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.

Development of measurement system of radioactive plume using unmanned airplane in the fiscal year 2018 (Contract research)

Sanada, Yukihisa; Ochi, Kotaro; Ishizaki, Azusa

JAEA-Research 2020-006, 60 Pages, 2020/07

JAEA-Research-2020-006.pdf:4.84MB

At the accident of nuclear facilities, a prediction of the behavior of released radioactive plume is indispensable to make a decision on a refuge plan of inhabitants. Currently, prediction system which is based on atmospheric dispersion simulation has been implemented as a tool of the atomic energy disaster prevention. However, the direct measurement method of the radioactive plume has not existed. In this study, some component technologies were developed for the establishment of direct measurement methods of radioactive plume using unmanned aerial vehicle whose technological innovation is remarkable. In addition, the spray test using mock aerosol was conducted to obtaining the deposition rate to the airplane body. The algorism of making a flight plan was developed based on a prediction model of the radioactive plume. This report summarized the outcome of the last year of the three-year plan.

Large-eddy simulation of plume dispersion during the Fukushima Daiichi Nuclear Power Plant accident by coupling with a meso-scale meteorological simulation model

Nakayama, Hiromasa; Takemi, Tetsuya*; Nagai, Haruyasu

no journal, , 

A significant amount of radioactive material was accidentally discharged into the atmosphere from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) from March 12, 2011. In conducting regional-scale atmospheric dispersion simulations, the nuclear emergency response system based on a meso-scale meteorological model (MM) was used. However, it is impossible to conduct detailed simulations of plume dispersion considering the turbulent effects in a local-scale because buildings, structures, and local terrain variability are not explicitly represented at high grid resolutions in those models. Therefore, an approach to couple an LES-based CFD model with a MM model should be promising. In this study, first we conduct LESs of plume dispersion around the FDNPP under a constant meteorological condition by prescribing constant mean wind velocities and directions at the inlet boundary condition, and then do them under a varying meteorological condition by coupling with a MM model. Our objective is to compare plume dispersion patterns under those different meteorological conditions and evaluate the effectiveness of the coupling computational method.