ML25223A205
| ML25223A205 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 08/14/2025 |
| From: | Mark Franke NRC/RGN-II/DORS |
| To: | Huecker J Duke Energy Carolinas |
| References | |
| EAF-RII-2025-0150 IR 2025002, IR 2025001 | |
| Download: ML25223A205 (1) | |
Text
EAF-RII-2025-0150 Jonathan Huecker Site Vice President Duke Energy Carolinas, LLC 4800 Concord Road York, SC 29745-9635
SUBJECT:
CATAWBA NUCLEAR STATION - INTEGRATED INSPECTION REPORT 05000413/2025002 AND 05000414/2025002 AND EXERCISE OF ENFORCEMENT DISCRETION; AND INSPECTION REPORT 07200045/2025001
Dear Jonathan Huecker:
On June 30, 2025, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at Catawba Nuclear Station. On July 24, 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.
No findings or violations of more than minor significance were identified during this inspection.
This inspection report documents an exercise of enforcement discretion in accordance with the Enforcement Policy, Section 3.10, Reactor Violations with No Performance Deficiencies, for an issue that closely aligned with a Severity Level III violation example in Section 6.1.c.2 of the Enforcement Policy. The inspectors concluded there was no performance deficiency associated with the violation of Technical Specification, AC Source - Operating, Limiting Condition for Operation 3.8.1.b. The equipment inoperability was not avoidable by reasonable licensee quality assurance measures or other related control measures. The NRC Enforcement Policy can be found at the NRCs website at https://www.nrc.gov/about-nrc/regulatory/enforcement/enforce-pol.html.
Based on the facts detailed in the enclosed report, and consultation with the Office of Enforcement and the Regional Administrator, I have been authorized to exercise enforcement discretion in accordance with Section 3.10 of the Enforcement Policy, and refrain from issuing enforcement for the violation. This violation will not be considered in the assessment process or the NRCs Action Matrix.
August 14, 2025
J. Huecker 2
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, Mark E. Franke, Director Division of Operating Reactor Safety Docket Nos. 05000413 and 05000414; 07200045 License Nos. NPF-35 and NPF-52
Enclosure:
As stated cc w/ encl: Distribution via LISTSERV Signed by Franke, Mark on 08/14/25
SUNSI Review x
Non-Sensitive
Sensitive x
Publicly Available
Non-Publicly Available OFFICE RII/DORS RII/DORS RII/DORS RII/ACES RII/RC NAME D. Rivard D. Jackson R. Williams M. Kowal S. Price DATE 8/11/25 8/11/25 8/12/25 8/12/25 8/12/25 OFFICE OE RII/DORS NAME J. Peralta M. Franke DATE 8/12/25 8/14/25
Enclosure U.S. NUCLEAR REGULATORY COMMISSION Inspection Report Docket Numbers:
05000413 and 05000414; 07200045 License Numbers:
NPF-35 and NPF-52 Report Numbers:
05000413/2025002 and 05000414/2025002; 07200045/2025001 Enterprise Identifiers: I-2025-002-0013; I-2025-001-0090 Licensee:
Duke Energy Carolinas, LLC Facility:
Catawba Nuclear Station Location:
York, South Carolina Inspection Dates:
April 1, 2025 to June 30, 2025 Inspectors:
D. Rivard, Senior Resident Inspector A. Wang, Resident Inspector L. Colon Fuentes, Construction Project Inspector P. Cooper, Senior Reactor Inspector K. Henry, Regional Governmental Liaison Officer J. Lizardi-Barreto, Reactor Inspector Approved By:
Robert E. Williams, Jr., Chief Reactor Projects Branch 1 Division of Operating Reactor Safety
2
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 No findings or violations of more than minor significance were identified.
Additional Tracking Items Type Issue Number Title Report Section Status EDG EAF-RII-2025-0150 Enforcement Discretion:
Emergency Diesel Generator (EDG) Fuel Oil Supply Line Leak Resulting in EDG Inoperability 71111.15 Closed LER 05000414/2024-002-00 LER 024-002-00 for Catawba Nuclear Station, Unit 2, Manual Reactor Trip and Auxiliary Feedwater Actuation Due to Water Intrusion 71153 Closed
3 PLANT STATUS Unit 1 operated at or near 100 percent rated thermal power (RTP) for the entire inspection period.
Unit 2 operated at or near 100 percent RTP for the entire 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 71111.01 - Adverse Weather Protection Seasonal Extreme Weather Sample (IP Section 03.01) (1 Sample)
(1)
The inspectors evaluated readiness for seasonal extreme weather conditions prior to the onset of seasonal high temperatures, including impending heat wave and extended high temperature conditions for the following systems:
standby shutdown facility ventilation components temperature control units for Unit 1 and Unit 2 6900v switchgear rooms 71111.04 - Equipment Alignment Partial Walkdown Sample (IP Section 03.01) (3 Samples)
The inspectors evaluated system configurations during partial walkdowns of the following systems/trains:
(1)
'A' train vital swing inverter, 2EIE, alignment while the swing inverter was in service to perform functional verification following maintenance (work order (WO) 20534145) on May 14, 2025 (2) 1B EDG room during 2A EDG maintenance window on June 6, 2025 (3)
Unit 1 auxiliary feedwater system following Unit 1 turbine driven auxiliary feedwater pump maintenance on June 13, 2025
4 71111.05 - Fire Protection Fire Area Walkdown and Inspection Sample (IP Section 03.01) (7 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 areas 9 and 10: Unit 1 auxiliary power and vital battery rooms and general area on April 4, 2025 (2)
Fire area 1: auxiliary building elevation 522, residual heat removal pump and containment spray pump areas on April 8, 2025 (3)
Fire area 20: Unit 1, auxiliary building, elevation 594, electrical penetration room (room 576) on May 8, 2025 (4)
Fire areas 13 and 15: Unit 1, auxiliary building, elevation 577, electrical penetration room (room 494), and essential switchgear room (room 496) on May 21, 2025 (5)
Fire area 40: Unit 1 turbine driven auxiliary feedwater pump pit (room 254) on June 12, 2025 (6)
Fire area SSF: safe shutdown facility on June 13 through 16, 2025 (7)
Partial fire area 22: auxiliary building, elevation 594, specifically room 560 and room 570, train A and B control room chill water and ventilation rooms, respectively on June 27, 2025 Fire Brigade Drill Performance Sample (IP Section 03.02) (1 Sample)
(1)
The inspectors evaluated the onsite fire brigade training and performance during an unannounced fire drill on the 2MXD switchgear in the Unit 2 turbine building on May 9, 2025.
71111.06 - Flood Protection Measures Flooding Sample (IP Section 03.01) (1 Sample)
(1)
The inspectors evaluated internal and external flooding mitigation protections for:
water intrusion in service water cable manholes 71111.11Q - Licensed Operator Requalification Program and Licensed Operator Performance Licensed Operator Requalification Training/Examinations (IP Section 03.02) (1 Sample)
(1)
The inspectors observed and evaluated licensed operator crew performance evaluation conducted in the plant reference simulator on May 29, 2025.
71111.12 - Maintenance Effectiveness Maintenance Effectiveness (IP Section 03.01) (1 Sample)
The inspectors evaluated the effectiveness of maintenance to ensure the following structures, systems, and components remain capable of performing their intended function:
5 (1)
Nuclear condition report (NCR) 02552001, 1B EDG functional failure due to fuel leak on April 23, 2025 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 associated with OP/0/A/6400/006 C, Enclosure 4.35, for maintenance of component cooling water heat exchanger outlet nuclear service water flow control valve, on April 16, 2025 (2)
Risk mitigation actions associated with work request (WR) 20289021 and NCR 02556466 for emergent maintenance associated with switchyard isolation breaker, PCB-15, disconnect which required emergent deenergizing of the "Yellow Bus" on May 30, 2025 (3)
Risk mitigation actions associated with control of maintenance activities using AD-WC-ALL-0260, "Nuclear Generation Response to High or Low Grid System Load," during Duke Energy Carolinas grid condition status of "Yellow," "Orange," and "Red," on June 23, 24, and 25, 2025 71111.15 - Operability Determinations and Functionality Assessments Operability Determination or Functionality Assessment (IP Section 03.01) (6 Samples)
The inspectors evaluated the licensee's justifications and actions associated with the following operability determinations and functionality assessments:
(1)
NCR 02549533, nuclear service water valve 2RN-847A inoperable (2)
WR 20287329, 1B EDG fuel oil leak (3)
NCR 02554185, 1B containment spray pump mechanical seal leakage evaluation (4)
NCR 02558395, standby nuclear service water pond (SNSWP) volume decreasing (5)
NCR 02559028, containment ventilation unit condensate drain tank level indication and impact to Technical Specification 3.4.15, "RCS Leakage Detection Instrumentation" (6)
Functionality of drinking water supply to cooling for 1A and 2A charging pumps as defined in Selective Licensing Commitment 16.9-24, "Alternate Cooling for Charging Pumps," during implementation of engineering change 425642, Unit 2 steam generator high temperature chemical cleaning 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:
6 Post-Maintenance Testing (PMT) (IP Section 03.01) (2 Samples)
(1)
PT/2/A/4200/013 C, "RN (nuclear service water) Valve Inservice Test (QU)," for valve 2RN-148A, 2A containment spray heat exchanger outlet isolation valve, following motor operator testing, under WO 20707461 on April 8, 2025 (2)
PT/1/A/4250/003 C, "Turbine Driven Auxiliary Feedwater Pump #1 Performance Test," following maintenance on June 12, 2025 Surveillance Testing (IP Section 03.01) (3 Samples)
(1)
IP/2/A/3222/015 D, "Reactor Coolant Flow, Loop D, Protection Ch.1, 2NCFT5090 (FT-444) Calibration," under WO 20680804 including card replacement on April 4, 2025 (2)
PT/2/A/4250/003C, "Turbine Driven Auxiliary Feedwater Pump #2 Performance Test,"
performed on May 22, 2025 (3)
PT/1/A/4250/001C, "(Steam Generator Power Operated Relief Valve) S/G 1A PORV Stroke Test," performed on May 24, 2025 Inservice Testing (IST) (IP Section 03.01) (1 Sample)
(1)
PT/1/A/4200/004C, "Containment Spray Pump 1B Performance Test," and associated reperformance of PT/1/A/4200/004C following misposition of valve 1NS-70, on April 18, 2025 Reactor Coolant System Leakage Detection Testing (IP Section 03.01) (1 Sample)
(1)
NCR 02553026, for Unit 1 elevated unidentified reactor coolant system leakage, on May 2, 2025 71114.06 - Drill Evaluation Required Emergency Preparedness Drill (1 Sample)
(1)
Emergency response organization drill, "CNS 2025 Off-Year Exercise" and critique on April 9, 2025, that included a steam generator tube leak degrading to a tube rupture coupled with a steam generator safety relief valve failure creating an offsite release.
Additional Drill and/or Training Evolution (2 Samples)
The inspectors evaluated:
(1)
Emergency response organization drill, "CNS 25-02" and critique that included a loss of coolant accident (LOCA) with a containment breach due to a series of earthquakes and aftershocks resulting in a final declaration of a Site Area Emergency on April 1, 2025.
(2)
Emergency response organization drill, "CNS 25-04" and critique that included an earthquake and aftershocks resulting in reactor fuel failure, a LOCA, and a breach of the containment equipment hatch, resulting in an offsite release and declaration of a Site Area Emergency on May 21, 2025.
7 OTHER ACTIVITIES - BASELINE 71151 - Performance Indicator Verification The inspectors verified licensee performance indicators submittals listed below:
MS06: Emergency AC Power Systems (IP Section 02.05) (2 Samples)
(1)
Unit 1 (April 1, 2024, through March 31, 2025)
(2)
Unit 2 (April 1, 2024, through March 31, 2025)
MS07: High Pressure Injection Systems (IP Section 02.06) (2 Samples)
(1)
Unit 1 (April 1, 2024, through March 31, 2025)
(2)
Unit 2 (April 1, 2024, through March 31, 2025)
MS08: Heat Removal Systems (IP Section 02.07) (2 Samples)
(1)
Unit 1 (April 1, 2024, through March 31, 2025)
(2)
Unit 2 (April 1, 2024, through March 31, 2025) 71152A - Annual Follow-up Problem Identification and Resolution Annual Follow-up of Selected Issues (Section 03.03) (2 Samples)
The inspectors reviewed the licensees implementation of its corrective action program related to the following issues:
(1)
Nuclear service water cable jacket cracking and manway sump pump functionality (2)
Diesel fuel system leakage history 71153 - Follow Up of Events and Notices of Enforcement Discretion Event Report (IP Section 03.02) (1 Sample)
The inspectors evaluated the following licensee event report (LER):
(1)
LER 05000414/2024-002-00, Manual Reactor Trip and Auxiliary Feedwater Actuation Due to Water Intrusion (ADAMS Accession No. ML24330A060); 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 associated with the event. This LER is closed.
OTHER ACTIVITIES - TEMPORARY INSTRUCTIONS, INFREQUENT AND ABNORMAL 60855 - Operation of an ISFSI 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-
8 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) 2690, Inspection Program for Storage of Spent Reactor Fuel and Reactor-Related Greater-than-Class C Waste at Independent Spent Fuel Storage Installations (ISFSI) and for 10 CFR Part 71 Transportation Packagings.
Operation of an ISFSI (1 Sample)
(1)
From May 19 - 22, 2025, the inspectors performed a review of the licensees ISFSI activities to verify compliance with regulatory requirements. During the on-site inspection, the inspectors observed and reviewed licensee activities in each of the five safety focus areas including occupational exposure, public exposure, fuel damage, confinement, and impact to plant operations.
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. Additionally, the inspectors performed independent walkdowns of the heavy load lifting equipment and the ISFSI haul path. The inspector also performed an independent radiation survey of the ISFSI pad.
INSPECTION RESULTS Enforcement Discretion Enforcement Action EAF-RII-2025-0150: Emergency Diesel Generator (EDG) Fuel Oil Supply Line Leak Resulting in EDG Inoperability 71111.15
==
Description:==
On April 23, 2025, during a periodic 24-hour technical specification (TS) surveillance test, the 1B emergency diesel generator (EDG) experienced a leak in a 1-inch fuel oil supply line. The licensee visually quantified the leak to be between 0.5-1.0 gpm, exceeding the licensees criteria for EDG operability. The licensee secured the EDG and declared it inoperable after approximately 11.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> into the test. The licensee replaced the leaking section of fuel oil supply line and discovered that one mounting clamp was degraded.
The 1B EDG was retested and declared operable on April 25, 2025, at approximately 0600.
The licensee's analysis of the fuel oil supply line confirmed a crack that propagated approximately 300 degrees around the tube circumference. The lab analysis summarized the condition as follows, Although it is not possible to precisely date the crack, darkly oxidized beach marks at the origin suggest that the crack initiated some time ago, possibly on the order of a few years. This would be consistent with a scenario where: (1) the tube support came loose, placing a cyclic bending moment on the upper compression fitting, (2) over a number of subsequent diesel test runs, the crack then initiated and began to slowly advance, then (3) relatively fast crack propagation occurred during the most recent diesel test run when the leak was discovered. The metallurgical analysis concluded that the failure was attributable to high cycle fatigue indicative of multiple periods of active crack growth, likely aligning with periodic operation of the diesel.
The inspectors concluded that a latent flaw had existed since at least March 30, 2025, the last successful EDG operability surveillance test. Additionally, recent vibration data taken on the 1B EDG was compared to historic data showing no significant increases, ruling out excessive vibrations as a potential cause for the current event. Based on the preponderance of the evidence, the inspectors determined the observed crack was a progressive flaw that
9 would have grown to a through-wall leak on the next EDG initiation signal and rendered the 1B EDG inoperable due to excessive fuel oil leakage. Based on a review of the licensees EDG maintenance strategy and corrective action program, the inspectors concluded that there was no performance deficiency associated with the failure since the fatigue crack was not reasonably within the licensees ability to foresee and correct, and it could not have been prevented by reasonable licensee quality assurance measures or management controls.
Corrective Actions: The licensee replaced the affected section of fuel oil tubing on the 1B EDG. The 1B EDG was retested and declared operable. A metallurgical analysis of the leak location was performed. The similar location of fuel oil tubing for the opposite train 1A EDG was removed, replaced and subjected to metallurgical analysis. The licensees extent of condition investigation revealed no evidence of similar issues on the remaining three EDGs.
Corrective Action Reference: NCR 02561360 Enforcement:
Significance/Severity: This violation was dispositioned in accordance with the traditional enforcement process using Section 2.3 of the NRCs Enforcement Policy. The inability of the emergency diesel generator to perform its safety-related function closely aligns with Severity Level III Example 6.1.c.2 of the Enforcement Policy, which states in part, a system that is part of the primary success path and which functions or actuates to mitigate a design basis accident or transient that either assumes the failure of or presents a challenge to the integrity of the fission product barrier not being able to perform its licensing basis safety function.
Violation: TS Limiting Condition for Operation (LCO) 3.8.1.b, states in part, that two EDGs capable of supplying the Onsite Essential Auxiliary Power Systems shall be OPERABLE in MODES 1 through 4.
TS 3.8.1, AC Sources-Operating, Condition B, states in part, when one LCO 3.8.1.b EDG is inoperable, then [B.6] Restore EDG to OPERABLE status, with a completion time of 14 days.
Technical Specification 3.8.1 AC Sources-Operating, Condition I states in part, when Required Action B.6 not met, then be in MODE 3 in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and be in MODE 5 in 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.
Contrary to the above, from at least March 30, 2025, through April 23, 2025, the licensee failed to maintain two EDGs capable of supplying the Onsite Essential Auxiliary Power Systems while in MODE 1. Specifically, the 1B EDG was inoperable for a period greater than the allowed completion time to restore the EDG to operable status (within 14 days) or place the unit in MODE 3 (within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />). The EDG was inoperable due to a fatigue crack in a fuel oil supply line that would have resulted in the failure of the EDG during operation at any point after the last successful surveillance on March 30, 2025, as evidenced by the fuel oil supply line leak observed on April 23, 2025.
Basis for Discretion: The NRC exercised discretion and refrained from issuing enforcement for this violation in accordance with Section 3.10, Reactor Violations with No Performance Deficiencies, of the Enforcement Policy because the 1B fuel line leak was the result of a failure mechanism concealed by the compression fitting configuration that was not reasonably within the licensee's ability to identify at an earlier opportunity. The equipment failure could not have been avoided or detected by the licensee's quality assurance program or other related control measures. As such, no performance deficiency was identified.
10 EXIT MEETINGS AND DEBRIEFS The inspectors verified no proprietary information was retained or documented in this report.
On May 22, 2025, the inspectors presented the ISFSI inspection results to Nicole Flippin, Site Vice President and other members of the licensee staff.
On July 24, 2025, the inspectors presented the integrated inspection results to Jonathan Huecker, Site Vice President and other members of the licensee staff.
11 DOCUMENTS REVIEWED Inspection Procedure Type Designation Description or Title Revision or Date Engineering Evaluations 10 CFR 72.212 Evaluation Report MAGNASTOR Casks 5
60855 Miscellaneous MAGNASTOR System FSAR, Docket No. 72-1031 10 71111.06 Corrective Action Documents 02553262, 02550687, 02554806, 02554809 CNC-1150.01 0001 SNSWP Thermal Analysis During One Unit LOCA and One Unit Shutdown 71111.15 Calculations CNC-1150.04 0009 Area and Volume of Stand By Nuclear Service Water Pond Type I Calc Corrective Action Documents 02551482 71111.24 Procedures OP/1/A/6200/007 Containment Spray System 69 Corrective Action Documents 02552001, 01424112, 01898120, 01491846, 01510211, 01535259, 01530868, 01538670, 01899142, 02101495, 02313603 CNM 1301.00-0237.001 Diesel Generator Instruction Manual Vol 1 Miscellaneous NUREG/CR-7000 Essential Elements of an Electric Cable Condition Monitoring Program 71152A Work Orders WR 20287329