What Happens During a Nuclear Meltdown?

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.

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What Happens During a Nuclear Meltdown?