Both units 2 and 3 of the San Onofre Nuclear Generating Station (SONGS) remain offline for steam generator inspection, plant operator Southern California Edison said, 15 March.
SCE reported that four additional unit 3 steam generator tubes failed during in-situ testing on 14 March, and that it immediately notified the US nuclear regulator.
Company engineers and independent experts are testing the steam generators in SONGS 3, following a water leak that was detected at the end of January. There are 19,454 steam generator tubes in unit 3. SCE is conducting in-situ tests on 129, or approximately 1 percent of the tubes, which show higher than normal wear.
Testing is also underway at SONGS 2, which has been out of service since 9 January for a planned refueling outage, inspections and maintenance. During these inspections, SCE engineers found some isolated areas of tube wear. This resulted in the plugging of approximately 1 percent of the tubes preventively in unit 2.
SCE said that although initial analysis from the inspections does not indicate any correlation between the leak in unit 3 and the tube wear seen in unit 2, it has decided not to restart unit 2 until it is satisfied that the issues in unit 3 will not occur there. It added that work on unit 2 is ‘nearly complete.’
The Nuclear Regulatory Commission (NRC) will send an augmented inspection team to the plant in California, where inspections expected to being on 19 March.
In a blog post the US regulator said: “The NRC inspectors will take a very comprehensive look at this unit 3 condition, including looking at the manufacturer’s steam generator design, construction and shipment to the site located near San Clemente, California. While other steam generators have shown wear after one cycle of operation, the level of wear at unit 3 is more than expected.”
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