TOKYO — Workers in Japan pressed their efforts on Monday to remove highly radioactive water from inside buildings at a crippled nuclear power plant, as reports surfaced that more radiation may be seeping into seawater.
Attempts to contain the contamination at the Fukushima Daiichi Nuclear Power Station suffered a setback on Sunday when alarmingly high radiation levels were discovered in a flooded area inside the complex.
The operator of the plant, Tokyo Electric Power Company, said the elevated radiation levels in the water, which had flooded the turbine buildings adjacent to the reactors, were at least four times the permissible exposure levels for workers at the plant and 100,000 times greater than water ordinarily found at a nuclear facility.
Alarm over the radiation levels grew last Thursday when two workers were burned after they stepped into highly radioactive water inside Reactor No. 3. Over the weekend, a worker trying to measure radiation levels of the water at Reactor No. 2 saw the reading on his dosimeter jump beyond 1,000 millisieverts per hour, the highest reading on the device. The worker left the scene immediately, said Takeo Iwamoto, a spokesman for Tokyo Electric Power.
The average amount of radiation workers at the Fukushima plant are exposed to in a year is at most 50 millisieverts. In emergency situations, the limit is usually raised to 100 millisieverts but it has been raised to 250 millisieverts during the crisis.
There was no evacuation of the roughly 1,000 workers stationed at Daiichi after the high radiation levels were discovered. Naoki Sunoda, a spokesman for Tokyo Electric Power, said that since the crisis began on March 11, 19 workers had been exposed to radiation levels of 100 millisieverts.
Despite the new problem, Mr. Sunoda said, workers on Monday were still trying to determine a way to approach the turbine building of Reactor No. 2 to extract the contaminated water.
The Nuclear Safety Commission of Japan advised Prime Minister Naoto Kan on Sunday that a pool of water found in the basement of the No. 2 unit’s turbine building may have been caused by the leak from the containment building, Kyodo news agency reported. Concern focused on whether the contaminated water had made its way to the ocean or was leaking into the ground. The commission also said that even if the leak continues in the containment building, they are confident that current efforts to cool the reactor would work.
Citing the country’s Nuclear and Industrial Safety Agency, Kyodo reported that radioactive iodine 131 was detected Sunday at a concentration 1,150 times the maximum allowable level in a seawater sample taken about a mile north of the drainage outlets of reactor units 1 through 4.
Hidehiko Nishiyama, a spokesman for the nuclear agency, said there were no health concerns, Kyodo reported, because fishing would not be conducted in the evacuation-designated area within about 12 miles of the plant.
The Fukushima Daiichi plant has been leaking radiation since a magnitude 9.0 quake and ensuing tsunami struck northeastern Japan’s coastline on March 11. The tsunami knocked out power to the plant’s system that cools the nuclear fuel rods.
Yukio Edano, the government spokesman, said on Monday it was too early for people to return to homes within a 12-mile radius of the Fukushima plant.
“We cannot guarantee safety at the moment as the situation is still under evaluation,” he said. Relief supplies are reaching more earthquake survivors, but low temperatures and aftershocks continue to make life miserable for the population.
On Monday morning, an aftershock with a magnitude of 6.5 off the coast of northeast Honshu triggered a tsunami alert, which was later canceled.
Meanwhile, public broadcaster NHK said the death toll from the quake and tsunami grew to more than 10,800, while more than 16,200 remained missing. More than 190,000 people remained housed in temporary shelters, the broadcaster said.