Fire in the spent fuel pool of Unit 4 at Fukushima-I

In the early morning of Tuesday 15 March 2011, the International Atomic Energy Agency (IAEA) released a statement saying that the Japanese authorities had informed the Agency that "the spent fuel storage pond at the Unit 4 of the Fukushima Daiichi plant is on fire and radioactivity is being released directly into the atmosphere. Dose rates of up to 400 millisievert per hour have been reported at the site. Japanese authorities are saying that there is a possibility that the fire was caused by a hydrogen explosion." A spent fuel fire is of great concern because radioactive emissions are directly released into the environment. The fire was reportedly put out by 2:00 UTC on March 15, 2011. However, some release of radioactivity has already occurred and the cause of the fire remains unknown. Unit 4 was in cold shutdown at the time of the earthquake.

Fukushima-I (Daiichi) has six boiling water reactors (BWR), ranging from 460 MW to 1100 MW, started up between 1970 and 1979. Fukushima-II (Daini) has four 1100 MW BWRs, commissioned between 1981 and 1986. Eleven nuclear reactors were in operation and three in planned outage in the coastal areas of Japan when the "Big One" turned cities, industrial facilities and harbors into a disaster zone on what might well be remembered as 3/11. All units had emergency shutdowns. In the follow-up, seven reactors declared a nuclear emergency, in particular because of lack of power supply and deficient cooling systems. Units 1, 2 and 3 of Fukushima-I are experiencing fuel damage and are still under threat of full-scale meltdown. The operator TEPCO that is now handling the crisis under government instructions, has decided to flood the entire containment building of unit 1 with sea water after attempts to cool the core by direct injection into the vessel failed. Massive explosions, most likely hydrogen explosions, ripped off the reactor buildings' roof and walls at units 1 and 3. During the explosion at unit 3, the containment of unit 2 has been damaged is loosing pressure. Attempts to cool the core through direct injection of seawater into the vessel failed and the fuel was dry again within hours. The meltdown of unit 2 bears additional risks because of the damaged containment.

The situation evolves permanently and we do not have the manpower to provide adequate coverage. For regular updates see the following sources:

UPDATE 03/15/2011: An article published in 2002 in Science and Global Security analysed the dangers associated with spent fuel pools at reactor sites: