protection and Research, 47(1), p.30 - 38, 2022/03

JAEA Reports

Radiation monitoring using manned helicopter around the Nuclear Power Station in the fiscal year 2020 (Contract research)

Futemma, Akira; Sanada, Yukihisa; Ishizaki, Azusa; Kawasaki, Yoshiharu*; Iwai, Takeyuki*; Hiraga, Shogo*; Sato, Kazuhiko*; Haginoya, Masashi*; Matsunaga, Yuki*; Kikuchi, Hikaru*; et al.

JAEA-Technology 2021-029, 132 Pages, 2022/02

JAEA-Technology-2021-029.pdf:24.58MB

By the nuclear disaster of Fukushima Daiichi Nuclear Power Station (FDNPS), Tokyo Electric Power Company (TEPCO), caused by the Great East Japan Earthquake and the following tsunami on March 11, 2011, a large amount of radioactive material was released from the FDNPS. After the nuclear disaster, airborne radiation monitoring using manned helicopter has been conducted around FDNPS. The results of the airborne radiation monitoring and the evaluation for temporal change of dose rate in the fiscal 2020 were summarized in this report. Analysis considering topographical effects was applied to the result of the airborne monitoring to improve the accuracy of conventional method. In addition, technique for discriminating gamma rays from the ground and those from the airborne Rn-progenies was also utilized to evaluate their effect on airborne radiation monitoring.

JAEA Reports

Investigations on distribution of radioactive substances owing to the Fukushima Daiichi Nuclear Power Station Accident in the fiscal year 2020 (Contract research)

Group for Fukushima Mapping Project

JAEA-Technology 2021-025, 159 Pages, 2022/01

JAEA-Technology-2021-025.pdf:46.66MB

This report presents results of the investigations on the distribution-mapping project of radioactive substances owing to TEPCO Fukushima Daiichi Nuclear Power Station (FDNPS) conducted in FY2020. Car-borne surveys, a flat ground measurement using survey meters, a walk survey and an unmanned helicopter survey were carried out to obtain air dose rate data. Air dose rate distribution maps were created and temporal changes of the air dose rates were analyzed. Regarding radiocesium deposition into the ground, surveys on depth profile of radiocesium and in-situ measurements were performed. Based on these measurement results, effective half-lives of the temporal changes in the air dose rates and the deposition were evaluated. In the examination of scoring for classifying the importance of measurement points, a score map was created for Fukushima Prefecture and the 80 km zone from the FDNPS, and the factors causing changes in the score when monitoring data from multiple years were used were discussed. Using the Bayesian hierarchical modeling approach, we obtained maps that integrated the air dose rate distribution data obtained from aircraft monitoring, car-borne surveys, and walk surveys with respect to the region within 80 km from the FDNPS and Fukushima Prefecture. The measurement results for FY2020 were published on the "Expansion Site of Distribution Map of Radiation Dose", and measurement data were stored as CSV format. Radiation monitoring and analysis of environmental samples owing to the comprehensive radiation monitoring plan were carried out.

Journal Articles

Air dose rates and cesium-137 in urban areas; Deposition, migration, and time dependencies after nuclear power plant accidents

Yoshimura, Kazuya

Journal of Nuclear Science and Technology, 59(1), p.25 - 33, 2022/01

 Times Cited Count:1 Percentile:39.48(Nuclear Science & Technology)

Journal Articles

Characterization of radiocesium-bearing microparticles with different morphologies in soil around the Fukushima Daiichi Nuclear Power Plant

Hagiwara, Hiroki; Funaki, Hironori; Shiribiki, Natsu*; Kanno, Marina*; Sanada, Yukihisa

Journal of Radioanalytical and Nuclear Chemistry, 331(1), p.415 - 426, 2022/01

 Times Cited Count:1 Percentile:39.48(Chemistry, Analytical)

Journal Articles

Radiocesium transfer into freshwater planktonic ${it Chlamydomonas}$ spp. microalgae in a pond near the Fukushima Dai-ichi Nuclear Power Plant

Sasaki, Yoshito; Funaki, Hironori; Fujiwara, Kenso

Limnology, 23(1), p.1 - 7, 2022/01

 Times Cited Count:0 Percentile:0.04(Limnology)

We investigated the transfer behavior of radiocesium in living cells and remains of a bloom of microalgae (${it Chlamydomonas}$ sp.) in a pond located about 5 km from the Fukushima Dai-ichi Nuclear Power Plant. As a positive correlation was detected between the cell number of microalgae and the radiocesium concentration (Bq/L) in the $$>$$ 0.45-$$mu$$m fraction, microalgae were the controlling factor for the radiocesium concentration of the $$>$$ 0.45-$$mu$$m fraction. The transfer factor of water-to-algae [($$^{137}$$Cs concentration Bq/kg $$>$$ 0.45-$$mu$$m fraction) $$times$$ ($$^{137}$$Cs concentration Bq/L water)$$^{-1}$$] was 1.6 $$times$$ 10$$^{3}$$. The radiocesium concentration of microalgae remains was the same as that in intact cells.

Journal Articles

The Formation mechanism of radiocesium-bearing microparticles derived from the Fukushima Daiichi Nuclear Power Plant using electron microscopy

Hagiwara, Hiroki; Kondo, Keietsu; Hidaka, Akihide

Journal of Radioanalytical and Nuclear Chemistry, 10 Pages, 2022/00

 Times Cited Count:0 Percentile:0.02(Chemistry, Analytical)

JAEA Reports

Upgrading of recovery method for radioactive microparticles by heavy liquid separation aiming to volume reduction of contaminated soil (Contract research); FY2020 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; University of Tsukuba*

JAEA-Review 2021-023, 49 Pages, 2021/12

JAEA-Review-2021-023.pdf:2.39MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2020. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2018, this report summarizes the research results of the "Upgrading of recovery method for radioactive microparticles by heavy liquid separation aiming to volume reduction of contaminated soil" conducted from FY2018 to FY2020. Since the final year of this proposal was FY2020, the results for three fiscal years were summarized. The present study aims to develop a novel method to reduce the volume of contaminated soil caused by an accident at the Fukushima Daiichi Nuclear Power Station. The heavy liquid separation method, which was optimized in the previous year, was applied to nine soils collected in Fukushima Prefecture. As a result, radioactivity concentration and weight of the contaminated soils were reduced by half at six sites by separating the soils into two fractions u

Journal Articles

Effect of B$$_{4}$$C absorber material on melt progression and chemical forms of iodine or cesium under severe accident conditions

Hidaka, Akihide

Insights Concerning the Fukushima Daiichi Nuclear Accident, Vol.4; Endeavors by Scientists, p.341 - 356, 2021/10

Journal Articles

Analytical study on removal mechanisms of cesium aerosol from a noble gas bubble rising through liquid sodium pool, 2; Effects of particle size distribution and agglomeration in aerosols

Miyahara, Shinya*; Kawaguchi, Munemichi; Seino, Hiroshi; Atsumi, Takuto*; Uno, Masayoshi*

Proceedings of 28th International Conference on Nuclear Engineering (ICONE 28) (Internet), 6 Pages, 2021/08

In a postulated accident of fuel pin failure of sodium cooled fast reactor, a fission product cesium will be released from the failed pin as an aerosol such as cesium iodide and/or cesium oxide together with a fission product noble gas such as xenon and krypton. As the result, the xenon and krypton released with cesium aerosol into the sodium coolant as bubbles have an influence on the removal of cesium aerosol by the sodium pool in a period of bubble rising to the pool surface. In this study, cesium aerosol removal behavior due to inertial deposition, sedimentation and diffusion from a noble gas bubble rising through liquid sodium pool was analyzed by a computer program which deals with the expansion and the deformation of the bubble together with the aerosol absorption considering the effects of particle size distribution and agglomeration in aerosols. In the analysis, initial bubble diameter, sodium pool depth and temperature, aerosol particle diameter and density, initial aerosol concentration in the bubble were changed as parameter, and the results for the sensitivities of these parameters on decontamination factor (DF) of cesium aerosol were compared with the results of the previous study in which the effects of particle size distribution and agglomeration in aerosols were not considered. From the results, it was concluded that the sensitivities of initial bubble diameter, the aerosol particle diameter and density to the DF became significant due to the inertial deposition of agglomerated aerosols. To validate these analysis results, the simulation experiments have been conducted using a simulant particles of cesium aerosol under the condition of room temperature in water pool and air bubble systems. The experimental results were compared with the analysis results calculated under the same condition.

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:3 Percentile:52.89(Environmental Sciences)

Journal Articles

The Effect and effectiveness of decontaminating a pond in a residential area of Fukushima

Katengeza, E. W.*; Ochi, Kotaro; Sanada, Yukihisa; Iimoto, Takeshi*; Yoshinaga, Shinji*

Health Physics, 121(1), p.48 - 57, 2021/07

 Times Cited Count:0 Percentile:0.01(Environmental Sciences)

Special reconstruction and revitalization bases were designated in Fukushima's difficult-to-return zones by the Japanese government as targets of intensive decontamination to drastically lower air dose rates and enable residents to return. A pond amidst residences of one of these bases was targeted for decontamination and this study aimed at evaluating the effect and effectiveness of the decontamination by decontamination factor, air dose rate reduction factor, and the additional annual effective dose to residents. Air dose rates were measured in-situ with KURAMMA-II while soil core samples were collected and measured for radioactivity in the laboratory by gamma spectrometry. Lower decontamination factors were observed for more deeply distributed radiocesium soil profiles whereas areas covered with gravel demonstrated the largest reduction in air dose rates. Decontamination effectively lowered the radiocesium inventory and air dose rates by 51% and 37-91% respectively. Moreover, the additional annual effective dose to the public changed from 1.7$$pm$$0.79 mSv to 1.2$$pm$$0.57 mSv because of decontamination representing a dose aversion of 29%. These findings demonstrate how decontaminating ponds in residential areas can help to further lower the external exposure.

Journal Articles

Impacts of freeze-thaw processes and subsequent runoff on $$^{137}$$Cs washoff from bare land in Fukushima

Igarashi, Yasunori*; Onda, Yuichi*; Wakiyama, Yoshifumi*; Yoshimura, Kazuya; Kato, Hiroaki*; Kozuka, Shohei*; Manome, Ryo*

Science of the Total Environment, 769, p.144706_1 - 144706_9, 2021/05

 Times Cited Count:1 Percentile:21.03(Environmental Sciences)

JAEA Reports

Radiation monitoring using manned helicopter around the Nuclear Power Station in the fiscal year 2019 (Contract research)

Futemma, Akira; Sanada, Yukihisa; Ishizaki, Azusa; Kawasaki, Yoshiharu*; Iwai, Takeyuki*; Hiraga, Shogo*; Sato, Kazuhiko*; Haginoya, Masashi*; Matsunaga, Yuki*; Kikuchi, Hikaru*; et al.

JAEA-Technology 2020-018, 121 Pages, 2021/02

JAEA-Technology-2020-018.pdf:15.15MB

By the nuclear disaster of Fukushima Daiichi Nuclear Power Station (FDNPS), Tokyo Electric Power Company (TEPCO), caused by the Great East Japan Earthquake and the following tsunami on March 11, 2011, a large amount of radioactive material was released from the FDNPS. After the nuclear disaster, airborne radiation monitoring using manned helicopter has been conducted around FDNPS. The results in the fiscal 2019 were summarized in this report. Analysis taken topographical effects into consideration was applied to the result of airborne monitoring to improve the precision of conventional method. In addition, discrimination method of gamma rays from Rn-progenies was also utilized to evaluate their effect on aerial radiation monitoring.

247 (Records 1-20 displayed on this page)