UPDATED February 2nd, 2012 – 5:50 P.M. EST
Unusual wear has been found on hundreds of tubes that carry radioactive water at Southern California‘s San Onofre Unit 2 nuclear plant, in more than 871, the thinning was at least 10 percent. This has raised the level of local alarm dramatically in California, and is also raising questions about the integrity of equipment the company installed in a multimillion-dollar makeover in 2009.
The news could be catastrophic for San Onofre, which spent $680 million to replace the plant’s four steam generators and expected them to last for decades.
According to the Nuclear Regulatory Commission, more than a third of the wall had been worn away in two tubes at Unit 2, which will require them to be plugged and taken out of service. At least 20 percent of the tube wall was worn away in 69 other tubes, and in more than 800, the thinning was at least 10 percent.
Meanwhile, plant workers continued to prepare to open the access hatch in the side of the concrete containment dome that protects San Onofre’s Unit 3 reactor. Once inside, technicians will need to begin diagnostic probes to find the location of the leak that caused Edison to shut the unit down at 5:31 p.m. Tuesday.
“The amount of wear that we are seeing on these tubes is unusual for a new steam generator,” NRC spokesman Victor Dricks said. “If you have that kind of thinning anywhere along the length of the tube, you have a problem because it degrades the integrity of the tube, which can contribute to leaks.”
He continued by confirming that Edison will have to file a special “justification for continued operation” document before the regulator will allow the Unit 2 reactor to be restarted.
“They will have to specify what steps they’re taking to ensure that, if the tubes are damaged, they have been repaired in a safe manner,” Dricks said. He added that Edison will also have to diagnose why the generators appear to be degrading more quickly than expected and come up with a plan to address accelerated wear.
Gil Alexander, a spokesman for Edison, said that he was working to confirm Dricks information Wednesday morning. Plant operator Southern California Edison did not dispute the figures released by the NRC, but cautioned that testing on the tubes is preliminary. Spokesman Gil Alexander called the tests “an initial snapshot” and said more sophisticated tests will take place.
He did not know if the testing would delay the reactor’s planned two-month shutdown. ”It’s not unprecedented in the industry for there to be accelerated wear in small sections of tubes in early years of usage,” he said.
According to company officials, the new steam generators were manufactured by Japan-based Mitsubishi Heavy Industries. The company did not respond to an email sent Wednesday. Alexander said Mitsubishi officials are assisting with the tube analysis at the plant.
Retired NRC engineer and researcher Joram Hopenfeld said the company will have to determine why the tubing is degrading so quickly “before they do anything else.” “I’ve never heard of anything like that over so short a period of time,” Hopenfeld said.
“The safety implications could be very, very severe,” Hopenfeld added. “Usually the concern is in older steam generators, when they have cracks all over the place.”
Source: Contra Costa Times
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- NRC: We know California nuke plant vented some radioactive gases – Paper: No ‘significant’ danger to workers or public (enenews.com)
- California’s San Onofre Nuke Plant Shut Down Unit 3, Due to Potential Leak in Steam Generator Tube (ex-skf.blogspot.com)
- *Just In* AP: Many tubes found damaged at San Diego-area nuke plant – “Unusual” says NRC – Cause unknown – Radiation could have escaped… Developing (enenews.com)
- NRC says low level gas might’ve escaped from San Onofre – Other damage is unusual (enformable.com)
- LA Times: Small leak at San Onofre nuclear power plant investigated (ex-skf.blogspot.com)
- Radioactive release possible at California nuke plant: “We can’t make a black and white statement that absolutely none escaped” – Workers unable to enter to check if leaking (enenews.com)
- Nuclear News Update – February 2nd, 2011 (enformable.com)