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Overview of the nuclear power station accident
"～Fukushima Today～Steps for Reconstruction and Revitalization in Fukushima Prefecture"
Status
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.
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 No. |
Operational Condition |
Reactor fuel （Unit：rod） |
Fuel in Pool （Unit:rod） |
ACPower Source |
DC Power Source |
Emergency AC Power Source |
|---|---|---|---|---|---|---|
| 1 | Operating | 400 | 392 | Unusable | Unusable | Unusable |
| 2 | Operating | 548 | 615 | Unusable | Unusable | Unusable |
| 3 | Operating | 548 | 566 | Unusable | Partially usable |
Unusable |
| 4 | Suspended | 0 | 1,535 | Unusable | Unusable | Unusable |
| 5 | Suspended | 548 | 994 | Unusable | Usable | Unusable |
| 6 | Suspended | 764 | 940 | Unusable | Usable | Usable |
The site shortly after the accident
Current situation of units
Reactor decommissioning operations are currently underway for Units 1-6 at the Fukushima Diichi NPS
(As of September 2017)
Temperatures inside containment vessel air conditioners
- Reactor temperatures are stable at below 45℃
Amount of radio cesium per hour dispersed from nuclesr reactor buildings
- Concentrations of radioactive substances are being monitored and no signs of recriticality have been observed.
Current Situation（2017）of the site of Fukushima Daiichi NPS
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.
*Total beta activity includes naturally occurring radionuclides such as K-40.
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