Climate & Energy Blog

Nuclear engineer warns: Keep troubled San Onofre reactors shut down

Posted Mar. 27, 2012 / Posted by: Kelly Trout

Friends of the Earth released today a new analysis by one of the nation’s leading independent nuclear engineers, Arnie Gunderson. The report has revealed serious unresolved safety problems at Southern California Edison’s San Onofre nuclear reactors which could lead to significant radiation releases if the plant is allowed to restart.  The paper also documents that Edison misled the federal Nuclear Regulatory Commission about changes made to the plant, which have led to unforeseen and undiagnosed safety problems. To date, Edison has failed to provide substantive information to the public about the safety problems and testing at San Onofre.

Read the report.

Key findings of the new analysis of the San Onofre Nuclear Generation Station

Edison kept steam generator replacement details secret from NRC

The San Onofre reactors near San Diego have significant problems because their four steam generators have extensive degradation.

Although the reactors are almost 30 years old, these steam generators are new – they were replaced in 2009/2010. The original steam generators lasted for over 25 years, but the new ones have shown “astronomical wear rates” in only two years. Southern California Edison had told the Nuclear Regulatory Commission that the new steam generators would be an exact replacement -- a “like for like” swap -- which meant that NRC approval was not required. Yet clearly something is different about the new generators, though Southern California Edison has not said what and is not taking the necessary steps to find out.

Fairewind Associates identified four changes that could account for the rapid deterioration:

  • the tube alloy was changed;
  • reactor flow rate was changed;
  • more steam generator tubes were added;
  • and/or modifications were made to the “egg crate” that holds the tubes separate and apart.

Push to restart reactors even though cause of deterioration not known

Steam tube failures in reactors designed like San Onofre cause a significant nuclear safety issue by substantially increasing the risk of an accident that releases radioactivity into the environment. Simple inspections conducted by using Eddy Current tests indicate that more than 100 tubes show astronomical wear rates, need further evaluation, and must be plugged prior to resuming plant operation. Southern California Edison has pressure tested only the tubes in San Onofre unit 3 and failed to perform similar tests on unit 2. In addition, the NRC has sent an inspection team only to unit 3. Without pressure testing unit 2, Southern California Edison cannot know the full extent of this critical safety and reliability issue.

“Fairewinds Associates recommends that both [San Onofre] Unit 2 and Unit 3 remain shut down until the root cause of each nuclear reactor rapid steam generator tube failures are understood and repaired, reliability is assured, and radioactive releases are prevented,” Gundersen concludes in the report.

Read the news release | APNewsBreak: Report warns of nuke risk in Calif. | AP: Feds say troubled San Onofre nuclear plant will remain shut until tubing probe completed | LA Times: San Onofre nuclear power plant prohibited from restarting | Orange County Register: Irvine recommends shutting down San Onofre power plant | The San Diego Union-Tribune: Feds: San Onofre to remain shut indefinitely

Steam Generator Failures at San Onofre (Report)

Report examines steam generator problems at the San Onofre nuclear reactors. Recommends that the need for a thorough root cause analysis requires no early restart of reactors.

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