The U.S. Nuclear Regulatory Institute said this week that Southern California Edison (SCE) has taken significant steps to address the failures that led to a mishap last year in the transfer of used fuel at its San Onofre Nuclear Generating Station (SONGS). However, the agency said a follow-up inspection identified five additional minor violations of safety requirements.
From January to April, NRC personnel conducted a supplemental inspection to its initial probe of the August 2018 incident at the retired nuclear power plant in San Diego County. The follow-up was intended broadly to determine whether SCE understood the causes of the mishap and had taken steps to prevent recurrence.
“The NRC determined that your staff’s causal evaluations to address the previously issued violations were adequately performed to the depth and breadth required,” Greg Warnick, chief of the Reactor Inspection Branch at the NRC’s Division of Nuclear Materials Safety, wrote in a July 9 letter to SCE Vice President and Chief Nuclear Officer Doug Bauder. Warnick added: “The NRC determined that your staff identified and implemented appropriate corrective actions to revise loading procedures, revise the reportability program, utilize equipment enhancements, require adequate training, enhance oversight of operations, and enhance the corrective action program at SONGS.”
Southern California Edison, the plant’s majority owner and federal licensee, permanently retired SONGS’ last two operational reactors in 2013 after they were equipped with faulty steam generators. The company in 2014 hired Holtec International to move the reactors’ used fuel from wet to dry storage. Last August, one canister of fuel assemblies was left at risk of a nearly 20-foot drop for about an hour after it became stuck on the shield ring to its underground storage slot.
In March, the NRC fined the utility $116,000 after a special inspection that identified two violations of federal nuclear safety rules: failure to deploy backup gear to prevent a canister drop and failing to alert the regulator to the event within 24 hours.
Southern California Edison and Holtec paused the fuel offload while the NRC conducted its initial inspection. The agency in May approved work to resume, but SCE is continuing practice runs and other readiness preparation ahead of the actual restart, spokesman John Dobken said Thursday. Once resumed, the project is expected to be completed in early 2020. At that point, roughly 3.5 million pounds of used fuel assemblies from three reactors would be in dry storage on the SONGS property.
The 2018 incident revived simmering local concerns about long-term storage of radioactive waste in a densely populated region along the Pacific Ocean that is given to seismic activity. Two earthquakes last week in Southern California drew new coverage to the issue. Southern California Edison acknowledged that shaking from the earthquakes could be felt at San Onofre, but that they caused no problems for any equipment or systems.
The NRC supplemental inspection involved site visits in February, March, and April, along with evaluation of data from Southern California Edison from last November to May, according to Warnick. The aim was to ensure SCE understood the root and contributing causes to the “significant performance issues” that led to the 2018 incident; had identified the extent of condition and extent of cause for those issues; had taken quick corrective actions to resolve those issues and ensure they did not happen again; and that those corrective action plans ensure follow-on steps toward that same end.
While finding that SCE had met those expectations, this year’s NRC supplemental inspection identified the following Severity Level IV, non-cited violations of low safety significance at SONGS: “failures to: (1) ensure appropriate quality standards on new equipment for downloading/withdrawal operations; (2) ensure purchased material conformed to the procurement documents for load sensing shackles; (3) ensure the loaded transfer cask and its conveyance was evaluated under the site-specific design basis earthquake; (4) provide adequate written basis for the initial 10 CFR 72.48 scratch evaluation; and (5) request the certificate holder to obtain a Certificate of Compliance amendment for use of the intermediate shelf in the spent fuel pool.”
None of the violations could have led to additional fines, the NRC said this week.
Southern California Edison has addressed the non-cited violations listed in the NRC report over a period of months, Dobken said by email. “Resolving these issues included work by SCE to develop and implement additional corrective actions; engineering evaluations; visual assessments of canister surfaces; and to update procedures. The NRC, through its onsite inspection activities conducted January through April, validated these additional actions taken by SCE were appropriate and sufficient.”
