By Yoko Kubota and Taiga Uranaka
TOKYO (Reuters) - Japanese authorities evacuated workers on Sunday from a reactor building they were working in after high doses of radiation were detected at a crippled nuclear power plant, the plant's operator said.
Tokyo Electric Power Co said radiation 10 million times the usual level was detected in water that had accumulated at the No. 2 reactor's turbine housing unit.
A Tokyo Electric official said workers left the No. 2 reactor's turbine housing unit to prevent exposure to radiation.
They had been struggling to pump radioactive water out of the nuclear power station, battered by a huge earthquake and a tsunami just over two weeks ago, after it was found in buildings housing three of the six reactors.
On Thursday, three workers were taken to hospital from reactor No. 3 after stepping in water with radiation levels 10,000 times higher than usually found in a reactor. But it was not immediately clear if the numbers were comparable with Sunday's reading at reactor No. 2.
However, it was yet another indication that the crisis at the plant was far from over, a point the world's chief nuclear inspector underlined at the weekend.
Yukiya Amano, the director general of the International Atomic Energy Agency (IAEA), cautioned that Japan's nuclear emergency could go on for weeks, if not months more.
"This is a very serious accident by all standards," he told the New York Times. "And it is not yet over."
Radiation levels in the sea off the Fukushima Daiichi plant rose on Sunday to 1,850 times normal just over two weeks after the disaster struck, from 1,250 on Saturday, Japan's Nuclear and Industrial Safety Agency said.
"Ocean currents will disperse radiation particles and so it will be very diluted by the time it gets consumed by fish and seaweed," said Hidehiko Nishiyama, a senior agency official.
The crisis at the plant, 240 km (150 miles) north of Tokyo, has overshadowed a relief and recovery effort from the magnitude 9.0 quake and the huge tsunami it triggered on March 11 that left more than 27,100 people dead or missing in northeast Japan.
Amano, a former Japanese diplomat who made a trip to Japan after the quake, said authorities were still unsure about whether the plant's reactor cores and spent fuel were covered with the water needed to cool them.
He told the newspaper he saw a few "positive signs" with the restoration of some electric power to the plant.
But he said: "More efforts should be done to put an end to the accident," while adding he was not criticizing Japan's response.
The IAEA, the U.N. nuclear watchdog, said it had sent two additional teams to Japan over the past two days, one to help in monitoring radiation and one to assess food contamination.
The Japanese government estimated last week the material damage from the March 11 catastrophe could top $300 billion, making it the world's costliest natural disaster.
In addition, power cuts have disrupted production while the drawn-out battle to prevent a meltdown at the 40-year-old plant has hurt consumer confidence and spread contamination fears well beyond Japan.
U.N. Secretary-General Ban Ki-moon said it was time to reassess the international atomic safety regime.
Japan's nuclear crisis also looks set to claim its first, and unlikely, political casualty. In far away Germany, Chancellor Angela Merkel's party faces a defeat in a key state on Sunday, largely because of her policy U-turns on nuclear power.
A Tokyo Electric official told a news conference on Saturday experts were still trying to figure out where to put the contaminated water they're trying to pump out of the reactors.
Two of the plant's reactors are now seen as safe but the other four are volatile, occasionally emitting steam and smoke.
The government has said the situation is nowhere near to being resolved, although it was not deteriorating.
"We are preventing the situation from worsening -- we've restored power and pumped in fresh water -- and making basic steps toward improvement but there is still no room for complacency," Chief Cabinet Secretary Yukio Edano told a news conference on Saturday.
At Chernobyl in Ukraine, the worst nuclear accident in the world, it took weeks to "stabilize" what remained of the reactor that exploded and months to clean up radioactive materials and cover the site with a concrete and steel sarcophagus.
So far, no significant levels of radiation have been detected beyond the vicinity of the plant in Fukushima.
The U.S. Department of Energy said on its website (http://blog.energy.gov/content/situation-japan/)
no significant quantities of radiological material had been deposited in the area around the plant since March 19, according to tests on Friday.
In Tokyo, a metropolis of 13 million, a Reuters reading on Sunday morning showed ambient radiation of 0.22 microsieverts per hour, about six times normal for the city. That was well within the global average of naturally occurring background radiation of 0.17-0.39 microsieverts per hour, a range given by the World Nuclear Association.
In Japan's northeast, more than a quarter of a million people remain in shelters, and the impact on livelihoods is becoming clearer. The quake and tsunami not only wiped out homes and businesses, but also a fishing industry that was the lifeblood of coastal communities.
"Fishermen lost their gear, ships and just about everything. About half will probably get out of the business," said Yuko Sasaki, a fishmonger in the tsunami-hit city of Kamaishi.
(Additional reporting by Kiyoshi Takenaka, Chizu Nomiyama, Shinichi Saoshiro and Phil Smith in Tokyo, Jon Herskovitz in Kamaishi, Editing by Bill Tarrant and Raju Gopalakrishnan)