Used fuel transfer to resume at US San Onofre NPP

28 May 2019

US power utility Southern California Edison (SCE) has been approved to resume efforts to transfer used nuclear fuel at the two unit San Onofre Nuclear Generating Station (SONGS) into dry storage, the Nuclear Regulatory Commission (NRC) said on 21 May SCE has yet to determine when it will officially restart loading the nuclear fuel into canisters for transfer to its storage facility. “The ultimate decision on when fuel transfer operations will resume will be made following a careful review of operational readiness by SCE and our contractor,” SCE said in a press release. 

Edison and its contractor, Holtec International, suspended transfer operations following an incident in August  2018 as used fuel was being transferred from the storage pool to a Hi-Storm Umax dry cask storage facility. However, the canister carrying used fuel that was being lowered into a vertical receptacle was not aligned properly and it became stuck on a guiding ring. The plant personnel believed the canister had been fully inserted, because the rigging that supported the canister had gone slack until a radiation protection technician registered radiation readings higher than expected for a properly loaded cask.

The misalignment was corrected and the canister properly stored, but the incident was not notified to NRC within 24 hours as required. NRC imposed a fine of $116,000 on Edison for the incident but not for missing the 24-hour notification deadline. The failure of lifting equipment placed the canister in what the NRC described as "an unanalysed condition", and created the possibility of a "load drop event"," as the canister could have fallen  5.5 metres into the storage vault if it had slipped off of the inner ring assembly. Since then SCE has conducted a “comprehensive review” of its transfer operations and has made adjustments to its programme “through better procedures, better training, and more intrusive oversight.”

“This, in part, includes the addition of cameras and load monitoring equipment, which will provide valuable information during download operations,” John Dobken, the media relations manager at SCE, said in an email. “We have demonstrated these improvements are effective and sustainable through numerous dry runs, regulatory inspections and independent reviews.” NRC said its decision to allow Edison to resume operations was based on an “extensive review of technical data” that SCE submitted “regarding the possible effects of scratching on spent fuel canisters” during operations.

Protesters have alleged that damage to the canisters could weaken their structure but both Edison and NRC say any contact sustained would be minimal. However, Congressman Mike Levin, who has insisted on the used fuel being removed to permanent storage, said there are still unanswered questions regarding the safety of loading fuel at SONGS and has called for a full-time NRC inspector at the facility. SCE retired SONGS in June 2013 after a contractor provided faulty steam generators. The plant is now undergoing decommissioning.

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