The Nuclear Regulatory Commission staff is evaluating an incident that occurred August 3, 2018, at the San Onofre Nuclear Generating Station (SONGS) during fuel transfer operations. Plant personnel were transferring a multipurpose canister filled with spent nuclear fuel from the spent fuel pool to the HI-STORM UMAX dry cask storage facility. As the canister was being lowered from the transport cask into the underground storage vault, it became stuck on the gusset or inner ring assembly near the top of the vault's inner liner, known as the "divider shell."
Figure 1 – Divider Shell
The plant personnel believed the canister had been fully inserted, because the rigging that supported the canister had gone slack. After a radiation protection technician registered radiation readings higher than expected for a properly loaded cask, the personnel performing the operation realized the problem. They then corrected the canister's alignment and successfully completed the operation.
San Onofre personnel failed to observe (1) that the canister was misaligned, (2) that the canister had made contact with and was resting on the divider shell assembly, and (3) that the lifting devices and equipment – considered "important to safety" because of their role in ensuring safe storage and handling of the waste – were no longer supporting the canister weight. The failure of lifting equipment placed the canister in what the NRC calls "an unanalyzed condition," and created the possibility of a "load drop event," as the canister could have fallen 18 feet into the storage vault if it had slipped off of the inner ring assembly.
San Onofre personnel implemented appropriate immediate corrective actions. These included restoring the control of the load to the rigging and lifting devices, properly placing the canister in the storage vault, suspending all movement of spent fuel, and initiating an investigation of the event.
San Onofre informed NRC Region IV staff of the incident on Monday, August 6, 2018, when the licensee provided a courtesy notification and described it as a near-miss or near-hit event. San Onofre personnel did not report the event as required by regulations. Following prompting by NRC staff, San Onofre submitted an event report (required by 10 CFR 72.75(d)(1)) on September 14, 2018.
Please see Figure 2 – Isometric View of Downloading Configuration.
The NRC initiated a Special Inspection during the week of September 10, 2018. The Special Inspection team investigated the "near miss" drop event, interviewed personnel involved, and observed equipment operation and preliminary corrective actions put in place to prevent recurrence of the event.
The following links provide additional information about the event and the NRC's special inspection.
- Special Inspection Charter
- Frequently Asked Questions
- NRC's Special Inspection and Preliminary Observations
- NRC Surveys of San Onofre Nuclear Generating Station ISFSI Pad, October 22, 2018
- San Onofre Special Inspection Webinar, November 8, 2018:
- NRC Routine Inspection Report 050-00206/2017-003, 050-00361/2017-003, 050-00362/2017-003, and 072-00041/2017-001, dated August 24, 2018
- NRC Special Inspection Report 050-00206/2018-005, 050-00361/2018-005,050-00362/2018-005, 072-00041/2018-001 and Notice of Violation, dated November 28, 2018
- Errata: San Onofre Nuclear Generating Station – NRC Special Inspection Report 050-00206/2018-005, 050-00361/2018-005, 050-00362/2018-005, 072-00041/2018-001 and Notice of Violation, dated December 19, 2018
- San Onofre Nuclear Generating Station Reply to a Notice of Violation, EA-18-155, dated December 26, 2018
- NRC Acknowledgement Letter regarding San Onofre Nuclear Generating Station Reply to a Notice of Violation, EA-18-155, dated January 17, 2019
- NRC Presentation provided to SONGS Community Engagement Panel on November 29, 2018
- NRC Inspection Report 072-01014/2018-201, Holtec International, dated November 29, 2018
- San Onofre Pre-decisional Enforcement Conference Webinar, January 24, 2019:
- San Onofre Nuclear Generating Station Webinar, March 25, 2019:
- San Onofre Community Engagement Panel Meeting – March 28, 2019:
- NRC Inspection Report 05000206/2018-004, 05000361/2018-004, and 05000362/2018-004, dated February 21, 2019 (Routine Decommissioning)
- NRC Inspection Report 050-00206/2019-001, 050-00361/2019-001, 050-00362/2019-001, dated March 18, 2019 (Routine Decommissioning)
- SCE Resumption of Fuel Loading, dated May 17, 2019
- NRC Press Release about Resumption of Fuel Transfer Operations, dated May 21, 2019
- NRC Acknowledgment of SCE letter for resumption of fuel loading, dated May 28, 2019
- San Onofre Nuclear Generating Station Webinar, June 3, 2019:
- Community Engagement Panel MTG on June 5, 2019
- NRC Supplemental Inspection Report 050-00206/2018-006, 050-00361/2018-006, 050-00362/2018-006, 072-00041/2018-002
- NRC Inspection Report 05000361/2019-003 and 05000362/2019-003, dated July 15, 2019 (Routine Decommissioning)
- Letter dated July 15, 2019, from Southern California Edison to the Nuclear Regulatory Commission regarding Resumption of Fuel Transfer Operations at San Onofre Nuclear Generating Station (SONGS)
- Letter dated July 16, 2019, from Kristine Svinicki, Chairman, Nuclear Regulatory Commission to the Honorable Mike Levin, United States House of Representatives, regarding NRC’s inspection plan for the SONGS decommissioning process
- NRC Press Release: NRC to Hold Public Meeting to Discuss Oversight Activities at San Onofre Nuclear Generating Station
- NRC Meeting Notice for "Town Hall" Style Meeting
- NRC Inspection Report 05000361/2019-004 and 05000362/2019-004, dated September 25, 2019 (Routine Decommissioning)
- NRC ISFSI Inspection Report 050-00206/2019-003, 050-00361/2019-005, 050-00362/2019-005, 072-00041/2019-001, dated November 22, 2019 (SCE Return to Fuel Transfer Operations)
- NRC Inspection Report 05000361/2019-006 and 05000362/2019-006, dated December 9, 2019 (Routine Decommissioning)
- Letter dated December 6, 2019, from Kristine Svinicki, Chairman, Nuclear Regulatory Commission to the Honorable Mike Levin, United States House of Representatives, regarding NRC's review of Southern California Edison’s analysis of and process to address scratches on multi-purpose canisters downloaded into cavity enclosure containers at SONG
- NRC ISFSI Inspection Report 050-00206/2019-004, 050-00361/2019-007, 050-00362/2019-007, 072-00041/2019-002, dated February 20, 2020 (SCE Fuel Transfer Operations)
- NRC Inspection Report 05000361/2020-001 and 05000362/2020-001, dated February 25, 2020 (Routine Decommissioning)
- San Onofre Nuclear Generating Station Lessons Learned from Canister Misalignment Event
- NRC ISFSI Inspection Report 050-00206/2020-005, 050-00361/2020-005, 050-00362/2020-005, 072-00041/2020-001, dated April 28, 2020 (SCE Fuel Transfer Operations)
- NRC Inspection Report 05000206/2020-002, 05000361/2020-002, and 05000362/2020-002, dated July 20, 2020 (Routine Decommissioning)
- NRC ISFSI Inspection Report 05000206/2020006; 05000361/2020006; 05000362/2020006; AND 07200041/2020002 dated August 4, 2020 (SCE Fuel Transfer Operations)
- Letter dated August 7, 2020, from Southern California Edison to the Nuclear Regulatory Commission regarding Registration of Dry Fuel Storage Canister and Certification of Permanent Removal of All Spent Fuel Assemblies from the Spent Fuel Pools at San Onofre Nuclear Generating Station (SONGS)
- NRC ISFSI Inspection Report 05000206/2020007; 05000361/2020007; 05000362/2020007; AND 07200041/2020003 dated September 14, 2020 (SCE Fuel Transfer Operations)
- NRC Inspection Report 05000361/2020-003 and 05000362/2020-003, dated October 22, 2020 (Routine Decommissioning)
Page Last Reviewed/Updated Friday, November 13, 2020