The pair of reactors at the San Onofre Nuclear Generating Station now slated for retirement will join more than a dozen other plants in the country that are in the process of being cleaned up and permanently shuttered.
It’s a long and costly process that won’t even begin for Units 2 and 3 at the San Onofre plant until all nuclear fuel has been removed from the reactors—something Ted Craver, Edison International Chief Executive, says could take up to three months to complete.
Precisely how much time and money the units' full retirement will require are tougher figures to estimate.
“The Nuclear Regulatory Commission considers the plant to still be an active operating plant,” Craver said on a call Friday morning with reporters, noting that, although Unit 2 has not been active for well over a year, it’s still holding fuel.
“The final point,” he added, “is that full decommissioning of the site is going to be a multi-decade process.”
The NRC, which closely monitors the process, gives operators up to 60 years to clean up a site—an intentionally wide window that allows radioactive materials to naturally break down, and a company's decommissioning funds to accrue interest.
Leaving behind traces of radioactive materials is by far the NRC's largest concern and the agency will therefore not sign off on a plant's retirement until residual radioactivity levels are deemed safe.
While some plants opt to safely store radioactive materials on site, relying on time to slowly break down the most dangerous components, other plants opt for a more immediate decontamination and dismantling process.
"It's a pretty gruesome, labor intensive activity," said Christine King from the Electric Power Research Institute, adding that the toughest part of the process is decontamination and waste management.
"A lot of this involves brute force—just taking apart really large pieces of equipment."
If San Onofre plans to begin dismantling the site right away, as opposed to going the so-called SAFSTOR or safe storage route—a decision Southern California Edison has not yet announced—plant operators would still have to wait a while before they could jump in and begin the decontamination process.
Even though the units have not been operating in about a year and a half, King points out, any spent fuel currently sitting at the plant would still need months to cool before it could be transferred to dry storage, one of the first steps of the retirement process.
Once that's done, it's more brute labor—sand blasting, laser ablation. "When you get into different systems, you're literally talking about cutting systems into a size that's transportable and disposable," King says.
Whichever route they take—immediate or deferred dismantling—the process is costly.
Carver said that the plant currently has $2.7 billion set aside for decommissioning, about 10 percent short of what's needed.
The cost and time needed for cleanup could vary depending on what plans Edison may have for the site's future, and what resources it will have at its disposal. A company aiming to leave the property available for "unrestricted" or "greenfield" use would face more stringent requirements than one opting for brownfield status post-cleanup.
Most plants, the NRC points out, at least plan to release their sites to the public for unrestricted use, meaning residual radiation levels would have to fall below a strict safety threshold.
Just 12 of the 31 plants that have entered decommissioning since 1963 have finished the retirement process, according to data from the NRC. San Onofre 1, located on the same site as San Onofre units 2 and 3, was closed in 1992 and is just now approaching completion.
Duke Energy's Crystal River plant in Florida and the Kewaunee plant in Wisconsin were the latest to enter the shuttering process, both opting for the deferred dismantling, or SAFSTOR route.
Whatever route is in store for the San Onofre units, King says, a couple things are for sure: There will be a lot of waiting before decommissioning can begin, and a long, long time before the process is complete.