IR 05000336/2025002

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Integrated Inspection Report 05000336/2025002 and 05000423/2025002
ML25223A194
Person / Time
Site: Millstone  
(DPR-065, NPF-049)
Issue date: 08/12/2025
From: Matt Young
Division of Operating Reactors
To: Carr E
Dominion Energy Nuclear Connecticut
References
IR 2025002
Download: ML25223A194 (1)
v • d • e


Text

August 12, 2025

SUBJECT:

MILLSTONE POWER STATION, UNITS 2 AND 3 - INTEGRATED INSPECTION REPORT 05000336/2025002 AND 05000423/2025002

Dear Eric Carr:

On June 30, 2025, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at Millstone Power Station, Units 2 and 3. On July 30, 2025, the NRC inspectors discussed the results of this inspection with Alex Trespalacios, Plant Manager, and other members of your staff. The results of this inspection are documented in the enclosed report.

No NRC-identified or self-revealing findings were identified during this inspection.

A licensee-identified violation which was determined to be of very low safety significance is documented in this report. We are treating this violation as a non-cited violation 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 Millstone 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 10 CFR 2.390, Public Inspections, Exemptions, Requests for Withholding.

Sincerely, Matt R. Young, Chief Projects Branch 2 Division of Operating Reactor Safety

Docket Nos. 05000336 and 05000423 License Nos. DPR-65 and NPF-49

Enclosure:

As stated

Inspection Report

Docket Numbers:

05000336 and 05000423

License Numbers:

DPR-65 and NPF-49

Report Numbers:

05000336/2025002 and 05000423/2025002

Enterprise Identifier: I-2025-002-0044

Licensee:

Dominion Energy Nuclear Connecticut, Inc.

Facility:

Millstone Power Station, Units 2 and 3

Location:

Waterford, CT

Inspection Dates:

April 1, 2025 to June 30, 2025

Inspectors:

E. Bousquet, Senior Resident Inspector

D. Antonangeli, Resident Inspector

N. Eckhoff, Health Physicist

S. Mercurio, Senior Emergency Preparedness Inspector

A. Turilin, Reactor Inspector

Approved By:

Matt R. Young, Chief

Projects Branch 2

Division of Operating Reactor Safety

SUMMARY

The U.S. Nuclear Regulatory Commission (NRC) continued monitoring the licensees performance by conducting an integrated inspection at Millstone 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. A licensee-identified non-cited violation is documented in report section: 71111.0

List of Findings and Violations

No findings or violations of more than minor significance were identified.

Additional Tracking Items

None.

PLANT STATUS

Unit 2 operated at or near rated thermal power for the entire inspection period.

Unit 3 began the inspection period at rated thermal power. On April 10, 2025, the unit shut down for a planned refueling outage and returned to rated thermal power on May 21, 2025. The unit remained at or near rated thermal power for the remainder of the inspection period.

INSPECTION SCOPES

Inspections were conducted using the appropriate portions of the inspection procedures (IPs) in effect at the beginning of the inspection unless otherwise noted. Currently approved IPs with their attached revision histories are located on the public website at http://www.nrc.gov/reading-rm/doc-collections/insp-manual/inspection-procedure/index.html. Samples were declared complete when the IP requirements most appropriate to the inspection activity were met consistent with Inspection Manual Chapter (IMC) 2515, Light-Water Reactor Inspection Program - Operations Phase. The inspectors performed activities described in IMC 2515, Appendix D, Plant Status, observed risk significant activities, and completed on-site portions of IPs. The inspectors reviewed selected procedures and records, observed activities, and interviewed personnel to assess licensee performance and compliance with Commission rules and regulations, license conditions, site procedures, and standards.

REACTOR SAFETY

71111.01 - Adverse Weather Protection

Seasonal Extreme Weather (IP Section 03.01) (1 Sample)

(1) The inspectors evaluated readiness for seasonal extreme weather conditions prior to the onset of seasonal extreme heat during a hot weather advisory and capacity deficiency for Units 2 and 3 service water systems at both intakes on June 24, 2025.

Impending Severe Weather (IP Section 03.02) (1 Sample)

(1) The inspectors evaluated the adequacy of the overall preparations to protect risk-significant systems from impending severe weather including high winds and heavy rain on May 22, 2025.

71111.04 - Equipment Alignment

Partial Walkdown (IP Section 03.01) (3 Samples)

The inspectors evaluated system configurations during partial walkdowns of the following systems/trains:

(1) Unit 2, charging system to emergency core cooling system alternative charging path from the charging pumps to the 'A' train of high-pressure safety injection to include 2-SI-417 on April 28, 2025
(2) Unit 2, service water system to include the 'A' service water pump, strainer, and associated piping and instrumentations on May 23, 2025
(3) Unit 2, 'B' emergency diesel generator (EDG) lube oil system from June 9 to 11, 2025

Complete Walkdown (IP Section 03.02) (1 Sample)

(1) The inspectors evaluated system configurations during a complete walkdown of the Unit 3 containment recirculation system on May 8, 2025.

71111.05 - Fire Protection

Fire Area Walkdown and Inspection (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) Unit 2, EDG 'A' and 'B' rooms on the 14'-6" elevation (fire areas A-15 and A-16) on April 4, 2025
(2) Unit 2, 480-volt motor control center B61 enclosure on the 14'-6" elevation (fire area A-13) on April 8, 2025
(3) Unit 3, containment on all elevations (fire area RC-1) during the planned refueling outage from April 10 to May 18, 2025
(4) Unit 2, enclosure building filtration room equipment area on the 14'-6" elevation (fire area A-14D) on June 2, 2025

Fire Brigade Drill Performance (IP Section 03.02) (1 Sample)

(1) The inspectors evaluated the on-site fire brigade training and performance during an unannounced fire drill on June 12, 2025.

===71111.08P - Inservice Inspection Activities (Pressurized-Water Reactor (PWR))

The inspectors verified that the reactor coolant system boundary, reactor vessel internals, risk-significant piping system boundaries, and containment boundary were appropriately monitored for degradation and that repairs and replacements were appropriately fabricated, examined, and accepted by reviewing the following activities in Unit 3 during refueling outage

==3R23 from April 14 to 25, 2025.

==

PWR Inservice Inspection Activities - Nondestructive Examination (NDE) and Welding Activities (IP Section 03.01)===

Main article: IP 71111.08
(1) Ultrasonic Examination
  • Ultrasonic testing of high-pressure safety injection (reactor coolant system loop D) cold leg elbow to pipe weld, RCS-506-1-SW-4 (NDE Report M3-UT-25-003)

Dye Penetrant Examination

Visual Examination

Welding Activities

  • Welding activities associated with the safety injection vent valve installation on M33-SIL-008-014-2 per Engineering Change MP3-23-01013 under WO53203409652. The post-welding NDE included liquid penetrant testing of welds 25 and 26 (NDE Report BOP-PT-25-014) and welds 22 and 23 (NDE Report BOP-PT-25-015).

PWR Inservice Inspection Activities - Vessel Upper Head Penetration Inspection Activities (IP Section 03.02) (1 Sample)

The inspectors verified that the licensee conducted the following vessel upper head penetration inspections and addressed any identified defects appropriately:

(1)

  • Bare metal visual examination of all penetrations and its adjacent head surfaces under WO53203400419 (NDE Solutions Report 180-9391915-000)dated April 14, 2025

PWR Inservice Inspection Activities - Boric Acid Corrosion Control Inspection Activities (IP Section 03.03) (1 Sample)

The inspectors verified the licensee is managing the boric acid corrosion control program through a review of the following evaluations:

(1)

  • Direct observation inside the containment building on April 16, 2025
  • Boric acid evaluation for pressurizer level transmitter M33RCS*LT461, packing nuts (CR1289735)
  • Boric acid evaluation for pressurizer level cold indication level transmitter M33RCS*LT462, packing nuts (CR1289739 and CR1289741)

71111.11Q - Licensed Operator Requalification Program and Licensed Operator Performance

Licensed Operator Performance in the Actual Plant/Main Control Room (IP Section 03.01) (2 Samples)

(1) The inspectors observed and evaluated licensed operator performance in the Unit 3 control room during a planned shutdown on April 10, 2025.
(2) The inspectors observed and evaluated licensed operator performance in the Unit 2 control room during testing of engineered safety features actuation system, reserve station service transformer, and sequencer testing in addition to reactivity manipulations on June 12, 2025.

Licensed Operator Requalification Training/Examinations (IP Section 03.02) (2 Samples)

(1) The inspectors observed and evaluated licensed operator requalification training in the Unit 2 simulator on June 13, 2025.
(2) The inspectors observed and evaluated licensed operator requalification training in the Unit 3 simulator on June 17, 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 remain capable of performing their intended function:

(1) Unit 2, maintenance rule functional failure evaluation for the 'B' EDG when jacket water temperature fell below its minimum value causing the EDG to be inoperable on April 22, 2025 (CR1289631)
(2) Unit 3, maintenance rule functional failure evaluation for the 'B' steam generator steam line pressure circuit card failure on May 22, 2025 (CR1283485)
(3) Unit 2, preventative maintenance strategy of the EDG fire sprinkler system on June 23, 2025 (CR1284191 and CR1285477)

71111.13 - Maintenance Risk Assessments and Emergent Work Control

Risk Assessment and Management (IP Section 03.01) (5 Samples; 1 Partial)

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) Units 2 and 3, switchyard south bus planned maintenance outage on March 1, 2025
(2) Unit 3, elevated risk due to reduced reactor inventory for the refueling outage on April 14, 2025
(3) Unit 3, spent fuel cooling risk planned during maintenance window for service water inspections on April 26, 2025 (4)

(Partial)

Unit 3, increased risk due to the emergent through-wall leak on service water piping inside the enclosure tube on May 20, 2025

(5) Unit 2, increased risk due to the emergent through-wall leak on the 'A' service water strainer shell on May 21, 2025
(6) Unit 2, elevated risk due to the 'B' EDG maintenance outage with 'C' reactor building component cooling water heat exchanger out of service for cleaning on June 9, 2025

71111.15 - Operability Determinations and Functionality Assessments

Operability Determination or Functionality Assessment (IP Section 03.01) (6 Samples)

The inspectors evaluated the licensee's justifications and actions associated with the following operability determinations and functionality assessments:

(1) Unit 2, use-as-is structural integrity evaluation for degraded wall-mounted strut plates for the enclosure building on April 8, 2025 (CR1278402, CR1287263, and CR1287379)
(2) Unit 3, feedwater check valve, 3FWS*V921, did not meet design requirements on April 10, 2025 (CR1288369 and WO53203405816)
(3) Unit 3, steam generator 'B' feedwater flow control valve reduced valve belly wall thickness due to flow accelerated washout on April 15, 2025 (CR1288794)
(4) Unit 2, high-pressure safety injection header 'A' relief valve, 2-SI-417, did not meet design requirements on April 25, 2025 (CR1289766 and CR1286184)
(5) Unit 2, 'B' EDG unexpected downward trend in jacket water level on May 14, 2025 (CR1291799)
(6) Unit 3, through-wall leak on the 'A' train of service water return line on May 22, 2025 (CR1292364)

71111.18 - Plant Modifications

Temporary Modifications and/or Permanent Modifications (IP Section 03.01 and/or 03.02) (3 Samples)

The inspectors evaluated the following temporary or permanent modifications:

(1) Unit 3, permanent change to the allowable leakage from the reactor plant component cooling water surge tank on April 14, 2025
(2) Unit 3, permanent replacement of residual heat removal system inlet isolation motor operated valve, 3RHS*MV8702B, on April 29, 2025
(3) Unit 3, permanent replacement of reactor plant component cooling system heat exchanger 'C', MP3 CCP*E1C, on May 5, 2025

71111.20 - Refueling and Other Outage Activities

Refueling/Other Outage (IP Section 03.01) (1 Sample)

(1) The inspectors evaluated Unit 3 planned refueling outage 3R23 from April 10 to May 18, 2025.

71111.24 - Testing and Maintenance of Equipment Important to Risk

The inspectors evaluated the following testing and maintenance activities to verify system operability and/or functionality:

Post-Maintenance Testing (PMT) (IP Section 03.01) (8 Samples)

(1) Unit 3 main steam safety valve lift-setpoint verification after adjustment during simmer testing on April 8, 2025 (WO53203404247)
(2) Unit 3 service water thermal relief valve testing after replacement on the safety injection pump 'B' cooler on April 14, 2025 (WO53203344816)
(3) Unit 3 motor operated valve stroke time test for the service water strainer blowdown valve, 3SWP*MOV24B, on April 16, 2025 (WO53203298771)
(4) Unit 3 post-maintenance testing of safety injection accumulator tank 'A' outlet motor operate valve, 3SIL*MV8808A, on April 18, 2025 (WO53102960458)
(5) Unit 3 bus tie relay testing of 34B to 34D after breaker preventative maintenance on April 23, 2025 (WO53203163512)
(6) Unit 3 'B' EDG jacket water heat exchanger after preventative maintenance on May 1, 2025 (WO53203404573)
(7) Unit 3 post-maintenance testing on containment recirculation train 'C' butterfly valve, RSS*MOV23C, after valve disassembly on May 5, 2025 (WO53203408336)
(8) Unit 3 reactor coolant pump seal 'C' replacement on May 14, 2025 (WO53203443764)

Surveillance Testing (IP Section 03.01) (2 Samples)

(1) Unit 3 cold shutdown over pressurization protections system train 'A' operability test on April 8, 2025 (WO53203358700)
(2) Unit 2 'B' EDG monthly operability run on May 14, 2025

Inservice Testing (IP Section 03.01) (1 Sample)

(1) Unit 2, 'B' reactor building closed-cooling water pump quarterly inservice testing on April 28, 2025

Containment Isolation Valve Testing (IP Section 03.01) (1 Sample)

(1) Unit 3, CDS-CTV91B from April 29 to 30, 2025 (CR1289410 and WO53203454651)

71114.02 - Alert and Notification System Testing

Inspection Review (IP Section 02.01-02.04) (1 Sample)

(1) The inspectors evaluated the licensee's maintenance and testing of the station alert and notification system from May 19 to 22, 2025, for the period of May 2023 through April 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 licensee's Emergency Preparedness Organization from May 19 to 22, 2025.

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:
  • MP-24-21-0, Revision to MP-26-EPA-REF02, Unit 2 Emergency Action Level Technical Bases Document; MP-26-EPI-FAP0G-002, Unit 2 Emergency Action Level Matrix; MP-26-EPA-REF03, Unit 3 Emergency Action Level Technical Bases Document; and MP-26-EPI-FAP0G-003, Unit 3 Emergency Action Level Matrix
  • MP-25-01-0, Reference Change 10 CFR 73.1 to 10 CFR 73.1200
  • MP-25-03-0, MP-26-EPI-FAP07, Notifications/Communications R28

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 from May 19 to 22, 2025, for the period of May 2023 through April 2025.

71114.06 - Drill Evaluation

Required Emergency Preparedness Drill (1 Sample)

(1) Unit 3, emergency planning drill on June 18,

RADIATION SAFETY

71124.01 - Radiological Hazard Assessment and Exposure Controls

Radiological Hazard Assessment (IP Section 03.01) (1 Sample)

(1) The inspectors evaluated how the licensee identifies the magnitude and extent of radiation levels, identifies the concentrations and quantities of radioactive materials, and assesses radiological hazards.

Instructions to Workers (IP Section 03.02) (1 Sample)

(1) The inspectors evaluated how the licensee instructs workers on plant-related radiological hazards and the radiation protection requirements intended to protect workers from those hazards.

Contamination and Radioactive Material Control (IP Section 03.03) (2 Samples)

The inspectors observed/evaluated the following licensee processes for monitoring and controlling contamination and radioactive material:

(1) Workers exiting the Unit 3 radiologically controlled area
(2) Licensee surveys of potentially contaminated material leaving the Unit 3 radiologically controlled area

Radiological Hazards Control and Work Coverage (IP Section 03.04) (4 Samples)

The inspectors evaluated the licensee's control of radiological hazards for the following radiological work:

(1) In-core instrumentation work at the seal table
(2) Refueling water storage tank foreign material retrieval
(3) Unit 3 reactor disassembly - phase 1 (Radiation Work Permit #3250301)
(4) Unit 3 valve inspections and repairs (Radiation Work Permit #3250327)

High Radiation Area and Very High Radiation Area Controls (IP Section 03.05) (3 Samples)

The inspectors evaluated licensee controls of the following high radiation areas and very high radiation areas:

(1) Unit 3 under vessel access
(2) Unit 3 Regen heat exchanger room
(3) Seal table room

Radiation Worker Performance and Radiation Protection Technician Proficiency (IP Section 03.06) (1 Sample)

(1) The inspectors evaluated radiation worker and radiation protection technician performance as it pertains to radiation protection requirements.

71124.07 - Radiological Environmental Monitoring Program

Environmental Monitoring Equipment and Sampling (IP Section 03.01) (1 Sample)

(1) The inspectors evaluated environmental monitoring equipment and observed a collection of environmental samples.

Radiological Environmental Monitoring Program (IP Section 03.02) (1 Sample)

(1) The inspectors evaluated the implementation of the licensees radiological environmental monitoring program.

GPI Implementation (IP Section 03.03) (1 Sample)

(1) The inspectors evaluated the licensees implementation of the groundwater protection initiative program to identify incomplete or discontinued program elements.

OTHER ACTIVITIES - BASELINE

===71151 - Performance Indicator Verification

The inspectors verified licensee performance indicators submittals listed below:

IE01: Unplanned Scrams per 7000 Critical Hours (IP Section 02.01)===

Main article: IP 71151
(1) Unit 2, April 1, 2024 through March 31, 2025
(2) Unit 3, April 1, 2024 through March 31, 2025

IE03: Unplanned Power Changes per 7000 Critical Hours (IP Section 02.02) (2 Samples)

(1) Unit 2, April 1, 2024 through March 31, 2025
(2) Unit 3, April 1, 2024 through March 31, 2025

IE04: Unplanned Scrams with Complications (USwC) (IP Section 02.03) (2 Samples)

(1) Unit 2, April 1, 2024 through March 31, 2025
(2) Unit 3, April 1, 2024 through March 31, 2025

EP01: Drill/Exercise Performance (IP Section 02.12) (1 Sample)

(1) April 1, 2024 through March 31, 2025

EP02: Emergency Response Organization Drill Participation (IP Section 02.13) (1 Sample)

(1) April 1, 2024 through March 31, 2025 EP04: Emergency Response Facility and Equipment Readiness (ERFER) (IP Section 02.14) (1 Sample)

This is a new NRC performance indicator, introduced in Nuclear Energy Institute 99-02, Revision 8 (ML24331A114). The licensees began collecting data for this performance indicator on January 1, 2025.

(1) January 1, 2025 through March 31, 2025

71153 - Follow-Up of Events and Notices of Enforcement Discretion Personnel Performance (IP Section 03.03)

Main article: IP 71153
(1) The inspectors evaluated the operators response to an inadvertent actuation of safety injection, containment isolation Phase A, main steam line isolation, and actuation of the EDGs on May 6, 2025, when the plant was at zero percent power and Mode 5.

Reporting (IP Section 03.05) (2 Samples)

The inspectors evaluated the following licensees event reporting determinations to ensure they complied with reporting requirements:

(1) Reportability evaluation for Unit 3 inadvertent actuation of safety injection, containment isolation Phase A, main steam line isolation, and actuation of the EDGs on May 6, 2025, when the plant was at zero percent power and Mode 5
(2) The retraction of EN57615 associated with the Unit 3 secondary containment boundary on April 7,

OTHER ACTIVITIES

- TEMPORARY INSTRUCTIONS, INFREQUENT AND ABNORMAL

71003 - Post-Approval Site Inspection for License Renewal Post-Approval Site Inspection for License Renewal

Main article: IP 71003
(1) The team conducted a Phase 1 license renewal inspection at Unit 3 from April 14 to 25, 2025. The following aging management programs were evaluated by the team:

1. Electrical Cables Not Subject to 10 CFR 50.49, Environmental Qualification

Requirements Used in Instrumentation Circuits (AMP 8), Commitment 7 a. Non-EQ Instrument Cable Testing of Radiation Monitoring System M33RMS*RE41 (WO53203412111)b. Non-EQ Instrument Cable Testing of Radiation Monitoring System M33RMS*RE42 (WO53203412112)

2. Buried Pipe Inspection Program (AMP 3), Commitment 3

a. Excavation for Buried Piping Inspection 3-IAS-150-32-4 (WO53203340001)b. Excavation for Buried Piping Inspection 3-SAS-001-130-4 (WO53203340000)c. Unit 3, Buried Piping Inspection of Condensate Return Lines ETE-MP-2017-1037 (WO53103110032)d. Unit 1, Fire Hydrant (1-FH-5) will not close (replace hydrant)

(WO3203289327)e. Fire Header Underground Break North of U3 Auxiliary Building (WO53203344436)

3. Work Control Process (AMP 24), Commitment 31

a. Underground Piping and Tank Inspection Report (WO53203388294)b. Valve Replacement - DC MP3-24-01006, M33SWP*V082 (WO53203438205)c. Valve Replacement - DC MP3-24-01006, M33SWP*V083 (WO53203438206)d. Valve Replacement - DC MP3-23-01136, M33SWP*V194 (WO53203408536)

4. Tank Inspection Program (AMP 23), Commitment 24

a. M33QSS*TK1, Refuel Water Storage Tank (WO53103134220)b. M33BRS*TK1, Boron Recovery Tank A (WO53203386015)c. M33FWA*TK1, Demin Storage Water Tank (WO53203246628)

5. Infrequently Accessed Areas Inspection Program (AMP 14), Commitment 12

a. License Renewal Commitment #12 - Auxiliary Building Demineralizer Alley (inside the cubicles (WO53203438684))

b. License Renewal Commitment #12 - Regenerative Heat Exchanger Room in Containment (WO53203438685)

INSPECTION RESULTS

Licensee-Identified Non-Cited Violation 71111.05 This violation of very low safety significance was identified by the licensee and has been entered into the licensee corrective action program and is being treated as a non-cited violation, consistent with Section 2.3.2 of the Enforcement Policy.

Violation: The Unit 2 License Condition 2.C(3) requires the licensee to implement and maintain in effect all provisions of the approved fire protection program as described in the final safety analysis report and as approved through safety evaluation reports. Final Safety Analysis Report, Chapter 9.10, Fire Protection System, states waterspray systems were designed in accordance with National Fire Protection Association (NFPA), Standard Number 15, 1985 Edition. NFPA, Standard Number 15, Section 6-2.3, states, in part, all piping shall be examined at regular intervals to determine condition and proper drainage.

Contrary to the above, prior to February 26, 2025, the licensee did not implement and maintain in effect all provisions of the approved fire protection program, in that, they failed to periodically determine condition and proper drainage of the EDG 'A' fire protection preaction sprinkler system. Specifically, the licensee failed to ensure the system is drained and remains dry during normal standby conditions and following routine surveillance tests. As a result, sediment and corrosion products were found in the normally dry sprinkler system of the EDG

'A' room which could block sprinkler heads and restrict fire water flow.

Significance/Severity: Green. The inspectors assessed the significance of the finding using IMC 0609, Appendix F, Fire Protection and Post - Fire Safe Shutdown Significance Determination Process. The issue is associated with a fixed fire protection system category and was determined to be a low degradation rating using IMC 0609, Appendix F, 2, Degradation Rating Guidance, for water-based suppression findings.

Specifically, less than 10 percent of heads are obstructed or nonfunctional, there is a functional head within 10 feet of combustibles of concern (or the maximum spacing allowed between sprinklers by NFPA 13), and the system is nominally code compliant. Therefore, the issue was determined to be of very low safety significance (Green).

Corrective Action References: CR1284191 and CR1285477

EXIT MEETINGS AND DEBRIEFS

The inspectors verified that no proprietary information was retained or documented in this report.

  • On April 25, 2025, the inspectors presented the inservice inspection results to James Petty, Site Vice President, and other members of the licensee staff.
  • On April 25, 2025, the inspectors presented the license renewal Phase 1 inspection results to James Petty, Site Vice President, and other members of the licensee staff.
  • On May 2, 2025, the inspectors presented the radiological hazards and assessment inspection results to James Petty, Site Vice President, and other members of the licensee staff.
  • On May 22, 2025, the inspectors presented the emergency preparedness program inspection results to James Petty, Site Vice President, and other members of the licensee staff.
  • On May 23, 2025, the inspectors presented the radiological environmental monitoring program inspection results to James Petty, Site Vice President, and other members of the licensee staff.
  • On July 30, 2025, the inspectors presented the integrated inspection results to Alex Trespalacios, Plant Manager, and other members of the licensee staff.

DOCUMENTS REVIEWED

Inspection

Procedure

Type

Designation

Description or Title

Revision or

Date

71003

Corrective Action

Documents

CR1292711

Miscellaneous

DMNMIL-00064-

REPT-002

Millstone Unit 3 Selective Leaching Sample Plan

Revision 1

ETE-MP-2024-

1047

Work Control Process

Revision 0

ETE-MP-2024-

1063

Buried Piping

Revision 0

ETE-MP-2024-

1064

Tank Inspections

Revision 0

ETE-MP-2024-

1070

Infrequently Accessed Areas

Revision 0

ETE-MP-2024-

1075

Electrical Cables Not Subject to 10 CFR 50.49

Revision 0

MPS-3 FSAR

Millstone Power Station Unit 3 Safety Analysis Report,

Chapter 19: License Renewal

Revision

37.03

NUREG-1838

Safety Evaluation Report with Open Items Related to the

License Renewal of the Millstone Power Station, Units 2

and 3

February

2005

71111.05

Corrective Action

Documents

CR1284191

CR1285477

Engineering

Evaluations

ETE-MP-2025-

1048

Evaluation of 'A' EDG Sprinkler System Functionality

Revision 1

71111.08P Corrective Action

Documents

CR1289664

CR1289696

CR1289835

CR1289838

Miscellaneous

MP-24-CII-PRG

Containment Inservice Inspection Program

Revision 009

MPS3 Ten-Year

ISI Plan

Millstone Station Unit 3 Fourth Ten-Year Interval Inservice

Inspection Plan

Revision 2

71111.13

Procedures

WM-AA-301

Operational Risk Assessment

Revision 27

Work Orders

WO53203460467

Inspection

Procedure

Type

Designation

Description or Title

Revision or

Date

71111.15

Engineering

Evaluations

ETE-MP-2025-

1003

Unit 2 Enclosure Building Structural Assessment of

As-Found Wall Strut Plate

Revision 0

ETE-MP-2025-

25

MPS3 Feedwater Control Valve M33FWS*FCV520

Structural Integrity Assessment

Revision 0

71111.18

Calculations

Calc Number:

P(R)-711

Reactor Plant Component Cooling System Surge Tank

Sizing

Revision 3A

Engineering

Evaluations

ETE-MP-2025-

1019

Implementation of the Unit 3 RPCCW Surge Tank Allowable

Leakage Limit Calculation

Revision 0

71111.24

Corrective Action

Documents

CR1289086

Corrective Action

Documents

Resulting from

Inspection

CR1293600

71114.02

Miscellaneous

300-08-090928

Dominion Millstone Alert and Notification System Upgrade

Project FEMA REP-10 Design Report Addendum

Revision 0

71114.03

Corrective Action

Documents

CR1291662

05/13/2025

Miscellaneous

Millstone Unit 2 On-Shift Staffing Analysis

Revision 0

Millstone Unit 3 On-Shift Staffing Analysis

Revision 0

71114.04

Procedures

EP-AA-101

CFR 50.54(q) Change Evaluation

Revision 14

71114.05

Miscellaneous

Millstone Power Station Emergency Plan

Revision 67

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