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Journal Articles

Which radionuclides contribute most to seafood ingestion dose?

Johansen, M. P.*; Gwynn, J. P.*; Carpenter, J. G.*; Charmasson, S.*; Mori, Airi; Orr, B.*; Simon-Cornu, M.*; Osvath, I.*; McGinnity, P.*

Journal of Environmental Radioactivity, 287, p.107706_1 - 107706_8, 2025/07

 Times Cited Count:0 Percentile:0.00(Environmental Sciences)

Journal Articles

Ingestion doses from radionuclides in seafood before and after the Fukushima Daiichi Nuclear Power Plant accident

Mori, Airi; Johansen, M. P.*; McGinnity, P.*; Takahara, Shogo

Communications Earth & Environment (Internet), 6, p.356_1 - 356_11, 2025/05

 Times Cited Count:0 Percentile:0.00(Environmental Sciences)

Journal Articles

Visualization of radioactive contamination around the startup transformer of the Fukushima Daiichi Nuclear Power Station Unit 3 using an integrated radiation imaging system based on a Compton camera

Sato, Yuki; Terasaka, Yuta; Ichiba, Yuta*

Journal of Nuclear Science and Technology, 62(4), p.389 - 400, 2025/04

 Times Cited Count:0 Percentile:0.00(Nuclear Science & Technology)

JAEA Reports

Investigations on distribution of radioactive substances owing to the Fukushima Daiichi Nuclear Power Station Accident in the fiscal year 2023 (Contract research)

Group for Fukushima Mapping Project

JAEA-Technology 2024-017, 208 Pages, 2025/03

JAEA-Technology-2024-017.pdf:27.32MB

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 FY2023. Car-borne surveys, a measurement using survey meters, a walk survey and an unmanned helicopter survey were carried out to obtain air dose rate data to create their distribution maps, and temporal changes of the air dose rates were analyzed. Surveys on depth profile of radiocesium and in-situ measurements as for radiocesium deposition were performed. Based on these measurement results, effective half-lives of the temporal changes in the air dose rates and the deposition were evaluated. Score maps to classify the importance of the measurement points were created, and the temporal changes in the score were analyzed. A system to report the tritium concentration level in seawater to the Nuclear Regulation Authority was operated, and the variation of tritium concentration before and after the discharge of ALPS treated water to the ocean was analyzed. Monitoring data in coastal area performed owing to the comprehensive radiation monitoring plan until FY2023 was analyzed. Using the Bayesian hierarchical modeling approach, we obtained maps that integrated air dose rate distribution data acquired through surveys such as car-borne and walk surveys. Representative life patterns that can be expected after the return to the evacuation-designated restricted area were set, and the cumulative exposure doses were evaluated for the local governments and residents in the area. The measurement results for FY2023 were published on the Web site 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

Radiological dose from seafood ingestion; A Global summary from 40 years of study

Johansen, M. P.*; Gwynn, J. P.*; Carpenter, J. G.*; Charmasson, S.*; McGinnity, P.*; Mori, Airi; Orr, B.*; Simon-Cornu, M.*; Osvath, I.*

Critical Reviews in Environmental Science and Technology, 55(6), p.422 - 445, 2025/00

 Times Cited Count:3 Percentile:32.78(Environmental Sciences)

JAEA Reports

Development of a high-resolution imaging camera for alpha dust and high-dose rate monitor (Contract research); FY2022 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Tohoku University*

JAEA-Review 2024-016, 61 Pages, 2024/12

JAEA-Review-2024-016.pdf:2.88MB

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 FY2022. 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 FY2022, this report summarizes the research results of the "Development of a high-resolution imaging camera for alpha dust and high-dose rate monitor" conducted in FY2022. The present study aims to develop a high-resolution imaging camera for alpha dust and a high-dose rate monitor. To realize the high-resolution imaging camera for alpha dust, we have developed novel scintillation materials with emission bands of 500-800 nm. Moreover, we have prepared several materials for the camera and software. We have also developed novel scintillation materials with emission bands of 650-1,000 nm, and simulation studies have been conducted for the high-dose-rate monitor system consisting of optical fiber.

Journal Articles

Assessment of individual external exposure doses based on environmental radiation in areas affected by the Fukushima Daiichi Nuclear Power Station accident

Sato, Rina; Yoshimura, Kazuya; Sanada, Yukihisa; Mikami, Satoshi; Yamada, Tsutomu*; Nakasone, Takamasa*; Kanaizuka, Seiichi*; Sato, Tetsuro*; Mori, Tsubasa*; Takagi, Marie*

Environment International, 194, p.109148_1 - 109148_8, 2024/12

 Times Cited Count:1 Percentile:31.14(Environmental Sciences)

Assessment of individual external doses from ambient dose equivalents is used for predictive and retrospective assessments where personal dosimeters are not applicable. However, it tends to contain more errors than assessment by personal dosimetry due to various parameters. Therefore, in order to accurately assess the individual dose from ambient dose equivalents, a model that estimates effective doses considering life patterns and the shielding effects by buildings and vehicles, were developed in this study. The model parameters were examined using robust datasets of environmental radiation measured in the areas affected by the Fukushima Daiichi Nuclear Power Station accident in 2020 to 2021. The accuracy of the model was validated by comparison with 106 daily personal doses measured in Fukushima Prefecture in 2020. The measured personal dose was well reproduced by the model-estimated effective dose, showing that the model can be used to assess the individual exposure dose, similar to personal dosimetry. Furthermore, this model is an effective tool for radiation protection, as it can estimate the individual dose predictively and retrospectively by using environmental radiation data.

Journal Articles

Effect of neutron beam properties on dose distributions in a water phantom for boron neutron capture therapy

Ishikawa, Akihisa; Tanaka, Hiroki*; Nakamura, Satoshi*; Kumada, Hiroaki*; Sakurai, Yoshinori*; Watanabe, Kenichi*; Yoshihashi, Sachiko*; Tanagami, Yuki*; Uritani, Akira*; Kiyanagi, Yoshiaki*

Journal of Radiation Research (Internet), 65(6), p.765 - 775, 2024/11

 Times Cited Count:0 Percentile:0.00(Biology)

Journal Articles

Radioactivity estimation of radioactive hotspots using a Compton camera and derivation of dose rates in the surrounding environment

Sato, Yuki

Applied Radiation and Isotopes, 212, p.111421_1 - 111421_8, 2024/10

 Times Cited Count:1 Percentile:51.66(Chemistry, Inorganic & Nuclear)

Journal Articles

Analysis of the relationship between ambient dose, ambient dose equivalent and effective dose in operational neutron spectra

Endo, Akira

Radiation Protection Dosimetry, 200(13), p.1266 - 1273, 2024/08

 Times Cited Count:0 Percentile:0.00(Environmental Sciences)

This study examines the relationship between ambient dose $$H^*$$, ambient dose equivalent $$H^*(10)$$, and effective dose for external neutron irradiation over 163 operational spectra from different workplaces. The results show that $$H^*$$ provides a reasonable estimate with a controlled margin, even if overestimated, to assess effective dose compared with $$H^*(10)$$, which can lead to a significant overestimation or underestimation of effective dose depending on the neutron spectra. The results highlight the limitations of $$H^*(10)$$ and the superiority of $$H^*$$ in estimating effective dose according to the requirements of the operational quantity, especially in environments with high-energy neutrons.

JAEA Reports

Radiation tolerant rapid criticality monitoring with radiation-hardened FPGAs (Contract research); FY2021 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Okayama University*

JAEA-Review 2024-008, 59 Pages, 2024/07

JAEA-Review-2024-008.pdf:3.34MB

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 FY2021. 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 FY2019, this report summarizes the research results of the "Radiation tolerant rapid criticality monitoring with radiation-hardened FPGAs" conducted from FY2019 to FY2021. The present study aims to be developing a radiation-hardened optoelectronic FPGA with a 1 Grad total-ionizing-dose tolerance on which optical technologies are introduced onto a semiconductor technology and a radiation hardened FPGA with a 200 Mrad total-ionizing-dose tolerance not using any optical component. Moreover, Japanese research group will support hardware acceleration on FPGAs used for neutron-detection system developed by UK team. Finally, we will provide our radiation-hardened FPGA for the UK neutron-detection system.

Journal Articles

Evaluation of radiation dose caused by bremsstrahlung photons generated by high-energy beta rays using the PHITS and GEANT4 simulation codes

Shikaze, Yoshiaki

Journal of Nuclear Science and Technology, 61(7), p.894 - 910, 2024/07

 Times Cited Count:2 Percentile:43.92(Nuclear Science & Technology)

Among the radioactive nuclides inside the nuclear reactor buildings emitted by the Fukushima Daiichi nuclear reactor accident, high-energy beta-ray sources, such as strontium-90 and yttrium-90, generate bremsstrahlung photons in the building materials, comprising the wall, floor, and interior structure. Therefore, evaluating the radiation dose of the bremsstrahlung to the workers in the nuclear reactor building is crucial for radiation protection. The precision of the evaluation calculation of the bremsstrahlung dose was investigated by comparing the Particle and Heavy Ion Transport code System (PHITS) and the GEometry ANd Tracking (GEANT4) simulation code results. In the calculation, behind various shielding plates (lead, copper, aluminum, glass, and polyethylene, with thicknesses ranging from 1.0 to 40 mm), the water cylinder was set as the evaluated material, the absorbed dose and the deposited energy spectrum by the bremsstrahlung photons were obtained, and the characteristics and differences for both simulation codes were investigated. In the comparison results of the deposited energy spectrum, the spectral shapes have consistent trends. In the energy range below several tens of keV, a peak is seen in the PHITS spectrum for the lead shielding material. In comparing the absorbed dose under various conditions of the shielding plate for generating bremsstrahlung photons, most results for both codes correlate within an $$sim$$10% difference for 2.280 MeV beta-ray sources and an $$sim$$20% difference for 0.5459 MeV beta-ray sources, except for $$sim$$30% for 20 mm thick lead. Although there were differences in some cases, the evaluation results of the two simulation codes were concluded to correlate well with the above precision.

Journal Articles

Detailed visualization of radioactive hotspots inside the Unit 1 reactor building of the Fukushima Daiichi Nuclear Power Station using an integrated Radiation Imaging System mounted on a Mecanum wheel robot

Sato, Yuki; Terasaka, Yuta; Oura, Masatoshi*

Journal of Nuclear Science and Technology, 61(7), p.856 - 870, 2024/07

 Times Cited Count:8 Percentile:91.24(Nuclear Science & Technology)

Journal Articles

Characteristics of smartphone-wirelessly-connected personal dosemeters

Mikami, Satoshi; Tokiyoshi, Masanori*; Sato, Rina*; Tanaka, Daisuke*; Yoshimura, Kazuya

Nihon Hoshasen Anzen Kanri Gakkai-Shi, 23(1), p.10 - 17, 2024/06

Taisei Corporation and Infocube LAFLA Co., Ltd. have developed the smartphone-wirelessly-connected dosemeters, aiming to apply it to real-time exposure management of multiple decontamination workers. In order to grasp the basic characteristics of the developed dosemeters, they were calibrated and tested their characteristics such as energy dependency, angle of incidence dependency, etc. at photon calibration fields in Japan Atomic Energy Agency. The results showed generally good characteristics in each test. We evaluated that the dosemeters can be effectively used for decontamination work.

JAEA Reports

Analysis of the relationship between operational quantity used for area monitoring and protection quantity for external exposure

Endo, Akira

JAEA-Research 2024-002, 90 Pages, 2024/05

JAEA-Research-2024-002.pdf:4.22MB

This report presents a comprehensive analysis of the relationship between three quantities used for area monitoring - ambient dose equivalent $$H^*(10)$$, maximum dose equivalent $$H^*_textrm{max}$$, and ambient dose $$H^*$$ - and effective dose for external irradiation by photons, neutrons, electrons, positrons, protons, muons, pions, and helium ions. For the analysis, calculations were performed using PHITS (Particle and Heavy Ion Transport code System) and the ICRU sphere. The analysis result shows that $$H^*(10)$$ and $$H^*_textrm{max}$$ can induce large differences in the estimation of effective dose over a wide energy range for various particle types covered by ICRP Publication 116 while $$H^*$$ can conservatively estimate effective dose within the acceptable range for area monitoring. In other words, $$H^*(10)$$ and $$H^*_textrm{max}$$ have limitations in estimating effective dose, and using $$H^*$$ is recommended as a more appropriate quantity for the purpose. This conclusion supports the proposal of ICRU Report 95 to use $$H^*$$ for estimating effective dose in various external exposure situations. The use of ambient dose $$H^*$$ is particularly important in situations where various types of radiation are encountered, such as the use of radiation in the medical and academic fields and exposure in aviation and can meet the evolving requirements of radiation monitoring for the expansion of the field of radiological protection.

JAEA Reports

Investigations on distribution of radioactive substances owing to the Fukushima Daiichi Nuclear Power Station Accident in the fiscal year 2022 (Contract research)

Group for Fukushima Mapping Project

JAEA-Technology 2023-024, 176 Pages, 2024/03

JAEA-Technology-2023-024.pdf:22.16MB

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 FY2022. Car-borne surveys, a measurement using survey meters, a walk survey and an unmanned helicopter survey were carried out to obtain air dose rate data to create their distribution maps, and temporal changes of the air dose rates were analyzed. Surveys on depth profile of radiocesium and in-situ measurements as for radiocesium deposition were performed. Based on these measurement results, effective half-lives of the temporal changes in the air dose rates and the deposition were evaluated. Score maps to classify the importance of the measurement points were created, and the factors causing changes in the score when monitoring data from multiple years were used were discussed. The range of fluctuation of past tritium concentration data in seawater was determined, and the causes of the fluctuation were discussed. Monitoring data in coastal area performed in 2022 owing to the comprehensive radiation monitoring plan was summarized, and temporal changes in cesium-137 were analyzed. Using the Bayesian hierarchical modeling approach, we obtained maps that integrated air dose rate distribution data acquired through surveys such as car-borne and walk surveys with respect to the region within 80 km from the FDNPS and Fukushima Prefecture. The measurement results for FY2022 were published on the "Database for Radioactive Substance Monitoring Data", 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.

JAEA Reports

Embedded system using a radiation-hardened processor (Contract research); FY2022 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Okayama University*

JAEA-Review 2023-038, 48 Pages, 2024/03

JAEA-Review-2023-038.pdf:2.58MB

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 FY2022. 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 FY2022, this report summarizes the research results of the "Embedded system using a radiation-hardened processor" conducted in FY2022. The present study aims to be developing a radiation-hardened optoelectronic processor with a 10 MGy total-ionizing-dose (TID) tolerance, a radiation-hardened processor without any optical component with a 4 MGy TID tolerance, a radiation-hardened memory with a 4 MGy TID tolerance, and a radiation-hardened power supply unit with a 1 MGy TID tolerance. Moreover, Japanese research group will support radiation- hardened field programmable gate arrays, power supply units, and radiation-hardened optical systems for radiation-hardened robot systems and radiation sensor systems developed by UK team.

Journal Articles

Survey of air dose rate distribution inside and outside of wooden houses in Fukushima Prefecture; Actual condition of dose reduction factor

Kim, M.; Malins, A.*; Machida, Masahiko; Yoshimura, Kazuya; Saito, Kimiaki; Yoshida, Hiroko*

Nihon Genshiryoku Gakkai Wabun Rombunshi (Internet), 22(4), p.156 - 169, 2023/11

Dose reduction factor of a Japanese house is important information in the external exposure estimation of returning residents. In 2019, a total of 19 wooden houses were surveyed in Iitate Village and Namie Town using a gamma plotter that can continuously measure the air dose rate. In addition, the characteristics of the reduction factor were investigated from the measured air dose rate. In the vicinity of houses, uncontaminated areas exist underneath houses and, the ratio of paved surfaces such as asphalt roads is relatively high; furthermore, the pavement has a tendency for the radiation source to decay quickly. Therefore, the air dose rate near the house showed a relatively low value in common at all sites. Air dose rates above unpaved surfaces showed higher values and larger variations than those above paved surfaces within a radius of 50 m form the center of a house. The reduction factor was widely distributed even for one house, if the ratio of every air dose rate observed inside and outside the house is considered. It is suggested that a realistic reduction factor may not be obtained when the reduction factor is obtained based on the measured values at a small number of points that do not have the representativeness of the radiation field to be measured.

Journal Articles

Radiation imaging of a highly contaminated filter train inside Fukushima Daiichi Nuclear Power Station Unit 2 using an integrated Radiation Imaging System based on a Compton camera

Sato, Yuki; Terasaka, Yuta

Journal of Nuclear Science and Technology, 60(8), p.1013 - 1026, 2023/08

 Times Cited Count:12 Percentile:96.70(Nuclear Science & Technology)

Journal Articles

A Source-related approach for discussion on using radionuclide-contaminated materials in post-accident rehabilitation

Miwa, Kazuji; Iimoto, Takeshi*

Journal of Radiation Protection and Research, 48(2), p.68 - 76, 2023/06

In the process of discussion on possibility of using radionuclide-contaminated soil and debris generated by radiation disasters, strategy on the proper management of radiation exposure protection while considering the source of the contaminated materials is necessary. We proposed five interpretations of radiation protection to contribute the promotion of discussion on possibility of using a part of low-level-radionuclide-contaminated soil and debris in post-accident rehabilitation. Interpretations I to III are based on the idea of "using a reference level to protect the public in post-accident rehabilitation," whereas IV and V are based on the idea of "using the dose constraint to protect the public in post-accident rehabilitation when the sources are handled in a planned activity."

474 (Records 1-20 displayed on this page)