Wednesday, March 16, 2011

What Happens During A Nuclear Meltdown?

By James Matson
Scientific American
March 15, 2011

Nuclear reactors at the Fukushima Daiichi station in Japan are critically endangered but have not reached full meltdown status. Our nuclear primer explains what that means and how the situation compares with past nuclear accidents

How does a nuclear reactor work?
Most nuclear reactors, including those at Japan's Fukushima Daiichi generating station, are essentially high-tech kettles that efficiently boil water to produce electricity. They rely on harnessing nuclear fission—the splitting of an atom into two smaller atoms, which also yields heat and sends neutrons flying. If another atom absorbs one of those neutrons, the atom becomes unstable and undergoes fission itself, releasing more heat and more neutrons. The chain reaction becomes self-sustaining, producing a steady supply of heat to boil water, drive steam turbines and thereby generate electricity.

How much electricity does nuclear power provide in Japan and elsewhere?
With 54 nuclear reactors generating 280 billion kilowatt-hours annually, Japan is the world's third-largest producer of nuclear power, after the U.S. and France, according to data from the International Atomic Energy Agency. The Fukushima Daiichi station, which has been hit hard by the March 11 earthquake, houses six of those reactors, all of which came online in the 1970s.

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