The brand-new steam generators were supposed to give San Onofre Nuclear Generating Station another 20 years of life.
Instead, they sealed its death.
Those $671 million generators, installed to replace the old ones in 2010, didn’t require Nuclear Regulatory Commission scrutiny or approval because they were supposedly the same as the originals. And now a version of the NRC’s “like for like” replacement rules has come into play at San Onofre again, this time allowing four nuclear waste canisters with a potentially defective design to be loaded with spent fuel and buried yards from the beach.
Southern California Edison, San Onofre’s majority owner, was preparing to load a canister with spent fuel in February when it discovered a loose bolt inside, according to Edison. An investigation revealed a potential flaw in the new design of the canisters, which the manufacturer believed was minor enough to not require NRC scrutiny.
What is the “like for like” replacement rule?
The NRC’s 72.48 provision allows licensees or certificate holders to make minor changes to design without prior NRC inspection – as long as they say the change does not significantly impact safety, said NRC spokesman David McIntyre.
What happened with the steam generators in 2010?
The replacement generators were essentially identical to their original counterparts, according to their manufacturer and Edison. But that wasn’t actually the case.
“On the outside, they may look identical, but on the inside, they’re dramatically different,” said Arnie Gundersen of Fairewind Associates, shortly after San Onofre’s reactors powered down for the final time in 2012. “It’s like taking a Model T and slapping a V-8 engine in it.
“Southern California Edison didn’t want to admit they were dramatically different, because that would open up a license amendment, and the public would get involved.”
The new steam generators shook and vibrated so much that the tubes inside them started breaking. That led to the release of a small amount of radioactive gas, which led to the power-down of both reactors, which led to San Onofre’s premature shutdown, which cost $4.3 billion. Parties are still squabbling over who should bear the brunt of that cost.
So what happened with the nuclear waste canisters?
Edison is moving tons of waste from the reactors’ two spent fuel pools into a Holtec HI-STORM UMAX dry storage system. Experts say dry storage is far safer than wet storage, and Edison aims to transfer it all to the Holtec system by mid-2019.
Holtec’s original canister design was approved by the NRC. The small alteration it made was not.
Edison was not informed of the redesign of the waste canisters, Edison officials said.
What was the small alteration?
Holtec revamped the shim design. “Shims,” as the Surfrider Foundation explains, “are hollow spacer devices made from aluminum, which are placed inside the spent fuel canister, between the basket (which holds the spent fuel assemblies) and the inner canister wall.
“Their purpose is twofold: to allow a path for the flow of helium throughout the canister to facilitate cooling, and to act as a support structure, securing the basket.”
At the bottom of the new shims are four bolts, or pins, which elevate the shim off the bottom of the canister to ensure that helium can flow more evenly.
The original shims had no pins. They were solid metal, with cut-outs at the bottoms to facilitate helium flow.
If Edison wasn’t told of the change by Holtec, how did it come to light?
In February, as Edison was preparing to load a canister with spent fuel, it discovered the loose bolt inside, about four inches long by a half-inch thick.
At first, workers thought an extra part was inadvertently placed or left inside the canister. The piece was returned to Holtec, which then determined that it was a piece of a stainless steel pin threaded into the bottom end of an aluminum shim within the canister. Holtec inspected and found another bolt inside another canister.
What caused the bolts to break loose?
One of the current theories is that the “laser peening” process – where the canisters are bombarded with high-energy lasers as they spin, to improve the strength and durability of the metal – may be the cause of the wayward bolts.
“Think of how a paper clip, if you bend it back and forth often enough, will break,” said Dave Lochbaum, Director of the Nuclear Safety Project for the nonprofit watchdog Union of Concerned Scientists. “As the canister turned so many times, that may have applied the load that ultimately broke the pin.”
Why did Holtec redesign the shims in the first place?
The company did not respond to repeated requests for comment, but NRC spokesman Scott Burnell said, “the vendor has indicated it made the change to improve the ability to fabricate the design.”
Donna Gilmore, a critic of Edison and activist at SanOnofreSafety.org, suspects that the redesign has to do with the canister’s heat rating.
“It’s clear from the photo that the new design allows more helium flow, which is part of the cooling system,” Gilmore said. “If I am right, it brings into question whether the cooling system of the older shim design provides sufficient cooling…. Holtec’s pattern is to push the safety limits.”
Has Holtec had any trouble with regulators?
Holtec has had its critics.
More than a decade ago, the company was working on storage casks for the giant Tennessee Valley Authority, America’s largest public power provider. A probe by the U.S. Attorney’s Office asserted that a subcontractor manufacturing Holtec’s casks – U.S. Tool & Die – wrote checks totaling $54,212 to the account of a TVA manager. That money, the U.S. Attorney’s Office said, originated with Holtec.
The TVA manager pleaded guilty to falsifying financial statements by not disclosing those payments. Holtec said it wasn’t privy to any of this, and was not charged.
Nonetheless, in 2010, Holtec paid a $2 million “administrative fee” to the TVA and became the first contractor in TVA history to be debarred. Its contract was suspended for 60 days, and it submitted to a yearlong monitoring program, according to the TVA’s inspector general.
Is this, in the end, the NRC’s responsibility?
“The NRC needs to look at how that change was justified by Holtec as something it could do on its own,” said Lochbaum of the Union of Concerned Scientists. “It doesn’t mean Holtec has to be right, but the decision needs to have been made on reasonable grounds. If it was a change that should have required NRC approval, the NRC will take action.”
Investigations are ongoing. The NRC’s Burnell and McIntyre said the agency will be inspecting Holtec in May, “and will be examining this change at that time to determine whether it was properly implemented under the regulation.”
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Source: Oc Register