The Japanese military is using high-pressure fire hoses to spray water on earthquake-damaged nuclear reactors in a desperate attempt to cool down dangerously-hot fuel rods, as it acknowledges that time is running out.
Earlier Thursday, the government used aerial water drops -- after aborting the plan a day earlier because of radiation danger to the helicopter pilots.
Defense Minister Toshimi Kitazawa said the government had decided it "could not delay the mission any further." But televised pictures showed much of the water being blown away from the target and the effort was suspended after four attempts.
High radiation levels around the plant 240 kilometers north of Tokyo are making it impossible for workers to stay at the facility for more than a few minutes at a time, and initial radiation readings suggest the first helicopter drops had little effect.
Officials said Thursday they soon hope to restore electricity to the plant, raising hopes that more efficient pumps can be deployed to apply water to the fuel rods at the crippled plant's six nuclear reactors.
US advises citizens to leave
The United States and other governments have advised their nationals to stay at least 80 kilometers from the plant -- a radius much larger than the Japanese exclusion zone -- and many governments are evacuating staff from embassies in Tokyo.
U.S. President Barack Obama telephoned Prime Minister Naoto Kan early Thursday in Tokyo to express his admiration for the courage of the Japanese people and renew his offer of assistance, including with the nuclear crisis.
The call came hours after nuclear power officials in Washington said they believe all water has dried up in the cooling tank at Fukushima's number 4 reactor, leaving the fuel rods exposed to the air. If the rods become hot enough, they can melt or burn through their outer casing, releasing high levels of radiation into the air.
Japanese nuclear officials said Thursday they could not confirm those remarks, made by U.S. Nuclear Regulatory Commission Chairman Gregory Jaczko. But they said water levels in the cooling tank at unit 3 are dangerously low.
The prime minister's office Thursday called on citizens to save electricity as it warned of a "massive power outage" in the area served by the Tokyo Electric Power Company.
What caused damage
Normal cooling systems for the plant were destroyed by last week's earthquake and tsunami, which knocked out electricity to the plant and damaged emergency backup generators.
Officials say they are close to having electricity restored, but chief government spokesman Yukio Edano warned that even then, much of the original pumping equipment has been damaged by seawater and will have to be replaced.
Three of the plant's six reactors were operating when the quake struck, while three others were shut down for maintenance. All three of the reactors that were operating have since suffered explosions that destroyed their outer housing. Officials believe that at two of the units, the explosions also ruptured the inner containment chambers which protect against radiation leaks.
Focus on cooling tanks
But current concerns are focused on cooling tanks at all six reactors where used fuel rods are stored. For months, these remain hot enough to catch fire and release lethal radiation unless they can be kept under sufficient amounts of water.
Japan has evacuated more than 200,000 people from a 20-kilometer radius around the plant and advised anyone within 30 kilometers to remain indoors. Many are huddled in makeshift facilities amid frigid temperatures and scarce food supplies.
In his phone call to Kan, Obama said the United States "is determined to do everything possible to support Japan in overcoming the effects" of last week's earthquake and tsunami.
He expressed his extraordinary admiration for the character and resolve of the Japanese people" and discussed U.S. assistance including "military assets with expertise in nuclear response and consequence management."