WASHINGTON (Reuters) - The United States is ramping up assistance to help Japan avert a major nuclear meltdown, U.S. officials said on Monday, as Washington wrestled with the risks of radiation exposure to aid workers.
The Japanese government has asked for more equipment to cool down three reactors damaged by last week's massive earthquake and tsunami, which triggered the worst nuclear crisis since the Chernobyl disaster in Ukraine in 1986.
The Fukushima complex, 240 km (150 miles) north of Tokyo, is trying to avoid a major radiation leak. Explosions at two reactors on Saturday and Monday sent a huge plume of smoke billowing above the plant.
"We continue to provide assistance where we can," Gregory Jaczko, head of the U.S. Nuclear Regulatory Commission, said at a White House press briefing.
"In particular, they have asked for additional types of equipment that will help provide water and other resources to ensure that the reactors continue to be cool."
The commission has already sent two experts to Japan, and Jaczko said it plans to send out another team of experts soon.
The nuclear crisis has posed some risk for workers attempting to battle the crisis. The Pentagon was trying to take precautions while moving ahead with relief efforts.
It was forced to reposition eight U.S. warships, including the aircraft carrier USS Ronald Reagan, after they got caught 115 miles downwind of the Fukushima nuclear complex.
Seventeen Americans on helicopter missions were exposed to the equivalent of a month's worth of normal radiation, even though they were 60 miles away from the nuclear plant.
"The immediate action was to get out of the area," said Commander Jeff Davis, a spokesman for the Seventh Fleet.
Asked about what steps the military was taking to avoid any more exposure, Davis said: "We're keeping a very close eye on which way the wind is moving."
He said the radiation risk would not stop rescue efforts.
"It's something we have to take into account -- it complicates things. But it's absolutely something we can mitigate," Davis said.
The ships in the area were the USS Ronald Reagan carrier strike group, which includes the cruiser USS Chancellorsville, the destroyer USS Preble and the combat support ship USNS Bridge.
The guided-missile destroyers USS John S. McCain and USS Fitzgerald, the destroyers USS McCampbell and USS Curtis Wilbur were also downwind of the plant on Sunday.
Jaczko said there was little threat of radiation spreading across the Pacific to U.S. territories.
"We see a very low likelihood...that there's any possibility of harmful radiation levels in the United States or in Hawaii or any other U.S. territories," Jaczko said.