Concerns about San Onofre are real, but experts debate level of risk

Let’s all agree that storing 3.6 million pounds of highly radioactive nuclear waste on a bluff beside the ocean in an earthquake zone near 8 million people is, at the risk of gross understatement, not ideal.

Let’s all agree that it should leave San Onofre and be safely ensconced in a federal graveyard as soon as humanly possible (if not sooner).

And let’s attempt to separate fact from fancy as we wait, and wait, and wait for that to happen — teasing what might be worth worrying about from, say, more performative panic. To that end, we’ll curate a debate between two nuclear experts who have very different ideas on what we should fret over when it comes to the spent fuel in dry storage at San Onofre Nuclear Generation Station.

Meet the experts!

On one side we have David Lochbaum, recently retired director of the Nuclear Safety Project for the nonprofit Union of Concerned Scientists. Lochbaum has a degree in nuclear engineering and worked in the industry before becoming one of its leading watchdog/critics.

On the other side, we have Paul Blanch, nuclear industry whistleblower, consultant and expert witness on regulatory matters. Blanch’s degree is in electrical engineering, and he worked in the nuclear industry as well.

What do they worry about? Very different things.

Let’s start with Blanch. “The bottom line is that there is a probability of flooding of the canisters in our present location. Should this occur, the impact on Southern California would be unimaginable.”

Blanch’s nightmare scenario plays out like this: A giant tidal wave inundates the “concrete monolith” that is San Onofre’s Holtec dry storage system. Most of the waste is inside canisters, inside vaults, inside that concrete monolith, just a few hundred feet from the ocean.

In this nightmare scenario, salt water and debris fill the vaults. The canisters inside are cool, as far as nuclear waste goes, at several hundred degrees. They’re kept cool by airflow — a passive system that sucks in cool air and releases hot air, not needing any electricity to get the job done. But what would happen if the vaults were submerged in water?

Well, water was fine when the waste was cooling in spent fuel pools (it cools in those pools for years after its tour of duty in the reactor core is done). So why fear water now? The presence of boron in cooling pool water, and the precise spacing between fuel assemblies, kept things under control, Blanch argues. Salt water would not have boron. Waste might not be spaced well enough to prevent “criticality.” After water boiled away, salt and debris could remain inside the vaults, potentially blocking cooling airflow to the hot canisters. Big trouble, he said.

And some of the waste canisters suffered scratches on their way into the vaults. If a scratched canister came into contact with cool water, would it crack like a 400-degree Pyrex bowl suddenly submerged in ice?

Edison and the NRC say this is just not a credible threat scenario. The area is prone to tsunamis in the 6-foot range, not the 30-foot range that could reach and flood the dry storage area. And if monster waves came anyway, the water would cool the canisters, then recede.

The seawall, which is not required, provides some protection from a tsunami — but it’s redundant, as the older storage system (NUHOMS) is designed to withstand complete submergence up to 50 feet, and the new Holtec HI-STORM UMAX is designed to withstand complete submergence up to 125 feet, Edison spokesman Jeff Monford said.

Not credible.

“What do you mean by ‘credible’?” Blanch asked. “They won’t define it. I’ll agree that getting hit by a meteorite is not credible because the probability is so low. But what is the probability here? One in a thousand years, one in a million years? What we’re really looking for is the analysis that shows, should these become flooded, what are the consequences? I cannot get an answer.”

A hydrology analysis was done in the 1970s by Basil Wilson, when the two newest reactors were planned — below sea level. San Onofre has had many serious issues over the years — culminating in its shutdown — but serious flooding has not been among them. Wilson’s hydrology analysis has been updated over the years, and potential flooding has been considered by the California Coastal Commission, the California Lands Commission, etc., and Edison must do state-mandated studies of sea level rise near the plant regularly.

Blanch argues that’s not enough. He says updates are based on Wilson’s very old study and fresh investigation should be done.

“A major accident is acceptable in the nuclear field if it’s one in 10 million in one year. That’s what we’re looking for. That’s more than safe. One in a million would probably be safe to me. But someone needs to say it. I don’t know what the probability is. They have not done it.”

He’s not saying flooding is a problem. But he wants to see an analysis showing it isn’t a problem, he said.

Other worries

Lochbaum, meanwhile, probably couldn’t disagree more.

“I have zero concerns about the spent fuel in dry storage at San Onofre being vulnerable to flooding from tsunamis,” he said. “Forget Dr. Wilson’s studies from the 1970s — SCE has commissioned more recent assessments that show the threat to be negligible. Zero concerns. At most.

“I do have concerns about dry storage of spent fuel, at San Onofre and elsewhere. But none are tsunami-related. None.”

Instead, Lochbaum’s concerns center on the dry storage systems themselves and what will happen to them over time.

Casks containing the waste are vulnerable to wear and tear and degradation as they age. Once ensconced in steel and concrete and locked away, it can be hard to assess how time is treating them.

“NRC requires — or ‘suggests,’ more accurately — and a very few casks get inspected every now and then,” Lochbaum said. “Not a safety spotlight, more like a very infrequent safety strobe light flashing, perhaps, once in awhile.

“Fortunately, a dry cask experiencing a through-wall crack isn’t like a balloon popping — all the contents won’t be swiftly released,” he said. “But the safety margins protecting the public will be reduced. That’s bad.”

Last September, Blanch, Lochbaum, Edison and others met to discuss such concerns. Lochbaum asked Edison if cask inspections would be required before shipping them off to federal storage somewhere (“in the off-chance that this day ever arrives,” he quipped).

Alas. Pre-shipment inspections are not required by the NRC. But Edison said it would inspect them anyway, because it’s a responsible actor.

“I have zero reason or evidence to doubt SCE’s sincerity,” Lochbaum said, “but I’d take more comfort in pre-shipment inspections being required by law rather than voluntary.

“If mandatory, and assuming San Onofre was not the first site to ship casks away, there’d be a database of inspections to show whether casks are, or are not, solid.”

Edison

San Onofre has two dry storage systems on that bluff over the blue Pacific.

The older one — the Orano TN-NUHOMS system that stores canisters horizontally — holds 50 canisters and is at that 20-year mark. In November 2021, Edison and Orano conducted a “baseline inspection,” finding no signs of degradation of inspected canisters, Edison said.

The other system is Holtec’s UMAX —the aforementioned “concrete monolith” — which stores canisters vertically. There are 73 waste canisters inside, the last of which were loaded in 2020.

Dry fuel storage systems are initially licensed for 20 years by the Nuclear Regulatory Commission. After that, an “aging management program” is required to evaluate “degradation mechanisms to determine if they could affect the ability of dry storage system components to fulfill their safety functions,” Edison explains. If all is well, the licenses can be renewed for 40-year intervals.

So while it won’t need an aging management program for the Holtec for years, Edison agreed to an “accelerated Inspection and Maintenance Program” nonetheless, including periodic canister inspections; a test canister program; radiation monitoring and reporting; and developing a way to inspect and repair canisters inside their vaults inside the concrete monolith.

In 2020, Edison 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.

When the time comes to move them to federal storage, each canister will be shipped inside a very heavy, shielded, sealed and helium leak-tested cask, adding another layer of containment, Monford said. Edison’s license does require that most, if not all, the canisters be inspected and/or tested prior to shipment.

Blanch doesn’t worry about flooding of the horizontal canister system — water can just drain out the bottom, he said — but he does worry about the vertical Holtec. “I don’t think, in the short term, we’re going to have any problems with spent fuel canisters, for the next 50 years or so,” he said. “But we’re going to start developing problems.”

He’d feel a lot better if the dry storage systems were hoisted another 20 feet in the air.

Lochbaum would feel a lot better if more regular and rigorous inspections of dry storage systems and canisters were required.

And all of us would feel a lot better if the federal government stopped dithering and finally found America’s commercial nuclear waste a permanent home, as it promised to do so many decades ago.

 

Source: Orange County Register