"They are up against a wall ... this is not just one Three Mile Island. It's effectively four," Sharon Squassoni, an expert on nuclear issues at the Center for Strategic and International Studies, told CBS' "The Early Show."
Since the last week's 9.0-magnitude earthquake and subsequent tsunami hit, authorities have been struggling to avert an environmental catastrophe at the Fukushima Dai-ichi complex, 140 miles north of Tokyo. The tsunami knocked out the backup diesel generators needed to keep nuclear fuel cool, setting off the atomic crisis.
There are six reactors at the plant. Units 1, 2 and 3, which were operating last week, shut down automatically when the quake hit. Since then, all three have been rocked by explosions. Compounding the problems, on Tuesday a fire broke out in Unit 4's fuel storage pond, an area where used nuclear fuel is kept cool, causing radioactivity to be released into the atmosphere.
Units 4, 5 and 6 were shut at the time of the quake, but even offline reactors have nuclear fuel -- either inside the reactors or in storage ponds -- that need to be kept cool.
On Wednesday, Japan ordered emergency workers to withdraw from the nuclear complex amid a surge in radiation, temporarily suspending efforts to cool the overheating reactors. Hours later, officials said they were preparing to send the team back in.
But details of the situation were murky. Chief Cabinet Secretary Yukio Edano said the workers, who had been dousing the reactors with seawater in a frantic effort to stabilize their temperatures, had no choice but to pull back from the most dangerous areas.
"The workers cannot carry out even minimal work at the plant now," he said Wednesday morning, as smoke billowed above the crippled Fukushima Dai-ichi nuclear complex. "Because of the