Preliminary Estimation of Release Amounts of 131I and 137Cs Accidentally Discharged from the Fukushima Daiichi Nuclear Power Plant into the Atmosphere

Abstract

The initial estimation of release amounts of 131I and 137Cs accidentally discharged from the Fukushima Daiichi Nuclear power plant into the atmosphere is presented. For the source term estimation, environmental monitoring data on air concentrations of iodine and cesium were mainly used. The System for Prediction of Environmental Emergency Dose Information (SPEEDI) network system) operated by MEXT was used for calculating air concentrations and dose rates. The simulation results were furnished from NSC for the purpose of the source term estimation. To estimate the total amounts of 131I and 137Cs discharged into the atmosphere, the 'Duration' is roughly estimated by assuming that the release with a certain release rate continued from/to the middle times between released times of sampled air.