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One week after a radiation leak prompted a shut down at San Onofre, the nuclear plant's Unit 3 reactor remains offline.
The reactor was finally cool enough on Monday for workers to install inspection equipment, but it was unclear how long the unit would remain out of service, according to plant operator Southern California Edison and officials at the Nuclear Regulatory Commission, reports U-T San Diego.
During an inspection, unusual wear was found on hundreds of steam generator tubes pumping radioactive water in Unit 2, however that reactor is still in service. The NRC said tubes showed excessive wear. Edison called the findings preliminary.
Over the past two years, generators in both reactors were replaced with $670 million worth of new equipment manufactured in Japan by Mitsubishi Heavy Industries.
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A veteran worker lost his balance at the San Onofre nuclear plant last week and fell into the Unit 2 reactor pool while trying to retrieve a flashlight. The pool, more than 20 feet deep, contains water that continually circulates through the reactor core.
The worker did not suffer significant radiation exposure in the incident, and was "wearing all of the appropriate safety equipment, including a life preserver vest," said Southern California Edison spokesman Gil Alexander told the L.A. Times.
Highly radioactive uranium fuel normally sits at the bottom of the pool, but it had been removed by workers, according to officials. Stray fuel particles may have been floating in the water and could have been swallowed. They would have been the most likely source of radiation, said Nuclear Regulatory Commission spokesman Victor Dricks.