CNN Wire Staff
Tokyo (CNN) - Authorities in Japan raised the prospect Friday of a likely breach in the all-important containment vessel of the No. 3 reactor at the stricken Fukushima Daiichi nuclear power plant, a potentially ominous development in the race to prevent a large-scale release of radiation.
Contaminated water likely seeped through the containment vessel protecting the reactor's core, said Hidehiko Nishiyama of the Japan Nuclear and Industrial Safety Agency.
Three employees working near the No. 3 reactor Thursday stepped into water that had 10,000 times the amount of radiation typical for a nuclear plant, Nishiyama said. An analysis of the contamination suggests "some sort of leakage" from the reactor core, signaling a possible break of the containment vessel that houses the core, he said.
The workers have been hospitalized and work inside the reactor building has been halted, according to the agency.
Work inside two other reactor buildings also had to stop and workers had to be pulled back Friday after the discovery of high levels of radiation in water at those locations, a Tokyo Electric Power Company official said Saturday. Water is still being pumped into the containment vessels, the utility official said.
Nuclear power experts cautioned against reading too much into the newest development, saying the workers exposed to radioactive water might not suffer injuries any more serious than a sunburn.
Moreover, evidence of radioactivity in the water around the plant is not necessarily surprising given the amount of water sprayed onto and pumped into the reactors, said Ian Hutchinson, professor of nuclear science and engineering at the Massachusetts institute of Technology.
"I am not particularly alarmed," he said.
The reactor thought to be leaking contaminated water is the same one cited in the dramatic evacuation last week of a small crew of workers who had stayed behind after the plant's owner pulled most employees from the area. The workers were pulled back March 16 after white smoke began billowing from the reactor and radiation levels spiked.
At the time, the Japanese nuclear safety agency said it suspected damage to No. 3's containment vessel, but a government spokesman the next day said there had been no indication of a "major breach of containment."
That reactor is of particular concern, experts have said, because it is the only one at the plant to use a combination of uranium and plutonium fuel, called MOX, that is considered to be more dangerous than the pure uranium fuel used in other reactors.
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