IR 05000454/2025004
| ML26016A573 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 01/20/2026 |
| From: | Dariusz Szwarc NRC/RGN-III/DORS/RPB3 |
| To: | Mudrick C Constellation Energy Generation |
| References | |
| IR 2025004 | |
| Download: ML26016A573 (0) | |
Text
SUBJECT:
BYRON STATION - INTEGRATED INSPECTION REPORT 05000454/2025004 AND 05000455/2025004
Dear Christopher H. Mudrick:
On December 31, 2025, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at Byron Station. On January 6, 2026, the NRC inspectors discussed the results of this inspection with Harris Welt, Site Vice President, 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 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, Dariusz Szwarc, Chief Reactor Projects Branch 3 Division of Operating Reactor Safety Docket Nos. 05000454 and 05000455 License Nos. NPF-37; NPF-66 Enclosure:
As stated cc w/ encl: Distribution via LISTSERV January 20, 2026 Signed by Szwarc, Dariusz on 01/20/26
Letter to Christopher
SUMMARY
The U.S. Nuclear Regulatory Commission (NRC) continued monitoring the licensees performance by conducting an integrated inspection at Byron 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
None.
PLANT STATUS
Unit 1 began the inspection period at rated thermal power and remained at or near full power throughout the remainder of the inspection period.
Unit 2 began the inspection period at rated thermal power and remained at or near full power throughout the remainder of the inspection period.
INSPECTION SCOPES
Inspections were conducted using the appropriate portions of the inspection procedures (IPs)in effect at the beginning of the inspection unless otherwise noted. Currently approved IPs with their attached revision histories are located on the public website at http://www.nrc.gov/reading-rm/doc-collections/insp-manual/inspection-procedure/index.html. Samples were declared complete when the IP requirements most appropriate to the inspection activity were met consistent with Inspection Manual Chapter (IMC) 2515, Light-Water Reactor Inspection Program - Operations Phase. The inspectors performed activities described in IMC 2515, Appendix D, Plant Status, observed risk significant activities, and completed on-site portions of IPs. The inspectors reviewed selected procedures and records, observed activities, and interviewed personnel to assess licensee performance and compliance with Commission rules and regulations, license conditions, site procedures, and standards.
REACTOR SAFETY
71111.04 - Equipment Alignment
Partial Walkdown Sample (IP Section 03.01) (2 Samples)
The inspectors evaluated system configurations during partial walkdowns of the following systems/trains:
(1)partial walkdown of the 2B auxiliary feedwater pump on October 30, 2025 (2)partial walkdown of the Unit 1 division 11 engineered safety features electrical distribution buses on December 16, 2025
71111.05 - Fire Protection
Fire Area Walkdown and Inspection Sample (IP Section 03.01) (4 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 11.3-0; north, south, and west, auxiliary building; elevation 364'-0";
general area on October 2, 2025
- (2) Fire Zone 11.4C-0, auxiliary building, elevation 383'-0", remote shutdown and radwaste panels on October 6, 2025
- (3) Fire Zone 5.5-1/2 and 2.1-0, auxiliary building, elevation 451'-0", Units 1 and 2 auxiliary electrical rooms and control room, elevation 451'-0" on October 10, 2025
- (4) Fire Zone 12.1-0, fuel handling building, elevations 401'-0" and 426'-0" on October 15, 2025
71111.11A - Licensed Operator Requalification Program and Licensed Operator Performance
Requalification Examination Results (IP Section 03.03) (1 Sample)
- (1) The inspectors reviewed and evaluated the licensed operator examination failure rates for the requalification annual operating exam and biennial comprehensive written examination administered from October 14, 2025, to November 21, 2025.
Sixty-five operators were examined. This population agrees with RPS OL Report 9.
One operator failed the written examination. The licensee developed a remediation plan and administered a re-examination, which the individual passed. No concerns related to exam failures and remediation. Additional action is not warranted per IP 71111.11A.
TABLE 03.03-1 EXAMINATION RESULTS
1. Total number of licensed operators: 65
2. Number of licensed operators administered a requalification examination
required by 10 CFR 55.59(a): 65
3. Number of individual licensed operators who failed any portion of a
re-qualification examination (written, JPM or individual simulator scenario failures): 1
4. Divide line 3 by line 2 to obtain the individual requalification examination
failure rate: Line 3/Line 2. 1.5%
5. Number of crews administered simulator scenarios as part of a requalification
examination required by 10 CFR 55.59(a): 11
6. Number of crews who performed unsatisfactorily on the simulator scenarios: 0
7. Divide line 6 by line 5 to obtain the crew simulator scenario failure rate:
Line 6/Line 5. 0%
The failure rates are below thresholds which require additional actions per IP 71111.11A.
The licensee and NRC staff discussed future dates for licensed operator requalification examinations.
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 various activities involving on-watch operations crews in the main control room during the week of October 20, 2025.
Licensed Operator Requalification Training/Examinations (IP Section 03.02) (1 Sample)
- (1) The inspectors observed and evaluated the performance of a complex graded scenario by a crew of licensed plant operators in the facilitys simulator on November 18, 2025.
71111.12 - Maintenance Effectiveness
Maintenance Effectiveness (IP Section 03.01) (3 Samples)
The inspectors evaluated the effectiveness of maintenance to ensure the following structures, systems, and components (SSCs) remain capable of performing their intended function:
(1)maintenance effectiveness review of DC Bus 112 battery charger following failure on November 2, 2025 (2)maintenance effectiveness review of diesel ventilation dampers following failure on December 2, 2025 (3)maintenance effectiveness review of the 0A essential service water makeup pump
71111.15 - Operability Determinations and Functionality Assessments
Operability Determination or Functionality Assessment (IP Section 03.01) (3 Samples)
The inspectors evaluated the licensees justifications and actions associated with the following operability determinations and functionality assessments:
(1)evaluation of operability of Unit 2 component cooling crosstie valve 2CC9473B, as documented in Action Request (AR) 4905730 (2)evaluation of operability of the 1B safety injection pump, as documented in AR 4910062 (3)evaluation of operability of 1B essential service water train with lower cubicle cooler isolated, as documented in Work Order (WO) 5606002
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) (2 Samples)
(1)functional and operational testing of Unit 1 N-42 power range detector following troubleshooting and repairs, as documented in WO 5733055 (2)functional and operational testing of 0FX02PC high head FLEX pump following rebuild and inspections, as documented in WO 5588857
Surveillance Testing (IP Section 03.01) (1 Sample)
(1)2BOSR 5.5.8.RH.5-2A, Group A Inservice Testing (IST) Requirements for Residual Heat Removal Pump 2RH01PB, as documented in WO 5701715
71114.04 - Emergency Action Level and Emergency Plan Changes
Inspection Review (IP Section 02.01-02.03) (1 Sample)
- (1) The inspectors evaluated the following submitted Emergency Action Level and Emergency Plan changes.
1. EP-AA-1000, Standardized Radiological Plan, Revision 34
This evaluation does not constitute NRC approval.
OTHER ACTIVITIES - BASELINE
71151 - Performance Indicator Verification The inspectors verified licensee performance indicators submittals listed below:
BI02: RCS Leak Rate Sample (IP Section 02.11) (2 Samples)
- (1) Unit 1 (October 1, 2024, through September 30, 2025)
- (2) Unit 2 (October 1, 2024, through September 30, 2025)
71152S - Semiannual Trend Problem Identification and Resolution Semiannual Trend Review (Section 03.02) (1 Sample)
- (1) The inspectors reviewed the licensees corrective action program to identify potential trends in site fire protection system impairments that might be indicative of a more significant safety issue.
INSPECTION RESULTS
Observation: Trend in Long-Term Fire Protection Impairments 71152S The inspectors conducted a review of recent plant issues, with a particular focus on items entered into the licensees corrective action program (CAP) over the past several months.
During this review, the inspectors identified a trend related to the extended duration of open fire protection system impairments. Specific CAP entries reviewed included:
- AR 4774574, Unit 1 CAF Fire Protection Inoperable
- AR 4791017, 2FP07J Not Functioning
- AR 4834798, Unit 1 CAF FP Header Pressurized with Water
- AR 4871268, Unit 2 369' Sprinkler Alarm Wont Reset
- AR 4889471, 1FP247B Leaking By
- AR 4911838, Letter of Concern: Byron Fire Protection KPI Decline The inspectors noted that several fire protection impairments have remained in place for extended periods, with one impairment active since May 16, 2024. In all cases, the site implemented appropriate compensatory actions. The most used compensatory action is to establish a fire watch. The extended use of fire watches creates fire protection program vulnerabilities by reducing monitoring capability from continuous to periodic in the affected fire zones and also introduces the possibility of missing required fire watches. The fire protection program is designed to limit fire damage to structures, systems, and components important to safety, ensuring the plant can be safely shut down if necessary. This priority is reinforced in LS-AA-1110, Revision 38, Safety (SAF) Reportability Manual, Reportable Event SAF 1.44, Impairments to Fire Suppression Systems, which states, in part, Impairments shall be as short in duration as possible, and every effort made to restore protection to service.
The site determined that an error in work order coding led to improper prioritization of fire impairment work requests. Corrective actions have been taken to ensure proper prioritization.
As a result, the number of open impairments was reduced from eight on November 27, 2025, to three by December 30,2025, with plans to complete remaining repairs during the first quarter of 2026.
No findings or violations of NRC requirements with more than minor safety significance were identified during this review.
EXIT MEETINGS AND DEBRIEFS
The inspectors verified that no proprietary information was retained or documented in this report.
- On January 6, 2026, the inspectors presented the integrated inspection results to Harris Welt, Site Vice President, and other members of the licensee staff.
- On December 8, 2025, the inspectors presented the emergency preparedness inspection results to Natalie Burton, Emergency Preparedness Manager, and other members of the licensee staff.
DOCUMENTS REVIEWED
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
1BOSR 8.9.1-1
Unit One ESF Onsite Power Distribution Weekly
Surveillance Division 11
Procedures
BOP AF-M2B
Auxiliary Feedwater System Train B Valve Lineup
Corrective Action
Documents
Missed Fire Watch
09/13/2025
Pre-Fire Plan
- 111
Fire Zone 11.3-0 South, Auxiliary Building 364'-0" Elev.
General Area South
Pre-Fire Plan
- 112
Fire Zone 11.3-0 West, Auxiliary Building 364'-0" Elev.
General Area West
Pre-Fire Plan
- 113
Fire Zone 11.3-0, North, Auxiliary Building 364'-0" Elev.
General Area North
Pre-Fire Plan
- 141
Fire Zone 11.4C-0, Auxiliary Building 383'-0" Elevation
Remote Shutdown and Radwaste Panels
Pre-Fire Plan
- 176
Fire Zone 12.1-0, Fuel Handling Bldg. 401'-0" Elev. Fuel
Handling Bldg.
Pre-Fire Plan
- 177
Fire Zone 12.1-0, Fuel Handling Bldg. 426'-0" Elev. Fuel
Handling Bldg.
Pre-Fire Plan #49
Fire Zone 5.5-1, Auxiliary Building 451'-0" Elevation Unit 1
Auxiliary Electrical Room
Fire Plans
Pre-Fire Plan #50
Fire Zone 5.5-2, Auxiliary Building 451'-0" Elevation Unit 2
Auxiliary Electrical Room
Miscellaneous
Byron TA-AA-
150-F25
LORT Annual Exam Status Report
11/21/2025
OP-A-101-111-
1001
Operations Standards and Expectations
Procedures
Conduct of Simulator Training and Evaluation
Calculations
BYR97-204
25 VDC Battery Sizing Calculation
2A DG Ventilation Inlet Damper Issues
2/01/2020
0A SX M/U Pump Failed to Start
04/24/2025
DC 112 Voltage Low
10/30/2025
DC Battery Charger 112 Float Voltage Low
11/01/2025
Corrective Action
Documents
25V DC Charger 112 Float Voltage Low
11/02/2025
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
Equipment Trend on DC 112 charger
11/07/2025
2A DG Room Temp Low-Failed Damper
2/02/2025
BMP 3222-2
Preventive Maintenance of Essential Service Water
Make-Up Pump Drive Unit
Compression Fittings Inspection, Installation, Remake and
Repair
Procedures
Hydramotor Actuator - Model AH91, NH91, and NH92
Preventive Maintenance
EWP-FNM 0A SX Makeup Pump Fuel Priming
01/23/2025
EWP EM T/S & Repair 125V DC Charger 112
11/06/2025
Work Orders
FNE TS Failed Damper-2VD09YA
2/04/2025
Calculations
VA-100
ESF Pump Cubicle Energy Calculation
2CC9473B Failed to Stroke
03/02/2025
2CC9473B - Potential Overthrust
10/14/2025
Corrective Action
Documents
Failure of Mod Acceptance Criteria
10/29/2025
Past Operability Evaluation for the 1B SI Pump
Engineering
Changes
1SX37AB-2" Pipe Size Reduction to Prevent Sediment
Buildup in 1B SI Bearing Oil Cooler (1SI01SB)
BOP SX-1
Essential Service Water Pump Startup
Motor Operated Valve Performance Trending
Procedures
Limitorque Actuator Overload Inspection Requirements
2CC9473B - Apparent High Stem to Stem-Nut COF Update
10/14/2025
LR 1VA01SB - Lower HX Insp per Generic Letter 89-13
2/18/2025
Work Orders
1SX37AB-2" Pipe Size Reduction EC 640818
08/13/2025
1RY-0457 NAL Card Failure
10/02/2025
Unit 1: Bistable TB431G
10/02/2025
Unit 1 N-42 Lower Detector Drifting
10/08/2025
2B RH Pump Vibes High
10/16/2025
Corrective Action
Documents
0C High Head FLEX Pump Unable to Develop Discharge
Pressure
10/31/2025
Drawings
DWG 6065D99
Schematic Diagram Power Range Nuclear Instrumentation
System 1PM07J and 2PM07J
E
Procedures
0BOSR FX-A1
FLEX Pump Annual Flow Surveillance
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
2BOSR 5.5.8.RH-
5.2A
Group A Inservice (IST) Requirements for Residual Heat
Removal Pump 2RH01PB
BISR 3.1.6-200
Day Surveillance Calibration of Power Range Nuclear
Instrumentation System (NIS)
Plant Instrumentation Test Matrix
0FX02PC High Head FLEX Pump 1Y Flow Test
10/31/2025
(NEIL) - RH01PB Group A IST Requirements for RH Pump
10/16/2025
Work Orders
FNI Troubleshoot 1NR-8042 Bottom Detector Flux Deviation
10/08/2025
Calculations
Evaluation No.:
24-49
§50.54(q) Program Evaluation Assessment Review for
Standardized Radiological Emergency Plan Revision 34
2/28/2025
Miscellaneous
EPID L-2018-
LLA-0045
Issuance of Amendments to Revise the Emergency
Response Organization Staffing Requirements
03/21/2019
Exelon Nuclear Standardized Radiological Emergency Plan
Standardized Radiological Emergency Plan
Procedures
EPA-400/R-
17/001
PAG Manual: Protective Action Guides and Planning
Guidance for Radiological Incidents
January
2017
71151
Miscellaneous
NRC Performance Indicator Data; Barrier Integrity - RCS
Identified Leakage
October
24 through
September
25
U1 CAF Fire Protection Inoperable
05/16/2024
2FP07J Not Functioning
07/31/2024
U-1 CAF FP Header Pressurized with Water
2/05/2025
U-2 369' Sprinkler Alarm Wont Reset
06/06/2025
1FP247B Leaking By
08/11/2025
Corrective Action
Documents
Letter of Concern - Byron Fire Protection (KPI) Decline
11/04/2025