Recently the reactor has been shut down to allow cooling and
so workers can install inspection equipment inside the reactor at the San Onofre nuclear power plant to help find a leak.
The problem was discovered during an inspection of a steam generator. Containing 9,700 tubes that have each been replaced in 2009, it is estimated that 800 or more have prematurely worn away at the walls.
Inspectors find ‘unusual’ wear on new tubes carrying radioactive water at Calif. nuclear plant
LOS ANGELES — Unusual wear has been found on hundreds of tubes that carry radioactive water at Southern California’s San Onofre Unit 2 nuclear plant, raising questions about the integrity of equipment the company installed in a multimillion-dollar makeover in 2009.
The disclosure came two days after a tube leak at the plant’s other unit prompted operators to shut down the reactor as a precaution. A tiny amount of radiation could have escaped, but officials say workers and the public were not endangered.
The problems at Unit 2 were discovered during inspections of a steam generator, after the plant 45 miles north of San Diego was taken off-line for maintenance and refueling. The two huge steam generators at Unit 2, each containing 9,700 tubes, were replaced in fall 2009, and a year later in its twin plant, Unit 3, as part of a $670 million overhaul.
According to the Nuclear Regulatory Commission, more than a third of the wall had been worn away in two tubes at Unit 2, which will require them to be plugged and taken out of service. At least 20 percent of the tube wall was worn away in 69 other tubes, and in more than 800, the thinning was at least 10 percent.
“The amount of wear that we are seeing on these tubes is unusual for a new steam generator,” NRC spokesman Victor Dricks said. “If you have that kind of thinning anywhere along the length of the tube, you have a problem because it degrades the integrity of the tube, which can contribute to leaks.”
Owner Southern California Edison disputes the figures released and says a tiny amount of radiation could have escaped into the atmosphere but no one was endangered.
The utility also has found unusual, premature wear found on hundreds of similar tubes in a twin reactor called Unit 2. That reactor is still in service while the tubes are plugged.
More inspections will have to continue to determine the changes that are required for proper operations under standard conditions.
Information from: U-T San Diego, http://www.utsandiego.com