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Tamatsukuri, Hiromu; Uchihara, Takeru*; Mitsuda, Setsuo*; Ishii, Yuta*; Nakao, Hironori*; Takehana, Kanji*; Imanaka, Yasutaka*
Physical Review B, 111(13), p.134403_1 - 134403_9, 2025/04
Ito, Tatsuya; Xu, S.*; Xu, X.*; Omori, Toshihiro*; Kainuma, Ryosuke*
Shape Memory and Superelasticity, 9 Pages, 2025/00
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：0 Percentile：0.00(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.
Sonehara, Masateru; Okano, Yasushi; Uchibori, Akihiro; Oki, Hiroshi*
Journal of Nuclear Science and Technology, 12 Pages, 2024/12
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)For sodium-cooled fast reactors, understanding sodium combustion behaviour is crucial for managing sodium leakage accidents. In this study, we perform benchmark analyses of the Sandia National Laboratories (SNL) T3 experiment using the multi-dimensional thermal hydraulic code AQUA-SF. Conducted in an enclosed space with a large vessel volume of 100 m
and a sodium mass flow rate of 1 kg/s, the experiment highlighted the multi-dimensional effects of local temperature increase shortly after sodium injection. This study aims to extend the capabilities of AQUA-SF by focusing on the simulation of these multi-dimensional temperature variations, in particular the formation of high temperature regions at the bottom of the vessel. The proposed models include the temporary stopping of sodium droplet ignition and spray combustion of sodium splash on the floor. Furthermore, it has been shown that additional heat source near the floor is essential to enhance the reproduction of the high temperature region at the bottom. Therefore, case studies including sensitivity analyses of spray cone angle and prolonged combustion of droplets on the floor are conducted. This comprehensive approach provides valuable insights into the dynamics of sodium combustion and safety measures in sodium-cooled fast reactors.
ionsShiina, Yoko*; Kinoshita, Ryo*; Funada, Shuhei*; Matsuda, Makoto; Imai, Makoto*; Kawatsura, Kiyoshi*; Sataka, Masao*; Sasa, Kimikazu*; Kaneko, Toshiaki*; Tomita, Shigeo*
Physical Review A, 110(6), p.062826_1 - 062826_7, 2024/12
Times Cited Count：0 Percentile：0.00(Optics)Collaborative Laboratories for Advanced Decommissioning Science; Tokyo Institute of Technology*
JAEA-Review 2024-026, 80 Pages, 2024/10
JAEA-Review-2024-026.pdf:1.96MB
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 FY2019, this report summarizes the research results of the "Study on degradation of fuel debris by combined effects of radiological, chemical, and biological functions" conducted from FY2019 to FY2022. In the project, radiochemists, nuclear chemists, nuclear physicists, material scientists, and environmental biologists are teamed to elucidate the mechanism of the degradation of fuel debris by combined effects of radiological, chemical, and biological functions.
Kai, Takeshi; Toigawa, Tomohiro; Matsuya, Yusuke*; Hirata, Yuho; Tezuka, Tomoya*; Tsuchida, Hidetsugu*; Yokoya, Akinari*
Scientific Reports (Internet), 14, p.24722_1 - 24722_15, 2024/10
Times Cited Count：0 Percentile：0.00(Multidisciplinary Sciences)Scientific insight of water radiolysis is essential to estimate the direct and indirect effects of radiation DNA damage. Secondary electrons produced by water radiolysis are responsible for both effects. Here, we use a first-principles code to calculate the femtosecond dynamics of secondary electrons produced as a result of 20-30 eV energy deposition to water and analyze the formation mechanism of radiolytic chemical species produced in a nano-size ultra-small space region. From the results, it was clarified that the chemical species produced by water radiolysis begin to densify in the ultra-small region of a few nanometers when the deposition energy exceeds 25 eV. Our results provide important scientific insights into the formation of clustered DNA damage, which is believed to cause biological effects such as cell death.
Collaborative Laboratories for Advanced Decommissioning Science; National Institute of Maritime, Port and Aviation Technology*
JAEA-Review 2024-020, 77 Pages, 2024/09
JAEA-Review-2024-020.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 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 FY2020, this report summarizes the research results of the "Research and development of the sample-return technique for fuel debris using the unmanned underwater vehicle" conducted from FY2020 to FY2022. The present study aims to develop a fuel debris sampling device that comprises a neutron detector with radiation resistance and enhanced neutron detection efficiency, an end-effector with powerful cutting and collection capabilities, and a manipulator under the Japan-UK joint research team. We will also develop a fuel debris sampling system that can be mounted on an unmanned vehicle.
Tamura, Koji; Nakanishi, Ryuzo; Oba, Hironori; Karino, Takahiro; Shibata, Takuya; Taira, Takunori*; Wakaida, Ikuo
Journal of Nuclear Science and Technology, 61(8), p.1109 - 1116, 2024/08
Times Cited Count：1 Percentile：30.19(Nuclear Science & Technology)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 
, ambient dose equivalent 
, and effective dose for external neutron irradiation over 163 operational spectra from different workplaces. The results show that provides a reasonable estimate with a controlled margin, even if overestimated, to assess effective dose compared with , which can lead to a significant overestimation or underestimation of effective dose depending on the neutron spectra. The results highlight the limitations of and the superiority of in estimating effective dose according to the requirements of the operational quantity, especially in environments with high-energy neutrons.
Zhang, Z.*; Hattori, Takanori; Song, R.*; Yu, D.*; Mole, R.*; Chen, J.*; He, L.*; Zhang, Z.*; Li, B.*
Journal of Applied Physics, 136(3), p.035105_1 - 035105_8, 2024/07
Times Cited Count：1 Percentile：53.26(Physics, Applied)Solid-state refrigeration using barocaloric materials is environmentally friendly and highly efficient, making it a subject of global interest over the past decade. Here, we report giant barocaloric effects in sodium hexafluorophosphate (NaPF
) and sodium hexafluoroarsenate (NaAsF) that both undergo a cubic-to-rhombohedral phase transition near room temperature. We have determined that the low-temperature phase structure of NaPF is a rhombohedral structure with space group R
and NaAsF, i.e., F
, E
, and A
. The phase transition temperature varies with pressure at a rate of dT
/dP = 250 and 310 K/GPa for NaPF and NaAsF. The pressure-induced entropy changes of NaPF and NaAsF are determined to be around 45.2 and 35.6J kg
K, respectively. The saturation driving pressure is about 40 MPa. The pressure-dependent neutron powder diffraction suggests that the barocaloric effects are related to the pressure-induced cubic-to-rhombohedral phase transitions.
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 , maximum dose equivalent 
, and ambient dose - 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 and 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 can conservatively estimate effective dose within the acceptable range for area monitoring. In other words, and have limitations in estimating effective dose, and using is recommended as a more appropriate quantity for the purpose. This conclusion supports the proposal of ICRU Report 95 to use for estimating effective dose in various external exposure situations. The use of ambient dose 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.
Seki, Takeshi*; Uchida, Kenichi*; Takanashi, Koki
Journal of Physics; Condensed Matter, 36(33), p.333001_1 - 333001_11, 2024/05
Times Cited Count：1 Percentile：0.00(Physics, Condensed Matter)Yuan, X.*; Hu, Q. H.*; Fang, X.*; Wang, Q. M.*; Ma, Y.*; Tachi, Yukio
Sedimentary Geology, 465, p.106633_1 - 106633_14, 2024/05
Times Cited Count：0 Percentile：0.00(Geology)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.
and Eu(As
P
)Onuki, Yoshichika*; Karube, Kosuke*; Aoki, Dai*; Nakamura, Ai*; Homma, Yoshiya*; Matsuda, Tatsuma*; Haga, Yoshinori; Takeuchi, Tetsuya*
Journal of the Physical Society of Japan, 92(11), p.114703_1 - 114703_12, 2023/11
Times Cited Count：1 Percentile：26.38(Physics, Multidisciplinary)Takagi, Hirotaka*; Takagi, Rina*; Minami, Susumu*; Nomoto, Takuya*; Oishi, Kazuki*; Suzuki, Michito*; Yanagi, Yuki*; Hirayama, Motoaki*; Khanh, N.*; Karube, Kosuke*; et al.
Nature Physics, 19(7), p.961 - 968, 2023/07
Times Cited Count：43 Percentile：98.80(Physics, Multidisciplinary)Collaborative Laboratories for Advanced Decommissioning Science; National Institute of Maritime, Port and Aviation Technology*
JAEA-Review 2022-070, 70 Pages, 2023/03
JAEA-Review-2022-070.pdf:5.27MB
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 FY2020, this report summarizes the research results of the "Research and development of the sample-return technique for fuel debris using the unmanned underwater vehicle" conducted in FY2021. The present study aims to develop a fuel debris sampling device that comprises a neutron detector with radiation resistance and enhanced neutron detection efficiency, an end-effector with powerful cutting and collection capabilities, and a manipulator under the Japan-UK joint research team. We will also develop a fuel debris sampling system that can be mounted on an unmanned vehicle. In addition, we will develop a positioning system to identify the system position, and a technique to project the counting information of optical cameras, sonar, and neutron detectors to be developed ...
Collaborative Laboratories for Advanced Decommissioning Science; Tokyo Institute of Technology*
JAEA-Review 2022-066, 91 Pages, 2023/03
JAEA-Review-2022-066.pdf:5.88MB
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 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 "Study on degradation of fuel debris by combined effects of radiological, chemical, and biological functions" conducted in FY2021. In the project, radiochemists, nuclear chemists, nuclear physicists, material scientists, and environmental biologists are teamed to elucidate the mechanism of the degradation of fuel debris by combined effects of radiological, chemical, and biological functions. In fiscal year 2021, the members of the project team have conducted on the microbial degradation of the simulated fuel debris under 
-ray irradiation, complex formation of pentavalent uranium, construction of microchannel system to detect micro-particles and the simulated fuel debris, sorption of tetravalent elements ...
Yuan, X.*; Hu, Q.*; Lin, X.*; Zhao, C.*; Wang, Q.*; Tachi, Yukio; Fukatsu, Yuta; Hamamoto, Shoichiro*; Siitari-Kauppi, M.*; Li, X.*
Journal of Hydrology, 618, p.129172_1 - 129172_15, 2023/03
Times Cited Count：4 Percentile：57.94(Engineering, Civil)