Development of portable VR system for radiation work environment using 3-D environmental map visualizing radiation information as input data

Sato, Yuki; Minemoto, Kojiro*; Nemoto, Makoto*; Matsuura, Yasutaka*; Hayashi, Keisuke*

Proceedings of International Conference on Nuclear Decommissioning; Addressing the Past and Ensuring the Future 2023 (Internet), 4 Pages, 2025/05

The development of technology to visualize the distribution of radioactive substances at the decommissioning site of the Fukushima Daiichi Nuclear Power Station (FDNPS) is important for reducing worker exposure and developing a detailed work plan. Sato, one of the authors, developed an integrated Radiation Imaging System (iRIS) that combines a Simultaneous Localization and Mapping (SLAM) device, a Compton camera (a type of gamma-ray imager), and a survey meter, and have successfully produced a 3-D map of the working environment inside the FDNPS that visualizes the location of radioactive hot spots and the distribution of air dose rates. In addition, the authors are developing a system that enables users to experience the radiation environment of the FDNPS in virtual reality (VR) using the 3-D map visualizing such radiation information as input data. This VR system can use a commercially available portable VR head-mounted display, which not only displays the location of the radiation source in a virtual space, but also has the ability to calculate the exposure dose according to the working time. The development status of this VR system, which is expected to be effective in educating inexperienced workers and planning work, will be presented at the conference.

Demonstration of COMRIS, a 3-D visualization software for radioactive substances based on Compton cameras and SLAM devices

Sato, Yuki; Minemoto, Kojiro*; Nemoto, Makoto*

Proceedings of Waste Management Conference 2025 (WM2025) (Internet), 9 Pages, 2025/03

Development of a high-resolution imaging camera for alpha dust and high-dose rate monitor (Contract research); FY2022 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Tohoku University*

JAEA-Review 2024-016, 61 Pages, 2024/12

JAEA-Review-2024-016.pdf:2.88MB

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 FY2022. 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 FY2022. 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.

Radioactivity estimation of radioactive hotspots using a Compton camera and derivation of dose rates in the surrounding environment

Sato, Yuki

Applied Radiation and Isotopes, 212, p.111421_1 - 111421_8, 2024/10

https://doi.org/10.1016/j.apradiso.2024.111421

Manuals for resonance analysis code for neutron IMaging "RAIM"

Hasemi, Hiroyuki; Kai, Tetsuya

JAEA-Testing 2024-001, 39 Pages, 2024/08

JAEA-Testing-2024-001.pdf:1.4MB

RAIM is an analysis code that analyzes resonance absorption spectra measured at pulsed neutron sources such as the Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC) to obtain information on nuclear densities and temperatures. By calculating the convolution of the pulse functions of neutron beam and the resonance capture function that is based on the nuclear cross section data, RAIM reproduces the resonance absorption spectrum measured by a pulsed neutron source. Then, RAIM determines the density and temperature of specific nuclides in a sample by performing spectral fitting on the resonance absorption spectrum data. In addition, RAIM is developed to facilitate the analysis of resonance imaging data by minimizing the number of parameters for calculation setup and by providing scripts for processing many resonance absorption spectra measured by a two-dimensional detector at once. This manual explains how to install RAIM on a computer and how to simulate resonance absorption spectra and fit them to measured data.

Establishment of characterization method for small fuel debris using the world's first isotope micro imaging apparatus (Contract Research); FY2021 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Kogakuin University*

JAEA-Review 2024-005, 79 Pages, 2024/06

JAEA-Review-2024-005.pdf:5.72MB

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 FY2021. 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 FY2021, this report summarizes the research results of the "Establishment of characterization method for small fuel debris using the world's first isotope micro imaging apparatus" conducted in FY2021. The present study aims to obtain, for the first time in the world, the important data necessary for clarifying the retrieval of small amounts of fuel debris, and to evaluate and examine them. SEM-EDS and TEM-EDS cannot be used for isotopic identification and analysis of Pu and B. On the other hand, bulk analysis such as ICP-MS lacks the information in a micro region.

Establishment of 3-D dose dispersion forecasting method and development of in-structure survey using the transparency difference of each line gamma-ray (Contract research); FY2022 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Kyoto University*

JAEA-Review 2023-028, 54 Pages, 2024/03

JAEA-Review-2023-028.pdf:3.81MB

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 FY2022. 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 FY2022, this report summarizes the research results of the "Establishment of 3-D dose dispersion forecasting method and development of in-structure survey using the transparency difference of each line gamma-ray" conducted in FY2022. We realized an electron track detecting Compton camera (ETCC) that can measure -ray images (linear images) with the bijective projection. In the "Quantitative analysis of radioactivity distribution by imaging of high radiation field environment using gamma-ray imaging spectroscopy" (hereinafter referred to as the previous project) adopted in FY2018, the 1 km square area including the reactor buildings was imaged at once.

Radioactivity estimation of multiple radiation sources using a Compton camera to investigate radioactively contaminated objects

Sato, Yuki

Applied Radiation and Isotopes, 203, p.111083_1 - 111083_9, 2024/01

https://doi.org/10.1016/j.apradiso.2023.111083

Quantitative visualization of a radioactive plume with harmonizing gamma-ray imaging spectrometry and real-time atmospheric dispersion simulation based on 3D wind observation

Nagai, Haruyasu; Furuta, Yoshihiro*; Nakayama, Hiromasa; Satoh, Daiki

Journal of Nuclear Science and Technology, 60(11), p.1345 - 1360, 2023/11

https://doi.org/10.1080/00223131.2023.2197445

A novel monitoring method for the quantitative visualization of 3D distribution of a radioactive plume and source term estimation of released radionuclides is proposed and its feasibility is demonstrated by preliminary test. The proposed method is the combination of gamma-ray imaging spectroscopy with the Electron Tracking Compton Camera (ETCC) and real-time high-resolution atmospheric dispersion simulation based on 3D wind observation with Doppler lidar. The 3D distribution of a specific radionuclide in a target radioactive plume is inversely reconstructed from line gamma-ray images from each radionuclide by several ETCCs located around the target by harmonizing with the air concentration distribution pattern of the plume predicted by real-time atmospheric dispersion simulation. A prototype of the analysis method was developed, showing a sufficient performance in several test cases using hypothetical data generated by numerical simulations of atmospheric dispersion and radiation transport.

Establishing an evaluation method for the aging phenomenon by physical force in fuel debris

Suzuki, Seiya; Arai, Yoichi; Okamura, Nobuo; Watanabe, Masayuki

Journal of Nuclear Science and Technology, 60(7), p.839 - 848, 2023/07

https://doi.org/10.1080/00223131.2022.2159559

The fuel debris, consisting of nuclear fuel materials and reactor structural materials, generated in the accident of Fukushima Daiichi Nuclear Power Plant can become deteriorated like rocks under the changes of environmental temperature. Although the fuel debris have been cooled by water for 10 years, they are affected by seasonal and/or day-and-night temperature changes. Therefore, in evaluating the aging behavior of the fuel debris, it is essential to consider the changes in environmental temperature. Assuming that the fuel debris are deteriorated, radioactive substances that have recently undergone micronization could be eluted into the cooling water, and such condition may affect defueling methods. We focused on the effect of repeated changes in environmental temperature on the occurrence of cracks, and an accelerated test using simulated fuel debris was carried out. The length of the crack increases with increasing number of heat cycle; therefore, the fuel debris become brittle by stress caused by thermal expansion and contraction. In conclusion, it was confirmed that the mechanical deterioration of the fuel debris is similar to that of rocks or minerals, and it became possible to predict changes in the length of the crack in the simulated fuel debris and environmental model.