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

A Study on the methodology for rational treatment/disposal of contaminated concrete waste considering volume reduction of waste (Contract research); FY2023 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Hokkaido University*

JAEA-Review 2025-037, 103 Pages, 2025/12

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 "A study on the methodology for rational treatment/disposal of contaminated concrete waste considering volume reduction of waste" conducted in FY2023. The present study aims to evaluate rational waste management strategies incorporating reuse and recycling focusing on radioactive concrete waste, which will be massively generated from dismantling. Feasibility and challenges of aggregate recycling are considered assuming a typical recycled aggregate production technique, based on the characteristics of the concrete. In 2023, the migration behaviors of radionuclides and ions in cementitious materials having interfacial transition zones (ITZ) were investigated through diffusion and leaching experiments using radioactive and non-radioactive tracers and modeled by random walk particle tracking method with a sampling technique using a probabilistic distribution model for two media with an interface. Properties of surrogate contaminated concrete samples prepared by immersing in Cs solution were examined. Migration of ions was studied for surrogate contaminated aggregates and recycled concrete using the surrogate. In addition, surrogate waste package was prepared using by-product powder to study mechanical and chemical properties as well as leaching behavior of radionuclides. Information on properties of the contaminated concrete and tools to estimate the amount of concrete were organized in order to evaluate different waste management scenarios incorporating reuse/recycling.

Development of importance measures reflecting the risk triplet in dynamic probabilistic risk assessment; The Concept and measures of risk importance

Narukawa, Takafumi*; Takata, Takashi*; Zheng, X.; Tamaki, Hitoshi; Shibamoto, Yasuteru; Maruyama, Yu; Takada, Tsuyoshi

Journal of Nuclear Engineering (Internet), 6(4), p.49_1 - 49_14, 2025/12

https://doi.org/10.3390/jne6040049

Investigation of effects of nano interfacial phenomena on dissolution aggregation of alpha nanoparticles by using micro nano technologies (Contract research); FY2023 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Institute of Science Tokyo*

JAEA-Review 2025-026, 72 Pages, 2025/11

JAEA-Review-2025-026.pdf:7.97MB

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 "Investigation of effects of nano interfacial phenomena on dissolution aggregation of alpha nanoparticles by using micro nano technologies" conducted in FY2023. To ensure the safety of retrieval and storage management of nuclear fuel debris generated by the Fukushima-Daiichi Nuclear Power Station accident, understanding of dissolution-denaturation behavior of the fuel debris alpha particles is one of the most crucial issues. This research aims to create novel microfluidic real-time measurement device for elucidating dissolution, aggregation, and denaturation processes of metal oxide nanoparticles under various solution environments, and clarify their nano-size and interfacial effects. In this year, we conducted bulk and micro dissolution tests of simulated fuel debris particles (UO mechanical-treated nanoparticles, UO chemical-treated nanoparticles, and (U,Zr)O nanoparticles), and successfully clarified that the effects of particle sizes, reaction times, and HO concentrations on the dissolution behavior of each nanoparticle. In particular, it was found that (U,Zr)O nanoparticles have different degrees of Zr catalytic reactions depending on HO concentrations, resulting in the generation of different amounts of gas and U. Moreover, we developed a new microfluidic device which enables to instantly react the nanoparticles with HO solutions, and determined dynamic aggregation and dissolution rates of the nanoparticles. The research was carried out in close collaboration with UK researchers, and achieved the expected goal of this year.

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 passive wireless communication systems operatable under inferior-wireless environment with obstacles (Contract research); FY2023 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Yokohama National University*

JAEA-Review 2025-025, 90 Pages, 2025/10

JAEA-Review-2025-025.pdf:5.59MB

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, 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 passive wireless communication systems operatable under inferior-wireless environment with obstacles" conducted in FY2023. This study aims to develop a wireless communication system for obstacle-dense environments by designing base stations, sensor nodes (SN), positioning algorithms, and wireless area formation methods for electromagnetic wave-shielded regions. Key outcomes are as follows: For direction-finding with high-performance antennas, triangulation positioning accuracy was evaluated, and a sensor information demodulation system was built. SNs with frequency-scanning analog and frequency-fixed digital methods achieved communication distances of 6-8 meters and wireless charging of 1-2 V in 3-15 minutes at 6 meters. Diode characteristics remained unchanged after 1,000 Gy radiation. Positioning algorithms using multipath tomography were validated with a high-resolution measurement system in the lab. Simulations with reactor building CAD diagrams optimized node numbers and arrangements. Wireless coverage in electromagnetic wave-shielded regions was tested using a composite antenna (patch array and waveguide), achieving a range of approximately 1.5 meters.

Nanostructural analysis of composite materials by spin-contrast variation small-angle neutron scattering and neutron reflectometry

Kumada, Takayuki

For the Future of Hydrogen Science and Technology, 3(1), p.2 - 6, 2025/10

Annual report of Engineering Services Department on JFY2023

Engineering Services Department, Nuclear Science Research Institute

JAEA-Review 2025-018, 83 Pages, 2025/09

JAEA-Review-2025-018.pdf:4.99MB

The Engineering Services Department is in charge of operation and maintenance of utility facilities (water distribution systems, electricity supply systems, steam generation systems and drain water systems etc.) in whole of the institute. And also is in charge of operation and maintenance of specific systems (power receiving and transforming facilities, an emergency electric power supply system, an air/liquid waste treatment system, a compressed air supply system) in nuclear reactor facilities, nuclear fuel material usage facilities and usual facilities or buildings. In addition, the department is in charge of maintenance of buildings, design and repair of electrical/mechanical equipment. This annual report describes summary of activities, operation and maintenance data and technical developments of the department carried out in JFY 2023. We hope that this report may help to future work.

Clarification of debris formation conditions on the basis of the sampling data and experimental study using simulated fuel debris and reinforcement of the analytical results of severe accident scenario (Contract research); FY2023 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; University of Fukui*

JAEA-Review 2025-007, 120 Pages, 2025/09

JAEA-Review-2025-007.pdf:8.13MB

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 FY2021, this report summarizes the research results of the "Clarification of debris formation conditions on the basis of the sampling data and experimental study using simulated fuel debris and reinforcement of the analytical results of severe accident scenario" conducted from FY2021 to FY2023. The present study aims to clarify the debris formation mechanism and utilize the results to refine the accident scenario. In the backward analysis of oxide debris formation, we prepared simulated fuel particles by the aerodynamic levitation method and ejection of melted oxides from a tungsten pipe with a small hole and summarized the relationship between preparation conditions and the properties of the particles. We also demonstrated the formation of simulated fuel debris obtained by the sampling in 1F and clarified the difference between the experimental results and thermodynamic calculation. From the estimation of mixing, melting and solidified states of metallic debris, it was found that the formation of thin reaction layer suppresses the damage of SUS in spite of Zr content around 1000 C, and we quantify the elution rate of BC and Zircaloy to the melted SUS. We extended reaction rate data between various pressure vessel with SUS and Zr and welding parts and suggested reaction rate equation for large scale experiment. We also estimated the failure behavior of lower plenum of pressure vessel and outflow behavior of melt. Furthermore, we estimated transition behavior of Uranium melt to metallic debris melt in the re-melting process of predropped metallic debris. As the experimental techniques in the future, we prepared the semi-melted debris from oxide and metals and analyzed the reaction products and discussed the formation of simulated debris with a small amount of uranium oxide using a CCIM furnace and the aerodynamic levitation method.

Pressure-driven solid-state radical polymerization toward carbon nanothread

Che, G.*; Tang, X.*; Liu, J.*; Lang, P.*; Fei, Y.*; Yang, X.*; Wang, Y.*; Gao, D.*; Wang, X.*; Ju, J.*; et al.

Nano Letters, 25(39), p.14467 - 14472, 2025/09

https://doi.org/10.1021/acs.nanolett.5c03977

Mechanochemical radical polymerization has unique advantages in the synthesis of polymer due to its reduced solvent consumption and adaptability of insoluble monomers. However, it suffers from the uncontrollable degradation of the formed polymers during reaction and new synthetic strategy with precise controllability needs to be developed. Here, by employing high static pressure up to 30 GPa, we found 1,3,5-trifluorobenzene undergoes radical polymerization by breaking the conjugated -bonds, and forms a carbon nanothread with high selectivity (Polymer-I polymorph). Based on the crystal structure at the threshold pressure and the calculated energy barriers for the bonding pathway, we concluded that the benzene-rings react via a 1-2 radical polymerization pathway. Our work highlights high pressure is a robust method to initiate the solid-state radical polymerization, even for very stable aromatics, and offers fresh insights for the synthesis of polymeric carbon-based materials with high selectivity.