SCE Looking Ahead to Re-start of Fuel Transfer Operations at San Onofre Nuclear Plant
ROSEMEAD, Calif., June 3, 2019 — The Nuclear Regulatory Commission (NRC) re-affirmed during a webinar today that Southern California Edison has satisfied all the requirements necessary to safely re-start transferring spent nuclear fuel from wet to dry storage at the San Onofre nuclear plant.
Fuel transfer operations (FTO) at San Onofre have been on hold since Aug. 3, 2018, when a spent fuel canister became wedged during downloading into its cavity enclosure container (CEC). The canister remained in this unsupported position for approximately 45 minutes before being successfully downloaded. SCE notified the NRC informally on Aug. 6 and eventually the NRC conducted a special inspection to further understand what happened and why.
SCE also undertook a comprehensive review of its fuel transfer operations. From that review, SCE and its vendor, Holtec International, developed more than 70 corrective actions to enhance and strengthen how it transfers the spent fuel to passive dry storage. Those improvements comprise five key areas:
- Corrective Action Program
SCE has full confidence in its internal team and external partner to safely recommence the fuel downloading campaign. The NRC conducted multiple inspections, observed dry runs and reviewed corrective actions before concluding fuel transfer operations could continue.
“Now that the NRC has said fuel transfers can safely resume, Holtec crews are being remobilized and retrained and SCE has several weeks’ worth of internal reviews to perform before we are ready to announce a date for again moving spent nuclear fuel from wet to dry storage,” said Doug Bauder, SCE vice president and chief nuclear officer. “It is critical to our employees, our stakeholders, and the community that we can complete FTO without further incident. That’s our focus.”
To date, 29 of 73 canisters have been loaded into the Holtec UMAX dry storage facility. At the time fuel transfer operations paused, one canister had been loaded and welded shut but remained safely stored in a fuel handling building.
Incidental Contact on Canisters
The NRC stated in a May 21 news release that its determination fuel transfer operations could resume safely came following “extensive review of technical data submitted by Edison regarding the possible effects of scratching on spent fuel canisters during fuel loading operations.”
In a letter to the NRC dated May 17, SCE explained its process for developing the data:
SCE performed a visual assessment of a series of loaded canisters using robotic, specialized, precision camera equipment to measure surface defects. A statistical evaluation was performed based on the wear marks observed for each MPC (multi-purpose canister). Based on the results of the visual assessment and associated statistical evaluation, SCE has concluded that given the potential for wear due to incidental canister contact, there is ample margin of safety under stringent American Society of Mechanical Engineers Boiler and Pressure Vessel Code requirements for canister integrity. SCE understands that the NRC agrees with this conclusion. A site-specific resolution to this issue was developed which included a revision to the 10 CFR 72.212 evaluation and a new 10 CFR 72.48 screening.
It is important to note the San Onofre canisters were built with walls that are 0.125 inches thicker than the standard Holtec canisters, which provides additional margin for wear and corrosion. As a result, potential wear marks, even the maximum predicted or observed depth, will still be well above the nominal licensed value for canister wall thickness of 0.50 inches.
The NRC reiterated during today’s webinar that an inspector was present for seven of the eight canister inspections, the data provided by SCE was independently validated, and that the incidental contact was not a safety related issue.
Read more about SCE’s analysis of incidental contact here.
Improvements to Fuel Transfer Operations
SCE and its vendor Holtec undertook a comprehensive review of significant aspects of fuel transfer operations at San Onofre. First, procedures were made more robust, identifying critical steps in the process and the qualifications necessary for personnel performing the work. Equally important, SCE outlined the criteria for stopping work when necessary.
A new San Onofre-specific training program was developed for fuel transfer operations, covering the positions involved in fuel transfer. SCE oversight personnel have new training requirements and a senior manager observation program has been added, as well as oversight personnel with specific fuel transfer experience.
A strengthened corrective action program will better capture lessons-learned that can be used to improve operations going forward.
Finally, new equipment additions will assist the team in monitoring every step of the downloading process. The new technology includes load shackles, cameras, monitors and alarms.
Prior to re-start, SCE oversight organizations will perform a thorough review to confirm all corrective actions developed over the past nine months remain firmly in place. SCE will initially commence with fuel transfer from one unit once all reviews are successfully completed. All fuel transfers are expected to be completed early next year.
Media Contact: John Dobken, (626) 302-2255
About Southern California Edison
An Edison International (NYSE:EIX) company, Southern California Edison is one of the nation’s largest electric utilities, serving a population of approximately 15 million via 5 million customer accounts in a 50,000-square-mile service area within Central, Coastal and Southern California.