ZAO, Japan — Japan deployed military helicopters, high-pressure water cannons and fire trucks in an increasingly desperate attempt to cool an overheated nuclear complex as U.S. officials warned the situation was deteriorating.
While the choppers flew combat-style missions to dump batch after batch of seawater onto a stricken reactor, plant operators said they were close to finishing a new power line that could restore cooling systems and ease the crisis at the Fukushima Dai-ichi complex on the country's northeast coast.
The top U.S. nuclear regulatory official gave a far bleaker assessment of the crisis than the Japanese, and the U.S. ambassador warned U.S. citizens within 50 miles (80 kilometers) of the complex to leave the area or at least remain indoors.
The Japanese government said it had no plans to expand its mandatory, 12-mile (20-kilometer) exclusion zone around the plant, while also urging people within 20 miles (30 kilometers) to stay inside.
The troubles at the nuclear complex were set in motion last week's 9.0-magnitude earthquake and tsunami knocked out power and destroyed backup generators needed for the reactors' cooling systems. That added a nuclear crisis on top of twin natural disasters that likely killed well more than 10,000 people and left hundreds of thousands homeless.
Four of the plant's six reactors have faced serious crises involving fires, explosions, damage to the structures housing reactor cores, partial meltdowns or rising temperatures in the pools used to store spent nuclear fuel. Officials also recently announced that temperatures are rising in the spent fuel pools of the last two reactors.
Two Japanese military CH-47 Chinook helicopters began dumping seawater on the complex's damaged Unit 3 at 9:48 a.m. (0048 GMT, 8:48 p.m. EDT), defense ministry spokeswoman Kazumi Toyama said. The choppers dumped at least four loads on the reactor in just the first 10 minutes, though television footage showed much of it appearing to disperse in the wind.