Building Housing Japan Nuclear Reactor Explodes

An explosion at a nuclear power station today destroyed a building housing the reactor amid fears that it was close to a disastrous meltdown after being hit by a powerful earthquake and tsunami. Footage on Japanese TV showed that the walls of the reactor's building had crumbled, leaving only a skeletal metal frame standing. Puffs of smoke were spewing out of the plant in Fukushima, 20 miles from Iwaki.

Adding to worries was the fate of nuclear power plants. Japan has declared states of emergency for five nuclear reactors at two power plants after the units lost cooling ability. The most troubled one, Fukushima Dai-ichi, is facing meltdown, officials have said. A "meltdown" is not a technical term. Rather, it is an informal way of referring to a very serious collapse of a power plant's systems and its ability to manage temperatures. It is not immediately clear if a meltdown would cause serious radiation risk, and if it did how far the risk would extend. "It's not a fast reaction like at Chernobyl," says a nuclear expert. "I think that everything will be contained within the grounds, and there will be no big catastrophe." (More 9.0 earthquake stories.)