IR 05000269/2025002
| ML25216A139 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 08/08/2025 |
| From: | Robert Williams NRC/RGN-II/DORS/PB1 |
| To: | Snider S Duke Energy Carolinas |
| References | |
| IR 2025001, IR 2025002 | |
| Download: ML25216A139 (1) | |
Text
SUBJECT:
OCONEE NUCLEAR STATION - INTEGRATED INSPECTION REPORT 05000269/2025002, 05000270/2025002, 05000287/2025002, AND 07200004/2025001
Dear Steven Snider:
On June 30, 2025, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at Oconee Nuclear Station. On July 21, 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.
Three findings of very low safety significance (Green) are documented in this report. Three of these findings involved violations of NRC requirements. We are treating these violations as non-cited violations (NCVs) consistent with Section 2.3.2 of the Enforcement Policy.
If you contest the violations or the significance or severity of the violations 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 Oconee Nuclear Station.
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 Oconee Nuclear Station.
August 8, 2025 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. 05000269, 05000270, 05000287, and 07200004 License Nos. DPR-38, DPR-47, DPR-55, and SNM-2503
Enclosure:
As stated
Inspection Report
Docket Numbers:
05000269, 05000270, 05000287, and 07200004
License Numbers:
DPR-38, DPR-47, DPR-55, and SNM-2503
Report Numbers:
05000269/2025002, 05000270/2025002, 05000287/2025002 and
07200004/2025001
Enterprise Identifier:
I-2025-002-0015 and I-2025-001-0089
Licensee:
Duke Energy Carolinas, LLC
Facility:
Oconee Nuclear Station
Location:
Seneca, South Carolina
Inspection Dates:
April 01, 2025, to June 30, 2025
Inspectors:
N. Smalley, Senior Resident Inspector
D. Dang, Resident Inspector
E. Robinson, Senior Project Engineer
B. Bowker, Senior Reactor Inspector
P. Cooper, Senior Reactor Inspector
K. Lei, Emergency Preparedness Inspector
D. Neal, Health Physicist
A. Ponko, Senior Construction Project Inspector
M. Rich, Emergency Preparedness Inspector
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 Oconee 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
Keowee Hydro Unit 1 Inoperable Following Governor Speed Switch Replacement Cornerstone Significance Cross-Cutting Aspect Report Section Mitigating Systems Green NCV 05000269,05000270,05000287/202500 2-01 Open/Closed
[H.12] - Avoid Complacency 71111.12 A self-revealed Green finding and associated non-cited violation (NCV) of 10 CFR 50, Appendix B, Criterion V, was identified when the licensee failed to implement work order instructions and post maintenance testing (PMT) procedures appropriate to the circumstances during a governor speed switch replacement which resulted in inoperability of Keowee Hydro Unit (KHU) 1.
Failure to Assess and Manage Maintenance Risk Following the Inadvertent Actuation of the Alternate Letdown Isolation System Cornerstone Significance Cross-Cutting Aspect Report Section Mitigating Systems Green NCV 05000269/2025002-02 Open/Closed
[H.7] -
Documentation 71111.13 The inspectors identified a Green finding and associated NCV of 10 CFR 50.65(a)(4) when the licensee failed to assess and manage the risk on Unit 1 following the inadvertent actuation of the alternate letdown isolation system.
Failure to Scope Spent Fuel Cooling Valves into the Inservice Testing Program Cornerstone Significance Cross-Cutting Aspect Report Section Barrier Integrity Green NCV 05000269,05000270,05000287/202500 2-03 Open/Closed
[P.3] -
Resolution 71152A The inspectors identified a Green finding and associated NCV of 10 CFR 50.55a(f)(4) when the licensee failed to scope and test check valves SF-44, SF-46, and 3SF-44 on the spent fuel cooling (SFC) system in accordance with American Society of Mechanical Engineers (ASME)
Operation and Maintenance of Nuclear Power Plants (OM) Code (2004 revision through 2006 addenda).
Additional Tracking Items
Type Issue Number Title Report Section Status LER 05000269,05000270,05 000287/2025-001-00 LER 2025-001-00 for Oconee Nuclear Station,
Units 1, 2, and 3,
Inoperability of Keowee Hydroelectric Unit due to Legacy Deficiencies in Generator Exciter Speed Switch Calibration Procedure resulting in a Condition Prohibited by Technical Specifications 71153 Closed
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.
Unit 3 operated at or near 100 percent RTP for the entire inspection period with the exception of a brief power reduction to 98 percent RTP on May 18, 2025, for a turbine valve movement test.
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 hot temperatures for the following systems: auxiliary building ventilation, turbine building ventilation, standby shutdown facility ventilation, B1T/B2T and 3B1T/3B2T blockhouses, on June 20, 2025.
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) Unit 3 high pressure injection (HPI) system with 3A HPI pump out of service for maintenance on April 21, 2025
- (2) Unit 3 motor driven emergency feedwater (EFW) pumps with the turbine driven EFW pump out of service for maintenance on May 13, 2025
- (3) Auxiliary service water (ASW) system post standby shutdown facility (SSF) outage on June 24, 2025
71111.05 - Fire Protection
Fire Area Walkdown and Inspection Sample (IP Section 03.01) (5 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 zone 112: Unit 3 control room on April 11, 2025
- (2) Fire zone 19: Unit 1 main feedwater pump area on April 15, 2025
- (3) Fire zone 89: Unit 3 equipment room on May 2, 2025
- (4) Fire zone 85: Unit 1 auxiliary building 200 level hallway on May 6, 2025
- (5) Fire zone 105: Unit 2 cable room on May 6, 2025
71111.06 - Flood Protection Measures
Flooding Sample (IP Section 03.01) (1 Sample)
- (1) The inspectors evaluated external flooding mitigation protections in the: KHU-1 turbine sump pump testing on April 24, 2025
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 degraded grid protection and isolation testing on May 15, 2025.
Licensed Operator Requalification Training/Examinations (IP Section 03.02) (1 Sample)
- (1) The inspectors observed and evaluated operator and simulator performance during a sitewide emergency preparedness drill on May 21, 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 (SSCs) remain capable of performing their intended function:
71111.13 - Maintenance Risk Assessments and Emergent Work Control
Risk Assessment and Management Sample (IP Section 03.01) (4 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) Unit 1 green risk following loss of alternate letdown isolation circuitry, on December 27, 2024
- (2) Sitewide elevated green risk due to maintenance on transformer CT-4 on April 22, 2025
- (3) Keowee unwater dual unit outage, on May 28, 2025
- (4) SSF annual outage, on the week of June 9, 2025
71111.15 - Operability Determinations and Functionality Assessments
Operability Determination or Functionality Assessment (IP Section 03.01) (3 Samples)
The inspectors evaluated the licensee's justifications and actions associated with the following operability determinations and functionality assessments:
- (2) NCR 2553882, weld indication at high pressure service water (HPSW) jockey pump supply joint
- (3) NCR 2556029, void indicated at 2LP-200, high point vent for the 2A low pressure injection pump suction
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) (3 Samples)
- (1) PT/2/A/0600/13A, Unit 2 A "Motor Driven Emergency Feedwater (MDEFW) Pump Test," following preventive maintenance, on April 23, 2025
- (2) PT/3/A/0600/012, "Turbine driven EFW Pump Test," following preventive maintenance, on May 13, 2025
- (3) PT/0/A/0400/011, "SSF Diesel Generator Test," following SSF annual outage, on June 14, 2025
Surveillance Testing (IP Section 03.01) (1 Sample)
- (1) PT/3/A/0203/006 A, "3C Low Pressure Injection Recirculation Pump Test," on April 7, 2025
Inservice Testing (IST) (IP Section 03.01) (1 Sample)
- (1) Review of IST requirements for preventing emergency core cooling system (ECCS)leakage and their applicability to spent fuel pool system check valves SF-43, SF-45, and 3SF-43, on April 9, 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 April 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 April 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 April 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 April 7, 2025.
71114.06 - Drill Evaluation
Required Emergency Preparedness Drill (1 Sample)
The inspectors evaluated:
- (1) Training drill 2025-01 on April 2, 2025, which included operations Shift B, emergency response organization Team 5, with participation from the emergency operations facility and the joint information center
Additional Drill and/or Training Evolution (1 Sample)
The inspectors evaluated:
- (1) Training drill 2025-02 on May 21, 2025, which included operations Shift D and emergency response organization Team
OTHER ACTIVITIES - BASELINE
===71151 - Performance Indicator Verification The inspectors verified licensee performance indicators submittals listed below:
MS05: Safety System Functional Failures (SSFFs) Sample (IP Section 02.04)===
- (1) Unit 1 (April 1, 2024, through March 31, 2025)
- (2) Unit 2 (April 1, 2024, through March 31, 2025)
- (3) Unit 3 (April 1, 2024, through March 31, 2025)
MS08: Heat Removal Systems (IP Section 02.07) (3 Samples)
- (1) Unit 1 (April 1, 2024, through March 31, 2025)
- (2) Unit 2 (April 1, 2024, through March 31, 2025)
- (3) Unit 3 (April 1, 2024, through March 31, 2025)
MS10: Cooling Water Support Systems (IP Section 02.09) (3 Samples)
- (1) Unit 1 (April 1, 2024, through March 31, 2025)
- (2) Unit 2 (April 1, 2024, through March 31, 2025)
- (3) Unit 3 (April 1, 2024, through March 31, 2025)
BI02: RCS Leak Rate Sample (IP Section 02.11) (3 Samples)
- (1) Unit 1 (April 1, 2024, through March 31, 2025)
- (2) Unit 2 (April 1, 2024, through March 31, 2025)
- (3) Unit 3 (April 1, 2024, through March 31, 2025)
EP01: Drill/Exercise Performance (DEP) Sample (IP Section 02.12) (1 Sample)
- (1) July 1 through Dec 31, 2024 EP02: Emergency Response Organization (ERO) Drill Participation (IP Section 02.13) (1 Sample)
- (1) July 1 through Dec 31, 2024 EP04: Emergency Response Facility and Equipment Readiness (ERFER) (IP Section 02.14)
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.
71152A - Annual Follow-up Problem Identification and Resolution Annual Follow-up of Selected Issues (Section 03.03)
The inspectors reviewed the licensees implementation of its corrective action program related to the following issues:
- (1) NCR 2119055, long term corrective action on restoring non-conformance of spent fuel pool boundary check valve leakage, on valves SF-44, SF-46 and 3SF-44
71152S - Semiannual Trend Problem Identification and Resolution Semiannual Trend Review (Section 03.02)
- (1) The inspectors reviewed the licensees corrective action program for potential adverse trends in post maintenance testing procedures that might be indicative of a more significant safety issue.
71153 - Follow Up of Events and Notices of Enforcement Discretion Event Follow up (IP Section 03.01)
- (1) The inspectors evaluated the loss of the Keowee overhead emergency power path, the loss of all offsite power on Units 2 and 3, and the licensees response on May 15, 2025. Per IMC 0309, Reactive Inspection Decision Basis for Power Reactors, the NRC considered whether this inspection sample should be the subject of a reactive inspection and determined that a reactive inspection was not necessary, as documented in ML25147A096.
Event Report (IP Section 03.02) (1 Sample)
The inspectors evaluated the following licensee event reports (LERs):
- (1) LER 05000269/2025-001-00, Inoperability of Keowee Hydroelectric Unit Due to Legacy Deficiencies in Generator Exciter Speed Switch Calibration Procedure Resulting in a Condition Prohibited by Technical Specifications (ADAMS Accession No. ML25111A260)
The inspection conclusions associated with this LER are documented in this report under Inspection Results Section 71111.12. This LER is closed.
OTHER ACTIVITIES
- TEMPORARY INSTRUCTIONS, INFREQUENT AND ABNORMAL
===60859 - Independent Spent Fuel Storage Installation (ISFSI) License Renewal Inspection 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 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."
Independent Spent Fuel Storage Installation (ISFSI) License Renewal Inspection===
- (1) The inspectors reviewed a sample of regulatory commitments, aging management programs (AMPs), and time-limited aging analyses (TLAAs) associated with the licensees implementation of the Site-Specific License SNM-2503 and General License CoC 72-1004. The inspection took place from April 28 to May 1, 2025. The inspectors observed activities, reviewed implementing documents, and conducted interviews with licensee staff to verify that the licensee completed the necessary actions to:
- (a) comply with the conditions stipulated in the renewed Certificate of Compliance and technical specifications; and
- (b) implement the AMPs and TLAAs as described in the NRC safety evaluation reports and Final Safety Analysis Report (FSAR) supplements.
The inspectors reviewed OSS-0121.00-00-0011, "Oconee Site-Specific Independent Spent Fuel Storage Installation Aging Management Review for License Renewal" and OSC-11848, "Oconee ISFSI CoC 1004 Aging Management Program Basis Document," which provides programmatic governance and implementation of the licensees site-specific and general license aging management programs.
Additionally, while onsite the inspectors directly observed activities associated with the dry shielded canister (DSC) External Surfaces Aging Management Program, the horizontal storage module (HSM) Aging Management Program for External and Internal Surfaces, and Transfer Cask Aging Management Program.
For those license renewal items that were not completed at the time of this inspection, the team verified that there was reasonable assurance that the items were on track for completion in accordance with an established implementation schedule consistent with the conditions of the certificate of compliance, technical specifications, the NRC safety evaluation report, and the FSAR.
INSPECTION RESULTS
Keowee Hydro Unit 1 Inoperable Following Governor Speed Switch Replacement Cornerstone Significance Cross-Cutting Aspect Report Section Mitigating Systems Green NCV 05000269,05000270,05000287/20250 02-01 Open/Closed
[H.12] - Avoid Complacency 71111.12 A self-revealed Green finding and associated NCV of 10 CFR 50, Appendix B, Criterion V, was identified when the licensee failed to implement work order instructions and PMT procedures appropriate to the circumstances during a governor speed switch replacement, which resulted in the inoperability of KHU-1.
Description:
The AC power system consists of the offsite power sources and the two onsite standby power sources, KHU-1 and KHU-2. The system is designed to supply the required engineered safeguards loads of one unit and safe shutdown loads of the other two units and is so arranged that no single failure can disable enough loads to jeopardize plant safety. Two KHUs are required to be operable with one capable of automatically providing power through the underground emergency power path to both main feeder buses, and the other capable of automatically providing power through the overhead emergency power path to both main feeder buses. An operable KHU and its required emergency power path are required to be able to provide sufficient power within specified limits of voltage and frequency within 23 seconds after an emergency start initiate signal.
On February 18, 2025, Oconee Nuclear Station (ONS) Units 1, 2, and 3 were all in Mode 1 operating at approximately 100 percent full power with KHU-1 aligned as the Overhead KHU and KHU-2 aligned as the Underground KHU. At 0814, KHU-1 was removed from service for a planned maintenance outage which included planned replacements of governor speed switches, designed to send a signal to the exciter to flash the field upon reaching a certain speed on startup. Following completion of maintenance and operational checks, KHU-1 was declared operable at 2236. An alignment swap of the KHUs was completed at 2309, resulting in KHU-1 being aligned as the Underground KHU and KHU-2 being aligned as the Overhead KHU. During the normal operational check of KHU-1 performed on February 18, following maintenance and subsequent operation over the next two days, operators noted that KHU-1 generator excitation seemed to take longer than usual. The exciter delays were observed again each time with a delay ranging from 50 seconds to two minutes. Engineering staff determined that both the normal start circuitry and the emergency start circuitry were affected by the exciter delays observed, rendering the unit unable to meet its design function. The licensee declared KHU-1 inoperable on February 20 at 2134, and entered Technical Specification (TS) 3.8.1 Condition D. Troubleshooting was performed, and it was discovered that two newly installed governor speed switches were out of calibration and could not be calibrated during field calibration attempts.
Work order (WO) 20570704 was planned in 2022 to replace the KHU-1 governor speed switches and perform the PMT using licensee procedure IP/1/A/0400/049, KHU-1 Governor Speed Switch Instrument Calibration. These speed switches operate by sensing a frequency input and sending a DC voltage signal to actuate two different relays, upon reaching a certain frequency in that range. The speed switch used for all of the replacements can be configured to fit multiple applications and frequency input ranges but needs to be set up to monitor a specific frequency range input by adjusting dip switches on the component first. Once dip switches are aligned to correspond to the specific frequency input needed for the switch application, then additional calibrations are required on the switch to align the frequency range to a DC voltage output as appropriate. The calibrations required for the speed switches in this case are located in a separate reference manual, KM 218.0017.001, Dynalco Speed Instrumentation Manual. The need to perform the speed switch setup and calibration in accordance with the KM 218 manual is highlighted in procedure IP/1/A/0400/049 in a Caution box. However, the WO instructions did not elaborate on how to replace the speed switches other than to reference IP/1/A/0400/049, did not reference the KM 218 manual as being required, and did not cross-reference the KM 218 manual in the WO documents and references. Licensee staff interviewed the technicians performing the maintenance and determined that there was a prevailing understanding that the statement in the Caution box referencing the KM 218 manual would only be applicable if the IP/1/A/0400/049 procedure could not be successfully completed, since a Caution box cannot direct work actions in procedures. Ultimately, the required calibration per the KM 218 manual was not performed.
Licensee procedure IP/1/A/0400/049 was used as the PMT for this maintenance activity. This procedure includes calibration steps for the relays that actuate in the speed switch and was identified as an appropriate PMT for a replacement of a speed switch component. To test the relays in each switch, a simulated frequency input using test equipment is sent to the switch to simulate the frequencies meant to actuate the relays. However, there were no steps in the procedure that would verify that the frequency range input on the switch was correctly set up, as designated by the dip switch settings, or to verify that the frequency range was correctly calibrated to the appropriate DC voltage output for the relays to actuate. The procedure as written could be performed successfully and not catch errors associated with the entire maintenance activity.
Corrective Actions: The licensee entered this issue into the corrective action program (CAP)as NCR 2544935. Maintenance technicians replaced the failed governor speed switches with those originally installed before the outage. Post maintenance testing, including verification of excitation timing, was completed and KHU-1 was declared operable on February 21 at 1429.
Work order instructions for similar maintenance tasks, applicable procedures, and PMT strategies are under further review for revision.
Corrective Action References: NCR 2544935
Performance Assessment:
Performance Deficiency: The licensees failure to implement work order instructions and PMT procedures appropriate to the circumstances during the replacement of the KHU-1 governor speed switches was a performance deficiency (PD). Specifically, on February 18, 2025, maintenance and testing activities of the KHU-1 governor speed switches resulted in the KHU-1 exciter not energizing in a timely manner and therefore KHU-1 not providing sufficient power to ONS units within 23 seconds of an emergency start signal as required by TS 3.8.1.
Screening: The inspectors determined the performance deficiency was more than minor because it was associated with the Procedure Quality 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, the PD resulted in the loss of function of KHU-1 to provide emergency AC power through the underground power path for 78 hours9.027778e-4 days <br />0.0217 hours <br />1.289683e-4 weeks <br />2.9679e-5 months <br />. The PD is also similar to Example 4.m in IMC 0612 Appendix E, Examples of Minor Issues.
Significance: The inspectors assessed the significance of the finding using IMC 0609 Appendix A, The Significance Determination Process (SDP) for Findings At-Power. IMC 0609 Appendix A, Exhibit 2, Question A3 can be answered YES since the equipment was unable to perform its Probabilistic Risk Assessment (PRA) function for greater than the TS allowed outage time. Therefore, this issue screened to requiring a detailed risk evaluation.
A regional Senior Reactor Analyst (SRA) performed a detailed risk assessment using the guidance in NRC Inspection Manual Chapter 0609 Appendix A and the RASP Manual Volume 1. The SRA modeled the condition using SAPHIRE 8 version 8.2.11 and the Oconee SPAR model version 8.82, dated September 27, 2023. The SRA set exposure time to three days and set ACP-HTG-TM-KU1 KEOWEE UNIT 1 HYDRO ELECTRIC UNAVAILABLE DUE TO T&M, ACP-HTG-FS-KU1 KEOWEE UNIT 1 HYDRO ELECTRIC FAILS TO START, and ACP-HTG-FR-KU1 KEOWEE UNIT 1 HYDRO ELECTRIC FAILS TO RUN, to True. This ensured that the common cause failure probabilities were adjusted for this maintenance induced failure. The dominant accident sequence was a weather-related loss of offsite power event, operators failing to align Keowee Unit 2, the Lee combustion turbines in test and maintenance, operators failing to control the turbine driven emergency feedwater pump, and failure to restore Keowee or offsite power in four hours. Due to the short exposure time, plant risk was less than 1E-7 which characterizes this condition as very low safety significance (Green).
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 same maintenance activity was successfully completed twice before using the same level of work order instruction and procedure guidance. Despite the previous success, potential gaps in work order clarity, risk recognition, or procedural deficiencies that could lead to mistakes in execution were not identified or mitigated during the work order planning process.
Enforcement:
Violation: 10 CFR Part 50, Appendix B, Criterion V, "Instructions, Procedures, and Drawings,"
states, in part, that activities affecting quality shall be prescribed by documented instructions, procedures, or drawings, of a type appropriate to the circumstances and shall be accomplished in accordance with these instructions, procedures, or drawings. Instructions, procedures, or drawings shall include appropriate quantitative or qualitative acceptance criteria for determining that important activities have been satisfactorily accomplished.
Contrary to the above, on February 18, 2025, the licensee failed to use documented instructions and procedures appropriate to the circumstances for an activity affecting quality.
Specifically, the work order instructions in WO 20570704 and post maintenance testing procedure IP/1/A/0400/049 failed to correctly replace and test the KHU-1 governor speed switches. As a result of the incorrectly configured governor speed switches, KHU-1, aligned to the underground power path, was rendered inoperable from 0814 on February 18, 2025, until 1429 on February 21, 2025.
Enforcement Action: This violation is being treated as a non-cited violation, consistent with Section 2.3.2 of the Enforcement Policy.
Failure to Assess and Manage Maintenance Risk Following the Inadvertent Actuation of the Alternate Letdown Isolation System Cornerstone Significance Cross-Cutting Aspect Report Section Mitigating Systems Green NCV 05000269/2025002-02 Open/Closed
[H.7] -
Documentation 71111.13 The inspectors identified a Green finding and associated NCV of 10 CFR 50.65(a)(4) when the licensee failed to assess and manage the risk on Unit 1 following the inadvertent actuation of the alternate letdown isolation system.
Description:
Each units high-pressure injection (HPI) system receives water returning from the reactor coolant system (RCS) by continuous letdown to the letdown storage tank, after passing through letdown coolers, a pressure reducing device, and a purification demineralizer. Most of the components in the HPI system are located outside of containment in the auxiliary building. HPI system valve HP-5 is normally open during power operation to allow letdown flow and serves as the outside containment isolation valve. This valve is automatically closed by an engineering safeguards (ES) signal as well as a high letdown temperature signal. These signals cause relays in the engineered safeguards relay cabinet ESTC to actuate and close HP-5.
The licensees response to the post-Fukushima Near Term Task Force (NTTF)
Recommendation 2.1, on seismic hazard re-evaluation, included an updated Seismic PRA model. One of the risk insights from that model was that the seismic large early release frequency (LERF) was dominated by failure of the ESTC cabinet supports. A failure of this cabinet could lead to a failure of HP-5 to close on an ES signal, therefore bypassing containment and allowing a direct release path to the environment. In an effort to reduce this risk, the licensee implemented a modification to install a seismically robust relay cabinet containing alternative isolation circuitry to close HP-5. The operation of this alternate letdown isolation system is independent of the potential failure of the ESTC cabinet.
On December 26, 2024, an inadvertent actuation of the Unit 1 alternate letdown isolation system caused 1HP-5 to close, isolating letdown. The control room crew performed immediate corrective actions to stabilize the plant and restore letdown to pre-event values.
The cause of the inadvertent actuation could not be initially determined, the system was placed in bypass for maintenance troubleshooting, and the licensee entered the issue into the CAP as NCR 2539278.
During power operation, the licensee manages and assesses risk through the requirements of AD-WC-ALL-0240, On-line Risk Management Process, which partially implements the requirements of 10 CFR 50.65, Requirements for monitoring the effectiveness of maintenance at nuclear power plants. Resident inspectors reviewed licensee procedure AD-WC-ALL-0240, CSD-WC-ONS-0240-00, ONS ERAT Guidance, unit operator logs, control room procedures, and the unit risk assessment in the licensees electronic risk assessment tool (ERAT). The inspectors did not find an entry in ERAT associated with the alternate letdown isolation system being bypassed and questioned the licensee on the current maintenance risk profile for the unit and any risk mitigating actions currently in effect. While operators were aware of the bypassed system, no additional risk assessment or management actions were taken. The licensee restored the alternate letdown isolation system on January 17, 2025.
Corrective Actions: After adding this issue to the CAP as NCR 2539278, the licensee conducted a cause evaluation for the system failure and conducted an updated PRA analysis for the system being bypassed.
Corrective Action References: NCR 2539278
Performance Assessment:
Performance Deficiency: The failure to assess and manage maintenance risk when required by licensee procedure AD-WC-ALL-0240 was a performance deficiency (PD). Specifically, the licensee failed to assess and manage the associated risk following the inadvertent actuation and subsequent troubleshooting of the Unit 1 alternate letdown isolation system.
Screening: The inspectors determined the performance deficiency was more than minor because it was associated with the Protection Against External Factors 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, the risk assessment was not completed and therefore did not account for the loss of the PRA function of the alternate letdown isolation system. The PD is also similar to Example 8.d in IMC 0612 Appendix E, Examples of Minor Issues.
Significance: A regional SRA performed a detailed risk evaluation using NRC IMC 0609 Appendix K, Maintenance Risk Assessment and Risk Management Significance Determination Process and IMC 0609 Appendix M, Significance Determination Process Using Qualitative Criteria. The licensee took the alternate letdown isolation system out of service without evaluating the online risk or establishing risk management actions (RMAs) if necessary. Seismic risk is assessed qualitatively. IMC 0609, Appendix K, Section 0609k-03, General Guidance, contains a note stating, This guidance does not apply to the following situations:
- (1) those licensees who only perform qualitative analyses of plant configuration risk due to maintenance activities, or
- (2) performance deficiencies related to maintenance activities affecting SSCs needed for fire (unless quantitatively analyzed) or seismic mitigation.
When performance deficiencies are identified with either 1 or 2 above, the significance of the deficiencies will be determined in accordance with IMC 0609, Appendix M Significance Determination Process Using Qualitative Criteria. However, quantitative evaluation is acceptable when a licensee has provided a qualitative evaluation, if the NRC staff internally possesses quantitative information that is adequate and best available to perform the assessment. The licensees seismic hazard re-evaluation suggested seismic risk impact of this system not being available was high enough to warrant RMAs. However, the licenses seismic re-evaluation was extremely conservative, and their current risk model was able to better evaluate the impact of the condition with more granularity and removing some extremely conservative seismic impact assumptions. The licensee was able to model the condition using their current risk model. The SRA reviewed the licensees evaluation and concluded it was the best available information for this issue. Using IMC 0609, Appendix K, Flowchart 1, Assessment of Risk Deficit, Incremental Large Early Release Probability Deficit was greater than 1E-7 but less than 5E-7. While formal RMAs were not established, operators were aware and briefed on the alternate letdown system status which can be credited as an RMA. Therefore, this issue is characterized as very low safety significance (Green).
Cross-Cutting Aspect: H.7 - Documentation: The organization creates and maintains complete, accurate and up-to-date documentation. Specifically, following the implementation of the plant modification for the alternate letdown isolation system, the licensee did not create or update procedural guidance for tracking system availability and the resulting impact to unit risk so that operators could perform required risk assessments.
Enforcement:
Violation: 10 CFR 50.65(a)(4) requires, in part, that before performing maintenance activities (including but not limited to surveillance, post-maintenance testing, and corrective and preventive maintenance), the licensee shall assess and manage the increase in risk that may result from the proposed maintenance activities. Contrary to the above, from December 26, 2024, until January 17, 2025, the licensee failed to assess and manage an increase in risk that resulted from maintenance associated with the inadvertent actuation and subsequent troubleshooting of the Unit 1 alternate letdown isolation system.
Enforcement Action: This violation is being treated as a non-cited violation, consistent with Section 2.3.2 of the Enforcement Policy.
Failure to Scope Spent Fuel Cooling Valves into the Inservice Testing Program Cornerstone Significance Cross-Cutting Aspect Report Section Barrier Integrity Green NCV 05000269,05000270,05000287/20250 02-03 Open/Closed
[P.3] -
Resolution 71152A The inspectors identified a Green finding and associated NCV of 10 CFR 50.55a(f)(4) when the licensee failed to scope and test check valves SF-44, SF-46, and 3SF-44 on the SFC system in accordance with ASME OM Code (2004 revision through 2006 addenda).
Description:
Oconee Nuclear Station possesses two independent spent fuel pools designed to contain spent fuel assemblies during intermediate storage. One pool is shared between Units 1 and 2, the second pool is dedicated solely to Unit 3. Each pool contains an SFC system with a purification loop to remove various impurities. In certain conditions, the purification loops can be aligned to discharge to the low pressure injection (LPI) system and borated water storage tank (BWST) of their respective units. This allows water in those systems to be purified utilizing these components. However, a check valve separates the purification loop from the LPI system, preventing backflow. During the maximum hypothetical accident (MHA), Oconee aligns LPI to allow for recirculation of water from the reactor building emergency sump to the reactor vessel, to allow for core cooling. Because the water contained in LPI during this scenario can become highly radioactive from being in contact with damaged fuel, leakage from LPI and other emergency core cooling systems (ECCS) is restricted to under 12 gallons per hour (GPH). Leakage is maintained under the limit and verified by leakage testing, under the inservice testing (IST) program of all potential ECCS leak paths, including back-leakage from the LPI system to the spent fuel pool (SFP) and BWST, through the aforementioned SFC check valves.
On May 19, 2016, the licensee discovered an unexpected loss of Unit 3 pressurizer volume over the course of their refueling outage. Following a leak hunt and outage activity review, this inventory loss was identified to have occurred via a leakage flow path past SFC check valve 3SF-44, allowing LPI water to leak to the vapor space of the BWST. This leakage path had not been previously identified, and neither 3SF-44, nor its corresponding Unit 1 and Unit 2 valves, SF-44 and SF-46, were scoped into the IST program, during the fifth interval period.
ASME OM Code (2004 Edition), ISTA-1100, Scope, states, Section IST establishes the requirements for preservice and in-service testing and examination of certain components to assess their operational readiness... apply to...
- (a) pumps and valves that are required to perform a specific function in shutting down a reactor to the safe shutdown condition, in maintaining the safe shutdown condition, or in mitigating the consequences of an accident.
As a result, these SFC check valves were required to be tested per ISTC-3630, Leakage Rate for Other than Containment Isolation Valves, at least once every two years. The licensee placed this issue into the CAP as NCR 2031073 with an action to add these check valves to the IST program and test them for leakage. At the time, the completion of these actions was thought to be dependent on modifications needed to the plant to allow testing of these valves. Since these modifications could only be completed during outage periods, a long-term action plan was created to complete the modifications, and the NCR was closed without scoping or testing these valves.
In March 2025, the inspectors identified that valves SF-44, SF-46, and 3SF44 were also not added to the sixth IST interval, which began on July 1, 2023. Through additional engagement with the resident inspector office, the licensee discovered that although the check valves met the ISTA-1100 scope, they were never formally added to the IST program.
Corrective Actions: The licensee added this issue to the CAP as NCR 2550577. Additionally, the licensee began monitoring BWST level trends when in lineups susceptible to leakage through these check valves. The licensee determined that Unit 2 and Unit 3 showed no signs of increasing level trends, but Unit 1 showed a trend of leakage ranging between 1.8-2.5 GPH. This leakage was accounted for in the Unit 1 ECCS leakage logs, and the licensee determined it was acceptable to maintain the MHA design requirement.
Corrective Action References: NCR 2550577
Performance Assessment:
Performance Deficiency: The failure to incorporate IST program scoping and testing requirements during the fifth and sixth intervals for SFC check valves SF-44, SF-46, and 3SF-44, as required by 10 CFR 50.55a(f)(4), was a performance deficiency.
Screening: The inspectors determined the performance deficiency was more than minor because if left uncorrected, it would have the potential to lead to a more significant safety concern. Specifically, these valves were credited to mitigate the consequences of an accident but were not being tested in accordance with the IST program to ensure their leakage rate remained within acceptable limits assumed in safety analyses. This is similar to Example 2.b in IMC 0612, Appendix E, Examples of Minor Issues.
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 3, Section C, the inspectors determined the finding to be of very low safety significance (Green) because it did not represent an actual open pathway in the physical integrity of reactor containment, failure of containment isolation system, failure of containment pressure control equipment, or failure of containment heat removal components.
Cross-Cutting Aspect: P.3 - Resolution: The organization takes effective corrective actions to address issues in a timely manner commensurate with their safety significance. Specifically, although the licensee initially identified that the SFC check valves needed to be scoped into the IST program, no effective corrective action was taken to restore compliance with requirements while the long-term plant modification was in progress.
Enforcement:
Violation: 10 CFR 50.55a(f)(4), Inservice Testing Standards Requirement for Operating Plants, requires, Throughout service life of a pressurized water-cooled nuclear power facility, pumps and valves that are within the scope of the ASME OM Code must meet the inservice test requirement set forth in the ASME OM Code. ASME OM Code (2004 Edition),
ISTA-1100, Scope, states, the requirements for preservice and inservice testing and examination of certain components to assess their operational readiness... apply to... (a)pumps and valves that are required to perform a specific function in shutting down a reactor to the safe shutdown condition, in maintaining the safe shutdown condition, or in mitigating the consequences of an accident.
Contrary to the above, since at least May 19, 2016, the licensee failed to scope and test SFC system check valves SF-44, SF-46, and 3SF-44 per ASME OM Code.
Enforcement Action: This violation is being treated as a non-cited violation, consistent with Section 2.3.2 of the Enforcement Policy.
Observation: Potential Adverse Trend in Post Maintenance Testing Procedures 71152S Inspectors identified four instances of issues documented in the CAP in the last year with a cause or contributing cause attributed to inadequate post maintenance testing procedures.
The outcomes of these separate, unrelated issues, referenced in NCR 2517161, 2517276, 2534840, and 2544935, have varying significance from resulting in minor plant impacts or maintenance schedule delays up to resulting in Green findings and associated non-cited violations. This potential adverse trend in post maintenance testing procedures might indicate the existence of a more significant programmatic issue related to effective maintenance practices. The licensee has entered this NRC observation in the CAP as NCR 2560959 and intends to evaluate this issue further.
EXIT MEETINGS AND DEBRIEFS
The inspectors verified no proprietary information was retained or documented in this report.
- On April 10, 2025, the inspectors presented the emergency preparedness program inspection results to Steven Snider and other members of the licensee staff.
- On May 1, 2025, the inspectors presented the ISFSI aging management inspection results to Steven Snider and other members of the licensee staff.
- On July 21, 2025, the inspectors presented the integrated inspection results to Steven Snider and other members of the licensee staff.
DOCUMENTS REVIEWED
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
60859
Corrective Action
Documents
Corrective Action
Documents
2551439
Drawings
OFD-101A-3.3
Flow Diagram of High Pressure Injection System Charging
Section
Drawings
OFD-121A-3.4
Flow Diagram of Condensate System (Hotwell Pumps,
Condensate Coolers, Generator Water Coolers, &
Hydrogen Coolers)
Drawings
OFD-121A-3.7
Flow Diagram of Condensate System (Upper Surge Tanks
3A & 3B, Upper Surge Tank Dome, & Condensate
Storage Tank)
Drawings
OFD-121A-3.8
Flow Diagram of Condensate System (Condensate Make-
up and Emergency Feedwater Pump Suction)
Drawings
OFD-121D-3.1
Flow Diagram of Emergency Feedwater System
Miscellaneous
Clearance PRT-3-25-3A HPIP OOS-0081
Miscellaneous
Clearance PRT-3-25-U3 TDEFW OOS-0131
Miscellaneous
Clearance OPS-3-25-EFW-U3 TDEFWP-0739
Miscellaneous
Clearance OPS-3-25-HPS-2HPSW-191 PM-0416
Miscellaneous
OSS-0254.00-00-
1001
(MECH) High Pressure Injection and Purification &
Deborating Demineralizer Systems
070
Calculations
OSC-10816
ONS TCCA A and OTHER Area Basis for AD-EG-ALL-
20
006
Calculations
OSC-9375
ONS Fire PRA - Fire Scenario Report
2
Corrective Action
Documents
2169391
Fire Plans
CSD-ONS-PFP-
Pre-Fire Plan for U1 Auxiliary Building Elevation 783
000
Fire Plans
CSD-ONS-PFP-
Pre-Fire Plan for U1 Turbine Building Elevation 775
000
Fire Plans
CSD-ONS-PFP-
Pre-Fire Plan for U2 Auxiliary Building Elevation 809
000
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
Fire Plans
CSD-ONS-PFP-
Pre-Fire Plan for U3 Auxiliary Building Elevation 796
001
Fire Plans
CSD-ONS-PFP-
Pre-Fire Plan for U3 Auxiliary Building Elevation 822
000
Miscellaneous
O-0310-FZ-011
Auxiliary Building - Units 3 Fire Protection Plan Fire Area
& Fire Zone Boundaries Plan at EL 796+6 & EL 797+6
Miscellaneous
O-0310-FZ-025
Turbine Building - Unit 1 Fire Protection Plan Fire Area &
Fire Zone Boundaries Plan at EL 775+0
Miscellaneous
O-0310-K-004
Auxiliary Building - Unit 1 Fire Protection Plan & Fire
Barrier, Flood, & Pressure Boundaries Plan at EL 783+9
Miscellaneous
O-0310-K-009
Fire Protect Aux Bldg Unit 3 EL 796+6
015
Miscellaneous
O-0310-K-011
Auxiliary Building Unit 2 Fire Protection Plan & Fire
Barrier, Flood, & Pressure Boundaries Plan at EL 809+3
Miscellaneous
O-0310-L-001
Turbine Building - Unit 1 Fire Protection Plan & Fire
Barriers, Flood, & Pressure Boundaries Plan at EL 775+0
Miscellaneous
O-0310-S2-015
Unit 2 Cable Room Sprinkler System Plan
Miscellaneous
OSS-0254.00-00-
4008
(MECH) Design Basis Specification for Fire Protection
051
Procedures
AD-FP-ALL-1520
Transient Combustible Control
Procedures
MP/0/A/1705/040
Fire Protection - Periodic Inspection of SLC Required Fire
004
Work Orders
20431707, 20431708, 20030025, 20034998, 20698768,
20030024, 20042885, 20698962, 20030023, 20042889,
20699239
Corrective Action
Documents
2552154
Drawings
KFD-102A-1.1
Flow Diagram of Turbine Sump Pump System
Miscellaneous
OSS-0254.00-00-
1047
(MECH) Design Basis Spec for Keowee Turbine Sump
Pump (TS) System
017
Procedures
PT/1/A/2200/019
KHU-1 Turbine Sump Pump IST Surveillance
031
Corrective Action
Documents
2549280
Miscellaneous
CSD-EP-ONS-0101-
EAL Technical Basis Document
005
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
Miscellaneous
CSD-EP-ONS-0101-
Oconee Nuclear Station Classification of Emergency
003
Procedures
AD-OP-ALL-1000
Conduct of Operations
26
Procedures
AP/1/A/1700/011
Recovery from Loss of Power
066
Procedures
EP/1/A/1800/001 00
Unit 1 EOP Immediate Manual Actions and Subsequent
Actions
003
Procedures
PT/0/A/0610/022
Degraded Grid and Switchyard Isolation Test
041
Corrective Action
Documents
2544935, 2555862,
2555868, 2554829
Miscellaneous
KM 218.0017.001
Dynalco Speed Instrumentation Manual
2
Procedures
AD-DC-ALL-0202
Writer's Manual for Procedures and Work Instructions
Procedures
AD-EG-ALL-1210
Procedures
AD-PI-ALL-0106
Cause Investigation Checklists
Procedures
IP/1/A/0400/049
KHU-1 Governor Speed Switch Instrument Calibration
Work Orders
20713656,
20570704,
20714278,
20579842
Calculations
OSC-10355
SDP Evaluation for Letdown Isolation Valve HP-5
Calculations
OSC-10360
Oconee Level 2/3 Analysis in Support of SDP Evaluation
for Letdown Isolation Valve HP-5
Calculations
OSC-11788
Oconee Seismic Probabilistic Risk Assessment
Quantification Notebook
2
Corrective Action
Documents
2539278
Drawings
O-0422-X-029
Instrument Detail Letdown Isolation Valve Control 1HP-5
Drawings
OEE-151-03
Elementary Diagram Letdown Isolation Valve 1HP
VA0005
Drawings
OEE-151-03-01
Elementary Diagram Letdown Isolation Valve 1HP
VA0005
Drawings
OFD-101A-1.1
Flow Diagram of High Pressure Injection System (Letdown
Section)
Miscellaneous
Risk Profile for Units 1, 2, and 3 for the week of April 21st
Miscellaneous
Clearance PRT-0-24-KHU1 TO OH-0167
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
Miscellaneous
Risk Profile for Units 1, 2, and 3 for the week of June 9th
Miscellaneous
Clearance PRT-0-25-SSF TEMP POW-0155
Miscellaneous
25 SSF Annual Outage Elevated Risk Activity Plan
Miscellaneous
Risk Profile for Unit 1 from December 27, 2024, until
January 17, 2024
Miscellaneous
Operator Logs on Unit 1 from December 27, 2024, until
January 17, 2024
Miscellaneous
Risk Profile for Units 1, 2, and 3 for the week of May 26th
Miscellaneous
Clearance PRT-0-25-DUAL OUTAGE-0112
Procedures
AD-NF-ALL-0501
Electronic Risk Assessment Tool (ERAT)
Procedures
AD-OP-ALL-0201
Protected Equipment
Procedures
AD-WC-ALL-0240
On-line Risk Management Process
Procedures
CSD-WC-ONS-
240-00
2
Procedures
OP/0/A/2000/038
KHS - Unwatering and Watering-Up Units
Procedures
OP/1/A/1104/002
HPI System
183
Work Orders
20582064, 20708737
Calculations
OSC-7371.01
GL 96-06 Water Hammer Operability Evaluation:
Operability Criteria for Evaluation of Piping, Components,
and Pipe Supports/Restraints
D2
Calculations
OSC-9592
Gas-Water Waterhammer Loads in Building Spray Header
(PIP O-08-5705, PDO)
Corrective Action
Documents
2553882, 2556029, 1787325, 2553663, PIP O-11-02685,
PIP O-10-09753, PIP O-04-09121
Drawings
OFD-102A-2.1
Flow Diagram of Low Pressure Injection System Borated
Water Supply and LPI Pump Sump
Drawings
OFD-102A-2.2
Flow Diagram of Low Pressure Injection System LPI Pump
Discharge
54E
Drawings
OFD-121B-1.3
Flow Diagram of Feedwater System (Final Feedwater)
Drawings
OFD-121D-1.1
Flow Diagram of Emergency Feedwater System
Drawings
OFD-124C-1.1
Flow Diagram of High Pressure Service Water System
HPSW Pumps
Drawings
OFD-133A-1.1
Flow Diagram of Condenser Circulating Water System
(CCW Intake Pumps Discharge)
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
Drawings
OFD-133A-2.5
Flow Diagram of Condenser Circulating Water System
SSF Aux Service
Miscellaneous
OSS-0254.00-00-
1005
(MECH) Design Basis Specification for the Standby
Shutdown Facility Auxiliary Service Water System
047
Miscellaneous
OSS-0254.00-00-
28
(MECH) Design Basis Specification for the Low Pressure
Injection and Core Flood System (LPI)
Miscellaneous
OSS-0254.00-00-
1039
(MECH) Design Basis Specification for the Low Pressure
Service Water System
067
Procedures
EP/1/A/1800/001 0P
Unit 1 EOP Enclosures 5.31-5.40
2
Procedures
NDE-NE-ALL-0002
Request for Miscellaneous Inspection/NDE
001
Work Orders
20516444, 20727375, 20727378, 20288947, 20288929
Calculations
OSC-9014
Corrective Action
Documents
2550577, 2542688, PIP O-14-02724
Drawings
OFD-122A-3.4
Flow Diagram of Main Steam System (Emergency FDW
Pump Turbine Steam Supply & Exhaust)
Drawings
OFD-124C-3.2
Flow Diagram of High Pressure Service Water System
Turbine Building
Drawings
OM 246.--0004.001
1/2" to 4" GDTELIST F5/5 3/600/5 5/59/600/5 FS/51/ 600
Drawings
OM 246.--0011.001
21/2" to 6", 600 LB. Bolted Bonnet Swing Check Valve
2B
Drawings
ONTC-1-121D-
0002-001
Oconee Nuclear Station Unit 1 Test Acceptance Criteria
for Turbine Driven EFW Pump
Engineering
Changes
20879
Miscellaneous
OSS-0254.00-00-
1000
(MECH) Design Basis Specification for the Emergency
Feedwater System
061
Miscellaneous
OSS-0254.00-00-
1008
(MECH) Design Basis Specification for the Standby
Shutdown Facility Diesel Support System
056
Miscellaneous
OSS-0254.00-00-
1037
(MECH) Design Basis Specification for Main Steam
System
058
Miscellaneous
OSS-0254.00-00-
1038
Design Basis Specification for the Auxiliary Steam System
21
Procedures
IP/0/B/0275/005 H
Emergency Feedwater System Motor Driven Emergency
Feedwater Pump - Non-Safety Related Instrument
063
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
Calibration
Procedures
OP/0/A/1600/010
Operation of the SSF Diesel-Generator
2
Procedures
PT/0/A/0400/011
SSF Diesel Generator Test
016
Procedures
PT/0/A/0600/021
Standby Shutdown Facility Diesel - Generator Operation
018
Procedures
PT/2/A/0600/013
Motor Driven Emergency Feedwater Pump Test
Procedures
PT/3/A/0150/022L
TDEFDW Pump Backup Cooling Water Supply Test
27
Procedures
PT/3/A/0203/006 A
Low Pressure Injection Pump Test - Recirculation
095
Procedures
PT/3/A/0600/012
Turbine Driven Emergency Feedwater Pump Test
097
Work Orders
20707124, 20711119, 20616233, 20648102, 20700448,
20552427, 20710874, 20521411
Procedures
CSD-EP-ONS-0101-
ONS EAL Technical Basis Document
Procedures
EP-ONS-EPLAN-
ANNEX
DUKE ENERGY OCONEE EMERGENCY PLAN ANNEX
Procedures
Duke Energy Common Emergency Plan
Corrective Action
Documents
2487778
Miscellaneous
MSEL 25-0 - ONS Drill 25-01
Miscellaneous
ONS Drill 25-01 - Drill Objective Sheet
Miscellaneous
Duke Energy Common Emergency Plan
Miscellaneous
MSEL Drill 25-02
ONS Drill 25-02
Procedures
EG/0/A/OSAM/SAG-
TSC Severe Accident Guideline Control SFP Level
000
Procedures
EG/1/A/OSAM/SAG-
Main Control Room Severe Accident Guideline Initial
Response
001
71151
Corrective Action
Documents
2518069, 2534840, 2538150
71151
Miscellaneous
Oconee Nuclear Station Units 1, 2, and 3 Mitigating
Systems Performance Index (MSPI) Basis Document
71151
Miscellaneous
MSPI Derivation and Margin Reports for Cooling Water
System for Units 1, 2, and 3 from July 2024 to March 2025
71151
Miscellaneous
OSC-8901
Oconee PRA Input for MSPI Basis Document
010
71151
Procedures
AD-EG-ALL-1217
Mitigating System Performance Index (MSPI)
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
71151
Procedures
PT/2/A/0600/010
Reactor Coolant Leakage
080
Corrective Action
Documents
2031073, 2114982, 2119055, 2526306, 2534740,
2333218, 1907965, 1908544, 2282359, 1798149,
1810130, 1838276, 1866347, 1906137, 1798422, PIP-O-
07-5237
Drawings
OFD-102A-3.1
Flow Diagram of Low Pressure Injection System (Borated
Water Supply and LPI Pump Suction)
Drawings
OFD-104A-01-02
Flow Diagram of Spent Fuel Cooling System Purification
Loop
Drawings
OFD-104A-3.1
Flow Diagram of Spent Fuel Cooling System
Drawings
OFD-104A-3.2
Flow Diagram of Spent Fuel Cooling System Purification
System
Engineering
Changes
23133
Miscellaneous
Groundwater Protection Initiative Tritium Summary
Reports for Wells GM-16R, GM-17R, and GM-24R for
October, November, and December 2024
Miscellaneous
Site Characterization Report Addendum, 05/05/2011
Miscellaneous
Updated Groundwater Drawings Report, 01/10/2019
Miscellaneous
Site Modifications Review Report, 01/10/2019
Miscellaneous
Updated Groundwater Drawings Report, 03/01/2024
Miscellaneous
Site Modifications Review Report, 03/01/2024
Miscellaneous
Groundwater Protection Initiative Support Report
06/25/2025
Miscellaneous
AD-CP-ALL-0017
Radiological Groundwater Protection
Miscellaneous
LTAM-ON-17-0030
Additional ECCS Leakage path to the BWST (OBDM)
Miscellaneous
OSC-10546
Qualification of Cured-in-Place-Pipe (CIPP) for Corrugated
Metal Pipe (CMP) Repair
Miscellaneous
OSS-0254.00-00-
1006
(MECH) Design Basis Specification for the Spent Fuel
Cooling System
035
Procedures
PT/1/A/0203/004
Low Pressure Injection System Leakage
040
Work Orders
2182726
Corrective Action
Documents
2539278, 2504847, 2533422, 2545420, 2544538,
25104, 2515376, 2517161, 2527276, 2533976,
2538150,
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
Corrective Action
Documents
2554852, 2554827, 2554829, 2554830, 2554832,
2554850, 2544935
Miscellaneous
CSD-EP-ONS-0101-
Oconee Nuclear Station Classification of Emergency
005
Procedures
AD-EG-ALL-1311
Failure Investigation Process
Work Orders
20607025, 20288371, 20288383