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ICRP International

Conference on Recovery After Nuclear Accidents

Radiological Protection Lessons
from Fukushima and Beyond

December 1 - 18, 2020

L. Cui, Y. Taira, M. Matsuo, M. Orita, Y. Yamada, N.Takamura

Updated: Dec 11, 2020

Environmental Remediation of the Difficult-to-Return Zone in Tomioka Town, Fukushima Prefecture

L. Cui, Y. Taira, M. Matsuo, M. Orita, Y. Yamada, N. Takamura (Nagasaki University, Japan)


Temporal variations in ambient dose rates in a restricted area designated as “difficult-to-return” for residents of Tomioka Town, Fukushima Prefecture were evaluated in a car-borne survey during 2018-2019. The median dose rates in the “Decontaminated area” in the difficult-to-return zone decreased rapidly from 1.0 μSv/h to 0.32 μSv/h; however, the median dose rates in the “Non-decontaminated area” and “Radioactive waste storage area” fluctuated between 1.1-1.4 μSv/h and 0.46-0.61 μSv/h, respectively. The dose rates in the Decontaminated area dramatically decreased due to decontamination work aiming to help residents return home. Moreover, the estimated external exposure dose of workers during the present survey was 0.66 mSv/y in the Decontaminated area and 0.55 mSv/y in the Radioactive waste storage area, respectively. This case of Tomioka Town within the “difficult-to-return zone” may be the first reconstruction model for evaluating environmental contamination and radiation exposure dose rates due to artificial radionuclides derived from the disaster.

福島県富岡町の帰還困難区域の環境修復

L. Cui, Y. Taira, M. Matsuo, M. Orita, Y. Yamada, N. Takamura (長崎大学、日本)


福島県富岡町の住民に対し「帰還困難」と指定された制限区域における空間線量率の時間的変化が、2018~2019年の自動車探査で評価された。帰還困難区域の「除染区域」における中央線量率は1.0 μSv/時から0.32 μSv/時へと急激に低下した。しかし、「非除染区域」及び「放射性廃棄物保管区域」の中央線量率はそれぞれ1.1~1.4 μSv/時及び0.46~0.61 μSv/時で推移していた。除染区域の線量率は住民の帰宅支援を目的とした除染作業により劇的に低下した。さらに、現調査時における作業員の推定外部被ばく線量は除染区域で0.66 mSv/年、放射性廃棄物保管区域で0.55 mSv/年だった。「帰還困難区域」内での富岡町のこの事例は、災害で生じた人工放射性核種による環境汚染と放射線被ばく線量率を評価する初の再建モデルとなりうる。

Poster-C4_LCui-etal
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