A restart plan for the shuttered San Onofre Nuclear Generating Station in northern San Diego County has been submitted to the Nuclear Regulatory Commission for approval, plant operators announced today.
The plan, which gives no specific restart date, calls for one of two units at the plant to be restarted at 70 percent power for a five-month trial period, according to operator Southern California Edison, which owns the plant along with San Diego Gas & Electric and the city of Riverside.
The units — called Unit 2 and Unit 3 — were each shut down in January.
Unit 2 was shut down for planned maintenance, while Unit 3 was abruptly taken offline after a leak was detected in one of its steam generator tubes.
Edison is proposing to restart Unit 2 while Unit 3 remains offline for further inspection, analysis, and testing.
“Safety is our top priority, and after conducting more than 170,000 inspections to understand and prevent the problem, and confirming the corrective actions we have taken to solve the problem with the top experts from around the world, we have concluded that Unit 2 at San Onofre can be operated safely and within industry norms,” Southern California Edison President Ron Litzinger said in a statement.
“When implemented, this plan will get San Onofre Unit 2 back to providing reliable and clean energy to Southern Californians.”
The leak in Unit 3 was caused by tube-to-tube wear due to a phenomenon called fluid elastic instability, Edison reported. It said a combination of high-steam velocity and low-moisture conditions in specific locations of tube bundles and ineffective tube support systems in the same bundle locations causes the phenomenon and subsequent wear, leading to leaks.
Unit 2 was also susceptible to the same vibration-causing environment but to a lesser degree than Unit 3, officials said, noting Unit 2 can be safely restarted at 70 percent power without triggering fluid elastic instability.
Edison officials said if the restart plan is approved, they would operate Unit 2 for five months and then shut it down to inspect it for leaks.
The plan also envisions Edison installing early warning monitors on the unit that can detect extremely small leaks faster, and plant employees receiving additional training on how to respond to a leak.