Analysis of fracture conditions of Cr-coated Zr alloy claddings under LOCA conditions calculated using FEMAXI fuel performance code

Luu, V. N.; Taniguchi, Yoshinori; Udagawa, Yutaka; Tasaki, Yudai; Katsuyama, Jinya

Annals of Nuclear Energy, 230, p.112114_1 - 112114_14, 2026/06

https://doi.org/10.1016/j.anucene.2026.112114

Implementation of a new function for handling nuclear data of outgoing particles and residual excitation states in PHITS

Furuta, Takuya; Hashimoto, Shintaro; Ogawa, Tatsuhiko; Tanimura, Yoshihiko

Nuclear Instruments and Methods in Physics Research A, 1086, p.171320_1 - 171320_8, 2026/06

https://doi.org/10.1016/j.nima.2026.171320

A new function to incorporate nuclear data libraries with outgoing particles plus residual nuclei in specific excitation states for neutron-induced reactions has been implemented in a Monte Carlo simulation code, Particle and Heavy Ion Transport code System (PHITS). With this function, accurate predictions of outgoing particle spectra and angular distributions according to the nuclear data libraries become possible, while accounting for production of residual nuclei and de-excitation gammas, conserving total energy and momentum in each event. This feature allows users to perform high-precision simulations of detector responses and radiation damage in materials.

Background aerial monitoring and UAV radiation monitoring technology development for emergency response and preparedness in the fiscal year 2024 (Contract research)

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.

Annual report for FY2024 on the activities of radiation safety in Nuclear Science Research Institute and so on (April 1, 2024 - March 31, 2025)

Department of Radiation Protection, Nuclear Science Research Institute; Nuclear Facilities Management Section, Aomori Research and Development Center

JAEA-Review 2025-055, 107 Pages, 2026/03

JAEA-Review-2025-055.pdf:2.26MB

This annual report describes the activities in the 2024 fiscal year of Department of Radiation Protection at Nuclear Science Research Institute, Harima Synchrotron Radiation Radioisotope Laboratory, and Nuclear Facilities Management Section at Aomori Research and Development Center. The activities described in this report are environmental monitoring, radiation protection practices in workplaces, individual monitoring, maintenance of monitoring instruments, and research and development of radiation protection. At these institutes, the occupational exposures did not exceed the dose limits. The radioactive gaseous and liquid discharges from the facilities were well below the prescribed limits. The research and development activities in the field of radiological protection were continued.

Temperature effect on radiolytically generated hydrogen yield from a plutonium nitric acid aqueous solution

Toigawa, Tomohiro; Hotoku, Shinobu; Kumagai, Yuta; Abe, Yuma*; Oyama, Kanichi*; Fukaya, Hiroyuki; Ban, Yasutoshi; Kida, Takashi; Hasegawa, Satoshi*; Nakano, Masanao*; et al.

Journal of Nuclear Science and Technology, 63(3), p.322 - 327, 2026/03

https://doi.org/10.1080/00223131.2025.2541067

The effect of temperature on hydrogen production generated from radiolysis was investigated to determine the associated implications for nuclear fuel reprocessing safety. The hydrogen yield from radiolysis of plutonium nitric acid solution was measured at temperatures up to the boiling temperature of the solution. The results showed no notable temperature dependence even under boiling conditions. The impact of solution agitation on hydrogen production was also assessed, which revealed minor differences in the hydrogen yield between static and agitated conditions at room temperature. These findings suggest that high temperatures or boiling the solution do not considerably enhance hydrogen generation, and provide crucial information for accurately modeling hydrogen risks under severe accidents.

Development of a high-resolution imaging camera for alpha dust and high-dose rate monitor (Contract research); FY2023 Nuclear Energy Science & Technology and Human Resource Development Project

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.

Ambient dose rate variation in the Fukushima region visualized using explainable AI techniques

Yoshida, Ryu*; Kurikami, Hiroshi; Nagao, Fumiya; Takahashi, Shigeo*; Sanada, Yukihisa

Journal of Environmental Radioactivity, 293, p.107900_1 - 10790_13, 2026/02

https://doi.org/10.1016/j.jenvrad.2026.107900

Feasibility study of machine learning-based discrimination of , and particles from grayscale radiation images

Laffolley, 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

https://doi.org/10.1016/j.nima.2025.171029

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.

Separation of Rh(III) and direct electrodeposition in phosphonium-based ionic liquids with electrochemical and spectroscopic analyses for extracted Rh(III) complex

Tokumitsu, Shun*; Matsumiya, Masahiko*; Sasaki, Yuji

Separation and Purification Technology, 382(Part 2), p.135631_1 - 135631_9, 2026/02

https://doi.org/10.1016/j.seppur.2025.135631

Development of an innovative n/ scintillation detection system for simple non-destructive measurements (Contract research); FY2023 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative 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.