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San Onofre to remain closed indefinitely, NRC chief says

April 6, 2012 |  5:57 pm

Nuclear Regulatory Commission Chairman Gregory Jaczko, who toured the shuttered San Onofre nuclear plant Friday, assured reporters that the plant would not restart until officials understand the root cause of the cause of systems failures that forced the plant's closure.

Jaczko made a trip, accompanied by Sen. Dianne Feinstein and Rep. Darrell Issa (R-Vista), to tour the plant and talk to Edison officials about the unexpected wear in steam generator tubes that carry radioactive water in the plant's two working reactor units.

The steam generators at both of the plant's reactor units were installed within the last two years, at a cost of $671 million.

"The issue of the steam generators is a very serious issue, we take it seriously, and after some very frank discussions today, I can say that Southern California Edison takes it seriously, too," Jaczko told reporters.

The plant has been out of commission since a tube in the Unit 3 reactor, where the steam generators were installed about a year ago, sprung a leak and released a small amount of radioactive steam. Since then, Edison, the plant's operator, has found unexpected wear in more tubes at both of the reactor units, and eight tubes in the Unit 3 reactor have failed pressure tests.

The tubes in Unit 2, which was already offline for planned maintenance when the issues were discovered, also showed wear, and 192 were taken out of service.

Jaczko called the wear, particularly in Unit 3, highly unusual for such new equipment.

"It's certainly a very unique phenomenon, and particularly in Unit 3," he said.

According to the NRC, the tubes in Unit 3 were vibrating and rubbing against each other, while the tubes in Unit 2 were rubbing against support structures but not against each other. Officials have not determined why the excessive vibration is occurring.

The steam generators were manufactured by Mitsubishi Heavy Industries, which has only produced steam generators for one other plant in the United States, but the design at San Onofre is unique.

A report commissioned by the advocacy group Friends of the Earth charged that design changes in these generators -- including a different alloy used to make the tubes, a change in the flow rate, addition of more tubes and changes in the support structures that hold the tubes in place — probably caused the unexpected wear.

It also suggested that Edison had sidestepped NRC review of the design changes by representing the new steam generators as being essentially like the old ones.

Jaczko said part of the NRC's inspection of the plant will be reviewing documentation relating to the replacement. He did not comment on the question of whether the design changes might have led to the wear.

--Abby Sewell, reporting from San Onofre

Photo: Gregory Jaczko, chairman of the U.S. Nuclear Regulatory Commission, speaks at a news conference after taking a tour of the troubled San Onofre nuclear plant Friday. Christina House / For The Times.