The Nuclear Regulatory Commission's inspector general has concluded that the agency missed an opportunity to flag design changes to the faulty steam generators that eventually shuttered the San Onofre nuclear plant.
The report (.pdf) comes as Southern California Edison and the NRC continue to face scrutiny from Congress and plant opponents related to the handling of the steam generators. One experienced a small leak in 2012 a year after it was installed. Premature wear was subsequently found in the steam generators of both San Onofre units that the NRC later blamed on vibration caused by modifications to their design.
NRC experts have suggested that those modifications should have required a license amendment – an intensive process that might have identified the flaws before the steam generators were installed. In 2009, though, an NRC inspection team reviewed the paperwork from SCE supporting its case that a license amendment was not required (under what is known as the 10 CFR 50.59 rule) and agreed with the utility's conclusions.
Additionally, the Office of the Inspector General, "found that NRC does not consistently use one of its primary oversight methods to assess whether licensees are keeping their power plant licensing basis documentation up to date." The report noted that biennial updates on modifications made to reactors outside the license amendment process were frequently reviewed by agency staff well after a recommended 90-day timeframe, and in some cases not for a year or longer. At San Onofre, the report also found that NRC staff documented only two reviews of updates to the plant's updated final safety analysis report over a 10-year span, when the plant had submitted six of them, as required. Also, the report noted that earlier inspections identified many changes made to San Onofre steam generators over a 25-year period that were not reflected in its UFSAR.
In response, NRC officials quoted in the report said that reviews of 10 CFR 50.59 paperwork are not intended to catch design flaws, and that deadlines for reviewing UFSAR updates are a matter of internal guidelines rather than law.