California's San Onofre Nuke Plant Unit 2: Steam Generator Tubes Showing "Many, Many Years" Worth of Wear

even though they are only 22 months old.

Overload, most likely. Mitsubishi's design flaw?

From LA Times (2/3/2012):

San Onofre nuclear plant radiation leak, worn tubes raise concerns

A week of problems at the San Onofre nuclear power plant has raised new safety concerns among some activists.

Officials of Southern California Edison, which operates the facility and is a majority owner, insist that the plant is perfectly safe, but others say the mishaps are one more sign of problems.

The situation is "further evidence that California should move beyond nuclear power. California should plan for the orderly phase out of ... aging nuclear power plants, including San Onofre, and shift to clean-energy alternatives like energy efficiency and renewable power," Bernadette Del Chiaro, director of clean-energy programs for the advocacy group Environment California, said in a statement.

Nuclear regulation officials said Thursday that extensive wear had been found on tubes inside a unit at the San Onofre nuclear plant.

Another unit at the plant was taken off-line after a small radiation leak earlier this week.

Dozens of relatively new tubes that carry radioactive water in a steam generator showed "many, many years" worth of wear, even though the tubing is 22 months old, said Victor Dricks, a spokesman for the Nuclear Regulatory Commission.

Nearly 70 tubes, made from a metal alloy and formed into a U-shape, had 20% of their interior lining worn off, while hundreds more had 10% of the lining deteriorated, Dricks said. More than 9,000 tubes are in the generator.

Dricks said that some of the tubes will require repair, while others will probably have to be replaced.

But Edison officials say it's too early to make any determination on a course of action, and that additional tests will be conducted. The unit was off-line for a scheduled maintenance period of several months to deal with technology upgrades and fuel replacement, said Gil Alexander, an Edison spokesman.

It is unclear why the tubes are showing so much wear.

The NRC's findings come on the heels of a leak in a tube Tuesday, prompting operators to shut down a reactor. However, officials said, the amount of radiation released was minuscule and did not endanger the public.

"San Onofre has had such a troubled history in terms of the safety culture that each of these incidents shakes me further,” Daniel Hirsch with the group Committee to Bridge the Gap told the Orange County Register.

As for the Unit 3 that was tripped (scrammed) after a minute radiation leak was detected in the turbine building, the inspection won't be done until middle of next week due to the still high temperature (105 degrees Fahrenheit) in the building, according to San Francisco Chronicle.

Mitsubishi Heavy Industries' SG, as it was getting ready to be moved into the reactor building of Unit 2 in 2009 (from The Orange County Register):

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