Japan ordered emergency workers to withdraw from its stricken nuclear power complex Wednesday amid a surge in radiation, temporarily suspending efforts to cool overheating reactors.
Chief Cabinet Secretary Yukio Edano said the workers dousing the reactors in an effort to cool them needed to withdraw.
"The workers cannot carry out even minimal work at the plant now," Mr. Edano said. "Because of the radiation risk we are on standby."
Radiation levels had gone down by later Wednesday, but it was not immediately clear if the workers had been allowed back in.
A new fire was blazing at the Fukushima nuclear plant as dawn broke Wednesday, a grim beginning to another day in Japan's escalating nuclear crisis.
The outer housing of the containment vessel at the No. 4 unit at the Fukushima Daiichi nuclear complex erupted in flames, said a spokesman for plant operator Tokyo Electric Power Co. The new fire came just hours after another blaze at the same reactor had been extinguished in what was a rare and needed victory for those desperately trying to bring the situation at Fukushima back under control.
The four reactors at Fukushima Daiichi have now been collectively hit by four explosions and two fires since a magnitude-9.0 earthquake on Friday shook the region 260 kilometres northeast of Tokyo.
On Tuesday, the government ordered 140,000 people in the Fukushima region to seal themselves indoors.
Japan's nuclear safety agency said 70 per cent of the nuclear fuel rods may have been damaged at Fukushima Reactor No. 1, which suffered an explosion Saturday, triggering the crisis. The Kyodo news agency said 33 per cent of the fuel rods at Reactor No. 2, which was hit by an explosion on Tuesday, have also been damaged. The reactors' cores are believed to have partly melted after the cooling mechanisms shut down.
"The possibility of further radioactive leakage is heightening," Prime Minister Naoto Kan said in a televised news conference before the latest fire. "We are making every effort to prevent the leak from spreading. I know that people are very worried but I would like to ask you to act calmly."
Earlier, officials said about 70 workers were remaining at the Fukushima complex, struggling with its myriad problems. Clad in protective gear, they worked in shifts to reduce their radiation exposure.
Tokyo Electric Power Co. has already evacuated 800 staff. Fifteen workers have been injured, and up to 190 have been exposed to elevated radiation during the battle to keep Fukushima from complete meltdown. Fourteen pumps are being used to bring seawater into the failing reactors to compensate for cooling systems that have been failing since a power outage caused by Friday's earthquake and tsunami.
The country now faces the prospect of large-scale evacuations, depending on how fast workers can cool the partly exposed reactor cores - and which way the wind blows over the coming days. Some 200,000 people have already been evacuated from a 20-kilometre radius around the plant.
A 30-km no-fly zone is also being enforced around the plant to prevent planes from spreading the radiation further.
The next concern is Tokyo and its metropolitan population of 39 million. Radiation levels 10 times normal were detected in the city Tuesday, not yet high enough to pose a threat to human health, the city government said.
France has advised its citizens to leave the Japanese capital, while Canada and the United States have warned against unnecessary travel to Tokyo and the Fukushima region. Citing radiation concerns, Austria moved its embassy from Tokyo to Osaka, further to the south and away from Fukushima.
Though the streets remained calm and orderly - even as people waited hours for food and fuel - many foreign tourists and residents packed the airports looking for a flight out of the country.
The French Nuclear Safety Authority said on Tuesday that the accident at Fukushima now ranked a 6 on an international scale of 1 to 7. That would make the disaster already worse than the 1979 radiation leak at Three Mile Island in Pennsylvania, which ranked a 5 and saw a reactor meltdown but no breach of the steel containment shell.
The only 7 ever assessed was the 1986 disaster at the Chernobyl nuclear plant in northern Ukraine, which saw far more radioactive material released into the atmosphere because there was no containment shell.
Most experts say it's improbable Fukushima will get as bad as Chernobyl because Fukushima automatically shut down after the earthquake, removing the worst-case scenario of a chain reaction at the reactors.
Nonetheless, the unfolding nuclear drama is seen as so dangerous that it has pushed onto the back pages - even in Japan -news of the country's efforts to recover the dead and discover the fates of the tens of thousands of people still missing. The death toll is expected to go well past 10,000 and more than 500,000 people have been made homeless.
The country has been hit by some 200 aftershocks, including three sizable tremors late Tuesday that shook buildings in both Tokyo and Morioka, some 550 kilometres to the north.
The earthquake, tsunami and nuclear crises have badly hurt Japan's economy, which was already struggling to pull out of a long period of stagnation. The benchmark Nikkei 225 stock average plunged for a second day Tuesday, dropping more than 10 per cent while the broader Topix lost more than 8 per cent. The Nikkei, however, rebounded at the opening of trading on Wednesday.
Initial estimates put the costs of rebuilding at tens of billions of dollars. That kind of public spending would add to an already massive public debt. At 200 per cent of gross domestic product, Japan's debt is already the biggest among industrialized nations.
- With a report from the Associated Press
State of disaster
Fukushima Daiichi reactors:
No. 1: Cooling failure, partial melting of core, vapour vented, hydrogen explosion, seawater pumped in.
No. 2: Cooling failure, seawater pumped in, fuel rods fully exposed temporarily, vapour vented, damage to containment system, potential meltdown feared.
No. 3: Cooling failure, partial melting of core feared, vapour vented, seawater pumped in, hydrogen explosion, high-level radiation measured nearby.
No. 4: Under maintenance when quake struck, fire caused possibly by hydrogen explosion at pool holding spent fuel rods, pool water level feared receding.
No. 5 & 6: Under maintenance when quake struck, temperature slightly rising at spent fuel pools.
Levels in areas around nuclear plant, which rose early Tuesday afternoon to harmful levels, appeared to subside by evening. Elevated levels were measured in Tokyo, but were not high enough to cause damage.
Japanese: People within 20 kilometres of troubled reactors told to leave; those between 20 and 30 kilometres told to stay indoors.
Foreigners: Several foreign countries and companies are organizing travel for their workers and citizens out of Japan.
Disaster relief: Those trying to deal with the dead and provide for the living are struggling with shortages of body bags, coffins, food and fuel for vehicles.
Human toll: There were 3,373 confirmed dead as of Tuesday, with 1,897 injured and 6,746 missing, but those numbers are expected to rise considerably.
Aftershocks: Some of the strongest since the initial 9.0 magnitude quake came Tuesday, with at least two over 6.0.
Sources: AP, AFP, Reuters