King tides, groundwater rise: Threats to nuclear waste at San Onofre?

Gary Headrick walked the soggy sea wall between the nuclear plant and the roiling ocean at king tide. Wild waves crashed just yards from where millions of pounds of nuclear waste sat, encased in steel and concrete. It felt scary.

As sinkholes appear in the road to the beach near the shuttered San Onofre Nuclear Generating Station, Headrick and many others say the radioactive detritus must move to higher ground as quickly as possible. But evidence shows that’s not necessary just yet, said Southern California Edison, which oversees the plant’s tear-down.

Edison presented its state-mandated study of sea level rise near the plant on March 7 — 238 pages chock full of pictures and measurements and graphs and projections — concluding that, “as designed and with minimum regular maintenance,” the rocks, sea wall and retaining wall between the waste storage area and the ocean will be just fine through at least 2050, and likely well beyond.

Another worry of critics — that groundwater will eventually rise higher than the concrete floor of the dry storage system, soaking into the concrete and perhaps corroding the steel canisters encasing the waste — is not a realistic threat either, the study concludes.

SONGS reactors 1, 2 and 3 were built dozens of feet below sea level, said Ron Pontes, Edison’s decommissioning manager for San Onofre, at the online Community Engagement Panel meeting Thursday. “Even then, we never saw evidence of water infusion.”

Below-sea-level structures have been demolished over recent years, and were “bone dry,” Pontes said.

So a rising sea should pose no threat to the integrity of the systems protecting 3.6 million pounds of spent nuclear fuel for many decades, even if there’s flooding. And officials hope the federal government — which is contractually obligated to dispose of commercial nuclear waste, but hasn’t, which is why it has piled up at San Onofre and other nuclear plants nationwide — will find a solution before anything major needs to be done shore up/relocate/etc. San Onofre’s dry storage systems.

Critics, however, aren’t disposed to believe the study’s charts and graphs and measurements.

“We all know the danger,” said Alice McNally. “Saying everything is hunky dory is a disservice. … It’s time to stop painting a rosy picture and make the public aware of the danger of the status quo.”

High seas

Yes, the walkway behind the rocks is relatively low and “likely will be overtopped under large wave conditions, especially if these occur during extreme high water levels,” the study said.

“However, the impact of wave run-up and overtopping on the walkway itself or on public access is limited and temporary, since the beach will not be accessible during such conditions, and floodwater has adequate drainage from the site and off the public walkway.”

Yes, sea level rise “will likely increase both the wave forces on the rocks (due to greater water depth and wave height fronting the revetment), and sand scour undermining that could lower and destabilize the revetment (due to beach retreat),” the study said. “The major threats to revetment stability in the future include wave storms, or clusters of wave storms, such as those that occurred from 1981 to 1983.”

But the revetment has high “adaptive capacity … in the sense that its current stable condition, along with occasional maintenance, will allow it to continue functioning as intended,” the study said. “The revetment, in its present condition, is likely to tolerate wave forces with acceptable rock movement that will not affect the integrity of the revetment as a whole…. as designed and with minimum regular maintenance, the revetment will withstand wave forces over the next 30 years,” while the retaining wall, and walkway will provide additional protection to the seawall.

Over time, as waves act on the rocks, they move around, Pontes said. Edison restacks them every five years or so. The last time was around 2016, and planning is underway to decide when to do it again.

The seawall itself is not meant to block a tsunami, but simply to protect the site from erosion. And despite its weathered appearance, it continues to do exactly that.

In the unlikely event that the dry storage systems were flooded, they’d simply drain, officials said.

Groundwater

As sea levels rise, groundwater levels are expected to rise as well.

What if the water table rises higher than the bottom of the waste storage system? Will the concrete suck up water? Will the water seep into the vaults holding the steel canisters holding the radioactive waste? Will water degrade those canisters — especially the ones that were scratched on their way into the vaults?

No,  Ponte said. Even under the most extreme scenarios, groundwater is predicted to remain below the bottom of the storage systems by almost one foot. The floor of the structure is 3 feet thick, and the concrete is dense — the same kind of concrete used to construct underwater structures like piers and dams. Even if groundwater did rise above the floor, the concrete wouldn’t wick up water, he said.

Garry Brown, of Orange County Coastkeeper, was skeptical. “We use the word predicted a lot,” he said. “It means we really don’t know. … When you have small tolerances, it’s a cause for concern.”

“You’re right, we don’t know what the future holds,” Pontes shot back, explaining that Edison is required to report based on older state guidance that actually predicts more extreme water rise than we’ve been seeing.

“Let’s assume it’s much more aggressive,” Pontes said. “If the water table exceeds the bottom of (the storage system), the question we should be asking is, ‘Is that a problem?’ The answer is no. It’s not a problem. Groundwater could continue to rise above the bottom and not be a problem.

“Why? Because the concrete is very dense. Water would have to find a way to migrate through the concrete to find its way to a canister. Let’s say it did. That stainless steel cavity enclosure is closed and welded on the bottom. It’s three-fourths of an inch thick. It would take a long, long time for anything to corrode through that — decades, hundreds of years, maybe never, before you would see a problem. It shouldn’t be a concern.”

How do we know that? The nuclear plant itself was built below sea level back in the 1970s. “Bone dry,” Pontes said. “We’re fulfilling our duty. We don’t think there’s a problem here.”

In 2035, Edison will have to tell the state when the waste will be moved to federal storage. There will be more data on sea level rise by then. If the waste is still there and risks increase, they’ll be dealt with.

Disappointed

Headrick, of San Clemente Green and the soggy sea wall, was disappointed.

“I’d say there are plenty of reasons to at least take a closer look at the situation with the latest technology, as recommended by one of the researchers,” he said by email. “It’s my understanding that they have the power to give that direction immediately….

“We all hope it turns out to be in a safe, dry condition, but even so, there are other things to be looked at more closely. There are canisters with obvious damage and no way to repair them if they continue to get worse and possibly fail.”

Edison said it has, indeed, developed a way to repair canisters inside their vaults. In 2020, it sent repair robots — sort of like high-tech St. Bernards — into a test vault to find and fix a test-damaged canister. One robot carried inspection cameras. The other, a nozzle mounted on a movable arm. Using magnetic wheels to crawl around, the robots found the trouble spots and applied a metallic overlay of nickel, effectively sealing them.

That doesn’t much comfort Headrick. Water inundation damages pipes and foundations, he said, and it needs more study at San Onofre. Replacing the canisters with something thicker, that can be used for long-term federal storage, seems prudent. There’s no time to waste getting the waste moved to higher ground, he has said.

An unlikely scenario, at best. Other locations on the Navy property were considered and rejected. The storage systems in place cost hundreds of millions of dollars to build and maintain. Entrepreneurs try to drum up enthusiasm for temporary waste sites, where America’s commercial nuclear waste might be consolidated, but those efforts are always blocked by lawsuits from folks in the surrounding communities.

The best bet continues to be prodding the federal government, which bears the ultimate responsibility, and has some $46 billion set aside to do it to boot.

We’re waiting.

Source: Orange County Register