This New York Times interactive animation shows what happens in a boiling-water reactor (such as Japan's failed Fukushima reactor) when water levels in the cooling pools drop near the level of the radioactive fuel rods.

This NPR article summarizes the findings of a 2011 U.S. Nuclear Regulatory Commission report on nuclear power plant safety. The conclusions: American power plants need changes to prevent a recurrence of the accident that destroyed Japan's Fukushima plant.