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Edison Reveals Design Flaws In New Canisters Storing Nuclear Waste At San Onofre

The site of spent nuclear fuel storage at the San Onofre nuclear power plant is shown in this photo, January 2018.
Southern California Edison
The site of spent nuclear fuel storage at the San Onofre nuclear power plant is shown in this photo, January 2018.

Southern California Edison stopped loading spent nuclear fuel rods into canisters at San Onofre for about a week, after discovering a design flaw in the new containers built for the nuclear waste.

Edison’s Chief Nuclear Officer Tom Palmisano revealed the problem Thursday night at Edison's Community Engagement Panel meeting in Laguna Hills. The panel meets quarterly in public to review the decommissioning process.

Holtec International, which designed the storage system known as HI-STORM UMAX, made a design change to an internal component of the storage canisters. SCE discovered a loose pin at the bottom of aluminum shims, designed to create space for helium to flow around the fuel assemblies and cool them.


"We directed the manufacturer to conduct extensive evaluations to ensure we have a comprehensive understanding of this change," Palmisano said.

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Edison has resumed loading fuel rod assemblies into canisters with the original design. The company said 30 of the 73 canisters supplied to store the spent nuclear fuel have the original design, which meets the Nuclear Regulatory Commission's criteria, and is used extensively in the industry.

Ray Lutz of the group "Citizens Oversight" said he is very concerned by Palmisano’s response to questions about the problem with the canisters.

"It’s pretty worrisome that the first four canisters that they loaded, already, we're notified that they are having these defects,” Lutz said, “and now, when they were asked, 'Can we open them up and replace these parts?' they said, 'No, no one has ever opened these canisters up, we don’t know how to do it — it would take years of research."


RELATED: Edison Names Panel Of San Onofre Nuclear Waste Advisors

Edison began moving hundreds of spent nuclear fuel rods from cooling pools at the now-shuttered power plant into dry cask storage in January. The stainless steel canisters are partially buried, encased in concrete, next to the beach at San Onofre.

Gary Headrick, of the group San Clemente Green, spoke at the Citizens Engagement Panel meeting. He is concerned about how experimental the process is, and how fast Edison is moving forward with the process of moving the waste.

Palmisano described a radiation monitoring system that would publish results once a month. Several members of the public requested permanent radiation monitoring at the nuclear power plant as it is being decommissioned.

A newly appointed panel of experts is due to meet at San Onofre next Tuesday to discuss how and where to store the fuel rods, which remain radioactive for tens of thousands of years. There is currently nowhere to store them safely long term.