IR 05000413/2025003
| ML25345A070 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 12/18/2025 |
| From: | Robert Williams NRC/RGN-II/DORS |
| To: | Huecker J Duke Energy Carolinas |
| References | |
| IR 2025003 | |
| Download: ML25345A070 (0) | |
Text
SUBJECT:
CATAWBA NUCLEAR STATION - INTEGRATED INSPECTION REPORT 05000413/2025003 AND 05000414/2025003
Dear Jonathan Huecker:
On September 30, 2025, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at Catawba Nuclear Station. On December 16, 2025, the NRC inspectors discussed the results of this inspection with you and other members of your staff. The results of this inspection are documented in the enclosed report.
Due to the temporary cessation of government operations, which commenced on October 1, 2025, the NRC began operating under its Office of Management and Budget-approved plan for operations during a lapse in appropriations. Consistent with that plan, the NRC operated at reduced staffing levels throughout the duration of the shutdown. However, the NRC continued to perform critical health and safety functions and make progress on other high-priority activities associated with the ADVANCE Act and Executive Order 14300. On November 13, 2025, following the passage of a continuing resolution, the NRC resumed normal operations. However, due to the 43-day lapse in normal operations, the Office of Nuclear Reactor Regulation granted the Regional Offices an extension on the issuance of the calendar year 2025 inspection reports that should have been issued by November 13, 2025, to December 31, 2025. The NRC resumed the routine cycle of issuing inspection reports on November 13, 2025.
One finding of very low safety significance (Green) is documented in this report. This finding involved a violation of NRC requirements. We are treating this violation as a non-cited violation (NCV) consistent with Section 2.3.2 of the Enforcement Policy.
If you contest the violation or the significance or severity of the violation documented in this inspection report, you should provide a response within 30 days of the date of this inspection report, with the basis for your denial, to the U.S. Nuclear Regulatory Commission, ATTN:
Document Control Desk, Washington, DC 20555-0001; with copies to the Regional Administrator, Region II; the Director, Office of Enforcement; and the NRC Resident Inspector at Catawba Nuclear Station.
December 18, 2025 If you disagree with a cross-cutting aspect assignment in this report, you should provide a response within 30 days of the date of this inspection report, with the basis for your disagreement, to the U.S. Nuclear Regulatory Commission, ATTN: Document Control Desk, Washington, DC 20555-0001; with copies to the Regional Administrator, Region II; and the NRC Resident Inspector at Catawba Nuclear Station.
This letter, its enclosure, and your response (if any) will be made available for public inspection and copying at http://www.nrc.gov/reading-rm/adams.html and at the NRC Public Document Room in accordance with Title 10 of the Code of Federal Regulations 2.390, Public Inspections, Exemptions, Requests for Withholding.
Sincerely, Robert E. Williams, Jr., Chief Projects Branch 1 Division of Operating Reactor Safety Docket Nos. 05000413 and 05000414 License Nos. NPF-35 and NPF-52
Enclosure:
As stated
Inspection Report
Docket Numbers:
05000413 and 05000414
License Numbers:
Report Numbers:
05000413/2025003 and 05000414/2025003
Enterprise Identifier:
I-2025-003-0022
Licensee:
Duke Energy Carolinas, LLC
Facility:
Catawba Nuclear Station
Location:
York, South Carolina
Inspection Dates:
July 1, 2025, to September 30, 2025
Inspectors:
D. Rivard, Senior Resident Inspector
A. Wang, Resident Inspector
W. Deschaine, Senior Technical Training Program Specialist
S. Downey, Senior Reactor Inspector
C. Dykes, Senior Health Physicist
D. Jackson, Senior Project Engineer
K. Lei, Emergency Preparedness Inspector
A. Nielsen, Branch Chief
J. Walker, Senior Emergency Preparedness Inspector
Approved By:
Robert E. Williams, Jr., Chief
Projects Branch 1
Division of Operating Reactor Safety
SUMMARY
The U.S. Nuclear Regulatory Commission (NRC) continued monitoring the licensees performance by conducting an integrated inspection at Catawba Nuclear Station, in accordance with the Reactor Oversight Process. The Reactor Oversight Process is the NRCs program for overseeing the safe operation of commercial nuclear power reactors. Refer to https://www.nrc.gov/reactors/operating/oversight.html for more information.
List of Findings and Violations
2B EDG failed to flash due to open sliding link Cornerstone Significance Cross-Cutting Aspect Report Section Mitigating Systems Green NCV 05000414/2025003-01 Open/Closed
[H.12] - Avoid Complacency 71153 A self-revealed Green finding and associated non-cited violation of Technical Specification 5.4, Procedures, was identified when the licensee failed to properly perform maintenance activities as required by Regulatory Guide (RG) 1.33, "Quality Assurance Program Requirements (Operations), Revision 2, Section 9.a. Specifically, the licensee failed to properly restore sliding link TS1-3 following calibration activities, in accordance with procedure IP//2/A/3680/008B, "DG-2B EQC System Time Delay and Undervoltage Relays Calibration," rendering the 2B Emergency Diesel Generator (EDG) inoperable.
Additional Tracking Items
Type Issue Number Title Report Section Status LER 05000413/2025-001-00 LER 2025-001-00 for Catawba Nuclear Station,
Unit 1, Plant Shutdown Required by Technical Specifications Due to Unidentified Reactor Coolant System Leakage 71153 Closed LER 05000413,05000414/
2025-002-00 LER 2025-002-00 for Catawba Nuclear Station,
Units 1 and 2, Inoperability of 1 B Emergency Diesel Generator due to Fuel Oil Leak 71153 Closed LER 05000413,05000414/
2025-003-00 LER 2025-003-00 for Catawba Nuclear Station,
Units 1 and 2, 2B Emergency Diesel Generator Field Failed to Flash 71153 Closed
PLANT STATUS
Unit 1 operated at or near 100 percent rated thermal power (RTP) for the entire inspection period.
Unit 2 began the inspection period at or near 100 percent RTP. On August 25, 2025, Unit 2 commenced a power coast down. On September 3, 2025, the unit was shut down from 94 percent RTP for scheduled refueling outage C2R27. The unit remained shut down for the remainder of the inspection period.
INSPECTION SCOPES
Inspections were conducted using the appropriate portions of the inspection procedures (IPs) in effect at the beginning of the inspection unless otherwise noted. Currently approved IPs with their attached revision histories are located on the public website at http://www.nrc.gov/reading-rm/doc-collections/insp-manual/inspection-procedure/index.html. Samples were declared complete when the IP requirements most appropriate to the inspection activity were met consistent with Inspection Manual Chapter (IMC) 2515, Light-Water Reactor Inspection Program - Operations Phase. The inspectors performed activities described in IMC 2515, Appendix D, Plant Status, observed risk significant activities, and completed on-site portions of IPs. The inspectors reviewed selected procedures and records, observed activities, and interviewed personnel to assess licensee performance and compliance with Commission rules and regulations, license conditions, site procedures, and standards.
REACTOR SAFETY
71111.04 - Equipment Alignment
Partial Walkdown Sample (IP Section 03.01) (2 Samples)
The inspectors evaluated system configurations during partial walkdowns of the following systems/trains:
(1)2A EDG room during 2B EDG inoperability due to failed PT/2/A/4350/002 B, "Diesel Generator B Operability Test," on July 15, 2025
- (2) Nuclear service water (RN) alignment in accordance with OP/0/A/6400/006 C, 4.12A, "Alignment for Single Pump Flow Balance Due To One Train A RN Pump Inoperable," on September 12, 2025
71111.05 - Fire Protection
Fire Area Walkdown and Inspection Sample (IP Section 03.01) (2 Samples)
The inspectors evaluated the implementation of the fire protection program by conducting a walkdown and performing a review to verify program compliance, equipment functionality, material condition, and operational readiness of the following fire areas:
- (1) Fire area 21: auxiliary building elevation 594, Unit 1 and 2 control room on July 31, 2025
- (2) Fire area 12: Unit 2 electrical penetration room (484), auxiliary building elevation 577 on September 17, 2025
===71111.08P - Inservice Inspection Activities (PWR) The inspectors verified that the reactor coolant system boundary, reactor vessel internals, risk significant piping system boundaries, and containment boundary are appropriately monitored for degradation and that repairs and replacements were appropriately fabricated, examined, and accepted by reviewing the following activities for Unit 2 during refueling outage C2R27 from September 8, to September 21, 2025.
PWR Inservice Inspection Activities Sample - Nondestructive Examination and Welding Activities (IP Section 03.01)===
The inspectors verified that the following nondestructive examination and welding activities were performed appropriately:
(1)
- Liquid penetrant examination o
2NV116-19, pipe to pipe weld, ASME Class 2
- Magnetic particle examination o
2-R-SV-1573, welded attachment, ASME Class 2
- Radiographic examination o
2CA102-13, pipe to pipe weld, ASME Class 2. This included a review of the associated welding activities.
o 2CA102-14, pipe to pipe weld, ASME Class 2. This included a review of the associated welding activities.
- Ultrasonic examination o
2NC140-5, nozzle to pipe weld and base metal, ASME Class 1 o
2NC52-3, elbow to pipe weld and base metal, ASME Class 1 o
2NC-PUMP-C (reactor coolant pump C) shaft
- Visual examination o
Bare metal visual examination of 2RPV-BMI-NOZZLES, reactor vessel bottom-mounted instrumentation nozzles, ASME Class 1 PWR Inservice Inspection Activities Sample - Vessel Upper Head Penetration Inspection
Activities (IP Section 03.02) (1 Sample)
The inspectors verified that the licensee conducted the following vessel upper head penetration inspections and addressed any identified defects appropriately:
(1)
- Bare metal visual examination of 2RPV-HEAD-SURFACE, reactor pressure vessel closure head, ASME Class 1
- Liquid penetrant examination of penetration 74 weld overlay, ASME Class 1
- Visual examination (VT-1) of penetration 80 (auxiliary head adapter) inner radius, ASME Class 1 PWR Inservice Inspection Activities Sample - Boric Acid Corrosion Control Inspection Activities (IP Section 03.03) (1 Sample)
The inspectors evaluated the licensees boric acid control program performance, which included the following activities:
(1)
- Boric Acid Walkdown - Tuesday, September 9, 2025
- Review of the following boric acid evaluations (by condition report number):
o Nuclear condition report (NCR) 2445203 o
NCR 2562616 o
NCR 2563087
- Review of the following corrective actions performed for evidence of boric acid leaks that were identified (by work request (WR) number):
o WR 20255010 o
WR 20291270 PWR Inservice Inspection Activities Sample - Steam Generator Tube Inspection Activities (Section 03.04) (1 Sample)
The inspectors verified that the licensee is monitoring the steam generator tube integrity appropriately through a review of the following examinations:
(1)
- Steam generator 2A - eddy current testing (ECT) for tubes R1C9, R1C10, R1C11, R38C97, R41C81, R42C38
- Steam generator 2B - ECT for tube R32C69
- Steam generator 2C - ECT for tubes R25C40, R38C99, R49C60
- Steam generator 2D - ECT for tubes R43C78, R48C61, R48C72, R49C59
71111.11Q - Licensed Operator Requalification Program and Licensed Operator Performance
Licensed Operator Performance in the Actual Plant/Main Control Room (IP Section 03.01) (1 Sample)
- (1) The inspectors observed and evaluated licensed operator performance in the control room during reactor shutdown and unit placement in Mode 4 for refueling outage C2R27 on September 3, 2025.
Licensed Operator Requalification Training/Examinations (IP Section 03.02) (1 Sample)
- (1) The inspectors observed and evaluated licensed operator annual simulator exam conducted in the plant reference simulator on August 6, 2025.
71111.12 - Maintenance Effectiveness
Maintenance Effectiveness (IP Section 03.01) (3 Samples)
The inspectors evaluated the effectiveness of maintenance to ensure the following structures, systems, and components (SSCs) remain capable of performing their intended function:
- (1) NCR 2564969, standby shutdown facility (SSF) diesel batteries found below selected licensee commitments limit and NCR 02564963, no spare SSF batteries available
- (2) Engineered safeguards protective system (ESPS) diesel equipment reliability, including NCR 02565086, ESPS diesel trip due to coolant level sensor wiring on August 15, 2025
- (3) NCR 02561360, 2B emergency diesel generator failure to flash field
71111.13 - Maintenance Risk Assessments and Emergent Work Control
Risk Assessment and Management Sample (IP Section 03.01) (3 Samples)
The inspectors evaluated the accuracy and completeness of risk assessments for the following planned and emergent work activities to ensure configuration changes and appropriate work controls were addressed:
- (1) Risk mitigation actions for emergent inoperability of 2B emergency diesel generator and Duke Energy Carolinas grid reserve generation challenges addressed by procedure AD-WC-ALL-0260, "Nuclear Generation Response to High or Low Grid System Load," on July 15, 2025
- (2) Lowered inventory for reactor head removal during refueling outage C2R27, on September 9, 2025
- (3) AD-WC-CNS-0420, "Catawba Nuclear Station Shutdown Risk Management, for High Risk Plant Operating States (HRPOS)," specifically for reduced inventory for steam generator nozzle dam removal with fuel reloaded, on September 27, 2025
71111.15 - Operability Determinations and Functionality Assessments
Operability Determination or Functionality Assessment (IP Section 03.01) (4 Samples)
The inspectors evaluated the licensee's justifications and actions associated with the following operability determinations and functionality assessments:
- (1) NCR 02561360, 2B emergency diesel generator inoperable due to field flash failure on July 15, 2025
- (2) NCR 2562090, power range nuclear instrument rate trip time constant not measured during channel operational test July 21, 2025
- (3) NCR 02563483, standby shutdown facility diesel non-functional due to water jacket piping leak on August 1, 2025
- (4) NCR 02563911, water impacting steam supply piping to turbine driven auxiliary feed water pump near 2S10 heat trace on August 5, 2025
71111.20 - Refueling and Other Outage Activities
Refueling/Other Outage Sample (IP Section 03.01) (1 Partial)
(1)
(Partial)
The inspectors evaluated refueling outage C2R27 activities from September 3, 2025, to September 30, 2025.
71111.24 - Testing and Maintenance of Equipment Important to Risk
The inspectors evaluated the following testing and maintenance activities to verify system operability and/or functionality:
Post-Maintenance Testing (PMT) (IP Section 03.01) (8 Samples)
- (1) Work order (WO) 20648193 for 2C vital bus inverter major component replacement, on July 9, 2025
- (2) NCR 02561360, 2B emergency diesel generator field flash failure due to open sliding link TS1-3, on July 15, 2025
- (3) NCR 02563483, SSF diesel non-functional due to water jacket piping leak, on August 1, 2025
- (4) PT/0/A/4200/017A, "Standby Shutdown Facility (SSF) Diesel Test," following completion of SSF diesel maintenance window, on August 14, 2025
- (5) OP/0/B/6350/010, "Emergency Supplemental Power Source (ESPS) D/G Operation,"
testing of #1 and #2 ESPS diesels following completion of ESPS diesel maintenance window, on August 15,2025
- (6) PT/2/A/4200/007 A, "Centrifugal Charging Pump 2A Test," following replacement of pump seals on September 23, 2025
- (7) PT/A/2/4450/005B, "Containment Air Return Fan 2B and Hydrogen Skimmer Fan 2B Performance Test," following replacement of air return fan damper (2ARF-D-4) delay timer unit under WR 20705340, on September 24, 2025
- (8) WOs 20695024 and 20748353 for containment spray system test loop isolation valves 2NS-118 and 2NS-119, replacement of bent stems, on September 27, 2025
Surveillance Testing (IP Section 03.01) (2 Samples)
- (1) IP/0/A/4974/0/014, "Power Cable Inspection and Insulation Testing," using TanDelta Measurement System on 2A nuclear service water pump, on September 11, 2025
- (2) PT/2/A/4200/004 C, Containment Spray Pump 2B Performance Test, for comprehensive test on September 27, 2025
Containment Isolation Valve (CIV) Testing (IP Section 03.01) (1 Sample)
- (1) PT/2/A/4200/001 C, Enclosure 13.31, "Penetration M437 As Left Type C Leak Rate Test," on September 18, 2025
Diverse and Flexible Coping Strategies (FLEX) Testing (IP Section 03.02) (1 Sample)
- (1) WO 20713978 and WO 2071397, biennial and annual FLEX equipment maintenance and testing, on August 25-27, 2025
71114.02 - Alert and Notification System Testing
Inspection Review (IP Section 02.01-02.04) (1 Sample)
- (1) The inspectors evaluated the maintenance and testing of the alert and notification system during the week of July 7, 2025.
71114.03 - Emergency Response Organization Staffing and Augmentation System
Inspection Review (IP Section 02.01-02.02) (1 Sample)
- (1) The inspectors evaluated the readiness of the Emergency Response Organization during the week of July 7, 2025.
71114.04 - Emergency Action Level and Emergency Plan Changes
Inspection Review (IP Section 02.01-02.03) (1 Sample)
- (1) The inspectors evaluated submitted Emergency Action Level, Emergency Plan, and Emergency Plan Implementing Procedure changes during the week of July 7, 2025. This evaluation does not constitute NRC approval.
71114.05 - Maintenance of Emergency Preparedness
Inspection Review (IP Section 02.01 - 02.11) (1 Sample)
- (1) The inspectors evaluated the maintenance of the emergency preparedness program during the week of July 7,
RADIATION SAFETY
71124.01 - Radiological Hazard Assessment and Exposure Controls
Radiological Hazard Assessment (IP Section 03.01) (1 Sample)
- (1) The inspectors evaluated how the licensee identifies the magnitude and extent of radiation levels, identifies the concentrations and quantities of radioactive materials, and assesses radiological hazards.
Instructions to Workers (IP Section 03.02) (1 Sample)
- (1) The inspectors evaluated how the licensee instructs workers on plant-related radiological hazards and the radiation protection requirements intended to protect workers from those hazards.
Contamination and Radioactive Material Control (IP Section 03.03) (2 Samples)
The inspectors observed/evaluated the following licensee processes for monitoring and controlling contamination and radioactive material:
- (1) Workers exiting contaminated areas and monitoring and exiting the radiologically controlled area (RCA)
- (2) Licensee radiation protection (RP) technicians and station workers survey potentially contaminated material leaving the RCA
Radiological Hazards Control and Work Coverage (IP Section 03.04) (3 Samples)
The inspectors evaluated the licensee's control of radiological hazards for the following radiological work:
- (1) Unit 2 steam generator eddy current activities
- (2) Unit 2 vessel head inspection activities
- (3) Remote RP coverage in high radiation areas (HRAs) and RCAs in containment and the refuel floor High Radiation Area and Very High Radiation Area Controls (IP Section 03.05) (2 Samples)
The inspectors evaluated licensee controls of the following HRA and very high radiation area:
- (1) Unit 2 steam generator manway entry locked HRA
- (2) Mixing and settling tank room, room 221 Radiation Worker Performance and Radiation Protection Technician Proficiency (IP Section 03.06) (1 Sample)
- (1) The inspectors evaluated radiation worker and RP technician performance as it pertains to RP requirements.
71124.08 - Radioactive Solid Waste Processing & Radioactive Material Handling, Storage, &
Transportation
Radioactive Material Storage (IP Section 03.01)
The inspectors evaluated the licensees performance in controlling, labeling and securing the following radioactive materials:
- (1) Radioactive materials stored in the radwaste processing facility
Radioactive Waste System Walkdown (IP Section 03.02) (1 Sample)
The inspectors walked down the following accessible portions of the solid radioactive waste systems and evaluated system configuration and functionality:
- (1) Primary resin processing in the auxiliary building and radwaste solidification facility
Waste Characterization and Classification (IP Section 03.03) (2 Samples)
The inspectors evaluated the following characterization and classification of radioactive waste: (1)2023 dry active waste (DAW)
(2)2024 resin batch tank primary resin
Shipment Preparation (IP Section 03.04) (1 Sample)
Shipping Records (IP Section 03.05) (3 Samples)
The inspectors evaluated the following non-excepted radioactive material shipments through a record review:
- (1) Shipment 23-26, type B, filters
- (3) Shipment 24-27, type B, primary resin
OTHER ACTIVITIES - BASELINE
===71151 - Performance Indicator Verification The inspectors verified licensee performance indicators submittals listed below:
IE03: Unplanned Power Changes per 7000 Critical Hours Sample (IP Section 02.02)
=
- (1) Unit 1 (July 1, 2024, through June 30, 2025)
- (2) Unit 2 (July 1, 2024, through June 30, 2025)
MS09: Residual Heat Removal Systems (IP Section 02.08) (2 Samples)
- (1) Unit 1 (July 1, 2024, through June 30, 2025)
- (2) Unit 2 (July 1, 2024, through June 30, 2025)
OR01: Occupational Exposure Control Effectiveness Sample (IP Section 02.15) (1 Sample)
- (1) March 23, 2024, through July 21, 2025 PR01: Radiological Effluent Technical Specifications/Offsite Dose Calculation Manual Radiological Effluent Occurrences (RETS/ODCM) Radiological Effluent Occurrences Sample (IP Section 02.16) (1 Sample)
- (1) August 3, 2024, through July 31, 2025
EP01: Drill/Exercise Performance (DEP) Sample (IP Section 02.12) (1 Sample)
- (1) April 1, 2024, through March 31, 2025 EP02: Emergency Response Organization (ERO) Drill Participation (IP Section 02.13) (1 Sample)
- (1) April 1, 2024, through March 31, 2025 EP04: Emergency Response Facility and Equipment Readiness (ERFER) (IP Section 02.14)
(1 Partial)
(1)
(Partial)
This is a new NRC performance indicator, described in NEI 99-02, Revision 8 (ML24331A114). Licensees began collecting data for this performance indicator January 1, 2025. Therefore, at the time of inspection there was no quarterly data compiled and submitted to the NRC.
71152S - Semiannual Trend Problem Identification and Resolution Semiannual Trend Review (Section 03.02)
- (1) The inspectors reviewed the licensees corrective action program to identify potential trends in structures condition monitoring as a continuation of licensees response to water intrusion during Hurricane Helene (NCR 02530207) and water intrusion, into the switchgear rooms for 6900V buses feeding the essential switchgear transformers, caused by a severe thunderstorm on May 8, 2025 (NCRs 2553908, 2553909). Based on the licensees response, no potential trends were identified that would be indicative of a more significant safety issue.
71153 - Follow-Up of Events and Notices of Enforcement Discretion Event Report (IP Section 03.02)
The inspectors evaluated the following licensee event reports (LERs):
- (1) LER 05000413/2025-001-00, Plant Shutdown Required by Technical Specifications Due to Unidentified Reactor Coolant System Leakage (ADAMS Accession No.
ML25090A171). The licensee's planned corrective actions include additional analysis of the issue and applicable revisions to the cause evaluation and LER if necessary.
The inspectors determined that the cause of the condition described in the LER was not reasonably within the licensee's ability to foresee and correct and therefore was not reasonably preventable. No performance deficiency nor violation of NRC requirements was identified. This LER is Closed.
- (2) LER 05000413, 05000414/2025-002-00, Inoperability of 1B Emergency Diesel Generator due to Fuel Oil Leak (ADAMS Accession No. ML25202A164). The inspection conclusions associated with this LER was documented in Inspection Report 05000413/2025002 and 05000414/2025002 and Exercise of Enforcement Discretion; and Inspection Report 07200045/2025001, under Inspection Results Section 71111.15. This LER is Closed.
- (3) LER 05000413, 05000414/2025-003-00, 2B Emergency Diesel Generator Field Failed to Flash (ADAMS Accession No. ML25258A159. The inspection conclusions associated with this LER are documented in this report under Inspection Results Section 71153. This LER is Closed.
INSPECTION RESULTS
2B EDG failed to flash due to open sliding link Cornerstone Significance Cross-Cutting Aspect Report Section Mitigating Systems Green NCV 05000414/2025003-01 Open/Closed
[H.12] - Avoid Complacency 71153 A self-revealed Green finding and associated non-cited violation of Technical Specification (TS) 5.4, Procedures, was identified when the licensee failed to properly perform maintenance activities as required by Regulatory Guide (RG) 1.33, "Quality Assurance Program Requirements (Operations), Revision 2, Section 9.a. Specifically, the licensee failed to properly restore sliding link TS1-3 following calibration activities, in accordance with procedure IP//2/A/3680/008B, "DG-2B EQC System Time Delay and Undervoltage Relays Calibration," rendering the 2B emergency diesel generator (EDG) inoperable.
Description:
On July 15, 2025, the 2B EDG failed to flash its field during its monthly surveillance testing, preventing the EDG from reaching the required voltage. The licensee declared the 2B EDG inoperable and performed troubleshooting. Sliding link TS1-3 was found open and its associated hold down screw loose. The licensee closed the link and securely fastened the screw. The licensee ran the 2B EDG successfully on July 16, 2025, at 0521. Following the successful run, the licensee replaced the sliding link and performed another 2B EDG run to revalidate operability.
The last known manipulation of sliding link TS1-3 was January 16, 2025, during the 2B EDG maintenance outage period. The link was operated for calibration of the field flash cutout timer within WO 20696841, with instructions to perform enclosure 11.1.12 of procedure IP/2/A/3680/008B, DG-2B EQC System Time Delay and Undervoltage Relays Calibration.
Various other sliding links in the same cabinet were also manipulated during performance of WO 2069841, which the licensee verified to be correctly positioned and secured during extent of condition inspections. The licensee also performed extent of condition inspections for sliding links on all EDGs and verified that all EDG sliding links were correctly positioned and secured.
The licensee performed a metallurgical analysis of the open sliding link and determined that it was in excellent condition and only exhibited signs of minor wear. The 2B EDG had been operated multiple times since January 16, 2025, for monthly operability surveillances. The last known successful operation of the 2B EDG was on July 1, 2025. Although the sliding link was initially placed in the closed position following calibration activities, the hold down screw was not tightened sufficiently to prevent movement of the sliding link. As a result, system vibration eventually caused the sliding link to shift to the open position, rendering the 2B EDG inoperable.
Corrective Actions: In addition to replacing and securing the sliding link, and performing an extent of condition evaluation, the licensee held a crew learning with the maintenance organization and updated training. The licensee also updated maintenance practices and procedures.
Corrective Action References: NCR 02564360
Performance Assessment:
Performance Deficiency: The licensees failure to restore sliding link TS1-3 as required by calibration procedure instruction IP/2/A/3680/008B, during maintenance on the 2B EDG, was a performance deficiency. Specifically, the licensee did not securely fasten sliding link TS1-3 in the closed position.
Screening: The inspectors determined the performance deficiency was more than minor because it was associated with the Configuration Control attribute of the Mitigating Systems cornerstone and adversely affected the cornerstone objective to ensure the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. Specifically, with sliding link TS1-3 not in the closed position, the EDG field did not flash, and prevented the EDG from reaching the required voltage. This resulted in the inoperability of the 2B EDG.
Significance: The inspectors assessed the significance of the finding using IMC 0609 Appendix A, The Significance Determination Process (SDP) for Findings At-Power. Using Exhibit 2, Mitigating Systems Screening Questions, the inspectors determined that the issue required a detailed risk evaluation because the finding represents an actual loss of probabilistic risk assessment (PRA) function of a single train for greater than its technical specification allowed outage time. A detailed risk evaluation was performed by a regional senior reactor analyst (SRA) using Systems Analysis Program for Hands-On Integrated Reliability Evaluations (SAPHIRE) Version 8.2.12 and Catawba Unit 1 and 2 Standardized Plant Analysis Risk (SPAR) model Version 8.84. The SRA modeled the failure as a failure to start of the 2B emergency diesel generator, with a 15-day exposure time, crediting both FLEX equipment and procedures and the ESPS. The SRA also adjusted the model to remove the probability of the ESPS being aligned to an energized emergency bus. Finally, the SRA determined that some credit for recovery was warranted due to clear cues of the EDG field failing to flash, existing troubleshooting plans, and the simple nature of the recovery action once diagnosed (reposition and tighten the link). These actions were demonstrated by plant personal following the test failure. Licensee PRA data was considered best available information for internal fire and internal flooding sequences. The dominant accident sequence was a site wide weather-related loss of offsite power with a failure of either ESPS generator, A EDG unavailable due to test and maintenance, failure of the FLEX EDG, operators failing to manually control the turbine driven auxiliary feedwater (TDAFW) pump, and failure to recover offsite or onsite power in two hours. The SRA determined that the estimated change in core damage frequency (Delta CDF) and change in large early release frequency (Delta LERF) were less than 1E-06/year for Delta CDF and less than 1E-07/year for Delta LERF, representing a finding of very low safety significance (GREEN) for Unit 2.
Cross-Cutting Aspect: H.12 - Avoid Complacency: Individuals recognize and plan for the possibility of mistakes, latent issues, and inherent risk, even while expecting successful outcomes. Individuals implement appropriate error reduction tools. Specifically, the licensee failed to recognize that sliding link TS1-3 was not securely fastened. Operation of sliding links is considered to be a skill of the craft task that involves sliding the link into the desired position, tightening the hold down screw, and verifying tightness with a screwdriver. Multiple sliding links were operated successfully during calibration procedure IP/2/A/3680/008B, with the exception of sliding link TS1-3, resulting in the inoperability of the 2B EDG.
Enforcement:
Violation: TS 5.4, Procedures, states in part that written procedures shall be established, implemented, and maintained covering applicable procedures recommended in RG 1.33, Revision 2, Appendix A, February 1978.
Section 9.a. of RG 1.33, Appendix A, requires in part that maintenance that can affect the performance of safety-related equipment should be properly preplanned and performed in accordance with written procedures, documented instructions, or drawings appropriate to the circumstances.
Licensee procedure IP/2/A/3680/008B, DG-2B EQC System Time Delay and Undervoltage Relays Calibration, Enclosure 11.1.12 requires in part that sliding link TS1-3 be restored following calibration of the field flash cutout timer.
Contrary to the above, on January 16, 2025, the licensee failed to implement calibration procedure IP/2/A/3680/008B, during maintenance on the 2B EDG. Specifically, the licensee did not properly restore sliding link TS1-3, following calibration activities. Sliding link TS1-3 was not securely fastened in the closed position, which allowed it to shift to the open position due to system vibrations, rendering the 2B EDG inoperable.
Enforcement Action: This violation is being treated as a non-cited violation, consistent with Section 2.3.2 of the Enforcement Policy.
EXIT MEETINGS AND DEBRIEFS
The inspectors verified no proprietary information was retained or documented in this report.
- On July 10, 2025, the inspectors presented the emergency preparedness program inspection results to S. Milton and other members of the licensee staff.
- On September 18, 2025, the inspectors presented the radiation protection inspection results to J. Smith and other members of the licensee staff.
- On September 19, 2025, the inspectors presented the inservice inspection results to A. Tuckman and other members of the licensee staff.
- On December 16, 2025, the inspectors presented the integrated inspection results to J. Huecker and other members of the licensee staff.
DOCUMENTS REVIEWED
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
Miscellaneous
Catawba Unit 2EOC27: Steam Generator Degradation
Assessment
DE_C_2_2CA102-
13_20240321
Radiographic Examination of Weld 2CA102-13
03/24/2024
DE_C_2_2CA102-
14_20240321
Radiographic Examination of Weld 2CA102-14
03/24/2024
MT-25-002
Magnetic Particle Examination of 2-R-SV-1573
09/12/2025
UT-25-001
Ultrasonic Examination of Reactor Coolant Pump C Pump
Shaft
09/13/2025
UT-25-007
Ultrasonic examination of 2NC52-3
09/13/2025
UT-25-008
Ultrasonic examination of 2NC140-5
09/16/2025
VT-25-007
Visual examination of 2RPV-BMI-NOZZLES
09/10/2025
VT-25-020
Visual Examination of 2RPV-HEAD-SURFACE
09/16/2025
NDE Reports
WDI-PJF-353004-
NDE-001
25 Reactor Vessel Head Penetration 74 Weld Overlay
Examination Summary
Corrective Action
Documents
2564790, 2564660, 2564659
Calculations
CNC-1223.43-02-
0009
SA (main steam supply to auxiliary equipment) System
TDAWFP (turbine driven auxiliary feedwater pump) System
Steam Supply Pipe Trace Heating Operability Evaluation
Work Orders
292219
20 EP Public Information; information packet to the public.
06/26/2025
CNS-ANS-05171984; CNS Alert and Notification System
Design Report for Catawba Nuclear Station
05/17/1984
Miscellaneous
AD-EP-ALL-0305; Fleet Emergency Preparedness Alert and
Notification System Siren Program
11/04/2024
Calculations
EP-CNS-OSSA; Catawba On-Shift Staffing Analysis
2/29/2024
Procedures
AD-EP-ALL-0500; Emergency Response Training
09/22/2022
Catawba EAL Technical Basis
CSD-EP-CNS-
0101-02
Catawba EAL Wallchart
Procedures
Duke Energy Common Emergency Plan
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
EP-CNS-EPLAN-
ANNEX
Duke Energy Catawba Emergency Plan Annex
AD-PI-ALL-0100; Corrective Action Program
2/05/2025
AD-EP-ALL-0203; Field Monitoring During Declared
Emergency
04/07/2025
Procedures
AD-EP-CNS-0203; CNS Site Specific Field Monitoring
Shipping Records
Shipment 25-10,