Japanese military helicopters dumped seawater onto a stricken nuclear reactor today, trying to avoid full meltdowns as plant operators said they were close to finishing a new power line that could restore cooling systems and ease the crisis.
U.S. officials in Washington, meanwhile, warned that the Fukushima Dai-ichi plant in northeastern Japan may be on the verge of spewing more radioactive material because water was gone from a storage pool for spent nuclear fuel rods.
The troubles at several of the plant's reactors were set off when last week's earthquake and tsunami knocked out power and ruined backup generators needed for their cooling systems, creating a major nuclear crisis for Japan as it dealt with twin natural disasters that killed more than 10,000 people and left hundreds of thousands homeless.
A Japanese military CH-47 Chinook helicopter began dumping seawater on the damaged reactor of Unit 3 at the Fukushima complex at 9:48 a.m., said Defense Ministry spokeswoman Kazumi Toyama. The aircraft dumped at least four loads on the reactor, though much of the water appeared to be dispersed in the air.
The dumping was intended both to help cool the reactor and to replenish water in a pool holding spent fuel rods, Toyama said. The plant's owner, Tokyo Electric Power Co., said earlier that the pool was nearly empty, which might cause the rods to overheat.
Comments from U.S. officials indicated there were similar problems at another unit of the Fukushima complex.
U.S. Nuclear Regulatory Commission Chairman Gregory Jaczko said at a congressional hearing in Washington that all the water was gone from a separate spent fuel pool at the plant's Unit 4. Japanese officials expressed similar worries about that unit, but said it was impossible to be sure of its status.
If Jaczko is correct, it would mean there is nothing to stop the used fuel rods from getting hotter and ultimately melting down. The outer shells of the rods could also ignite with enough force to propel the radioactive fuel inside over a wide area.
"My understanding is there is no water in the spent fuel pool," Jaczko said after the hearing. "I hope my information is wrong. It's a terrible tragedy for Japan."
He said the information was coming from Nuclear Regulatory Commission staff in Tokyo who are working with the utility in Japan. He said the staffers continue to believe the spent fuel pool is dry.
Emergency workers, who had been manually pumping seawater into the overheated reactors, were forced to retreat from the plant Wednesday when radiation levels soared, losing precious time. They resumed work after radiation levels dropped, but much of the monitoring equipment in the plant is inoperable, complicating efforts to assess the situation.
"We are afraid that the water level at Unit 4 is the lowest," said Hikaru Kuroda, facilities management official at Tokyo Electric. But he added, "Because we cannot get near it, the only way to monitor the situation is visually from far away."
Japanese officials raised hopes of easing the crisis, saying early today that they may be close to bringing power back to the plant and restoring the reactors' cooling systems.
The new power line would revive electric-powered pumps, allowing the company to control the rising temperatures and pressure that have led to at least partial meltdowns in three reactors. The company is also trying to repair its existing disabled power line.
As fear, confusion and unanswered questions swirled around the Fukushima Dai-ichi complex, and Japan suffered other trials from last week's earthquake and tsunami, its emperor took the unprecedented step of directly addressing his country on camera, urging his people not to give up. "It is important that each of us shares the difficult days that lie ahead," Akihito said Wednesday. "I pray that we will all take care of each other and overcome this tragedy."
The emperor, 77, expressed deep concern about the "unpredictable" nuclear crisis. "With the help of those involved I hope things will not get worse," he said.
Other countries have complained that Japan has been too slow and vague in releasing details about its rapidly evolving crisis at the complex of six reactors along the northeastern coast, which was ravaged by Friday's magnitude-9.0 earthquake and subsequent tsunami.
The chief of the U.N. nuclear agency, Yukiya Amano, said he would go to Japan to assess what he called a "very serious" situation and urged Tokyo to provide better information to his organization.
Several countries have advised their citizens to consider leaving Tokyo and earthquake-affected areas. The White House recommended Wednesday that U.S. citizens stay 50 miles away from the Fukushima plant, not the 20-mile radius recommended by the Japanese government.
Late Wednesday, government officials said they asked special police units to bring in water cannons to spray water onto the spent-fuel storage pool at Unit 4. The cannons are thought to be strong enough to allow emergency workers to remain a safe distance from the complex, said Minoru Ogoda of Japan's nuclear safety agency.
Units 1, 2 and 3 of Fukushima Dai-ichi have all been rocked by explosions, and officials have acknowledged that their cores have begun to melt down. Compounding the problems, a fire broke out Tuesday and Wednesday in the Unit 4 fuel storage pond, causing radioactivity to be released into the atmosphere. Temperatures also have been rising in Units 5 and 6.
White smoke was seen rising Wednesday above Unit 3, but officials could not ascertain the source.
The nuclear crisis has partly overshadowed the human tragedy caused by Friday's massive earthquake, one of the strongest ever recorded.
Millions of Japanese have been with little food and water in heavy snow and rain. In some towns, lines of cars waited outside the few open gas stations, while others lined up at rice-vending machines.
More than 4,300 people are officially listed as dead, but officials believe the toll will climb to well over 10,000. Police say more than 452,000 people are staying in temporary shelters such as school gyms.
"The anxiety and anger being felt by people in Fukushima have reached a boiling point," the governor of Fukushima prefecture, Yuhei Sato, fumed in an interview with NHK. He criticized preparations for an evacuation if conditions worsen. He said centers do not have enough hot meals and basic necessities.
In the city of Fukushima, about 40 miles inland from the nuclear complex, hundreds of harried government workers, police officers and others struggled to stay on top of the situation in a makeshift command center.