If spent fuel rods catch fire from lack of coolant, the intense heat will lift radiation plumes high into the atmosphere that will drift around the world. That's the nightmare scenario, clouds of radioactive material showering the planet with lethal toxins for months on end. And, according to the Central Institute for Meteorology and Geodynamics of Vienna, that deadly process has already begun. The group told New Scientist that:
"Japan's damaged nuclear plant in Fukushima has been emitting radioactive iodine and caesium at levels approaching those seen in the aftermath of the Chernobyl accident in 1986. Austrian researchers have used a worldwide network of radiation detectors - designed to spot clandestine nuclear bomb tests - to show that iodine-131 is being released at daily levels 73 per cent of those seen after the 1986 disaster. The daily amount of caesium-137 released from Fukushima Daiichi is around 60 per cent of the amount released from Chernobyl. (New Scientist, March 24 ---thanks to Michael Collins "They said it wasn't like Chernobyl and they were wrong")