Consideration on utilization of atmospheric dispersion models for a nuclear emergency preparedness and response

Togawa, Orihiko; Okura, Takehisa; Kimura, Masanori; Nagai, Haruyasu

JAEA-Review 2021-021, 61 Pages, 2021/11

JAEA-Review-2021-021.pdf:3.72MB

Triggered by the Fukushima Daiichi Nuclear Power Station accident, there have been a lot of arguments among various situations and levels about utilization of atmospheric dispersion models for a nuclear emergency preparedness and response. Most of these arguments, however, were alternative and extreme discussions on whether predictions by computational models could be applied or not for protective measures in a nuclear emergency, and it was hard to say that these arguments were politely conducted, based on scientific verification in an emergency response. It was known, on the other hand, that there were not a few potential users of atmospheric dispersion models and/or calculation results by the models within the Japan Atomic Energy Agency (JAEA) and outside. However, they seemed to have a lack of understanding and a misunderstanding on proper use of different kinds of atmospheric dispersion models. This report compares an outline of models and calculation method in atmospheric dispersion models for a nuclear emergency preparedness and response, with a central focus on the models which have been developed and used in the JAEA. Examples of calculations by these models are also described in the report. This report aims at contributing to future consideration and activities for potential users of atmospheric dispersion models within the JAEA and outside.

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.

Reconstruction of residents' thyroid equivalent doses from internal radionuclides after the Fukushima Daiichi Nuclear Power Station accident

Oba, Takashi*; Ishikawa, Tetsuo*; Nagai, Haruyasu; Tokonami, Shinji*; Hasegawa, Arifumi*; Suzuki, Gen*

Scientific Reports (Internet), 10(1), p.3639_1 - 3639_11, 2020/02

https://doi.org/10.1038/s41598-020-60453-0

Internal doses of residents after the Fukushima Daiichi Nuclear Power Station accident have been reconstructed. In total 896 behaviour records in the Fukushima Health Management Survey were analysed to estimate thyroid doses via inhalation, using a spatiotemporal radionuclides concentration database constructed by atmospheric dispersion simulations. After a decontamination factor for sheltering and a modifying factor for the dose coefficient were applied, estimated thyroid doses were close to those estimated on the basis of direct thyroid measurement. The median and 95th percentile of thyroid doses of 1-year-old children ranged from 1.2 to 15 mSv and from 7.5 to 30 mSv, respectively.

Development of measurement system of radioactive plume using unmanned airplane in the fiscal year 2017 (Contract research)

Sanada, Yukihisa; Nishizawa, Yukiyasu*; Ochi, Kotaro; Yuki, Yoichi*; Ishizaki, Azusa; Osada, Naoyuki*

JAEA-Research 2018-009, 48 Pages, 2019/01

JAEA-Research-2018-009.pdf:14.77MB

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 second year of the three-year plan.

Atmospheric modeling of Cs plumes from the Fukushima Daiichi Nuclear Power Plant; Evaluation of the model intercomparison data of the Science Council of Japan

Kitayama, Kyo*; Morino, Yu*; Takigawa, Masayuki*; Nakajima, Teruyuki*; Hayami, Hiroshi*; Nagai, Haruyasu; Terada, Hiroaki; Saito, Kazuo*; Shimbori, Toshiki*; Kajino, Mizuo*; et al.

Journal of Geophysical Research; Atmospheres, 123(14), p.7754 - 7770, 2018/07

https://doi.org/10.1029/2017JD028230

We compared seven atmospheric transport model results for Cs released during the Fukushima Daiichi Nuclear Power Plant accident. All the results had been submitted for a model intercomparison project of the Science Council of Japan in 2014. We assessed model performance by comparing model results with observed hourly atmospheric concentrations of Cs, focusing on nine plumes over the Tohoku and Kanto regions. The results showed that model performance for Cs concentrations was highly variable among models and plumes. We also assessed model performance for accumulated Cs deposition. Simulated areas of high deposition were consistent with the plume pathways, though the models that best simulated Cs concentrations were different from those that best simulated deposition. The ensemble mean of all models consistently reproduced Cs concentrations and deposition well, suggesting that use of a multimodel ensemble results in more effective and consistent model performance.

Oceanic dispersion of Fukushima-derived Cs-137 simulated by multiple oceanic general circulation models

Kawamura, Hideyuki; Furuno, Akiko; Kobayashi, Takuya; In, Teiji*; Nakayama, Tomoharu*; Ishikawa, Yoichi*; Miyazawa, Yasumasa*; Usui, Norihisa*

Journal of Environmental Radioactivity, 180, p.36 - 58, 2017/12

https://doi.org/10.1016/j.jenvrad.2017.09.020

This study simulates the oceanic dispersion of Fukushima-derived Cs-137 by an oceanic dispersion model and multiple oceanic general circulation models. The models relatively well reproduced the observed Cs-137 concentrations in the coastal, offshore, and open oceans. Multiple simulations in the coastal, offshore, and open oceans consistently suggested that Cs-137 dispersed along the coast in the north-south direction during the first few months post-disaster, and were subsequently dispersed offshore by the Kuroshio Current and Kuroshio Extension. Quantification of the Cs-137 amounts suggested that Cs-137 actively dispersed from the coastal and offshore oceans to the open ocean, and from the surface layer to the deeper layers in the North Pacific.

Development of a long-range atmospheric transport model for nuclear emergency and its application to the Chernobyl nuclear accident

Terada, Hiroaki; Chino, Masamichi

Proceedings of 2nd International Conference on Radioactivity in the Environment, p.15 - 18, 2005/10

The previous version of Worldwide version of System for Prediction of Environmental Emergency Dose Information (WSPEEDI) has been composed of mass-consistent wind field model WSYNOP and particle dispersion model GEARN. Because WSYNOP has no capability to predict meteorological fields, its accuracy and resolution depends on meteorological input data, and it is impossible to treat physical processes realistically. To improve these problems, an atmospheric dynamic model MM5 is introduced and applied to the Chernobyl accident for the verification. Two calculation cases are conducted, CASE-1 a calculation for European region Domain-1, and CASE-2 a domain nesting calculation for Domain-1 and the region around Chernobyl Domain-2. The air concentration and surface deposition of Cs calculated by CASE-1 agree well with the measurements by statistical analysis and comparison for the horizontal distribution. In the result of CASE-2, the detailed distribution of surface Cs deposition around Chernobyl which was impossible to calculate in CASE-1 is predicted with high accuracy.

Real-time simulation and analysis on long-range atmospheric dispersions of volcanic gases discharged from the Miyake Island

Furuno, Akiko; Nagai, Haruyasu; Umeyama, Nobuaki; Chino, Masamichi

Taiki Kankyo Gakkai-Shi, 37(1), p.23 - 34, 2002/01

http://ci.nii.ac.jp/naid/110003840994

The active volcano Oyama in the Miyake Island has been emitting a huge amount of volcanic gases since the first eruption in July 2000. High concentrations of SO2 gas originated in Oyama frequently appear in the wide area from the northeast to the west part of Honshu, Japan. This paper describes real-time prediction of SO2 dispersion covering the Tokai and Kanto District and its verification by comparing with SO2 observation data from October to November 2000. Atmospheric dispersions of SO2 are calculated by using our software system that combines a regional atmospheric dynamic model and a particle random walk model. It was proved that the real-time prediction of our system has adequate precision. The importance of including the effect of wet deposition was also shown. The release amounts estimated from the comparison between the calculation result and the monitoring data are 20,000 - 50,000 ton/day, which is consistent to measured ones at the Miyake Island.

WSPEEDI: Worldwide version of System for Prediction of Environmental Emergency Dose Information

Chino, Masamichi; Yamazawa, Hiromi; Nagai, Haruyasu; Furuno, Akiko

Mathematics and Computation, Reactor Physics and Environmental Analysis in Nuclear Applications, 1, p.1521 - 1529, 1999/00

no abstracts in English

Updating source term and an atmospheric transport, dispersion and deposition model, WSPEEDI

Nagai, Haruyasu; Terada, Hiroaki; Tsuzuki, Katsunori; Ota, Masakazu; Furuno, Akiko; Akari, Shusaku; Katata, Genki

no journal, , 

In order to assess the radiological dose to the public resulting from the Fukushima Daiichi Nuclear Power Station accident in Japan, the spatial and temporal distribution of radioactive materials in the environment are reconstructed by computer simulations. In this study, by refining the source term of radioactive materials discharged into the atmosphere and modifying the atmospheric dispersion model, the atmospheric dispersion simulation of radioactive materials is improved. Then, a database of spatiotemporal distribution of radioactive materials in the air and on the ground surface is developed from the output of the simulation, and is used for the dose assessment by coupling with the behavioral pattern of evacuees from the nuclear accident. In this year, (1) investigation of the source term, (2) improvement of atmospheric dispersion simulation, and (3) acquisition and organization of measured data have been conducted.