| Description | JAEA has been trying to estimate the source term of iodine and cesium discharged from the Fukushima Daiichi Nuclear Power Plant to the atmosphere. As the first step, the source term was preliminary estimated by coupling environmental monitoring data with atmospheric dispersion simulations by SPEEDI and WSPEEDI. Then, detailed analysis on the local atmospheric dispersion has been carried out, and revealed the formation process of high dose rate zone around north-west direction from the plant. With this analysis and further analysis for the early phase of the accident, the release rates and total amounts of 131I and 137Cs discharged into the atmosphere were re-estimated for the period from 12 to 15 March, 2011. Finally, the validity of revised source term was also examined by comparing daily and monthly surface deposition (fallout) over land in eastern Japan between measurements and outputs from the regional scale atmospheric dispersion simulation. |
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