Just two years after it was replaced, the Nuclear Regulatory Commission has reported significant wear in a steam generator at California’s San Onofre Nuclear Plant.
Earlier in the week, San Onofre unit 3 was taken out of service because of a leaking steam generator tube that resulted in a small release of radioactive steam into an auxiliary building. On Thursday initial reports from NRC inspectors also outlined wear in similar equipment at neighboring unit 2. During a scheduled outage for maintenance and inspections, the NRC found the thickness of two tubes in one of unit 2's two steam generators had been worn away by a third. Of 9,700 tubes in the steam generator, 69 were found to be at least 20 percent worn, and 800 tubes were at least 10 percent worn.
An NRC spokesman told the Associated Press that accelerated wear in the early years of a steam generator’s life is not unprecedented, and inspectors will conduct further tests.
Southern California Edison replaced all four steam generators at SONGS for a reported cost of $671 million, with installation at unit 2 in 2009 followed by installation at unit 3 last year. They were supplied by Mitsubishi Heavy Industries.
Both units are roughly 1,100 megawatt Combustion Engineering pressurized water reactors first licensed in 1982, according to the Nuclear Regulatory Commission.