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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.
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
This 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.
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
Suyama, Kenya
Kaku Deta Nyusu (Internet), (143), p.52 - 62, 2026/02
The Seminar on Nuclear Data holds the longest history as a domestic conference on nuclear data. It has played a vital role as a forum for addressing challenges and identifying new themes in this field, bringing together participants from numerous Japanese universities, research institutions, and industry. With many students attending each session, it offers young researchers who will lead the future an opportunity to present their work and gain exposure to cutting-edge research. As announced at last year's conference, this year's event was held jointly with the ERATO Sekiguchi Three-Nucleon Force Project (TOMOE Project) as the "025 Nuclear Data + TOMOE Project Joint Seminar," aiming to leverage synergies with the latest results in nuclear physics research. While the Seminar on Nuclear Data has been reported, the practical preparation procedures have not been covered extensively in Nuclear Data News. Intended also as handover material, this article covers preparations for the event.
underwater radiation monitoring detectorJi, W.*; Lee, E.*; Ji, Y.-Y.*; Ochi, Kotaro; Yoshimura, Kazuya; Funaki, Hironori; Sanada, Yukihisa
Nuclear Engineering and Technology, 58(2), p.103933_1 - 103933_6, 2026/02
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)We aimed to validate the performance of an in situ underwater radiation detector, MARK-U1 (Monitoring of Ambient Radiation of KAERI - Underwater), was used to estimate Cs activity concentration in river and reservoir sediment at predicted sites of contamination. Additionally, underwater core samples were collected to measure the radioactivity using a high-purity germanium (HPGe) detector. To estimate radioactivity, a conversion factor was derived by comparing the measured spectrum and Cs activity in the sample. A Monte Carlo N-Particle (MCNP) simulation was conducted to determine the effective source geometry for in situ measurement. The simulation results correlated well with the on-site MARK-U1 monitoring results, with a deviation of 31.62%. These findings validate the performance of the in situ detector. This device can therefore be used to estimate Cs activity concentration in the underwater sediment via on-site monitoring, without requiring sample collection.
, 
and particles from grayscale radiation imagesLaffolley, H.; Tsubota, Yoichi; Tsuji, Tomoya; Honda, Fumiya
Nuclear Instruments and Methods in Physics Research A, 1082(Part 2), p.171029_1 - 171029_11, 2026/02
Times Cited Count：0 Percentile：0.00(Instruments & Instrumentation)In the framework of the decommissioning of the Fukushima Daiichi Nuclear Power Station, the Japan Atomic Energy Agency analyses and classifies a variety of radioactive samples. The objective is to simplify the sample characterization process by developing multipurpose analysis tools that quickly produce results for different types of samples while reducing labor. The development of an analytical device has been started, based on the MiniPIX TPX standard detector, a hybrid semiconductor pixelated radiation detector. This detector creates grayscale images that show the interaction of ionizing particles, where brightness directly indicates energy. The final aim is to build a fast mapping device that generates 2D activity maps, distinguishing between , , and radiation, and includes simple local spectrometry for highly contaminated samples. The shape of the cluster created by the interaction between an incident particle and the semiconductor is typical of the said particle. Thus, eight supervised machine learning models have been trained on a dataset made of 9 features extracted from pure images of , and particles collected from 
Co, 
Sr, Cs and 
Am standard sources. The best models can distinguish the particles with nearly 80% accuracy, reaching 96% accuracy for low-energy rays exposition only, with a processing time of a few microseconds per frame. The identification of particles is 100% accurate.
Cs in stream water in forested catchmentsSakuma, Kazuyuki; Yoshimura, Kazuya; Nakanishi, Takahiro; Hayashi, Seiji*; Tsuji, Hideki*; Funaki, Hironori; Iijima, Kazuki
Science of the Total Environment, 1014, p.181397_1 - 181397_9, 2026/02
The Fukushima Daiichi Nuclear Power Plant accident released substantial radiocesium into terrestrial environments in 2011. Understanding the sources of dissolved radiocesium and the factors controlling its seasonal variation in stream water is crucial for assessing and mitigating environmental radioactive contamination. From 2015 to 2021, we investigated dissolved Cs concentrations and dissolved organic carbon (DOC) in stream water, spring water, groundwater, litter leachate, soil pore water, and infiltrated water. In the headwater area, dissolved Cs concentrations increased just after spring compared to the concentrations in the groundwater. During approximately three years of stream water monitoring, dissolved Cs concentrations correlated with water temperature, concentrations of DOC, and K
. A three-component mixture model revealed that stream water composition is derived mainly from groundwater, leaching from forest litter/surface soil, and soil pore water. The soil pore water particularly influenced summer stream water, likely due to the water table fluctuations with precipitation. The leaching water also influenced the summer stream water compared to the winter stream water. These findings suggest that seasonal variations in dissolved Cs are driven by temperature-dependent leaching from surface forest litter/soil and increased contributions from soil pore water. This study is the first to identify the sources and seasonal drivers of dissolved Cs in forested headwater streams.
scintillation detection system for simple non-destructive measurements (Contract research); FY2023 Nuclear Energy Science & Technology and Human Resource Development ProjectCollaborative Laboratories for Advanced Decommissioning Science; Tohoku University*
JAEA-Review 2025-046, 70 Pages, 2026/01
JAEA-Review-2025-046.pdf:5.46MB
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 (1F), 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 FY2023, this report summarizes the research results of the "Development of an innovative n/ scintillation detection system for simple non-destructive measurements" conducted in FY2023. At 1F, removal of fuel debris from the primary containment vessel (PCV) is scheduled for FY2023, and a phased expansion of the removal scale is being considered in the future. As a solution to the above problem, this study will develop an innovative scintillation radiation detection system for screening and continuous monitoring during target sample removal. To develop a remote measurement system that contributes to in-vessel investigations for decommissioning of nuclear facilities such as 1F. More specifically, we will develop vertically integrated research into the following elemental technologies: (1) development of innovative high-performance scintillation materials for thermal neutron / gamma-ray discrimination (Tohoku University), (2) downsizing of censer and signal processing system (the University of Tokyo), (3) construction and characterization of various radiation fields (National Institute of Advanced Industrial Science and Technology), and (4) development of a simple non-destructive measurement system and hot cell demonstration test (JAEA). By vertically integrating elemental technologies, R&D on each research item planned in FY2023 was conducted to develop a detector that can discriminate gamma-ray and neutron radiation in environments exceeding 10 Gy/h and simultaneously identify the dose rate and nuclide of each in PCVs and in each acceptance cell.
addition on decontamination of radioactive Cs in soil via heat treatmentShimoyama, Iwao; Kogure, Toshihiro*; Okumura, Taiga*; Baba, Yuji*
Journal of Environmental Management, 397, p.128239_1 - 128239_11, 2026/01
Times Cited Count：0 Percentile：0.00(Environmental Sciences)The effectiveness of CaCl addition in thermal soil decontamination was investigated by performing heat treatment on radioactive Cs-contaminated Fukushima soil under both atmospheric and vacuum conditions, and comparing the results with NaCl addition. When CaCl was added, a decontamination ratio exceeding 95% was achieved at approximately 740
C under both atmospheric and vacuum conditions, showing slightly higher efficacy than NaCl addition. For the removal of non-radioactive Cs adsorbed onto weathered biotite by heat treatment, CaCl exhibited a distinctly greater effect than NaCl. While NaCl induces rapid ion exchange (RIE) in clay minerals of the soil under vacuum conditions, CaCl was found to trigger RIE at the initial stage of the heat treatment under both atmospheric and vacuum conditions, subsequently promoting the decomposition and phase transformation of clay minerals leading to the removal of radioactive Cs. These results indicate that CaCl is an effective additive for heat treatment even when used alone.
Igarashi, Junya*; Ninomiya, Kazuhiko*; Zheng, J.*; Zhang, Z.*; Fukuda, Miho*; Aono, Tatsuo*; Minowa, Haruka*; Yoshikawa, Hideki*; Sueki, Keisuke*; Satou, Yukihiko; et al.
Journal of Environmental Radioactivity, 291, p.107856_1 - 107856_8, 2026/01
Times Cited Count：1 Percentile：0.00(Environmental Sciences)no abstracts in English
Shi, W.*; Machida, Masahiko; Yamada, Susumu; Okamoto, Koji*
Measurement, 258(Part D), p.119444_1 - 119444_15, 2026/01
Times Cited Count：0 Percentile：0.00(Engineering, Multidisciplinary)Imabuchi, Takashi; Kawabata, Kuniaki
Proceedings of 2026 IEEE/SICE International Symposium on System Integration (SII2026), p.1105 - 1109, 2026/01
Tanifuji, Yuta; Imabuchi, Takashi; Kawabata, Kuniaki
Proceedings of the 31st International Symposium on Artificial Life and Robotics (AROB 31st 2026), p.1011 - 1016, 2026/01
In decommissioning work at the Fukushima Daiichi Nuclear Power Station (1F), operators must rely on robot camera images degraded by turbidity, floating matter, lens contamination, and radiation induced noise, with no clean reference images available. This study investigates a lightweight restoration pipeline combining Noise2Noise (N2N) denoising and FSRCNN super resolution, and shows that the N2N
FSRCNN configuration most consistently improves visibility while suppressing noise and artificial textures, according to NIQE and PIQE scores and subjective evaluation.
Takahashi, Hiroki*; Kato, Toru*; Yamashita, Meguru*; Doi, Akio*; Imabuchi, Takashi
Artificial Life and Robotics, 13 Pages, 2026/00
Batsaikhan, M.; Oba, Hironori*; Karino, Takahiro; Akaoka, Katsuaki; Wakaida, Ikuo*; Iwata, Yoshihiro; Sakamoto, Kan*
Journal of Analytical Atomic Spectrometry, 21 Pages, 2026/00
Times Cited Count：0