Development of prediction models for radioactive caesium distribution within the 80-km radius of the Fukushima Daiichi Nuclear Power Plant

Kinase, Sakae   ; Takahashi, Tomoyuki*; Sato, Satoshi; Sakamoto, Ryuichi*; Saito, Kimiaki  

Preliminary prediction models have been studied for radioactive caesium distribution within the 80 km radius of the Fukushima Daiichi Nuclear Power Plant to follow up radiological situations after the accident. The models were represented by exponential functions using ecological half-life of radioactive caesium in the environment. The ecological half-lives were derived from the changes in ambient dose equivalent rates through vehicle-borne surveys. It was found that ecological half-lives of radioactive caesium were not constant within the 80 km radius of the Fukushima Daiichi Nuclear Power Plant. The ecological half-life for forest areas was found to be much larger than that for urban and water areas.