Meltdown! Meltdown! What is Meltdown?

The core of the Japanese nuclear power stations might melt down, which scares the hell out of everyone who saw the movie "The China Syndrome". Fortunately, The China Syndrome was fiction. It was also anti-nuke propaganda. A core meltdown is bad for the electric utility, because it means an expensive loss of equipment, as well as laborious cleanup of the containment vessel(s). But it doesn't mean widespread catastrophe. If you actually want to understand nuclear reactor design, you should read this.

The journalists have their agenda, and far too few are interested in learning the truth. The short explanation for the rest of you is this: The nuclear chain reaction was shut down immediately after the earthquake. But the radioactive decay of reactor by-products continue to produce heat for some time, and that requires coolant. Newer designs do not require active cooling, by the way. The earthquake destroyed the power grid, so the power for the coolant pumps had to be supplied by auxiliary diesel generators. The diesel generators were destroyed by the tsunami, so the pumps ran on batteries while operators waited for replacement generators to arrive. Unfortunately, the replacement generators were not compatible with the cooling pumps. When the batteries were exhausted, the cooling to the reactor was lost, and the reactor gradually reached the melting point. The plant was designed for this eventuality, so no China Syndrome will occur. What radioactive elements are released into the atmosphere are light elements -- hydrogen, oxygen, nitrogen, etc., with half-life measured in seconds. They will decay back to their normal state almost immediately.