IR 05000277/2025003
| ML25356A003 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 12/22/2025 |
| From: | Nicole Warnek Division of Operating Reactors |
| To: | Mudrick C Constellation Energy Generation, Constellation Nuclear |
| References | |
| IR 2025003 | |
| Download: ML25356A003 (0) | |
Text
December 22, 2025
SUBJECT:
PEACH BOTTOM ATOMIC POWER STATION, UNITS 2 AND 3 -
INTEGRATED INSPECTION REPORT 05000277/2025003 AND 05000278/2025003
Dear Christopher Mudrick:
On September 30, 2025, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at Peach Bottom Atomic Power Station, Units 2 and 3. On December 9, 2025, the NRC inspectors discussed the results of this inspection with Martin Bonifanti, Site Vice President, 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 made 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, third quarter integrated inspection reports normally issued by November 15, 2025, to December 31, 2025. The NRC will resume the routine cycle of issuing inspection reports on a quarterly basis beginning with the calendar year 2025, fourth quarter integrated inspection reports, which will be issued 45 days after the fourth quarter ends on December 31, 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 I; the Director, Office of Enforcement; and the NRC Resident Inspector at Peach Bottom Atomic Power Station, Units 2 and 3.
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, Nicole S. Warnek, Chief Projects Branch 3 Division of Operating Reactor Safety
Docket Nos. 05000277 and 05000278 License Nos. DPR-44 and DPR-56
Enclosure:
As stated
Inspection Report
Docket Numbers:
05000277 and 05000278
License Numbers:
Report Numbers:
05000277/2025003 and 05000278/2025003
Enterprise Identifier: I-2025-003-0040
Licensee:
Constellation Energy Generation, LLC
Facility:
Peach Bottom Atomic Power Station, Units 2 and 3
Location:
Delta, PA 17314
Inspection Dates:
July 1, 2025 to September 30, 2025
Inspectors:
L. Cline, Senior Resident Inspector
C. Dukehart, Resident Inspector
D. McHugh, Reactor Inspector
E. Miller, Senior Reactor Inspector
Approved By:
Nicole S. Warnek, Chief
Projects Branch 3
Division of Operating Reactor Safety
SUMMARY
The U.S. Nuclear Regulatory Commission (NRC) continued monitoring the licensees performance by conducting an integrated inspection at Peach Bottom Atomic Power Station,
Units 2 and 3, 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
Improperly Protected Direct Current (DC) Control Circuits Could Result in Preventing Appendix R Safe Shutdown Cornerstone Significance Cross-Cutting Aspect Report Section Mitigating Systems Green NCV 05000277,05000278/2025003-01 Open/Closed None (NPP)71152A The inspectors identified a Green non-cited violation (NCV) of Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Appendix R,Section III.G.2. The performance deficiency was related to unprotected direct current (DC) control cables which would not ensure that one train of systems necessary to achieve and maintain hot shutdown conditions be free of fire damage. Specifically, six DC control circuits lacked properly coordinated overcurrent protection due to inadequate fuse sizing. The licensee implemented additional compensatory actions to achieve safe shutdown during Appendix R fire scenarios.
Additional Tracking Items
Type Issue Number Title Report Section Status URI 05000277,05000278/2024011-01 Uncoordinated Control Cable DC Circuits 71152A Closed LER 05000277, 05000278/2025-002-00 LER 2025-002-00 for Peach Bottom Atomic Power Station (PBAPS), Units 2 and 3, Uncoordinated DC Circuits Cause Unanalyzed Condition 71153 Closed
PLANT STATUS
Unit 2 began the inspection period at rated thermal power (RTP). On September 12, 2025, the unit was down powered to 54 percent for a control rod pattern adjustment and turbine valve testing and returned to RTP the following day. The unit remained at or near RTP for the remainder of the inspection period.
Unit 3 began the inspection period at RTP. On July 18, 2025, the unit was down powered for a rod pattern adjustment and returned to RTP the following day. The unit remained at or near RTP for the remainder of the inspection period and ended the inspection period in end-of-cycle coastdown.
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) (3 Samples)
The inspectors evaluated system configurations during partial walkdowns of the following systems/trains:
- (1) Units 2 and 3, emergency service water (ESW) booster pump ventilation supply fan restoration following maintenance on August 11, 2025
- (2) Unit 2, high-pressure coolant injection (HPCI) during Unit 2 reactor core isolation cooling (RCIC) system maintenance on August 28, 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) Unit 2, turbine building, emergency battery switchgear rooms elevation 135'-0", fire area/zone PF-127, on August 12, 2025
- (2) Unit 2, reactor building, HPCI room elevation 91'-6", fire area/zone PF-59, on August 28, 2025
- (3) Unit 3, reactor building, 3A and 3C core spray rooms elevation 91'-6", fire area/zone PF-13D, on September 10, 2025
- (4) Unit 3, turbine building, emergency battery switchgear rooms elevation 135'-0", fire area/zone PF-117, on September 11, 2025
- (5) Unit 2, reactor building, 2A and 2C core spray rooms elevation 91'-6", fire area/zone PF-5A, on September 11, 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 August 13, 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 operator turnover on September 17, 2025.
Licensed Operator Requalification Training/Examinations (IP Section 03.02) (1 Sample)
- (1) The inspectors observed and evaluated a licensed operator requalification training scenario that involved a recirculation pump trip resulting in thermal hydraulic instabilities and an anticipated transient without a scram that included a radiation release leading to a General Emergency declaration on August 25, 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:
- (1) Units 2 and 3, offsite power/switchyard, 2 startup transformer load tap changer (Issue reports (IRs) 04867486, 04863063, 04860176, and 04823412)
71111.13 - Maintenance Risk Assessments and Emergent Work Control
Risk Assessment and Management Sample (IP Section 03.01) (2 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 2, emergent failure of the Unit 2 instrument nitrogen compressor suction outboard isolation valve, AO-2-16-4235, that required risk informed completion time assessment and risk management action evaluation on July 21, 2025 (IR 04884251)
- (2) Unit 2, emergent failure of the Unit 2 wide range reactor pressure transmitter, PT-2-02-3-404B, that required risk informed completion time assessment and risk management action evaluation on July 27, 2025 (IR 04886333)
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:
- (1) Unit 2, nitrogen compressor suction valve from drywell, AO-2-16-4235, exceeding allowable stroke time for a primary containment isolation valve on July 21, 2025 (IR 04884251)
- (2) Unit 2, pressure input to 'B' XAM microprocessor for density compensation of the emergency core cooling system (ECCS) level control system, PT-2-02-3-404B, failed downscale affecting wide range level indication and ECCS level initiation signals on July 27, 2025 (IR 04886333).
- (3) Unit 3, 3A core spray motor oil cooler service water leak on September 7, 2025 (IR 04895832)
71111.18 - Plant Modifications
Temporary Modifications and/or Permanent Modifications (IP Section 03.01 and/or 03.02) (1 Sample)
The inspectors evaluated the following temporary or permanent modifications:
- (1) Unit 3, loading of Westinghouse TRITON11 lead use assemblies in non-limiting core locations co-resident with GNF3 fuel assemblies for three fuel cycles beginning in cycle 26 (Engineering Change (EC) 641996)
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) Units 2 and 3, E-3 emergency diesel generator (EDG) exhaust leak repair (work order (WO) 05621847), on July 14, 2025
- (2) Unit 3, core spray pump 'A' motor oil cooler leak repair (WO 05720095-17), on September 11, 2025
- (3) Unit 2, RCIC preventative maintenance window (WO 04272158, WO 05654967, WO 05647238), on August 28, 2025
Surveillance Testing (IP Section 03.01) (2 Samples)
- (1) Units 2 and 3, ST-O-052-202-2, E-2 diesel generator slow start and full load test on July 9, 2025
- (2) Unit 3, ST-O-011-301-3, standby liquid control pump 'A' test for inservice testing on July 10, 2025
71114.06 - Drill Evaluation
Required Emergency Preparedness Drill (1 Sample)
- (1) The inspectors observed and evaluated the conduct of an emergency preparedness drill in the main control room simulator and technical support center involving failures that resulted in the declaration of a General Emergency on September 9,
OTHER ACTIVITIES - BASELINE
===71151 - Performance Indicator Verification
The inspectors verified licensee performance indicators submittals listed below:
MS07: High Pressure Injection Systems (IP Section 02.06)===
- (1) Unit 2, October 1, 2024 to September 30, 2025
- (2) Unit 3, October 1, 2024 to September 30, 2025
MS08: Heat Removal Systems (IP Section 02.07) (2 Samples)
- (1) Unit 2, October 1, 2024 to September 30, 2025
- (2) Unit 3, October 1, 2024 to September 30, 2025
MS09: Residual Heat Removal Systems (IP Section 02.08) (2 Samples)
- (1) Unit 2, October 1, 2024 to September 30, 2025
- (2) Unit 3, October 1, 2024 to September 30, 2025
MS10: Cooling Water Support Systems (IP Section 02.09) (2 Samples)
- (1) Unit 2, October 1, 2024 to September 30, 2025
- (2) Unit 3, October 1, 2024 to September 30, 2025
===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) IR 04895246, Appendix R non-compliances due to DC short circuits
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 2025-002-00, "Uncoordinated DC Circuits Cause Unanalyzed Condition,"
(Agencywide Documents Access and Management System (ADAMS) Accession No.
ML25281A104). The inspection conclusions associated with this LER are documented in this report under Inspection Results Section 71152A. This LER is closed.
INSPECTION RESULTS
Improperly Protected Direct Current (DC) Control Circuits Could Result in Preventing Appendix R Safe Shutdown Cornerstone Significance Cross-Cutting Aspect Report Section Mitigating Systems
Green NCV 05000277,05000278/2025003-01 Open/Closed
None (NPP)71152A The inspectors identified a Green non-cited violation (NCV) of Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Appendix R,Section III.G.2. The performance deficiency was related to unprotected direct current (DC) control cables which would not ensure that one train of systems necessary to achieve and maintain hot shutdown conditions be free of fire damage. Specifically, six DC control circuits lacked properly coordinated overcurrent protection due to inadequate fuse sizing. The licensee implemented additional compensatory actions to achieve safe shutdown during Appendix R fire scenarios.
Description:
An analysis performed by Constellation identified that 327 uncoordinated control cables were inadequately protected based on the fuse characteristics and the minimum fault current for each circuit (i.e., fuse amperages were too high for the associated cables' conductor gauge size and will not deenergize the cable during certain postulated fires). This equipment configuration could create the potential for a fire in one area to damage cables located in a different fire area, which in turn can impact the equipment credited for fire safe shutdown and invalidate credited safe shutdown methods.
After an extensive evaluation using testing, minimum short circuit current, cable tray thermal heat load modeling, and specific cable routing, Constellation identified six cables in three different fire areas that violated the 10 CFR Part 50, Appendix R, Section III.G.2 requirement that one train of systems necessary to achieve and maintain hot shutdown conditions be free of fire damage. The remaining cables were evaluated as meeting Appendix R requirements using EC 641735 and EC 643927. Compensatory actions were identified and implemented.
Constellation issued LER 2025-002-00 to document the non-compliance.
Corrective Actions: Following NRC inspection, compensatory measures were identified and put in place for the six cables that were not in compliance with Appendix R. An engineering evaluation is in progress to identify the required fuse replacements to ensure the control cables are protected.
Corrective Action References: IR 04445172, IR 04895246, EC 643927
Performance Assessment:
Performance Deficiency: The performance deficiency was that multiple DC circuit protection issues were not in accordance with design specifications associated with cable separation and wire protection. These issues represented a potential challenge to the licensing bases Appendix R safe shutdown required strategies. The improperly protected DC circuits were within Constellations ability to foresee and correct.
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 reliability of the associated safe shutdown cables was not ensured for fires in three fire areas. In addition, this finding is more than minor because it was similar to Example 3.m of IMC 0612, Appendix E, Examples of Minor Issues.
Specifically, the resulting condition was unacceptable and required interim compensatory actions to maintain operability/functionality.
Significance: The inspectors assessed the significance of the finding using IMC 0609, Appendix F, Fire Protection and Post - Fire Safe Shutdown SDP. This issue was determined to be High degradation in Step 1.3. The inspectors determined in step 1.4.7-C that the finding adversely affected the ability to reach and maintain hot shutdown using the credited safe shutdown success path. Step 1.5 required the issue to be screened by licensee Fire Probabilistic Risk Assessment (PRA)-Based Risk Evaluation.
Constellation completed a PRA-based risk evaluation of this issue, as documented in PB-MISC-067, "Peach Bottom DC Cable Hot Short Appendix R Non-Compliance Risk Evaluation," and concluded the change in core damage frequency (Delta CDF) and change in large early release frequency (Delta LERF) were less than 1E-6 and less than 1E-7, respectively, for both Unit 2 and Unit 3. A regional Senior Reactor Analyst (SRA) reviewed Constellation's risk evaluation, associated documentation, and conducted interviews with station personnel. Of note, for Fire Area 25, which had the largest impact on risk, the location of the affected cable was not close to any fixed ignition sources and would only be susceptible to a transient fire. Additionally, the subject fire would have to be severe enough to lead to main control room abandonment due to loss of equipment control or habitability.
Therefore, there were fewer credible fire scenarios that could fail the cable, and thus, the associated fire ignition frequencies were lower which reduced the risk of the issue. The SRA also noted that Constellation incorporated information into their model from the following NRC documents to further refine the risk assessment: NUREG/CR-7010, Volume 2, "Cable Heat Release, Ignition, and Spread in Tray Installations During Fire Phase 2: Vertical Shafts and Corridors"; NUREG-2230, "Methodology for Modeling Fire Growth and Suppression Response for Electrical Cabinet Fires in Nuclear Power Plants"; and NUREG-2178, Volume 2, "Refining and Characterizing Heat Release Rates from Electrical Enclosures During Fire." Overall, the SRA determined that Constellation's risk assessment was reasonable, and therefore concluded the risk associated with the performance deficiency was of very low safety significance (Green).
Cross-Cutting Aspect: Not Present Performance. No cross-cutting aspect was assigned to this finding because the inspectors determined the finding did not reflect present licensee performance.
Enforcement:
Violation: 10 CFR Part 50, Appendix R, Section III.G.2 requires that one train of systems necessary to achieve and maintain hot shutdown conditions be free of fire damage. This includes ensuring that fire damage will not prevent the operation of necessary systems and components, or cause spurious operation that could prevent safe shutdown. Licensees must provide fire detection and suppression systems and ensure that redundant trains are separated by fire barriers or alternative means.
Contrary to the above, from original plant design until September 4, 2025, six DC control circuits lacked properly coordinated overcurrent protection due to inadequate fuse sizing. As a result, a postulated fire in a single fire area could cause a short circuit that is not adequately protected, potentially leading to the loss of equipment credited for achieving and maintaining safe shutdown. This condition does not ensure that at least one train of safe shutdown equipment remains free of fire damage, as required by Appendix R,Section III.G.2.
This finding closes URI 05000277/05000278/2024011-01, Uncoordinated Control Cable DC Circuits, and LER 2025-002-00, "Uncoordinated DC Circuits Cause Unanalyzed Condition."
Enforcement Action: This violation is being treated as an NCV, consistent with Section 2.3.2 of the Enforcement Policy.
EXIT MEETINGS AND DEBRIEFS
The inspectors verified that no proprietary information was retained or documented in this report.
- On December 9, 2025, the inspectors presented the integrated inspection results to Martin Bonifanti, Site Vice President, and other members of the licensee staff.
DOCUMENTS REVIEWED
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
Corrective Action
Documents
Resulting from
Inspection
Unit 2 'B' Reactor Building Closed-Cooling Water Heat
Exchanger Leak
Corrective Action
Documents
Resulting from
Inspection
Housekeeping issues in Unit 2 HPCI room
Corrective Action
Documents
Resulting from
Inspection
Emergency light pack door ajar in E-33 switchgear room
(Unit 3)