The United States on Thursday began evacuating Americans from Japan amid fears that four tsunami-damaged nuclear reactors may be closer to a core meltdown.
The State Department said that it had arranged charter flights to South Korea and Taiwan for family members of embassy staff and other U.S. government personnel living in three major Japanese cities, Tokyo, Nagoya and Yokohama.
Any American in Japan can take advantage of the U.S. flights, the State Department said, but private citizens would be expected to reimburse the government for the expense.
The U.S. Navy said it, too, would begin evacuating families of sailors stationed at two bases near Tokyo, Yokosuka Naval Base and Naval Air Facility Atsugi, starting Thursday night or this morning. In northern Japan, the commander of Misawa Air Base said it also would evacuate family members.
The announcement of evacuations from the Tokyo area, 140 miles south of the damaged Fukushima Dai-ichi power plant, heightened tension among foreigners in the Japanese capital and on the country's U.S. military bases, home to more than 38,000 active duty troops and 43,000 family members.
Anxiety had been steadily rising in recent days as the extent of the reactors' problems became known, and conversation among Americans has focused on possible changes in wind direction that would blow more radioactive debris toward Tokyo, Yokohama and Nagoya.
Wednesday, the U.S. Embassy, acting on advice from the Nuclear Regulatory Commission in the United States, recommended that anyone living within 50 miles of the damaged reactors should leave, if possible. That's four times the size of the 12-mile evacuation zone Japan has ordered.
Meanwhile, emergency workers seemed to try everything they could think of Thursday to douse Japan's most dangerously overheated nuclear reactors: helicopters, heavy-duty fire trucks, even water cannons normally used to quell rioters. But they couldn't be sure any of it was easing the peril at the tsunami-ravaged facility.
Three reactors have had at least partial meltdowns at the Fukushima Dai-ichi plant, where wisps of white steam rose from the stricken units Friday morning. But Japanese and U.S. officials believe a greater danger exists in the pools used to store spent nuclear fuel: Fuel rods in one pool were believed to be at least partially exposed, if not dry, and others were in danger. Without water, the rods could heat up and spew radiation.
It could take days and "possibly weeks" to get the complex under control, U.S. Nuclear Regulatory Commission Chairman Gregory Jazcko said. He defended the U.S. decision to recommend a 50-mile evacuation zone for its citizens, a much stronger measure than Japan has taken.
A senior official with the U.N.'s nuclear safety agency said there had been "no significant worsening" at the Fukushima Dai-ichi nuclear plant but that the situation remained "very serious." Graham Andrew told reporters in Vienna that nuclear fuel rods in two reactors were only about half covered with water, and they were also not completely submerged in a third.
If the fuel is not fully covered, rising temperatures will increase the chances of complete meltdowns that would release much larger amounts of radioactive material than the failing plant has emitted so far.
Low levels of radiation have been detected well beyond Tokyo, which is 140 miles south of the plant, but hazardous levels have been limited to the plant itself. Still, the crisis triggered by last week's earthquake and tsunami has forced thousands to evacuate and drained Tokyo's normally vibrant streets of life, its residents either leaving town or holing up in their homes.
The official death toll from the disasters stood at 5,692 as of Friday morning, with 9,522 missing, the national police agency said.
President Obama appeared on television to assure Americans that officials do not expect harmful amounts of radiation to reach the United States or its territories. He also said the United States was offering Japan any help it could provide. He reaffirmed America's commitment to nuclear power and said he had asked the Nuclear Regulatory Commission to conduct a "comprehensive review" of the safety of all U.S. nuclear plants.
"When we see a crisis like the one in Japan, we have a responsibility to learn from this event and to draw from those lessons to ensure the safety and security of our people," Obama said.
There are 104 nuclear reactors in the United States, providing roughly 20 percent of the nation's electricity. "Nuclear energy is an important part of our own energy future," Obama said.
At a visit to the Japanese Embassy, Obama signed a condolence book and said: "We feel a great urgency to provide assistance to those who are suffering."
Japanese and American assessments of the crisis have differed, with the plant's owner denying Jazcko's report Wednesday that Unit 4's spent fuel pool was dry and that anyone who gets close to the plant could face potentially lethal doses of radiation. But a Tokyo Electric Power Co. executive moved closer to the U.S. position Thursday.
"Considering the amount of radiation released in the area, the fuel rods are more likely to be exposed than to be covered," Yuichi Sato said.
Another utility official said Wednesday that the company has been unable to get information such as water levels and temperatures from any of the spent fuel pools in the four most troubled reactors.
Tokyo Electric Power said it believed workers were making headway in staving off a catastrophe both with the spraying and, especially, with efforts to complete an emergency power line to restart the plant's own electric cooling systems.
Work on connecting the new power line to the plant was expected to begin today and take 10 to 15 hours, said nuclear safety agency spokesman Minoru Ohgoda.