Q&A: What caused the blast at nuclear plant in Japan, and why do officials fear a meltdown?
The cause of the explosion isn't yet clear, but the nuclear plant has lost the ability to cool its hot uranium fuel. The containment vessel hasn't been breached but officials fear a core meltdown. An untested method to cool the core before that happens is planned.An explosion overnight destroyed the building housing one of the nuclear reactors at Tokyo Electric Power Co.'s Fukushima No. 1 facility about 160 miles north of Tokyo, where authorities have been struggling to bring the reactor under control following the loss of backup power for the cooling system. Officials fear a meltdown of the reactor core at the plant, also known as Fukushima Daiichi, which could result in the release of large quantities of radioactivity into the environment.