Southern California Edison (SCE) has responded to charges by Senator Barbara Boxer that the utility may have misled regulators about the scope of the steam generator replacement at its San Onofre Nuclear Generating Station, and the utility's characterization of the events leading to the replacement couldn't be more different from the Senator's.
In a series of statements this week, Senator Boxer said that a November 2004 letter from SCE Vice President Dwight E. Nunn to Akira Sawa of generator manufacturer Mitsubishi Heavy Industries (MHI) offered evidence that SCE had later misled regulators at the Nuclear Regulatory Commission (NRC), which agency was charged with ensuring that changes to San Onofre wouldn't pose a public safety risk.
Those new steam generators, which were substantially larger than the ones they replaced, caused big problems for SCE and San Onofre. Premature wear in the generators' steam tubes apparently contributed to a leak of radioactive steam from one of the new generators in the plant's Unit 3 in January 2012. Unit 2 was shut down for maintenance at the time: both units have remained offline since.
The Boxer announcements come as SCE is waiting on a decision from the NRC over a proposed low-power restart of San Onofre's Unit 2, which the utility says will "prevent" the vibrations that caused the unexpected degree of tube wear.
In the letter, Nunn states that the new steam generators MHI was designing for San Onofre would not be a "like-for-like" replacement of the generators being retired. Boxer charged this week that SCE had subsequently described the steam generator replacement as a "like-for-like" replacement, a term of art that allows nuclear plant operators to avoid seeking a costly, time-consuming license amendment from the NRC.
But SCE says that the Senator has made a "fundamental error" in her reading of the history of the plant. Rather than certifying that San Onofre's replacement generators were a "like-for-like" replacement, says the utility, SCE sought and obtained a permit to replace the generators under a section of the NRC's rules covering Changes, tests and experiments in nuclear power plant design.
"In the November 2004 letter," said SCE in a statement released Tuesday, "SCE emphasized the care that would be needed during the design phase because of the differences between the new and old units. These differences -- which were intended to improve the overall performance of the new units -- were permitted under the NRC's 50.59 process, which allows changes to a nuclear facility if certain criteria are met. Contrary to Sen. Boxer's suggestion, Section 50.59 does not require that replacement equipment be 'like for like' or identical to the equipment being replaced."
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