High-speed 3D modeling for nuclear reactor environment based on feature extraction results from video images (Contract research); FY2024 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Sapporo University*

JAEA-Review 2026-020, 81 Pages, 2026/09

JAEA-Review-2026-020.pdf:6.0MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), has been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") from FY2019. 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 "High-speed 3D modeling for nuclear reactor environment based on feature extraction results from video images" conducted in FY2024. The present study aims to develop a methodology for 3D modeling of workspaces using video footage captured during surveys of the reactor containment vessel and reactor building at 1F. Based on features extracted from the video within a specified timeframe, the method selects a high-information-content 3D reconstruction approach while augmenting the surrounding contextual information. In fiscal year 2024, we developed a methodology to achieve high-precision photogrammetry-based 3D reconstruction within a specified time limit, using a single video sequence obtained from simulation as input. We also devised a 3D modeling algorithm based on structural grouping and concurrently implemented an optimization algorithm to reduce computation time for 3D reconstruction, thereby accelerating the overall modeling process. Furthermore, we quantitatively evaluated the generation accuracy of moving image data using generative models and continued to enhance both hardware construction and software development to further improve computational efficiency.

Development and evaluation of a real-time 3D positioning embedded system combining wireless UWB and camera image analysis (Contract research); FY2023 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Tokai National Higher Education and Research System*

JAEA-Review 2025-023, 63 Pages, 2025/11

JAEA-Review-2025-023.pdf:5.74MB

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 and evaluation of a real-time 3D positioning embedded system combining wireless UWB and camera image analysis" conducted in FY2023. The present study aims to realize an embedded system that combines two of the latest popular technologies, "wireless UWB (Ultra Width Band)" and "multi-camera object recognition" with the goal of simple real-time 3D positioning with less than 10 cm accuracy by a human or robot for measuring air doses in nuclear reactor buildings. In this research, Gifu Univ. and National Institute of Technology, Fukushima College have developed an embedded system with camera shooting function, camera analysis function, and wireless communication function, in order to realize real-time 3D positioning based on the analysis of camera images by using these multiple devices. The Univ. of Tokyo and LocationMind Inc. will apply UWB real-time positioning technology to the inside of nuclear reactor buildings and attempt to develop technology to improve stability. Nagoya Univ. will be in charge of verifying wireless UWB stability from the hardware side by using electromagnetic wave absorbing materials. The radiation resistance evaluation will be conducted in cooperation with the JAEA and National Institute of Technology, Fukushima College.

Image selection method from image sequence to improve computational efficiency of 3D reconstruction; Application of fixed threshold to remove redundant images

Hanari, Toshihide; Nakamura, Keita*; Imabuchi, Takashi; Kawabata, Kuniaki

Journal of Robotics and Mechatronics, 36(6), p.1537 - 1549, 2024/12

https://doi.org/10.20965/jrm.2024.p1537

This paper describes three-dimensional (3D) reconstruction processes introducing the image selection method for efficiently generating a 3D model from an image sequence. To obtain suitable images for efficient 3D reconstruction, we tried to apply the image selection method to remove the redundant images in the image sequence. By the proposed method, the suitable images were selected from the image sequence based on optical flow measures and a fixed threshold. As a result, the proposed method can reduce the computational cost for the 3D reconstruction processes based on the image sequence acquired by the camera. We confirmed that the computational cost of the 3D reconstruction processes can reduce while keeping the 3D reconstruction accuracy at a constant level.

The Behavior of a jet passing through a grid-type obstacle; An Experimental investigation

Abe, Satoshi; Shibamoto, Yasuteru

Annals of Nuclear Energy, 202, p.110461_1 - 110461_16, 2024/07

https://doi.org/10.1016/j.anucene.2024.110461

Gas entrainment phenomenon from free liquid surface in a sodium-cooled fast reactor; Measurements and evaluation on a gas core growth form the liquid surface

Uchida, Mao*; Alzahrani, H.*; Shiono, Mikihito*; Sakai, Takaaki*; Matsushita, Kentaro; Ezure, Toshiki; Tanaka, Masaaki

Proceedings of 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-19) (Internet), 16 Pages, 2022/03

Gas entrainment from cover gas is one of key issues for sodium-cooled fast reactors design to prevent unexpected effects to core reactivity. A vortex model based evaluation method has been developed to evaluate the surface vortex gas core growth at the free surface in the reactor vessel. In this study, water experiments were performed to clarify the prediction accuracy for the vortex gas core growth during the vortex drift motion using a circulating water tunnel with an open flow channel test section. Gas core growth were predicted by applying the evaluation method to the numerical analyses performed in the same geometry of the experiments, and compared with the experimental results. It was observed the gas core growth became large at downstream region where downward velocity became large in experiment. However, the gas core length which were predicted from numerical result showed a discrepancy with the experimental result on the peak position and an overestimation of peak value.

Water experiments on thermal striping phenomena at the core outlet of an advanced sodium-cooled fast reactor, 1; Proposal of countermeasures to mitigate temperature fluctuations around control rods

Kobayashi, Jun; Aizawa, Kosuke; Ezure, Toshiki; Kurihara, Akikazu; Tanaka, Masaaki

Hozengaku, 20(3), p.89 - 96, 2021/10

Hot sodium from the fuel assembly can mix with cold sodium from the control rod (CR) channel and the blanket assemblies at the bottom plate of the Upper Internal Structure (UIS) of Advanced-SFR. Temperature fluctuation due to mixing of the fluids at different temperature between the core outlet and cold channel may cause high cycle thermal fatigue on the structure around the bottom of UIS. A water experiment using a 1/3 scale 60 degree sector model simulating the upper plenum of the Advanced-SFR has been conducted to examine countermeasures for the significant temperature fluctuation generated around the bottom of UIS. We focused on the temperature fluctuations near the primary and backup control rod channels, and studied the countermeasure structure to mitigate the temperature fluctuation through temperature distribution and flow velocity distribution measurements. As a result, effectiveness of the countermeasure to mitigate the temperature fluctuation intensity was confirmed.

A Study of directional gamma-ray detector without shield by Monte Carlo simulation

Kitayama, Yoshiharu; Terasaka, Yuta; Sato, Yuki; Torii, Tatsuo

Proceedings of International Youth Nuclear Congress 2020 (IYNC 2020) (Internet), 4 Pages, 2020/05

Activity median aerodynamic diameter relating to contamination at Plutonium Fuel Research Facility in Oarai Research and Development Center; Particle size analysis for plutonium particles using imaging plate

Takasaki, Koji; Yasumune, Takashi; Hashimoto, Makoto; Maeda, Koji; Kato, Masato; Yoshizawa, Michio; Momose, Takumaro

JAEA-Review 2019-003, 48 Pages, 2019/03

JAEA-Review-2019-003.pdf:3.81MB

June 6, 2017, at Plutonium Fuel Research Facility in Oarai Research and Development Center of JAEA, when five workers were inspecting storage containers containing plutonium and uranium, resin bags in a storage container ruptured, and radioactive dust spread. Though they were wearing a half face mask respirator, they inhaled radioactive materials. In the evaluation of the internal exposure dose, the aerodynamic radioactive median diameter (AMAD) is an important parameter. We measured 14 smear samples and a dust filter paper with imaging plates, and estimated the AMAD by image analysis. As a result of estimating the AMAD, from the 14 smear samples, the AMADs are 4.3 to 11 m or more in the case of nitrate plutonium, and the AMADs are 5.6 to 14 m or more in the case of the oxidized plutonium. Also, from the dust filter paper, the AMAD is 3.0 m or more in the case of nitrate plutonium, and the AMAD is 3.9 m or more in the case of the oxidized plutonium.

A Three-dimensional radiation image display on a real space image created via photogrammetry

Sato, Yuki; Ozawa, Shingo*; Tanifuji, Yuta; Torii, Tatsuo

Journal of Instrumentation (Internet), 13(3), p.P03001_1 - P03001_8, 2018/03

https://doi.org/10.1088/1748-0221/13/03/P03001

Morphology change of CeO thin film induced by He precipitation

Serizawa, Hiroyuki; Yamamoto, Shunya*; Yasunaga, Kazushi*

QST-M-2; QST Takasaki Annual Report 2015, P. 68, 2017/03

https://repo.qst.go.jp/records/73804

Recent investigation examined by JAEA showed that a gas bubble bounded by facets is formed in UO during a process of a precipitation of helium followed by injection with HIP. The interest phenomena they found is that the shape of the negative crystal changes depending on the inner pressure of cavity, which implies that the shape of the cavity can be transformed by controlling the condition of helium release followed by the injection. This paper addresses the detailed observation of the gas bubble formation in the thin film using STEM.