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More problems found at San Onofre nuclear power plant

April 12, 2012 |  7:02 am

Southern California Edison officials said Wednesday that they are now seeing the same unusual type of wear on steam generator tubes at both of the San Onofre nuclear plant's reactor units.

In recent months, officials have found unexpected wear on more than 300 tubes that were installed as part of the $671-million replacement of the plant's four steam generators. The new steam generators were installed within the last two years, which made that rate of wear unexpected.

What was even more unusual was the type of wear at Unit 3, which has now also been discovered at Unit 2. Nuclear Regulatory Commission officials said the tubes in Unit 3 were vibrating excessively and rubbing against each other. Initially, they said that the wear occurring at Unit 2 appeared to be different.

But in a statement Wednesday, Edison said it had found "additional minor tube wear" in Unit 2 of a type that is "similar to the type of wear that was seen in Unit 3, but at a very low level." The power company, which operates San Onofre, is conducting additional inspections at Unit 2. San Onofre has been out of commission since Jan. 31, when a tube in Unit 3 sprung a leak, releasing a small amount of radioactive steam.

The event led to discovery of wear on more tubes, and the NRC dispatched a special inspection team to the plant. The NRC has prohibited the plant from firing up again until the cause of the wear is understood. Nuclear Regulatory Commission Chairman Gregory Jaczko toured the plant last week along with Sen. Dianne Feinstein (D-Calif.) and Rep. Darrell Issa (R-Vista).

Jaczko assured reporters, anti-nuclear activists and local elected officials that the plant would remain shut down until the problems are thoroughly investigated and fixed, although Issa expressed hope that the plant would be up and running again before summer.

Edison and NRC officials have not said what they believe is causing the wear. A report commissioned by the advocacy group Friends of the Earth contended that design changes in the new generators — including a different alloy used to make the tubes, a change in the flow rate, the addition of more tubes and changes in the support structures that hold the tubes in place — probably caused the issues.


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