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ROSEMEAD, Calif., March 14, 2012 — Southern California Edison's (SCE) San Onofre Nuclear Generating Station (SONGS), which is safely shut down for inspections and testing, had three Unit 3 steam generator tubes fail during a pressure stress test known as “in-situ testing.” Unit 3 has been shut down since Jan. 31 when it was safely taken off line after station operators detected a leak in one of the unit’s steam generator tubes.
Following industry standards and requirements, SCE has notified the Nuclear Regulatory Commission (NRC) of the tube test failures. SCE engineers and industry experts are on site to assist and oversee the ongoing testing process. There are 19,454 steam generator tubes in Unit 3. SCE is in the process of conducting “in-situ” tests on 129 of those tubes (approximately 1 percent), which show higher than normal wear.
"Tests at a nuclear plant are designed to detect potential safety issues, and these tests serve that purpose," said Ron Litzinger, president of SCE, which operates the plant as the majority owner. "Our tube testing plan, in accordance with industry standards, is designed to help us understand the safety issues and significance of this situation."
Both Unit 3 and Unit 2 are off line at this time. The two Unit 3 steam generators currently are undergoing extensive testing and inspections in order to fully assess their condition, as well as the cause of the Jan. 31 leak and the observed tube wear. Unit 2 was taken out of service for a planned outage on Jan. 9. The scheduled inspections and maintenance on Unit 2 are nearly completed. Repairs were made through plugging, in accordance with industry guidelines and protocols, of tubes found during the inspections that showed wear or susceptibility to wear.
SCE is committed to the safe operation of SONGS and will not return the plant’s generating units to service until the company is satisfied it is safe to do so.
"SCE is in close contact with state officials, local cities and community partners to provide regular updates," said Litzinger. "Our employees at SONGS make the safety of the public and plant workers their No. 1 decision-making principle."
Nineteen percent of all power used by SCE customers comes from nuclear generation.
In-situ testing is a standard engineering practice used to test piping systems and equipment in place at steam generators. In the case of the SONGS steam generator in-situ tests, the steam generator tubes are tested by being slowly pressurized with non-radioactive water in stages, using up to three times the normal operating condition pressure.
NRC inspectors are on site for these tests. Since three tubes have failed the “in-situ” test, SCE anticipates additional NRC inspections. Per normal industry practice, tubes undergoing this kind of testing are removed from service by plugging them, whether or not they pass the test. The generators are built with an allowance of extra tubes so that some can be taken out of service during the life of the plant.
More information is available at www.edison.com/songsupdate.
About Southern California Edison
An Edison International (NYSE:EIX) company, Southern California Edison is one of the nation’s largest electric utilities, serving a population of nearly 14 million via 4.9 million customer accounts in a 50,000-square-mile service area within Central, Coastal and Southern California.