NRC administrator says problems at San Onofre appear to be due to design flaws

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Federal regulators have finally indicated their determination that the cause of excessive wear in the steam generator tubes  at California’s troubled San Onofre nuclear power plant are in fact due to design flaws. The design of the generators is also under congressional scrutiny.

Meanwhile, the cost of the shutdown and any necessary repairs continues to mount—and it’s still unclear who will end up paying the bill.

Nuclear Regulatory Commission Regional Administrator Elmo Collins told The Associated Press Sunday that source of the problem appears to be the design of the heavily modified generators.  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.”

“It’s these four steam generators that either have, or are susceptible to, this type of problem,” Collins said, “These are significant technical issues. They are not resolved yet,” referring to the unusual damage caused when alloy tubes vibrate and rattle against each other or brackets that hold them in place.

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.

So far, a fix has remained elusive, and Collins couldn’t rule out that one or more of the generators that were installed in 2009 and 2010 may have to be replaced.

The eight tubes which failed during earlier pressure tests in the Unit 3 reactor caught regulators and workers off-guard, the NRC spokesperson oberserved  “we have not seen that in the industry before,”.

Edison Chief Executive Ted Craver said the new steam generators were designed to prevent such vibration, but that “the implementation of the design doesn’t appear to be meeting the specification.”

For months, Arnie Gundersen, a consultant for Friends of the Earth, argued that some of the design changes — including the addition of more tubes and the removal of a support structure — may have led to the unusual wear on the steam generator tubes.

After months of downplaying the significance of the problems and releasing a constant stream of forward looking statements, the disclosure has brought the overwhelming pressure of massive public attention crashing down 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 even possible operator Southern California Edison could face penalties stemming from the federal investigation, Collins said.  Inside the guts of the machinery, the original steam generators and the replacements “look substantially different,” he admitted.

“It’s not too hard to frame up the problem,” he added. “The answers are very difficult, or they already would have emerged.”

Last week, a LA Times poll  attempted to gauge the public sentiment about potentially restarting the San Onofre reactors, over 85% of the voters responded they would rather see the reactors permanently decommissioned, and no other option was able to attract 10% of the voters opinion.

The NRC is scheduled to discuss its findings Monday evening at a meeting near the plant.  During the meeting, which is open to public observation, the NRC staff will provide a summary of the Augmented Inspection Team’s findings followed by a response from the licensee.

After a short break, the NRC staff will be available to answer questions from the public and accept comments on San Onofre-related issues.

This will be the first in a series of public meetings to be held in the area to keep the public informed on the progress of NRC inspection and oversight activities at San Onofre.

Source: San Diego 6

Source: Chron

Source: LA Times

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