Radiation levels spiked at the stricken Fukushima Dai-ichi nuclear power complex for the second day in a row. Emergency workers were ordered to pull back to a safe distance while continuing their efforts to cool the plant's overheating reactors. Officials say the levels do not pose a threat to the public outside the plant.
Japan's NHK Television showed video of military helicopters preparing to dump water from buckets onto the overheating reactors, but NHK said that plan was aborted because the helicopter crews were being exposed to unacceptably high radiation levels. Water is desperately needed at the plant's reactors to cool them down and to block radiation from some spent fuel rods sitting in pools that are rapidly evaporating.
Chief Cabinet Secretary Yukio Edano said workers on the ground 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 nuclear complex. "Because of the radiation risk we are on standby."
As evening fell in Japan, radiation levels dropped again, so crews on the ground are preparing to go back inside and tackle multiple problems at the plant. An official with Tokyo Electric Power, which operates the plant, said the team had withdrawn about 500 yards from the complex, but were getting ready to go back in.
A core team of about 180 had been regularly rotated in and out of the danger zone to minimize their radiation exposure.
The spike in radiation Wednesday was apparently the result of a release of pressure that had built up in the complex's No. 2 reactor, officials said. Steam and pressure build up in the reactors as workers try to cool the fuel rods, leading to controlled pressure releases through vents — as well as uncontrolled explosions.
An explosion also destroyed part of the building surrounding the No. 4 reactor.
There are six reactors at the plant. No. 1, No. 2 and No. 3 were operating last week and 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.
The No. 4, No. 5 and No. 6 reactors 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.
The Nuclear and Industrial Safety Agency estimated that 70 percent of the rods have been damaged at the No. 1 reactor. The explosions can cause radiation to escape into the atmosphere, but fuel rods themselves cannot trigger a large scale nuclear explosion.
The government has ordered anyone within 20 kilometers (12 miles) of the nuclear complex to evacuate and those within 30 kilometers (about 19 miles) to stay indoors. A small amount of radiation was also detected in Tokyo, triggering some panic buying of food and water.
