Edison International said that without a restart of Unit 2 at its San Onofre Nuclear Generating Station (SONGS), it could decide by the end of the year to retire both units at the California nuclear plant. The units with a combined generating capacity of 2,350 MW have been offline since early 2012, the result of unexpected erosion and tube leaks in their steam generators. Costs tied to the shutdown now total around $553 million, including $109 million spent on inspections and repairs and $444 million for replacement power.

"Without a restart of Unit 2, a decision to retire one or both units would likely be made before year-end 2013," Theodore F. Craver, chairman, CEO and president said during an earnings conference call April 30.

The utility proposed to the Nuclear Regulatory Commission (NRC) restarting Unit 2 and operating it at a maximum of 70% power for five months, then taking it down and inspecting it. The utility’s decision on whether or not to retire one or both units hinges on the NRC’s decision on that proposal. Units 2 and 3 use Combustion Engineering pressurized water reactors, and have total generating capacities of 1,172 MW and 1,178 MW.

The company said limits exist to how much cost it can take on without regulatory certainty around cost recovery. “What we’re trying to signal is it’s difficult for us to see kind of continuing to underwrite the costs without clarity on the rate-making treatment, and without clarity on what the NRC decision is going to be. So there’s a practical limit to how much we can absorb of that risk.”

The twin reactors between San Diego and Los Angeles have not produced electricity since January 2012, when a radiation leak in Unit 3 led to the discovery of the damage to the steam generator tubes. The steam generators were replaced with Mitsubishi Heavy Industries equipment during a $670 million overhaul in 2009 and 2010. After the plant was shut down in 2012, tests found some generator tubes were so badly eroded that they could fail and possibly release radiation. The utility is seeking to recover some costs from Mitsubishi and others through its insurer, Nuclear Electric Insurer Ltd.

The Associated Press reported that last June, federal investigators announced that a flawed computer analysis resulted in design errors that largely are to blame for the unusual tube wear. The company argues that running the plant at lower power will halt the damage. Overall, investigators found wear from friction and vibration in 15,000 places, in varying degrees, in 3,401 tubes inside the four steam generators. And in about 280 spots—virtually all in Unit 3—more than 50% of the tube wall was worn away.

Sources: Edison International, NRC, Associated Press

—David Wagman, Executive Editor, and Thomas W. Overton, JD, Gas Technology Editor (@thomas_overton)

Note: This story was originally published on May 1