Ecological half-life of radioactive caesium within 80 km-radius of the Fukushima Daiichi Nuclear Power Plant

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

To obtain the perspective of assessing the evolution of the long-term exposure situation, prediction models have been developed for the radioactive caesium distribution within 80 km-radius of the Fukushima Daiichi Nuclear Power Plant. Exponential functions characterised by ecological half-lives of radioactive caesium were adapted for the preliminary prediction models. The ecological half-lives were evaluated using the changes in ambient dose equivalent rates. Cumulative distribution functions for the ecological half-lives of radioactive caesium were obtained for each land use. It was found that ecological half-life of radioactive caesium for forest areas is much larger than that for urban and water areas.