Application of numerical simulation to predict the environmental transport of radioactive materials discharged from Fukushima Daiichi Nuclear Power Plant due to accident

Nagai, Haruyasu  ; Chino, Masamichi; Terada, Hiroaki   ; Katata, Genki; Nakayama, Hiromasa   ; Ota, Masakazu  

In order to assess the radiological dose to the public resulting from the Fukushima Daiichi Nuclear Power Plant accident, the spatial and temporal distribution of radioactive materials in the environment have been and are planning to be analyzed by SPEEDI, WSPEEDI-II, and the numerical simulation system for material transport in the atmospheric, terrestrial, and oceanic environments, SPEEDI-MP. As the first step, the source term of radioactive materials discharged into the atmosphere has been estimated by coupling environmental monitoring data with atmospheric dispersion simulations by SPEEDI and WSPEEDI-II. As the next step, detailed analysis on the local dispersion around the plant by using WSPEEDI-II revealed the mechanism for the formation of high dose rate zone around north-west direction from the plant. Then, we are planning to apply SPEEDI-MP to provide more information on the distribution of radioactive materials in the whole environment.