Half-way Point Reached, Passed in Fuel Transfer Operations

On Friday, Oct. 25, crews successfully downloaded canister #37 into the Holtec dry storage system. This marked the half-way point in the campaign to store the remaining spent nuclear fuel assemblies on site. In all, 73 canisters of spent fuel will be placed into the Holtec system. This morning, canister #38 was safely stored.

Since re-starting fuel transfer operations (FTO) July 15, nine canisters have been loaded, sealed, transferred and stored (though canister #30 had been loaded and sealed prior to that date). Previous updates have summarized the operations involving canisters 30 and 31 and canisters 32 and 33.

So how are we doing?

“Overall, we continue to make improvements to the process through worker engagement and oversight,” said Doug Bauder, SCE vice president and chief nuclear officer. “I’m pleased to see the focus on safety over schedule, which includes stopping work to ensure our actions are correct and make process improvements.”

What We’ve Seen

During one of the recent downloading evolutions, the SCE oversight team identified an opportunity to clarify the training procedures for vertical cask transporter operators. The VCT is the vehical that is used to transport dry fuel storage canisters to the storage pad and position the canisters for lowering. The qualified VCT operator was found not to be in close enough proximity to the crew member undergoing qualification. It’s not unusual for final training qualifications to be done in the field. SCE is working with Holtec to continue improving the training process.

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The vertical cask transporter downloading canister #37 on Friday Oct. 25.

Due to increased focus by Holtec and SCE on soliciting craft feedback and maintaining a healthy safety culture, a Holtec craft worker identified a concern that in some wind conditions, exhaust fumes from the VCT could affect workers in close proximity. Holtec took timely action to have the vendor assess the problem and resolved the concern by modifying the VCT exhaust design. In another instance, a Holtec craft worker noticed the shield cone assembly on top of the canister was slightly tilted. The shield cone provides additonal radiation protection while the canister is being moved. Follow up inspections by Holtec and SCE engineering identified that the shield cone assembly should be modified to eliminate the tilt and in doing so improved the overall canister lifting capabilities and safety margins.

Besides getting onsite feedback about issues, we are also looking at industry operating experience to help us improve FTO. A report from another nuclear energy facility informed us that there may be deficiencies associated with the annual inspection requirements for critical lifting components. We immediately stopped all activities that required the use of the associated components and employed a recertification of all affected equipment using a conservative interpretation of the certification standard.

The continued use of the SCE corrective action program by Holtec personnel, especially craft, has resulted in timely screening of issues and concerns by both SCE and Holtec oversight. The CAP, as it is known, helps identify and track issues on site so they can be appropriately resolved. The items entered into the CAP are being evaluated and resolved in a timely manner in support of maintaining nuclear, radiological, and industrial safety performance. This supports continued improvement of fuel transfer operation performance.

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Keeping an eye on downloading operations at SONGS.

Changes Made to FTO are Helping

One of the many changes made to FTO was the addition of “underload sensors.” This is a system that alerts the crew when the spent fuel canister makes incidental contact with inner components of the cavity enclosure container during downloading, such as the shield ring or a seismic support. The monitor allows the operator to take action to ensure there’s not another event like happened Aug. 3, 2018. The sensors, along with the training and procedure changes made, have ensured that the enhanced safety margins are maintained.

Nuclear Regulatory Commission on Site

The NRC recently closed out one inspection period for fuel transfer operations and an inspection report will be issued in the future. The next inspection period began with an inspector on site during the week of Oct. 21 for an unannounced visit.

Watch for more updates in the weeks and months ahead as we work through safely storing the remaining spent fuel canisters at SONGS.

(Posted Nov. 1, 2019)