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Home > Fukushima Revitalization > The triple disaster of earthquake, tsunami and nuclear accident > TEPCO's Fukushima Daiichi Nuclear Power Station accident in 2011

TEPCO's Fukushima Daiichi Nuclear Power Station accident in 2011

2017年12月26日更新 Update


The Great East Japan Earthquake occurred on 11 March, 2011. A massive earthquake triggered tsunami which damaged the coastal areas of the Tohoku District, including Fukushima Prefecture.

Damage at the Power Station

Earthquake Damage

  • The Earthquake triggered the emergency stop of the operating reactors(1 - 3)
  • Emergency power supplies were triggered, starting fuel cooling operations for reactors 1-6

Tsunami Damage

  • Tsunami caused flooding of the emergency power supplies including batteries, which lead to a loss of power for reactors 1-5
  • Fuel melted in reactors 1-3 and radioactive substances were released into the air
  • Hydrogen explosions caused damage to the buildings containing reactors 1, 3, and 4.
  • Cooling function was lost for the spent fuel pools of reactors 1-6.

Photo:Power Station struck by tsunami
Power Station struck by tsunami

Damage Response

  • Fuel in Reactors 1-3 were cooled using water injection, and reached a stable condition
  • Reactor 5 resumed cooling operations using the emergency power facilities of Reactor 6.
  • Cooling of the spent fuel pools was resumed using pumping vehicles and other temporary equipment.

Fukushima Daiichi NPS - Situation after Tsunami Disaster

Reactor fuel
Fuel in Pool
DC Power
Emergency AC
Power Source

Current situation of reactors

Decommissioning operations are currently underway for reactors 1-6 at the F1NPS.

Reactor temperature

  • Roughly 300m3 of cooling water is being injected into the reactors every day
  • Reactor temperature is stable at below 50℃ (As of October, 2015)

Image:Reactor temperature

Amount of radioactive substances

  • Concentrations of radioactive substances are being monitored and no signs of recriticality have been observed(As of October, 2015)

Image:Amount of radioactive substances

Current Situation(2017)of the site of Fukushima Daiichi NPS

1F site

Marine monitoring

TEPCO is conducting marine monitoring in order to confirm the impact on the environment caused by the radioactive substances released from the F1NPS. There are also many measures in place for the processing and reduction of contaminated water.

TEPCO is making efforts to confirm the environmental impact of radioactive substances released from the F1NPS

  • Radiation levels inside and outside the power station are being measured.
  • In spite of the leak of contaminated water, no significant increase in radiation levels has been observed outside the port.
  • Radiation levels of sea water are well below standards for drinking water set by WHO.

Image : Marine monitoring 1

Image : Marine monitoring 2

*Total beta activity includes naturally occurring radionuclides such as K-40.


Videos Fukushima update

Living in Fukushima (Sep. 2013, Ministry of the Environment)
Fukushima Today-Toward new horizens (Jan. 2016, Ministry of Economy, Trade and Industry)