Predictions of the ambient dose equivalent rates in the early phase of the Fukushima Daiichi Nuclear Power Plant accident

福島第一原子力発電所事故初期の周辺線量当量率推定

木名瀬 栄   ; 本田 文弥*

Kinase, Sakae; Honda, Fumiya*

At the Japan Atomic Energy Agency, the long-term prediction models have been developed to assess how ambient dose equivalent rates might change during the intermediate and late phases and to analyze radiological situations within the 80 km radius of the F1NPP. In the present study, new prediction models for the early phase of the F1NPP accident were developed on the basis of the long-term prediction model. It was confirmed that the high ambient dose equivalent rate distribution stretches northwest from the F1NPP. The maximum ambient dose equivalent rate near the F1NPP as of the first month following the accident was found to be about 300 Sv h. The major parts of the dose contribution were from I, Cs, Cs and Cs. Radiation emitted from I contributed about 10% of the ambient dose equivalent rate.