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Batsaikhan, M.; Oba, Hironori*; Karino, Takahiro; Akaoka, Katsuaki; Wakaida, Ikuo*; Iwata, Yoshihiro; Sakamoto, Kan*
Journal of Analytical Atomic Spectrometry, 41(4), p.1324 - 1335, 2026/04
Times Cited Count：0Futemma, Akira; Ochi, Kotaro; Sasaki, Miyuki; Nakama, Shigeo; Kawasaki, Yoshiharu*; Iwai, Takeyuki*; Hiraga, Shogo*; Haginoya, Masashi*; Matsunaga, Yuki*; Yamada, Tsutomu*; et al.
JAEA-Technology 2025-016, 253 Pages, 2026/03
JAEA-Technology-2025-016.pdf:20.16MB
Aerial Radiation Monitoring (ARM) has been used to quickly and widely measure radiation distribution caused by the TEPCO's Fukushima Daiichi Nuclear Power Station (FDNPS) accident resulted from the tsunami accompanying the Pacific coast of Tohoku Earthquake on March 11, 2011. Since the accident, As a commissioned project of the Nuclear Regulation Authority, the Japan Atomic Energy Agency (JAEA) has continuously conducted ARM around FDNPS. This report summarizes the results of the 2024 monitoring activities, evaluates temporal changes in ambient dose rates, and identifies factors contributing to these changes. A terrain-corrected analysis was applied to improve dose rates conversion accuracy, and results with and without this correction were compared. A radon-progeny discrimination method was also used to assess its impact on manned-helicopter measurements. Furthermore, development of unmanned airplane monitoring technologies was advanced to enhance the efficiency of wide-area surveys.
Futemma, Akira; Ochi, Kotaro; Sasaki, Miyuki; Nakama, Shigeo; Kawasaki, Yoshiharu*; Iwai, Takeyuki*; Hiraga, Shogo*; Haginoya, Masashi*; Matsunaga, Yuki*; Sanada, Yukihisa; et al.
JAEA-Technology 2025-015, 171 Pages, 2026/03
JAEA-Technology-2025-015.pdf:11.43MB
On March 11, 2011, the 2011 off the Pacific coast of Tohoku Earthquake and tsunami caused the Fukushima Daiichi Nuclear Power Station accident, releasing radioactive material. Since then, Aerial Radiation Monitoring (ARM) with manned helicopters has been used to assess radiation distribution quickly. In FY2024, the Japan Atomic Energy Agency (JAEA), under commission from the Nuclear Regulation Authority, conducted ARM around the Shimane Nuclear Power Station, producing background dose rate maps validated against ground and other data. During a nuclear emergency drill, UAV training flights complemented manned monitoring, confirming the effectiveness of real-time communication and rapid mapping. The UAV data system was developed and demonstrated for real-time analysis and multi-platform use. Skill training for multicopters was also conducted to strengthen operational capability. Additionally, joint monitoring with the U.S., France, South Korea, and Canada provided insights into international technologies and practices, emphasizing the value of information sharing. This report summarizes the results and technical challenges from these FY2024 activities, contributing to the advancement of emergency radiation monitoring.
Group for Fukushima Mapping Project
JAEA-Technology 2025-013, 206 Pages, 2026/03
JAEA-Technology-2025-013.pdf:34.64MB
This report presents results of the investigations on the distribution-mapping project of radioactive substances conducted in FY2024. Car-borne and walk surveys, a measurement using survey meters, and an unmanned helicopter survey were carried out to obtain air dose rate data on land to create their distribution maps, and temporal changes of those air dose rates were analyzed. In order to confirm the applicability of unmanned aircraft to monitoring in mountainous areas, a basic performance of unmanned aircraft was investigated in mountainous areas. Surveys on depth profile of radiocesium and in-situ measurements as for radiocesium deposition were performed. These measurement results were published on the WEB site. Based on these measurement results, effective half-lives of the temporal changes in the air dose rates and the deposition were evaluated. 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. Radiation monitoring and analysis of environmental samples owing to the comprehensive radiation monitoring plan were carried out. 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. 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 FY2024 was analyzed.
Nagaoka, Mika; Maehara, Yushi; Ono, Masako*; Nihei, Hidekazu*; Hirao, Moe; Fujita, Hiroki
JAEA-Research 2026-001, 115 Pages, 2026/03
JAEA-Research-2026-001.pdf:6.32MB
In fiscal year 2021, Japan Atomic Energy Agency conducted a joint research with Tokyo Electric Power Company Holdings, Inc. to develop a bioassay method. This report presents the results of studies on a systematic analysis method for 
-ray and pure 
-ray nuclides in urine samples. Specifically, experiments with tracer-containing samples were conducted to verify the nuclide separation performance of the systematic analysis method utilizing multiple solid-phase extraction resins and the sample preparation method for radioactivity measurement. Furthermore, calculation methods for uncertainty and detection limit of radioactivity in -ray nuclide analysis were summarized.
Misono, Toshiharu; Shiribiki, Takehiko*; Urabe, Yoshimi*; Sanada, Yukihisa
JAEA-Research 2025-014, 88 Pages, 2026/03
JAEA-Research-2025-014.pdf:7.52MB
An accident occurred at the TEPCO's Fukushima Daiichi Nuclear Power Station (1F) in 2011 and a large amount of radioactive materials were deposited around the 1F. Japan Atomic Energy Agency has continued to conduct research on the dynamics of radioactive materials after the accident. This report summarizes the results of the survey conducted in FY 2022 on the status of marine monitoring survey on radioactive substances. Furthermore, in order to evaluate the inflow of radioactive Cs from the river, the horizontal distribution of the radioactive Cs concentration on the surface sediment in front of the rivers was measured. As basic information on the effects of radioactive materials on marine products, the distribution status of fish was investigated. From these results, we estimated the distribution and its dynamics of radioactive Cs in the sediments in the front area on the 1F.
Yamada, Taichi; Suzuki, Soichiro; Ito, Rintaro; Ota, Yua*; Kaneko, Eiichiro*; Ogane, Katsuji*; Kawabata, Kuniaki
Advanced Robotics, 40(5), p.259 - 270, 2026/03
Times Cited Count：0 Percentile：0.00(Robotics)We develop a test method to evaluate the vertical moving performance of an unmanned aircraft system (UAS) in a narrow environment, specifically performance for ascending through a narrow aperture. This research aims to boost the UAS industry by pushing for the expansion of UAS use into various places and situations. UAS users should know whether the UAS performance is enough to achieve their objectives and what UAS suits them. However, discussing what/how much UASs can do is complex, especially in a place or situation affecting some UAS functions. Thus, the test method provides an easy-to-understand evaluation of UAS performance for mobility to access a destination in a narrow environment, even for UAS users without technical knowledge. To develop an acceptable test method for the UAS industry, we repeatedly held demonstrations and discussions with UAS manufacturers and users to incorporate their opinions from the early stages of this research. In addition, the experiments show that the test method appropriately indicates the difference in UAS performance. This paper describes the approach of UAS performance evaluation to promote the UAS industry, the development along with UAS users' opinions, and the result of the experiments to compare the type of UAS and consideration.
Kim, M.; Yoshimura, Kazuya; Sakuma, Kazuyuki; Malins, A.*; Abe, Tomohisa; Nakama, Shigeo; Machida, Masahiko; Saito, Kimiaki
Journal of Environmental Radioactivity, 294, p.107931_1 - 107931_8, 2026/03
Times Cited Count：0This study quantitatively evaluated the effects of non-decontamination human activities, such as traffic, on ambient dose rates in residential areas near the Fukushima Daiichi Nuclear Power Plant through field measurements and simulations. Field surveys showed that areas with higher traffic had greater reductions in 
Cs deposition, suggesting that vehicular movement may enhance cesium weathering. Monte Carlo simulations using 3D-ADRES confirmed that human activities accelerate the decrease in ambient dose rates on paved surfaces, with reductions of up to approximately 50%. These results indicate that non-decontamination human activities significantly contribute to lowering ambient dose rates.
Yamada, Susumu; Machida, Masahiko
Nihon Oyo Suri Gakkai Rombunshi, 36(1), p.14 - 32, 2026/03
Estimating the distribution of radiation sources is crucial for the safe decommissioning of reactor buildings. LASSO regression has been applied to estimate radiation sources inside reactor buildings based on radiation measurements. However, LASSO regression requires air dose rates measured at appropriate points to produce accurate estimates. Although a strategy for adding observation points has been proposed, its effectiveness is limited depending on the model size. Therefore, we propose a new strategy that takes into account the estimated source distribution and demonstrate its effectiveness.
Machida, Masahiko; Yamada, Susumu; Yoshida, Toru*; Hasegawa, Yukihiro*; Yanagi, Hideaki*; Furutachi, Naoya*
Proceedings of Waste Management Symposia 2026 (WM2026) (Internet), 15 Pages, 2026/03
Yamada, Susumu; Machida, Masahiko
Proceedings of Waste Management Symposia 2026 (WM2026) (Internet), 14 Pages, 2026/03
Tateishi, Dai; Terasaka, Yuta; Morishita, Yuki; Sato, Yuki
Proceedings of Waste Management Symposia 2026 (WM2026) (Internet), 10 Pages, 2026/03
Hagiwara, Hiroki; Takaku, Atsushi*; Sagawa, Hiroshi*; Kanno, Futoshi*; Ito, Azusa; Ando, Taichi*; Ichihara, Masatsugu*; Watanabe, Yusuke; Koarai, Kazuma; Kato, Jun; et al.
Proceedings of Waste Management Symposia 2026 (WM2026) (Internet), 7 Pages, 2026/03
Usami, Hiroshi; Ito, Rintaro; Sanada, Yukihisa
JAEA-Review 2025-050, 57 Pages, 2026/02
JAEA-Review-2025-050.pdf:17.19MB
The decommissioning of the TEPCO's Fukushima Daiichi Nuclear Power Station is a long-term project, and the training of young engineers and researchers who will be responsible for future decommissioning is a necessary and urgent task. Since 2016, Collaborative Laboratories for Advanced Decommissioning Science has been continuously organizing "Conference for R&D Initiative on Nuclear Decommissioning Technology by the Next Generation (NDEC)" for students who are engaged in research activities for decommissioning. NDEC is a forum for students to present their research for the purpose of human resource development and networking among young researchers, and to increase their motivation for decommissioning research. NDEC-10 was held at "Plaza-Bansho" in Tsuruga-City, Fukui Prefecture, from February 26 - 27, 2025. This proceeding compiles the contents of report papers in the conference.
Collaborative Laboratories for Advanced Decommissioning Science; Tohoku University*
JAEA-Review 2025-048, 56 Pages, 2026/02
JAEA-Review-2025-048.pdf:2.89MB
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 FY2023. 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 FY2023. 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. In addition, we demonstrated this monitoring system, and the dose-rate dynamic range was found to be 20 mSv/h to 1 kSv/h.
Wells, S. R.*; Iwata, Yoshihiro; Miyabe, Masabumi; Hasegawa, Shuichi*
Applied Physics B, 132(3), p.32_1 - 32_8, 2026/02
Times Cited Count：0Odd-even isotope selectivity in calcium was investigated using a laser resonance ionization J:0-1-0 transition scheme, chosen so that angular momentum selection rules could be manipulated using linearly polarized light. Suppression of the abundant isotope 
Ca and selection of the rare isotope 
Ca was confirmed as a function of the linear polarization angle. A maximal separation coefficient value of 
was obtained.
Morishita, Yuki
Isotope News, (803), p.38 - 42, 2026/02
In this study, we developed an alpha ray imaging detector for the in-situ measurement of 
Pu and 
Np to identify alpha nuclides in real time on-site. The alpha ray imaging detector developed in this study was brought to Savannah River National Laboratory (SRNL) in the United States, where measurements were performed on actual Pu and Np oxide samples. These measurements confirmed the effectiveness of in-situ detection of Pu and Np. We also developed a detector that can directly measure alpha contamination inside pipes. We confirmed the detector's ability to distinguish between alpha and beta rays and evaluated its basic characteristics.
Yoshida, Ryu*; Kurikami, Hiroshi; Nagao, Fumiya; Takahashi, Shigeo*; Sanada, Yukihisa
Journal of Environmental Radioactivity, 293, p.107900_1 - 10790_13, 2026/02
Times Cited Count：0 Percentile：0.00(Environmental Sciences)
-ray spectroscopy system with high-count-rate pulse processing and simultaneous pulse-current operation mode for in-situ non-destructive assayKaburagi, Masaaki; Ishii, Junya*; Kato, Masahiro*; Kamada, Kei*; Yoshino, Masano*; Shimazoe, Kenji*
Journal of Instrumentation (Internet), 21(2), p.P02051_1 - P02051_19, 2026/02
$Pd in concrete rubbleOta, Yuki; Do, V.-K.; Banjarnahor, I. M.; Iwahashi, Hiroyuki; Furuse, Takahiro; Tanaka, Kosuke
Journal of Radioanalytical and Nuclear Chemistry, 335(1), p.939 - 948, 2026/02
Times Cited Count：0 Percentile：0.00(Chemistry, Analytical)