RadWaste Monitor Vol. 11 No. 41
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RadWaste & Materials Monitor
Article 4 of 6
October 26, 2018

NRC Finds ‘Multiple Performance Deficiencies’ in SONGS Spent Fuel Mishap

By ExchangeMonitor

By John Stang

“Multiple performance deficiencies” contributed to an August mishap in the transfer of spent reactor fuel at the San Onofre Nuclear Generating Station (SONGS) in California, and could have led to a storage container being dropped nearly 20 feet, according to initial findings from the U.S. Nuclear Regulatory Commission.

At the top of the list were failures in training, gear, oversight, and other operational areas by SONGS majority owner Southern California Edison (SCE), the NRC said in its Oct. 19 preliminary report on the incident.

Agency personnel are investigating the incident, including a site inspection last month.

“NRC inspectors are continuing to review the licensee’s calculations of potential damage to the canister and the fuel from the misalignment and from a potential drop if the cask had fallen,” the report says.

The NRC investigation is focusing on Southern California Edison, which is the plant licensee and responsible for the work on the site, all involved parties said. Holtec International is also involved in the transfer of used nuclear fuel in a subordinate role and as the manufacturer of the canisters.

The NRC is awaiting additional information from SCE before issuing its final report on the inspection, which began Sept. 10.

“SCE agrees with the commission on many aspects of the inspection so far amid continued discussions. Over the past few weeks, SCE has analyzed the event and developed its cause evaluations to help better understand performance gaps in the overall fuel transfer operation. SCE is implementing corrective actions,” the utility said in a statement.

Southern California Edison said it would discuss corrective actions in detail after the NRC investigation is complete. Holtec is working in its own responses, but will not unveil them until it gets a green light from SCE.

Meanwhile, “SCE won’t resume fuel transfer operations until the commission completes its inspection activities and SCE is satisfied the proper procedures and processes are in place,” according to the statement.

The utility in 2014 contracted Holtec to build the storage pad from for used fuel from reactor Units 2 and 3 at the San Diego County plant, which permanently closed in 2013. The contract also covers “pool-to-pad loading services” for 2,668 used fuel assemblies held in Holtec storage canisters.

On Aug. 3, a fuel canister was being placed into a below-ground slot in the oceanside storage pad. The canister’s rigging went askew so the container could not go smoothly into the silo, which took nearly an hour to fix. Workers did not notice that the canister was not correctly aligned, that it was resting on a “divider shell assembly,” that its weight was not supported by lifting gear, and that the situation left the canister susceptible to a drop, the NRC said.

That scenario had not been analyzed as a potential mishap, according to the agency.

The preliminary findings in the report, which the regulator noted are subject to change, said the incident led from SCE “deficiencies involving training, equipment, procedures, oversight, and corrective actions.” Also, the Aug. 3 procedure was not properly supervised, according to the NRC.

“The NRC observed instances where personnel involved in important-to-safety tasks were not trained and certified or under direct supervision,” the preliminary report said.

Southern California Edison did not informally tell the NRC about the incident until Aug. 6 — beyond the 24-hour legally required deadline. It issued a formal report on Sept. 14 after NRC prompting.

The NRC is also looking into an unspecified July incident at SONGS — which did not involve a dropped canister — about which SCE did not alert the public. The NRC said the July incident was not of the type that required the agency nor the public to be notified. As of Thursday, information of that July incident was not publicly available.

So far, the dropped canister appears to have sustained only paint scrapes and wear marks. However, studies of the canister’s bottom are ongoing, with the NRC reviewing SCE’s analysis.

The canister is a Holtec multipurpose container holding 37 fuel assemblies. As part of the investigation, Holtec did an initial drop analysis of a canister of the same model from 25 feet, and the NRC found that study inadequate. Holtec conducted a second revised analysis to meet the agency’s concerns. “That drop analysis showed that the canister and all associated welds would remain intact, preventing any kind of radioactive release, when dropped from 25 feet onto a hardened surface,” the NRC said in a document addressing public questions about the incident.

An analysis of the fuel in the dropped canister is ongoing; the NRC suspects the fuel assemblies might have suffered some damage. “With the container remaining intact, a release of radioactive material to the outside environment is not considered likely,” the NRC document said.

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DOE spent fuel lead Brinton accused of second luggage theft.



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