The Nuclear Regulatory Commission announced Wednesday that its chairman will visit the ailing San Onofre nuclear power plant on the California coast, where twin reactors have been sidelined because of excessive wear in tubing that carries radioactive water.
The visit by Chairman Gregory Jaczko underscores the agency’s concern over the faulty equipment, which came to light in January when the Unit 3 reactor was shut down as a precaution after a tube break. Traces of radiation escaped, but officials said there was no danger to workers or neighbors.
Last week, the agency announced that the plant located between San Diego and Los Angeles will remain offline while investigators determine why tubing in its massive steam generators is eroding at an unusual rate and repair the problem.
Operator Southern California Edison has said 321 tubes with excessive wear will be plugged and taken out of service at the two reactors, well within the margin to allow them to keep operating.
In a four-page letter to Edison last week, NRC Regional Administrator Elmo E. Collins scrolled out a series of steps the utility must take before restarting the seaside reactors.
“The agency is very concerned,” NRC spokesman Victor Dricks said. “The steam generators are a vital and very important piece of plant equipment, so ensuring their integrity is important” to the company and the NRC.
Jaczko will be joined by U.S. Sen. Dianne Feinstein, D-Calif., her office confirmed.
The plant’s four steam generators each contain nearly 10,000 alloy tubes that carry hot, pressurized water from the reactors. The Unit 2 reactor was shut down for maintenance when workers discovered extensive wear on its tubing.
The tubes are a critical safety barrier _ if one or more break, there is the potential that radioactivity could escape into the atmosphere. Also, serious leaks can drain cooling water from a reactor. If a leak becomes serious, a plant is required to shut down.
The steam generators were manufactured by Japan-based Mitsubishi Heavy Industries.
Edison did not immediately respond to a request for comment.
Authorities in California have been scrambling to find additional power in case the reactors remain idled through summer, when energy use typically peaks. That could include restarting retired plants in Huntington Beach in northern Orange County.
Last week, an environmental group claimed the utility misled the NRC about design changes that it said are the likely culprit in excessive tube wear. The report by nuclear consultants Fairewinds Associates, and produced for nuclear watchdog Friends of the Earth, warned that a more detailed study is needed on the tubing before the reactors are restarted.
Friends of the Earth issued a statement Wednesday with another environmental group, San Clemente Green, urging the chairman to make a “full determination” of problems at the plant. Meanwhile, some officials in nearby communities have been calling for the plant to shut down permanently.
“We deserve answers, and we better get them before they even think about turning these reactors back on,” said Gary Headrick of San Clemente Green.
The company has found that the tube wear is being caused by vibration and friction with adjacent tubes and bracing, however investigators don’t know why that’s happening.
The equipment is relatively new – the generators were installed in a multimillion-dollar makeover in 2009 and 2010.
The plant is owned by Southern California Edison, San Diego Gas & Electric and the City of Riverside. The plant can generate enough electricity to power 1.4 million homes.
San Onofre’s Unit 1 reactor operated from 1968 to 1992, when it was shut down and dismantled. The utility’s plan to ship the 600-ton reactor vessel on a 15,500-mile voyage around South America to a disposal site in South Carolina was thwarted and it remains at San Onofre, encased in concrete and steel.
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