A Novel kinetic model for dissolution and precipitation of oxide on stainless-steel surface in stagnant liquid sodium

Kawaguchi, Munemichi*; Ikeda, Asuka; Saito, Junichi

Annals of Nuclear Energy, 226, p.111880_1 - 111880_9, 2026/02

https://doi.org/10.1016/j.anucene.2025.111880

Experimental study of AESOP code for aerosol removal behavior from a rising gas bubble in water pool and parametric study for application to sodium pool system

Miyahara, Shinya*; Koie, Ryusuke*; Uno, Masayoshi*; Kawaguchi, Munemichi*; Sato, Rika; Seino, Hiroshi

Nuclear Engineering and Design, 446(Part A), p.114523_1 - 114523_14, 2026/01

https://doi.org/10.1016/j.nucengdes.2025.114523

Research and development of remote optical measurement technology for PCV gas-phase leakage location and leakage volume estimation (Contract research); FY2023 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Chiba University*

JAEA-Review 2025-038, 84 Pages, 2025/12

JAEA-Review-2025-038.pdf:6.08MB

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 FY2023, this report summarizes the research results of the "Research and development of remote optical measurement technology for PCV gas-phase leakage location and leakage volume estimation" conducted in FY2023. The present study aims to locate leakage points using a remote optical measurement system including Lidar, and to develop a visualization method for leakage at those points. The Lidar can be distance-resolved in the line-of-sight direction and can separate and observe signals from walls and pipes in the building and surrounding gas-phase molecules (nitrogen N, water vapor HO, etc.) and suspended particles (aerosols). In addition, flash Lidar, which combines a laser beam with a high-sensitivity imaging sensor, and high-sensitivity shearography, which uses interference of light waves, are used to image and visualize the leakage location and to estimate the amount of leakage. Through comparison of these methods, we will clarify the positional resolution in locating the leakage point and the lower detection limit of the leakage amount that can be visualized.

The Quadrupedal Robots (Spot) operation manual (The Emergency Response Team against nuclear accidents in JAEA)

Watanabe, Kaho; Nishiyama, Yutaka; Kakuta, Masakatsu*; Hayasaka, Toshiro*

JAEA-Testing 2025-003, 52 Pages, 2025/11

JAEA-Testing-2025-003.pdf:5.17MB

There is an emergency response team against nuclear facilities accidents of Japan Atomic Energy Agency (JAEA). The team is managed by the Maintenance and Operation Section for Remote Control Equipment. One of the important tasks of the team is purchasing remote-control robots, the quadrupedal robots (called Spot), were purchased in 2022 and 2023 to prepare for the nuclear disaster in JAEA. This report shows the remote-control manual for the quadrupedal robots (Spot), and it is focused on the necessary operations for the team.

Development of real-time mapping software for wide-area radiation survey

Takahashi, Tone; Koizumi, Mitsuo; Yoshimi, Yuki*; Mochimaru, Takanori*

JAEA-Technology 2025-007, 26 Pages, 2025/11

JAEA-Technology-2025-007.pdf:1.6MB

To prevent the smuggling of nuclear and radioactive materials into event venues for the purpose of terrorism, it is common practice to individually inspect people and vehicles entering and exiting using radiation detectors. However, since there remains a risk of such inspections being bypassed, it is necessary to complement them with a wide-area radiation survey to ensure that no nuclear or radioactive materials have been brought in. Radiation mapping is an effective method for efficiently surveying large areas. In this method, a gamma-ray detector equipped with GPS is used to record location data and radiation dose rates while moving. By utilizing network connectivity, measurement data from multiple detectors can be aggregated at a central command post, allowing real-time monitoring of survey progress. This system helps to prevent both redundant and missing measurements and enables the prompt detection of suspicious radiation sources. Furthermore, by incorporating spectrometers into the gamma -ray detectors, it becomes possible to identify radioactive isotopes, thereby enabling appropriate responses. To enable such wide-area radiation surveys, we developed real-time mapping software. The developed software receives measurement data transmitted from GPS-equipped gamma-ray spectrometers, processes it sequentially in real time, and plots it onto pre -downloaded map data. Additionally, by integrating the spectral data collected from regions showing abnormal radiation levels can be displayed immediately. To enhance information security, the software is designed to function within local networks without requiring internet connectivity. In this report, we introduce an overview of the developed software and provide a simplified version of the source code as an appendix. The provided code is developed using open and free operating systems, libraries, and environments, making it freely available and usable by anyone.

Development of inspection technology for pipes in high background radiation environments (Contract research); FY2023 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; University of Fukui*

JAEA-Review 2025-036, 88 Pages, 2025/11

JAEA-Review-2025-036.pdf:6.36MB

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 FY2023, this report summarizes the research results of the "Development of inspection technology for pipes in high background radiation environments" conducted in FY2023. The following two studies are being conducted with the aim of comprehensively developing technologies to address the three needs indicated in the hearing with TEPCO regarding observation of the inside of piping: (1) Hydrogen content, (2) Presence of precipitates, (3) Presence or absence of / radiation emitting nuclides. First, by downsizing existing nondestructive inspection equipment and developing a dedicated radiation detector capable of nondestructively imaging the inside of piping, we aim to obtain information on the inside of piping by nondestructive inspection using lasers, etc., and to clarify the presence or absence of -nuclides in piping and the internal conditions of piping, etc. In addition, we will develop equipment to visualize -nuclides and discriminate -nuclides in high dose rate environments, as well as technology to investigate the contents of the piping. Deployment of the developed technology is expected to be put into practical use by TEPCO and private companies.

Development of a prototype shielding-free radiation-resistant diamond neutron measurement system (Contract research); FY2023 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Hokkaido University*

JAEA-Review 2025-028, 66 Pages, 2025/11

JAEA-Review-2025-028.pdf:3.59MB

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 a prototype shielding-free radiation-resistant diamond neutron measurement system" conducted in FY2023. The present study aims to develop a prototype of a shielding-free neutron measurement system for 1F. The system consists of diamond neutron detectors and radiation-resistant silicon integrated circuits, and has radiation resistance of more than 10 MGy and 4 MGy, respectively, at the component level in terms of integrated dose, and has a track record of stable operation under -ray dose rate environment of 1.5 kGy/h. Future applications are expected to include neutron detectors for debris investigation, criticality proximity monitoring monitors, and neutron detectors for dry tube investigation in pressure vessels. In this development, a prototype consisting of 100 diamond detector elements of 5 mm square will be developed to obtain system construction technology and to evaluate system performance. In addition, a subcriticality evaluation method will be developed. This development will lead to the completion of system development, development of the actual system in collaboration with the manufacturer, and introduction of the system into 1F decommissioning project.

Optimising sodium incorporation into potassium-activated metakaolin-based alkali-activated materials

Chaerun, R. I.; Sato, Junya; Hiraki, Yoshihisa; Yoshida, Yukihiko; Sato, Tsutomu*; Osugi, Takeshi

Construction and Building Materials, 500, p.144270_1 - 144270_10, 2025/11

https://doi.org/10.1016/j.conbuildmat.2025.144270

Alkali-activated materials (AAMs), particularly those derived from metakaolin, have gained significant attention as sustainable binders for hazardous waste immobilisation, owing to their dense microstructure and chemical durability. Their amorphous aluminosilicate framework enables effective encapsulation of hazardous materials and reduces environmental risks. However, maintaining the stability of this amorphous network is challenging, particularly when sodium (Na)-rich precursors are used, as excess Na) promotes crystallisation and compromises matrix integrity. This study systematically investigates the influence of Na) concentration on the structural stability of metakaolin-based AAMs activated primarily with potassium (K)). The objective is to identify the threshold Na incorporation level that preserves the amorphous structure and maintains chemical stability. Transmission electron microscopy (TEM), Raman spectroscopy, and thermodynamic modelling were employed to examine the structural evolution of K-AAMs across a range of Na:K molar ratios. The results reveal that higher Na:K ratios induce nanopore formation and early crystallisation of Na-rich zeolitic phases, which can reduce matrix stability. In contrast, an optimal Na:K ratio was identified that maintains the amorphous network and preserves the aluminosilicate framework. These findings provide valuable insights into optimising K-AAMs for advanced, durable waste encapsulation technologies.

Development of elemental technologies of hand-foot-cloth monitors for -contamination visualization (Contract research); FY2023 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Hokkaido University*

JAEA-Review 2025-021, 63 Pages, 2025/10

JAEA-Review-2025-021.pdf:5.71MB

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 elemental technologies of hand-foot-cloth monitors for -contamination visualization" conducted in FY2023. The present study aims to develop hand-foot-monitors for -contamination visualization and cloth monitors for /-contamination visualization consisting of a portable phoswich detector. ZnS(Ag) thick films by AD method and rare earth complexes have been studied for development of -ray scintillator materials. The scintillator properties of the newly prepared ZnS(Ag) thick films were improved from those prepared in 2022. A rare earth complex shows strong emission intensity under -ray irradiation, which was 12.5 times higher than that of a commercially available plastic scintillator (Saint-Gobain, BC400). By optimizing the manufacturing process conditions (molding die, sintering conditions, cutting process, annealing conditions, grinding/polishing processes) for La-GPS polycrystalline thin plates, the preparing process for 50 mm square La-GPS was established. The prepared La-GPS provided excellent performance for -ray scintillators. The cloth monitors for /-contamination visualization were also improved for the reflection of the actual situation. Furthermore, the basic performance of the prototype cloth monitors was evaluated, and alpha-ray energy and position distribution information were obtained. In an evaluation test of the phoswich detector, a precise discrimination between - and -rays was achieved.

Neutron diffraction-assisted constitutive modeling of directed energy deposited CoCrFeMnNi high entropy alloy

Jeong, S. G.*; Kwon, J.*; Kim, E. S.*; Prasad, K.*; Harjo, S.; Gong, W.; Kawasaki, Takuro; Estrin, Y.*; Bouaziz, O.*; Hong, S. I.*; et al.

Materials Science & Engineering A, 942, p.148712_1 - 148712_11, 2025/10

https://doi.org/10.1016/j.msea.2025.148712