TEPCO Fukushima Daiichi Nuclear Power Station Accident

This nuclear power plant accident was caused by the Great East Japan Earthquake (magnitude 9.0) and the resulting tsunami on March 11, 2011. At the time of the earthquake, the TEPCO Fukushima Daiichi Nuclear Power Plant was able to safely shut down its operating reactors and secure power through the automatic startup of emergency diesel generators. However, the huge tsunami that followed inundated the main facilities and power supply equipment, rendering them inoperable and causing the loss of important safety functions. The loss of the reactor's cooling system resulted in a hydrogen explosion and the release of a large amount of radioactive material. As a result, approximately 160,000 residents of Fukushima Prefecture were evacuated (60,000 out of the prefecture and 100,000 within the prefecture) in May 2012. This accident is rated Level 7 (severe accident) on the International Nuclear Event Scale (INES), the same as the accident at the Chornobyl Nuclear Power Plant in the former Soviet Union (now Ukraine).

Condition of Unit 1 at the TEPCO Fukushima Daiichi Nuclear Power Plant after the Hydrogen Explosion
Source：TEPCO Holdings
(https://photo.tepco.co.jp/date/2012/201209-j/120911-07j.html)
(Accessed October 1, 2024)

You can search the following page for data on the results of fallout and land water (tap water) radioactivity surveys conducted immediately after the accident at TEPCO's Fukushima Daiichi Nuclear Power Station.

In addition, please use the Environmental Radiation Database to search for data on the results of environmental radioactivity surveys conducted by the Nuclear Regulation Authority with the cooperation of related ministries and agencies, 47 prefectures, etc.

Reference：

・TEPCO. “1. Overview of the Accident at the Fukushima Daiichi Nuclear Power Station.” https://www.tepco.co.jp/nu/fukushima-np/review/review1_1-j.html(Ref. 2024-10-01).

・Japan Nuclear Culture Foundation. “Illustrated Collection of Nuclear & Energy | EneHyakka | You, the Future, and Us.”https://www.ene100.jp/fukushima/487(Ref. 2024-10-01).

・Fukushima Prefectural Government. “Transition in the Number of Evacuees.”https://www.pref.fukushima.lg.jp/site/portal/hinansya.html(Ref. 2024-10-01).