Source term estimation during the Fukushima Dai-ichi Nuclear Power Plant accident by coupling atmospheric and oceanic dispersion models

Katata, Genki; Chino, Masamichi; Terada, Hiroaki   ; Kobayashi, Takuya ; Ota, Masakazu  ; Nagai, Haruyasu  ; Kajino, Mizuo*

It is important to estimate the time trend of atmospheric release and dispersion of radionuclides for evaluating the radiation doses to the public during the Fukushima Daiichi nuclear accident. The authors re-evaluated the time trend of atmospheric releases during March by comparing many kinds of environmental monitoring data and the results from the combination of atmospheric and oceanic models. The atmospheric dispersion simulations based on the estimated source term showed in good agreement with deposition distribution of I-131 and Cs-137 observed by aerial survey. It is cleared that the contamination areas at the Central Line of Fukushima Pref., Fukushima City and Iitate Village, and the northwest area of the site were created successively during the periods of 6:00-15:00, 15:00-21:00 15 March and 21:00 15 - 6:00 16 March.