Temporal change in radiological environments on land after the Fukushima Daiichi Nuclear Power Plant accident

福島事故後の陸域における放射線環境の経時変化

斎藤 公明  ; 三上 智   ; 安藤 真樹  ; 松田 規宏  ; 木名瀬 栄   ; 津田 修一  ; 佐藤 哲朗*; 関 暁之   ; 眞田 幸尚   ; Wainwright-Murakami, Haruko*; 吉村 和也  ; 武宮 博; 高橋 純子*; 加藤 弘亮*; 恩田 裕一*

Saito, Kimiaki; Mikami, Satoshi; Ando, Masaki; Matsuda, Norihiro; Kinase, Sakae; Tsuda, Shuichi; Sato, Tetsuro*; Seki, Akiyuki; Sanada, Yukihisa; Wainwright-Murakami, Haruko*; Yoshimura, Kazuya; Takemiya, Hiroshi; Takahashi, Junko*; Kato, Hiroaki*; Onda, Yuichi*

Massive environmental monitoring has been conducted continuously after the Fukushima accident with different monitoring methods having different features together with migration studies of radiocesium in diverse environments. At three months after the accident, multiple radionuclides were detected at many places; while it was confirmed that radiocesium was most important from the viewpoint of long-term exposures. The air dose rates in environments related to human living have decreased faster than expected from radioactive decay by a factor of 2-3 on average. An empirical model for predicting air dose rate distribution was developed based on statistical analysis of massive car-borne survey data. Some trials were performed to integrate different types of contamination maps to obtain an integrated map of better quantity. Annual external exposure doses for residents who would return to their home were estimated to less than a few mSv as a whole. The environmental data and knowledge have been provided for diverse-spectrum of people in different ways.