Feds: Design flaws at Calif. nuke plant behind leak
The San Onofre nuclear power plant in Southern California, shown in a 2004 file photo. / Getty Images
(AP) CAPISTRANO BEACH, Calif. - After months of investigation, federal regulators have determined that design flaws appear to be the cause of excessive wear in tubing that carries radioactive water through California's troubled San Onofre nuclear power plant, a top federal regulator said.
The twin-reactor plant between Los Angeles and San Diego has been idle since January, after a tube break in one of four, massive steam generators released traces of radiation. A team of federal investigators was dispatched to the plant in March after the discovery that some tubes were so badly corroded that they could fail and possibly release radiation, a stunning finding inside the virtually new equipment.
Flaws in fabrication or installation were considered as possible sources of the rapid tube decay but "it looks primarily we are pointed toward the design" of the heavily modified generators, Nuclear Regulatory Commission Regional Administrator Elmo Collins told The Associated Press in an interview Sunday.
Collins couldn't rule out that one or more of the generators, installed in a $670 million overhaul in 2009 and 2010, might have to be replaced.
Eight tubes failed during earlier pressure tests in the Unit 3 reactor and "we have not seen that in the industry before," Collins said.
"It's these four steam generators that either have, or are susceptible to, this type of problem," Collins said, referring to the unusual damage caused when alloy tubes vibrate and rattle against each other or brackets that hold them in place.
So far, a fix has remained elusive.
"It's not too hard to frame up the problem," he added. "The answers are very difficult, or they already would have emerged."
The disclosure will rivet new attention on a series of alterations to the equipment design, including the decision to add 400 tubes to each generator and installing V-shaped supports that were intended to minimize tube wear and vibration.
It's possible operator Southern California Edison could face penalties stemming from the federal investigation, Collins said.
The generators were designed to meet a federal test to qualify as "in-kind," or essentially identical, replacements for the original generators, which would allow them to be installed without prior approval from federal regulators.
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