In the aftermath of the Sendai earthquake and Tsunami, fears of a nuclear meltdown has been raised at Fukushima I nuclear power plant in Japan. The fear has been raised after the diesel generators to supply back-up power to three units of the plant has been damaged by the Tsunami.
A nuclear meltdown is a term used to describe an accident causing severe damage to the core of a nuclear power plant resulting from overheating. When the core is not properly cooled, the nuclear fuel assemblies can heat and 'melt'. This causes severe repercussions as radioactive material will be liberated to the environment in dangerous quantities. Also, the nuclear plant will not be reusable unless it is repaired, and it is also a difficult, costly process.
Nuclear meltdown has occurred several times in history, most notable incidents being the 'Three Mile Island' incident and the more notorious Chernobyl disaster. In Chernobyl, the damage would have become much more severe if all radioactive material was liberated.
Four reactors automatically shut down following the earthquake in Japan. After the damage of the generator at Fukushima I, warnings were issued to the residents of the area to evacuate. The 10km limit evacuation radius was later extended to 20 km from the plant which is 240 km North of Tokyo.
At 07:30 GMT, (4.30 p.m. local time) an explosion occurred in the plant. Although an alleged leak in radioactive material was reported but disputed by the government. The Chief Cabinet Secretary Yukio Edano declared that "The nuclear reaction facility is surrounded by a steel storage machine, which is then surrounded by a concrete building. This concrete building collapsed. We learnt that the storage machine inside did not explode" according to Reuters.
However, people are evacuating, fearing the worst. Only time will tell if more damage would occur.