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.

Grain refinement of dual phase steel maximizes deformation ability of martensite, leading to simultaneous enhancement of strength and ductility

Park, M.-H.*; Shibata, Akinobu*; Harjo, S.; Tsuji, Nobuhiro*

Acta Materialia, 292, p.121061_1 - 121061_13, 2025/06

https://doi.org/10.1016/j.actamat.2025.121061

Experimental investigation of phase transformations in steel using X-ray and neutron diffraction

Tomota, Yo*; Harjo, S.; Xu, P. G.; Morooka, Satoshi; Gong, W.; Wang, Y.*

Metals, 15(6), p.610_1 - 610_19, 2025/05

https://doi.org/10.3390/met15060610

Reduction and phase transformation of Ce-doped zirconolites

Hayashizaki, Kohei; Hirooka, Shun; Yamada, Tadahisa*; Sunaoshi, Takeo*; Murakami, Tatsutoshi; Saito, Kosuke

Ceramics (Internet), 8(1), p.24_1 - 24_12, 2025/03

https://doi.org/10.3390/ceramics8010024

Enhanced cryogenic mechanical properties of heterostructured CrCoNi multicomponent alloy; Insights from neutron diffraction

Naeem, M.*; Ma, Y.*; Knowles, A. J.*; Gong, W.; Harjo, S.; Wang, X.-L.*; Romero Resendiz, L.*; 6 of others*

Materials Science & Engineering A, 916, p.147374_1 - 147374_8, 2024/11

https://doi.org/10.1016/j.msea.2024.147374

Survey on research and development status of Japanese small modular reactors in OECD/NEA activities (2022-2023)

Takeda, Takeshi; Shibata, Taiju

JAEA-Review 2024-040, 29 Pages, 2024/09

JAEA-Review-2024-040.pdf:1.33MB

An important theme of Japan's 6th strategic energy plan is to indicate the energy policy path towards carbon neutrality by 2050. Policy responses for Japan's nuclear energy research and development (R&D) towards 2030 contain the demonstrations of technologies for small modular reactors (SMRs) through international cooperation by 2030. In light of this energy plan, basic policy initiatives over the next 10 years have been compiled to realize Green Transformation (GX), which simultaneously achieves decarbonization and economic growth. Looking overseas, activities of SMR R&D are active internationally, mainly in the US, Canada, Europe, China, and Russia. These activities are not only by heavy industry manufactures and R&D institutes, but also by venture companies. Under these circumstances, the NEA CSNI has gathered an Expert Group on SMRs (EGSMR) to help estimate the safety effects of SMRs. The EGSMR efforts required the submission of responses to several questionnaires whose main purpose was to collect the latest information on the efforts of SMR deployment and research. The first author of this report responded to this based on information from Hitachi-GE Nuclear Energy, Ltd. and Mitsubishi Heavy Industries, Ltd. as well as JAEA. Most of the responses from Japan to the questionnaires are the information that serves as the basis of CSNI Technical Opinion Paper No. 21 (TOP-21). In this report, the Japan's publicly available responses to the questionnaires arranged and additional information are explained, which complements some of the content of the TOP-21. In this manner, the investigation results of R&D related to SMR in Japan, focusing on the EGSMR activities (2022-2023), are summarized. The target of this report is to provide useful information for future discussions on international cooperation concerning SMR as well as nuclear power field human resources development internationally and domestically.

Dynamics of side chains in poly(quinoxaline-2,3-diyl)s studied via quasielastic neutron scattering

Inoue, Rintaro*; Nagata, Yuya*; Tominaga, Taiki*; Sato, Sota*; Kawakita, Yukinobu; Yamawaki, Tomonori*; Morishima, Ken*; Suginome, Michinori*; Sugiyama, Masaaki*

Journal of Chemical Physics, 161(5), p.054905_1 - 054905_8, 2024/08

https://doi.org/10.1063/5.0215603

Quantitative analysis of microstructure evolution, stress partitioning and thermodynamics in the dynamic transformation of Fe-14Ni alloy

Li, L.*; Miyamoto, Goro*; Zhang, Y.*; Li, M.*; Morooka, Satoshi; Oikawa, Katsunari*; Tomota, Yo*; Furuhara, Tadashi*

Journal of Materials Science & Technology, 184, p.221 - 234, 2024/06

https://doi.org/10.1016/j.jmst.2023.10.037

Uncertainty analysis of model selection based on information criterion; A Case study of a probability estimation model for fuel cladding tube fracture during LOCA

Narukawa, Takafumi; Udagawa, Yutaka

Transactions of the 27th International Conference on Structural Mechanics in Reactor Technology (SMiRT 27) (Internet), 10 Pages, 2024/03

Probing deformation behavior of a refractory high-entropy alloy using neutron diffraction

Zhou, Y.*; Song, W.*; Zhang, F.*; Wu, Y.*; Lei, Z.*; Jiao, M.*; Zhang, X.*; Dong, J.*; Zhang, Y.*; Yang, M.*; et al.

Journal of Alloys and Compounds, 971, p.172635_1 - 172635_7, 2024/01

https://doi.org/10.1016/j.jallcom.2023.172635