Three tubes fail testing at San Onofre nuclear plant

Three steam generator tubes in Unit 3 at the San Onofre Nuclear Generating Station have failed a pressure stress test, Southern California Edison officials said Wednesday.

Unit 3 has been shut down since Jan. 31 because of a leak in a steam generator tube at the plant just south of the Orange County line in northern San Diego County.

The utility notified the Nuclear Regulatory Commission of the testing failures, according to an agency statement.

“Engineers and industry experts are on site to assist and oversee the ongoing testing process,” officials said, adding that the type of trial is known as “in-situ testing.”...

Safety worries shut down San Onofre nuclear plant
Associated Press Friday, March 16, 2012

Los Angeles -- A nuclear reactor on the Southern California coast will remain shut down indefinitely while a team of federal inspectors determines why several relatively new tubes became so frail that tests found they could rupture and release radioactive water, a federal official said Thursday.

The Unit 3 reactor at the San Onofre Nuclear Generating Station, located about 45 miles north of San Diego, was shut down as a precaution on Jan. 31 after a water leak from another tube in a massive steam generator. Traces of radiation escaped, but officials say there was no danger to workers or neighbors.

Since then, investigators have been looking into excessive wear found on steam generator tubes in the seaside plant and its twin, Unit 2, which has been offline 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 Unit 3 as part of a $670 million overhaul.

The Nuclear Regulatory Commission dispatched a special, five-member team to Unit 3 on Thursday after pressure tests showed three of the metal-alloy tubes had become so degraded that they could rupture under some circumstances. Such ruptures can require a plant to shut down, if spewing water reaches 150 gallons a day.

Inside a steam generator, hot, pressurized water ...