Risk of Meltdown Grows at Damaged Nuclear Reactors

Wire services are scrambling to assess the danger surrounding Japan's damaged nuclear reactors, but this much is clear: At least two are in serious trouble, and officials were taking extraordinary measures to avert full-blown meltdowns. Phrases like "possible partial meltdown" (from AP) and "assuming the possibility of a meltdown" (CNN) are showing up in stories following a news conference by a government official, but interpretations of the risk vary widely.

The reactors posing the most trouble are units 1 and 3 at the same plant in northern Japan called Fukushima Dai-icha. Their cooling systems have failed, and authorities have taken steps such as pumping in seawater and venting radioactive vapor into the atmosphere. At unit 3, fuel rods were briefly exposed, which the New York Times describes as a "dangerous state that could lead to meltdown." About 200,000 people have now been evacuated from the area, though government officials say the public has not been exposed to dangerous amounts of radioactivity. Making matters worse, trouble is brewing at three reactors at a separate plant nearby. (More Japan stories.)