Evaluation of environmental contamination and estimated radiation doses for the return to residents' homes in Kawauchi Village, Fukushima prefecture.

Yasuyuki Taira,Noboru Takamura,Shunichi Yamashita,Naomi Hayashida,Hitoshi Yamaguchi,Yuukou Endo

doi:10.1371/journal.pone.0045816

Yasuyuki Taira, Noboru Takamura + Show 4 more

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https://doi.org/10.1371/journal.pone.0045816

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Journal: PloS one	Publication Date: Sep 26, 2012
Citations: 33	License type: CC BY 4.0

Affiliation: Nagasaki University, Osaka Prefectural Government

Abstract

To evaluate the environmental contamination and radiation exposure dose rates due to artificial radionuclides in Kawauchi Village, Fukushima Prefecture, the restricted area within a 30-km radius from the Fukushima Dai-ichi Nuclear Power Plant (FNPP), the concentrations of artificial radionuclides in soil samples, tree needles, and mushrooms were analyzed by gamma spectrometry. Nine months have passed since samples were collected on December 19 and 20, 2011, 9 months after the FNPP accident, and the prevalent dose-forming artificial radionuclides from all samples were 134Cs and 137Cs. The estimated external effective doses from soil samples were 0.42–7.2 µSv/h (3.7–63.0 mSv/y) within the 20-km radius from FNPP and 0.0011–0.38 µSv/h (0.010–3.3 mSv/y) within the 20–30 km radius from FNPP. The present study revealed that current levels are sufficiently decreasing in Kawauchi Village, especially in areas within the 20- to 30-km radius from FNPP. Thus, residents may return their homes with long-term follow-up of the environmental monitoring and countermeasures such as decontamination and restrictions of the intake of foods for reducing unnecessary exposure. The case of Kawauchi Village will be the first model for the return to residents’ homes after the FNPP accident.

Highlights

On March 11, 2011, a 9.0-magnitude earthquake (The Great East Japan Earthquake) struck the east coast near Iwate, Miyagi, and Fukushima Prefectures, Japan
The total amount of radioactive materials released into the atmosphere from Fukushima Dai-ichi Nuclear Power Plant (FNPP) corresponds to Level 7 of the International Nuclear and Radiological Event Scale (INES) by the International Atomic Energy Agency (IAEA)
According to the interim report of the Investigation Committee on the Accidents at Fukushima Nuclear Power Stations of Tokyo Electric Power Company, there were 2,900 evacuees of Kawauchi Village: 400 residents of the ‘‘access restricted area’’ and 2,500 residents of ‘‘areas previously designated as the emergency evacuation preparation zones’’ [15]

Summary

Introduction

On March 11, 2011, a 9.0-magnitude earthquake (The Great East Japan Earthquake) struck the east coast near Iwate, Miyagi, and Fukushima Prefectures, Japan. The total amount of radioactive materials released into the atmosphere from FNPP corresponds to Level 7 of the International Nuclear and Radiological Event Scale (INES) by the International Atomic Energy Agency (IAEA). This level corresponds to a major accident, the amount of radioactive materials released into the environment is estimated to be 10% [1.661017 Bq for 131I (half-life: 8.0 d) and 1.561016 Bq for 137Cs (30 y)] of the accident at the Chernobyl Nuclear Power Plant (CNPP, 1.861018 Bq for 131I and 8.561016 Bq for 137Cs), which was previously assessed at the same level [1]. In the emergency zone outside a 20-km radius from FNPP, there are certain areas where radioactive materials emitted from the power station have accumulated as a result of climatic and geographical conditions and some of these areas have shown high levels of radionuclides

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