After a devastating 8.9 earthquake off the coast of Japan, a few nuclear power plants sustained damage and were having trouble with their cooling systems. The Fukushima Nuclear Power Plant experienced an explosion that has been blamed on a failed pumping system.

The extent of the damage and severity of the explosion is not yet known, but early reports are saying that the containment unit was not damaged. The evacuation radius has been increased to 20km.

CNN:

The explosion at Japan’s Fukushima nuclear plant was not caused by the nuclear reactor but by “water vapor that was part of the cooling process,” Chief Cabinet Secretary Yukio Edano said Saturday. He said no harmful gases had been emitted by the explosion.

Detail are still coming in and I’ll update the post as they do.

UPDATE 1: A failed pumping system has been blamed for the explosion. Workers were using the system in an attempt to bring the reactor’s temperature down. -CNN

UPDATE 2: The next attempt to cool the reactor will be to flood the reactor’s containment structure with seawater. That process is expected to take 2 days. -CNN

UPDATE 3: The International Atomic Energy Agency (IAEA) says that Japan is planning to distribute iodine, a radiation antidote.

UPDATE 4: A collection of statements from experts on what may have happened at Fukushima: Reuters Factbox – Experts on explosion at Japan nuclear plant