Down the Tubes: San Onofre's Steam Generators in Worst Shape of all US Nuclear Plants

The problems with the steam generators at the San Onofre nuclear reactors are the most severe found in comparable generators across the U.S. nuclear industry, according to a new report commissioned by Friends of the Earth. The report by Fairewinds Associates also analyzes a leaked Southern California Edison document, which shows that despite assertions by Edison and the Nuclear Regulatory Commission, thousands of tubes inside both San Onofre reactors are severely damaged and both reactors should remain shut down.

San Onofre, on the Pacific Coast between Los Angeles and San Diego, has been shut down since January, after a leak of radiation from one of the almost 20,000 thin, tightly-packed tubes that lead from the plant's four steam generators to its turbines. In an attempt to stop further leaks, Edison has plugged 1,317 of the tubes that show wear. According to NRC data on 31 reactors with comparable replacement steam generators, San Onofre has more than three and a half times the number of steam tubes plugged as a safety measure than at all the other reactors combined.

In addition to the unprecedented scale of plugging at San Onofre, Fairewinds' analysis of the leaked data from Edison shows that more than 4,000 tubes are showing significant wear, while only 1,317 have been plugged. Fairewinds concludes that plugging the tubes will not eliminate the cause of damage. In fact, operating the reactors with the remaining unplugged but worn tubes could create cascading tube failures, leading to domino-like catastrophic failure that would release significant radiation to a large area of Southern California.

"Edison and the NRC have admitted that the problems with San Onofre's steam tubes are an anomaly, but they haven't been forthcoming about just how historically off-the-charts the damage is in comparison to the rest of the nuclear industry," said Arnie Gundersen, a nuclear engineer at Fairewinds and co-author of the report.

Edison has maintained -- without challenge from the NRC -- that the fact that fewer tubes have been plugged in Unit 2 than in Unit 3 proves Unit 2 is in better shape and should be considered for restart. But the NRC data show that the number of tubes plugged in Unit 2 is still almost five times higher than in any other comparable reactor.

A May 7, 2012 condition report from Edison, which has not been made public but was obtained by Friends of the Earth, confirms that Unit 2 is identical to Unit 3 and shares the same problems. Analyzing the findings of the condition report, Gundersen concluded:

"The replacement steam generators at San Onofre Unit 2 and Unit 3 were designed to the same specifications, were modeled using the same flawed and inadequate computer codes, and both units have the same ... instability that is one of the causes of the significant tube generation."

Dave Freeman, former head of the federal Tennessee Valley Authority and the Los Angeles Department of Water and Power, said the condition report shows clearly that the picture Edison and the NRC are painting -- that Unit 2 is in better shape than Unit 3 -- is false.

"The fact that the first tube leak occurred in Unit 3 is simply a sneak preview to what could happen if either unit is restarted," said Freeman, a senior advisor to Friends of the Earth. "The NRC needs to see through this blatant attempt to throw everyone off the real trail to safety. They need to keep both units shut down until the root cause is identified, an adjudicatory hearing is held and a determination is made on whether or how the steam generators could be fixed."

Friends of the Earth has petitioned the NRC to require a formal relicensing procedure to determine whether San Onofre should be restarted. The NRC has yet to respond to the petition.

Download the report as a pdf.

View the leaked document analyzed in the report.

Find more information on the report and the unprecedented steam generator problems at San Onofre.