IR 05000336/2024004

Integrated Inspection Report 05000336/2024004 and 05000423/2024004

ML25043A009
Person / Time
Site:	Millstone
Issue date:	02/12/2025
From:	Matt Young Division of Operating Reactors
To:	Carr E Dominion Energy
References
IR 2024004
Download: ML25043A009 (1)

Text

February 12, 2025

SUBJECT:

MILLSTONE POWER STATION, UNITS 2 AND 3 - INTEGRATED INSPECTION REPORT 05000336/2024004 AND 05000423/2024004

Dear Eric Carr:

On December 31, 2024, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at Millstone Power Station, Units 2 and 3. On January 29, 2025, the NRC inspectors discussed the results of this inspection with James Petty, Site Vice President, and other members of your staff. The results of this inspection are documented in the enclosed report.

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.

A licensee-identified violation which was determined to be Severity Level IV is documented in this report. We are treating this violation as a non-cited violation (NCV) consistent with Section 2.3.2 of the Enforcement Policy. We determined that additional follow-up using Inspection Procedure 92702, Follow-up on Traditional Enforcement Actions Including Violations, Deviations, Confirmatory Action Letters, Confirmatory Orders, and Alternative Dispute Resolution, was not warranted because the violation can be appropriately sampled using baseline inspection resources.

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 I; the Director, Office of Enforcement; and the NRC Resident Inspector at Millstone Power Station, Units 2 and 3.

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 I; 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:

05000336/2024004 and 05000423/2024004

Licensee:

Dominion Energy Nuclear Connecticut, Inc.

Facility:

Millstone Power Station, Units 2 and 3

Location:

Waterford, CT

Inspection Dates:

October 01, 2024 to December 31, 2024

Inspectors:

J. Fuller, Senior Resident Inspector

D. Antonangeli, Resident Inspector

E. Bousquet, Resident Inspector

B. Dyke, Operations Engineer

N. Eckhoff, Health Physicist

J. Morgan, Operations Engineer

M. Scheetz, Reactor Engineer

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: 7115

List of Findings and Violations

Failure to Implement Structures Monitoring, Infrequently Accessed Areas, and Buried Piping Aging Management Programs for the Condensate Storage Tank (CST) Pipe Trench Cornerstone Significance Cross-Cutting Aspect Report Section Mitigating Systems Green NCV 05000336/2024001-01 Closed

[H.5] - Work Management 71111.12 The inspectors identified a Green finding and associated NCV of the Millstone Unit 2 Operating License Condition 2.C.(11) when the licensee failed to complete certain activities described in Chapter 15, License Renewal, of the Final Safety Analysis Report (FSAR)supplement prior to July 31, 2015. Specifically, for the accessible portions of the CST pipe trench, the licensee did not include the area in the Infrequently Accessed Inspection Program, did not perform a baseline inspection of the piping or structure prior to the period of extended operation, and did not perform an inspection of the area once every five years. As a result, the licensee had not implemented license renewal commitments associated with the CST pipe trench, which contains both trains of auxiliary feedwater (AFW) piping, to evaluate for the effects of aging.

Additional Tracking Items

Type Issue Number Title Report Section Status LER 05000423/2023-006-00 LER 2023-006-00 for Millstone Power Station, Unit 3, Pressurizer Power Operated Relief Valve Failed to Stroke Open During Surveillance Testing Resulting In a Condition Prohibited by Technical Specifications 71153 Closed LER 05000423/2023-006-01 LER 2023-006-01 for Millstone Power Station Unit 3, Pressurizer Power Operated Relief Valve Failed to Open During Surveillance Testing Resulting in a 71153 Closed

Condition Prohibited by Technical Specifications

LER 05000423/2023-006-02 LER 2023-006-02 for Millstone, Unit 3, Pressurizer Power Operated Relief Valve Failed to Open During Surveillance Testing Resulting In a Condition Prohibited by Technical Specifications 71153 Closed LER 05000423/2024-002-00 LER 2024-002-00 for Millstone, Unit 3, Door Latch Failure Resulted In Loss Of Safety Function For Secondary Containment Boundary 71153 Closed LER 05000423/2024-001-00 LER 2024-001-00 for Millstone, Unit 3, Loss of Safety Function And Condition Prohibited by Technical Specifications For Loss Of Secondary Containment Boundary 71153 Closed

PLANT STATUS

Unit 2 began the inspection period at rated thermal power. On October 3, 2024, Unit 2 shutdown for a planned refueling outage and returned to rated thermal power on November 8, 2024. On November 13, 2024, Unit 2 reduced power to 11 percent and the turbine was taken offline to repair a hotspot on the 'A' motor operated disconnect switch. Unit 2 was restored to rated thermal power on November 15, 2024, and remained at or near rated thermal power for the remainder of the inspection period.

Unit 3 operated at or near rated thermal power for the entire inspection period.

INSPECTION SCOPES

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

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 cold temperatures for the following systems:

• Units 2 and 3 firewater storage tanks on October 21, 2024

• Unit 3 reactor water storage tank on October 24, 2024

• Units 2 and 3 emergency diesel generator rooms on October 31, 2024

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) Unit 2 AFW piping inside the CST pipe trench on October 7, 2024

(2) Unit 2 reactor building component cooling water system located within containment on October 25, 2024

Complete Walkdown Sample (IP Section 03.02) (1 Sample)

(1) Unit 2 containment spray system, 'A' and 'B' trains on October 18, 2024

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 containment building during the refueling outage (fire area C-1) from October 8 to November 1, 2024

(2) Unit 3 west motor control center and rod control air conditioning unit room (fire area AB-6B) on November 7, 2024

(3) Unit 3 fire seal between the auxiliary building and waste disposal building on the 24'-

6" elevation of the auxiliary building (Fire Area AB-1D) on November 18 and 19, 2024

(4) Unit 2 cable vault fire seals (Fire Area A-24) on November 19, 2024

(5) Unit 3 Auxiliary Building 4' elevation (Fire Area AB-1A/B) on December 9, 2024

===71111.08P - Inservice Inspection Activities (PWR)

The inspectors verified that the reactor coolant system (RCS) boundary, reactor vessel internals, risk-significant piping system boundaries, and containment boundary are appropriately monitored for degradation and that repairs and replacements were appropriately fabricated, examined and accepted by reviewing the following activities in Unit 2 during refueling outage

==2R29 from October 7 to 18, 2024.

==

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

The inspectors verified that the following nondestructive examination (NDE) and welding activities were performed appropriately:

(1) Ultrasonic Examination

• Ultrasonic Testing of RCS Hot Leg Drain Nozzle to Safe-End Weld overlay BPD-C-1001 (M2-VE-24-011)

• Ultrasonic Testing of RCS 12 inch pressurizer surge line pipe to elbow weld BPS-C-1021 (M2-UT-24-013)

• Ultrasonic Testing of RCS 12 inch pressurizer surge line elbow to pipe weld BPS-C-1013 (M2-UT-24-014)

Visual Examination

• AFW System, 8"-HBD(B)-45 and 10"-HBD(B)-46, Auxiliary Main Feed SP

===21160 Segment 1 (M2-VT2-24-012, -015, -016, and -019)

Welding Activities

• Welding activities associated with the replacement of the feedwater piping due to flow accelerated corrosion under Work Order (WO)532033971489. The post-welding NDE included ultrasonic testing (NDE Reports M2-UT-24-077,

-078, and -079) of welds W5, W6 and W8.

• Welding activities associated with the replacement of chemical volume control system nozzle check valve 2-CH-432 under WO53203440998. The post-welding NDE included ultrasonic testing (NDE Reports M2-UT-24-092, -095,

-093 and -096), phased array ultrasonic testing (NDE Reports BOP-VE-24-006 and -007) and liquid penetrant testing (BOP-PT-24-020) of shop welds W1 and W2.

• Welding activities associated with the replacement of chemical volume control system nozzle check valve 2-CH-432 under WO53203440824. The post-welding NDE included ultrasonic testing (NDE Reports M2-UT-24-090, -084,

-091 and -086) and phased array ultrasonic testing (NDE Reports BOP-VE-24-008 and -009) of field welds W20 and W21.

• Welding activities associated with the replacement of chemical volume control system nozzle check valve 2-CH-433 under WO53203441000. The post-welding NDE included ultrasonic testing (NDE Reports M2-UT-24-094 and

-097), phased array ultrasonic testing (NDE Reports BOP-VE-24-010) and liquid penetrant testing (BOP-PT-24-021) of shop weld W2.

• Welding activities associated with the replacement of chemical volume control system nozzle check valve 2-CH-433 under WO53203440825. The post-welding NDE included ultrasonic testing (NDE Reports M2-UT-24-089, -087,

-088 and -085) and phased array ultrasonic testing (NDE Reports BOP-VE-24-011 and -012) of field welds W10 and W11.

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

(1)

• Inspectors performed direct observation inside the containment building on October 9, 2024

• Boric Acid Evaluation for 'B' low pressure safety injection pump mechanical seal, low pressure injection system (CR1155384)

• Boric Acid Evaluation for valve 2-SI-735, high pressure injection system (CR1271556)

• Boric Acid Evaluation for valve 2-SI-446, low pressure injection system (CR1271099)

PWR Inservice Inspection Activities Sample - Steam Generator Tube Inspection Activities (Section 03.04) (1 Sample)

The inspectors verified that the licensee is monitoring the steam generator tube integrity appropriately through a review of the following examinations:

(1)

• Eddy current testing of inservice tubes in steam generators 25 and 26

• Secondary side visual examinations in steam generators 25 and 26

71111.11A - Licensed Operator Requalification Program and Licensed Operator Performance

Requalification Examination Results (IP Section 03.03) (2 Samples)

(1) The inspectors reviewed and evaluated the Unit 2 licensed operator examination failure rates for the Unit 2 requalification annual operating tests administered November - December 2024, and Unit 2 biennial written examinations administered August - September 2024.

(2) The inspectors reviewed and evaluated the Unit 3 licensed operator examination failure rates for the requalification annual operating exams completed on December 13, 2024, and the biennial written examinations completed on December 13, 2024.

71111.11B - Licensed Operator Requalification Program and Licensed Operator Performance

Licensed Operator Requalification Program (IP Section 03.04) (1 Sample)

(1) Biennial Requalification Written Examinations

The inspectors evaluated the quality of the Unit 2 licensed operator biennial requalification written examinations administered August - September 2024.

Annual Requalification Operating Tests

The inspectors evaluated the adequacy of the Unit 2 annual requalification operating tests administered week of November 18, 2024.

Administration of an Annual Requalification Operating Test

The inspectors evaluated the effectiveness of the facility licensee in administering requalification operating tests required by 10 CFR 55.59(a)(2), and that the facility licensee is effectively evaluating their licensed operators for mastery of training objectives.

Requalification Examination Security

The inspectors evaluated the ability of the facility licensee to safeguard examination material, such that the examination is not compromised.

Remedial Training and Re-examinations

The inspectors evaluated the effectiveness of remedial training conducted by the licensee, and reviewed the adequacy of re-examinations for licensed operators who did not pass a required requalification examination.

Operator License Conditions

The inspectors evaluated the licensees program for ensuring that licensed operators meet the conditions of their licenses.

Control Room Simulator

The inspectors evaluated the adequacy of the facility licensees control room simulator in modeling the actual plant, and for meeting the requirements contained in 10 CFR 55.46.

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 2 control room during periods of heightened activity associated with changing from Mode 4 to Mode 3 on November 4, 2024, during performance of post-maintenance testing (PMT) surveillances on November 5, 2024, and during an unplanned rapid down power on November 13, 2024.

(2) The inspectors observed and evaluated licensed operator performance in the Unit 3 control room during a winter storm on December 11, 2024.

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

(1) The inspectors observed and evaluated licensed operator requalification training in the Unit 3 simulator on December 10, 2024.

(2) The inspectors observed and evaluated licensed operator requalification training in the Unit 2 simulator on December 10, 2024.

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) Implementation of the Maintenance Rule and aging management inspections of the infrequently accessed Unit 2 CST pipe trench structure and the inspection of the AFW piping after the trench was opened during the refueling outage on October 7, 2024 (WO53203260542)

(2) Maintenance Rule functional failure evaluations for loose bonnet stud nuts discovered on 2-SI-614 and 2-SI-624, Unit 2 safety injection tank outlet valves, on December 6, 2024 (CR1271676 and CR1273446)

(3) Unit 3 Maintenance Rule (a)(1) evaluation and associated goals associated with the

'D' service water pump strainer's failure to blow down on high differential pressure due to the sensing lines being blocked on December 17, 2024 (CR1263835)

71111.13 - Maintenance Risk Assessments and Emergent Work Control

Risk Assessment and Management Sample (IP Section 03.01) (5 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 elevated risk and associated mitigating actions during decreased inventory shortly after the reactor was shut down for the refueling outage and decay heat was high on October 7, 2024

(2) Unit 3 elevated risk and associated mitigating actions during the planned removal of the Unit 1 tie line which required the South bus and Unit 3 reserve station service transformer to be removed from service on October 10, 2024 (WO53203403429)

(3) Unit 2 high-risk plan associated with the installation of a freeze seal on a section of non-isolable American Society of Mechanical Engineers (ASME), Class 1, pressure boundary piping during fuel movement on October 19, 2024

(4) Unit 3 medium risk plan and mitigating actions for repairs to the boric acid injection valve flow transmitter, 3CHS*FT110, on December 7, 2024

(5) Unit 3 elevated risk and associated mitigating actions with the 'C' reactor plant component cooling water pump and 'B' emergency diesel generator out of service on December 16, 2024

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 degraded support for the 'B' direct current switchgear room chiller on September 19, 2024 (CR1269315, CR1270048, CR1270050)

(2) Unit 3 operability decision-making evaluation for 'D' safety injection accumulator tank in-leakage from the RCS system on October 11, 2024 (CR1269394, CR1269823)

(3) Unit 2 'B' containment air recirculation cooler cooling water inlet valve (2-RB-28.1B)not operable for containment isolation on October 20, 2024 (CR1273002)

(4) Unit 2 spurious reactor protection system pre-trip alarm on 'D' channel received on November 17, 2024 (CR1276462)

(5) Unit 3 elevated unidentified RCS leakage on November 20, 2024 (CR1276668 and CR1276690)

(6) Unit 2 'B' train 125-volt direct current battery bus 201B battery cells found with cracks on December 10, 2024 (CR1278032 and CR1264577)

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 2 temporary modification associated with a freeze seal to allow replacement of two ASME, Class 1, charging system check valves on October 19, 2024

(2) Unit 2 permanent modification to structural supports for AFW piping in the CST pipe trench on October 28, 2024 (WO53203441461)

(3) Unit 3 permanent modification associated with the replacement of the boric acid injection valve flow transmitter, 3CHS*FT110, on December 13, 2024

71111.20 - Refueling and Other Outage Activities

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

(1) Unit 2 planned refueling outage from October 3 to November 7, 2024

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) (6 Samples)

(1) Unit 2 PMT of 2-SI-624 after packing gland maintenance on October 22, 2024

(2) Unit 2 pressurizer power operated relief valve, 2-RC-402, after replacement during the refueling outage on November 4, 2024

(3) Unit 2 restoration of AFW system after maintenance during refueling outage on November 5, 2024 (WO53203382990)

(4) Unit 2 'C' charging pump, P18C, packing replacement on November 20 to 23, 2024

(5) Units 2 and 3 technical support center emergency ventilation system testing after carbon filter bank troubleshooting and repair on December 17, 2024 (WO53203443858)

(6) Unit 3 'C' reactor plant component cooling water pump breaker after preventive maintenance on December 17, 2024 (WO53203410103)

Surveillance Testing (IP Section 03.01) (2 Samples)

(1) Unit 2 pressurizer power operated relief valve hot functional testing on October 3, 2024 (WO53203377681)

(2) Unit 2 reactor protection system channel 'A' wide range monitor drawer functional test on December 10, 2024

Inservice Testing (IST) (IP Section 03.01) (2 Samples)

(1) Unit 2 check valve non-intrusive test for 2-CH-432, loop 2A charging header non-return check valve on October 9, 2024 (WO53203378292)

(2) Unit 3 charging pump 'A' IST surveillance run on November 4, 2024 (WO53203415072)

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

(1) Unit 2 15-year containment integrated leak rate test on October 30,

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 and the concentrations and quantities of radioactive materials and how the licensee 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) Licensee surveys of potentially contaminated material leaving the Unit 2 radiologically controlled area

(2) Workers exiting the Unit 2 radiologically controlled area during a refueling outage

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) Observed reactor cavity saddles foreign material removal

(2) Reactor disassembly phase two; radiation work permit # 2240302

(3) Observed the controls established for reactor head lift and placement

(4) Unit 2 steam generator tube inspection staging

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 2 under vessel

(2) Unit 2 reactor head stand

(3) Unit 2 transfer cart with filters from reactor cavity

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.

OTHER ACTIVITIES - BASELINE

===71151 - Performance Indicator Verification

The inspectors verified licensee performance indicators submittals listed below:

OR01: Occupational Exposure Control Effectiveness Sample (IP Section 02.15)===

(1) October 1, 2023 through October 31, 2024 PR01: Radiological Effluent Technical Specifications/Offsite Dose Calculation Manual Radiological Effluent Occurrences (RETS/ODCM) Radiological Effluent Occurrences Sample (IP Section 02.16) (1 Sample)

(1) October 1, 2023 through October 31, 2024

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) Units 2 and Unit 3 lack of procedure acceptance criteria for internal flood seals (CR1168977)

(2) Unit 2 service water piping crack and material loss observed in Insituform liner near A-27 flange (CR1228436)

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 05000423/2023-006-00, LER 05000423/2023-006-01, and LER 05000423/2023-006-02, Unit 3, Pressurizer Power Operated Relief Valve Failed to Stroke Open During Surveillance Testing Resulting in a Condition Prohibited by Technical Specifications (Agencywide Documents Access and Management System (ADAMS)

Accession Nos. ML24123A227, ML24141A150, and ML24270A029). The inspection conclusions associated with this LER are documented in Millstone Power Station Integrated Inspection Report 05000423/2024002 (ADAMS Accession No.

ML24226A378) under the Inspection Results Section 71111.15. This LER is closed.

(2) LER 05000423/2024-002-00, Unit 3, Door Latch Failure Resulted in Loss of Safety Function for Secondary Containment Boundary (ADAMS Accession No.

ML24331A033): The inspectors determined that the cause of the condition described in the LER was not reasonably within the licensee's ability to foresee and correct, and therefore was not reasonably preventable. No performance deficiency nor violation of NRC requirements was identified. This LER is closed.

(3) LER 05000423-2024-001-00, Unit 3, Loss of Safety Function and Condition Prohibited by Technical Specifications for Loss of Secondary Containment Boundary (ADAMS Accession No. ML24288A015): The inspection conclusions associated with this LER are documented in Millstone Power Station Integrated Inspection Report

===05000423/2024003 (ADAMS Accession No. ML24311A220) under the Inspection Results Section 71111.04. This LER is closed.

Reporting (IP Section 03.05)===

The inspectors evaluated the following LER determinations to ensure it complied with reporting requirements.

(1) The inspectors reviewed CR1271746 which was associated with the failure of a Unit 3 hatch to properly close and latch. The failure to close and latch resulted in an unplanned technical specification entry for the supplementary leak collection and release system. The latch was repaired, and the licensee exited the technical specification within the allowed outage time; however, the licensee later determined that it failed to notify the NRC Operations Center via the Emergency Notification System within eight hours as required by 10 CFR 50.72(b)(3)(v). The inspection conclusions associated with the failure to make a required report are documented under the Inspection Results Section 71153 of this report.

INSPECTION RESULTS

Failure to Implement Structures Monitoring, Infrequently Accessed Areas, and Buried Piping Aging Management Programs for the Condensate Storage Tank (CST) Pipe Trench Cornerstone Significance Cross-Cutting Aspect Report Section Mitigating Systems

Green NCV 05000336/2024001-01 Closed

[H.5] - Work Management 71111.12 The inspectors identified a Green finding and associated NCV of the Millstone Unit 2 Operating License Condition 2.C.(11) when the licensee failed to complete certain activities described in Chapter 15, License Renewal, of the Final Safety Analysis Report (FSAR)supplement prior to July 31, 2015. Specifically, for the accessible portions of the CST pipe trench, the licensee did not include the area in the Infrequently Accessed Inspection Program, did not perform a baseline inspection of the piping or structure prior to the period of extended operation, and did not perform an inspection of the area once every five years. As a result, the licensee had not implemented license renewal commitments associated with the CST pipe trench, which contains both trains of auxiliary feedwater (AFW) piping, to evaluate for the effects of aging.

Description:

On March 19, 2024, during a walkdown of the Unit 2 AFW system piping from the CST to the suction of the AFW pumps, the inspectors noted that a section of the piping runs underground in a pipe trench with removable concrete plugs on top. This trench is referred to as the CST pipe trench. To determine the current condition of the CST pipe trench and the AFW piping contained within, the inspectors reviewed the licensee's license renewal aging management program for structures monitoring, which is also credited for condition monitoring under the maintenance rule program.

The inspectors identified and documented a finding with its safety significance to be determined and associated apparent violation of Millstone Unit 2 Operating License Condition 2.C.(11) in the first quarter 2024 Integrated Inspection Report 05000336/2024001 (ADAMS Accession No. ML24135A259) when the licensee failed to complete certain activities described in Chapter 15, License Renewal, of the FSAR supplement prior to July 31, 2015.

Specifically, for the accessible portions of the CST pipe trench, the licensee did not include the area in the Infrequently Accessed Inspection Program, did not perform a baseline inspection prior to the period of extended operation, and did not perform an inspection of the area once every five years. As a result, the licensee had not performed an inspection of the CST pipe trench, which contains both trains of AFW piping, to evaluate for the effects of aging.

Subsequently, the inspectors identified and documented, in the third quarter Integrated Inspection Report 05000336/2024003 (ADAMS Accension No. ML24311A220), a third aging management program commitment (Buried Pipe Inspection Program) that had not been implemented prior to entering the period of extended operation as required by Millstone Unit 2, License Condition 2.C.(11).

Because the licensee had not performed the required inspections of the accessible portions of the CST pipe trench, the inspectors identified that the licensee did not properly establish and implement the license renewal programs for the Infrequently Accessed Areas, Buried Pipe, and Structures Monitoring Programs prior to the period of extended operation.

Therefore, the licensee did not fully complete FSAR, Chapter 15, commitment items 3, 12 and 18.

During the Fall 2024 planned refueling outage, the licensee opened the CST pipe trench and performed all required inspections. The as-found inspection of the piping and pipe supports in the trench identified support material degradation along with several pipe support location and configuration discrepancies on the safety-related AFW lines, 8-HBD-45 and 10-HBD-46.

As a result, the AFW piping was not in conformance with the original pipe stress analyses.

The collective deviation in support locations was such that new pipe stress models were developed in NUPIPE-II for both safety-related lines. These analyses were used to determine the maximum pipe stress, support/anchor loading, and integral welded attachment stresses so that a new design basis configuration could be established. The material condition/configuration of the supports were repaired during the outage such that the as-left condition of the piping and supports was fully compliant with all applicable requirements.

To evaluate for past operability and reportability, the licensee created Engineering Technical Evaluation (ETE)-MP-2024-1107, "Millstone Unit 2 Condensate Storage Tank Trench Piping Reportability Evaluation," Revision 0. This evaluation of the Unit 2 CST trench piping, supports, and integral welded attachments for the as-found conditions were found to be below either the existing design Code allowable stresses or the operability limits described in the Unit 2 Piping Operability Determination Manual.

Therefore, the licensee determined that the AFW system maintained its operability and the degraded condition identified during the outage was not reportable to the NRC.

Corrective Actions: The licensee entered this issue in its corrective action program, performed a level of effort evaluation, and completed all required inspections during the Fall 2024 refueling outage. Any degraded conditions identified during the inspections were corrected prior to the end of the refueling outage.

Corrective Action References: CR1254027

Performance Assessment:

Performance Deficiency: The licensee failed to meet License Condition 2.C.(11) for its failure to complete certain activities described in Chapter 15, License Renewal, of the FSAR supplement prior to July 31, 2015. Specifically, for the accessible portions of the condensate pipe trench, the licensee did not include the area in the Infrequently Accessed Inspection Program, did not perform a baseline inspection of the piping or structure prior to the period of extended operation, and did not perform an inspection of the area once every five years.

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. The failure to perform the required condition monitoring inspections of the CST pipe trench, if left uncorrected, would have the potential to lead to a more significant safety concern because the aging effects on the concrete and safety-related piping and supports in the CST pipe trench would not have been identified, evaluated, and corrected in the period of extended operation, which could adversely impact both trains of the AFW system suction piping from CST.

Significance: The inspectors assessed the significance of the finding using IMC 0609, Appendix A, The Significance Determination Process (SDP) for Findings At-Power. When this finding was first identified, the actual condition of the AFW piping and the CST pipe trench structure were unknown, and the inspectors could not screen the issue using the guidance in IMC 0609, Appendix A. During the Fall 2024 refueling outage, the licensee completed all required inspections and based on additional inspector observations a senior reactor analyst performed a seismic screening risk assessment using SAPHIRE, Version 8.2.11, and NRC Millstone Unit 2 SPAR, Model 8.83. Specifically, the senior reactor analyst increased AFW functional failure rate (using CST failure as a surrogate) 150 percent across all seismic events. This estimated a delta core damage frequency/year of less than

<1E-6/year (Green). The dominant core damage sequence was a seismic event (Bin 3, 0.5g - 1.0g), CST and refueling water storage tank failure, and loss of offsite power. No other external events were assumed to occur concurrent with the seismic event. Following the Fall 2024 refueling outage, the licensee completed their engineering analysis and determined that the affected AFW piping, associated supports, and the CST trench structure maintained its operability and probabilistic risk analysis functionality; therefore, in accordance with IMC 0609, Appendix A, Exhibit 2, A.1, the issue was screened as very low safety significant (Green).

Cross-Cutting Aspect: H.5 - Work Management: The organization implements a process of planning, controlling, and executing work activities such that nuclear safety is the overriding priority. The work process includes the identification and management of risk commensurate to the work and the need for coordination with different groups or job activities. Specifically, the licensee did not effectively plan or implement the inspections of the CST pipe trench.

Enforcement:

Violation: License Condition 2.C.(11) states the FSAR supplement, as revised, describes certain future activities to be completed prior to the period of extended operation. Dominion Energy Nuclear Connecticut, Inc. shall complete these activities no later than July 31, 2015.

Updated FSAR, Chapter 15, Section 2.1.4, Buried Pipe Inspection Program, - Commitments states, in part:

The following program enhancements will be implemented prior to the period of extended operation:

• Baseline Inspection. A baseline inspection of the in-scope buried piping located in a damp soil environment has been performed for a representative sample of each combination of material and protective measures.

Updated FSAR, Chapter 15, Section 2.1.15, Infrequently Accessed Areas Inspection Program, - Commitments states, in part:

The following program enhancements will be implemented prior to the period of extended operation:

• Program Implementation. The Infrequently Accessed Inspection Program has been established. The establishment of the Infrequently Accessed Inspection Program completes the action required for Commitment Item 12 in Table 15.6-1.

Updated FSAR, Chapter 15, Section 2.1.23, Structures Monitoring Program, - Commitments states, in part:

The following program enhancements will be implemented prior to the period of extended operation:

• Addition of Structures to the Structures Monitoring Program. The Structures Monitoring Program did not initially monitor all structures in-scope for license renewal.

The Structures Monitoring Program and the implementing procedure have been modified to include all in-scope structures. Modification of the Program and the implementing procedure completes the actions required for Commitment Item 18 in Table 15.6-1.

ETE-MP-2013-1057, "Structures Monitoring Program, License Renewal Aging Management Program (MP-LR-3728/MP-LR-4728)," Revision 1, identifies the CST pipe trench (accessible portions) as in-scope of License Renewal Program, Maintenance Rule Program, and part of the Structures Monitoring Program. Section 2.5, Inaccessible and Infrequently Accessed Areas, states that for areas identified as infrequently accessed that have not otherwise been made accessible, inspected, and evaluated; a baseline inspection will be performed prior to the period of extended operation in accordance with AMP report MP-LR-3732/MP-LR-4732, Infrequently Accessed Areas. The ETE also states that the Structures Monitoring Program for Millstone Units 1, 2, and 3 is described in, and implemented by, Millstone Common Engineering Procedure C EN 104I (Condition Monitoring of Structures).

Section 1.5, Frequency, of C EN 104I, "Condition Monitoring of Structures," Revision 13, states that "Structures identified as in-scope for License Renewal will be inspected a minimum of once per 5 years." Step 5, Inspection of Inaccessible Areas, of Attachment 14, Methodology for Inspection of Structures, states in part, "infrequently accessed areas are a subset of inaccessible areas and are required by a License Renewal commitment to be inspected despite the lack of routine accessibility."

ETE-MP-2012-1248, "Underground Pipe and Tank Program Life Cycle Management Plan Technical Basis," identifies that the condensate storage and AFW lines 8-HBD-45 and 10-HBD-46, which supply AFW from the CST to all three AFW pumps, are contained in the CST pipe trench and are required to be visually inspected per WO53102501784 and procedure MP-VE-5, "Visual Examination Procedure for the Examination of Interior/Exterior Surfaces of Piping and Components," prior to the period of extended operation.

Contrary to the above, from July 31, 2015 to October 3, 2024, the licensee failed to complete certain future activities described in the FSAR supplement prior to the period of extended operation. Specifically, for the accessible portions of the CST pipe trench, the licensee did not include the area in the Infrequently Accessed Inspection Program, did not perform a baseline inspection of the piping or structure prior to the period of extended operation, and did not perform an inspection of the area once every five years. As a result, the licensee had not implemented license renewal commitments associated with the CST pipe trench, which contains both trains of AFW piping, to evaluate for the effects of aging.

Enforcement Action: This violation is being treated as a non-cited violation, consistent with Section 2.3.2 of the Enforcement Policy.

Licensee-Identified Non-Cited Violation 71153 This Severity Level IV violation 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: 10 CFR 50.72(b)(3)(v) requires, in part, that the licensee shall notify the NRC Operations Center via the Emergency Notification System within eight hours of the occurrence of any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to: (C) Control the release of radioactive material; or (D) Mitigate the consequences of an accident.

Contrary to the above, on October 10, 2024, the licensee did not notify the NRC Operations Center via the Emergency Notification System within eight hours of the occurrence of a condition that at the time of discovery could have prevented the fulfillment of the safety function of the Unit 3 secondary containment boundary. Specifically, the secondary containment was discovered inoperable and was inoperable for approximately three hours which is less than the 24-hour technical specifications allowed limit, but the licensee did not notify the NRC of a condition that could have prevented the fulfillment of the safety function within the eight hours as required. Upon discovery of missing the notification, the licensee made the notification on November 13, 2024.

Significance/Severity: Minor Performance Deficiency. Severity Level IV. The inspectors determined this violation was associated with a minor performance deficiency under the reactor oversight process because there was no underlying technical issue that impacted the reactor oversight process cornerstones. The inspectors determined that traditional enforcement applies because the failure to make a timely eight hour report in accordance with 10 CFR 50.72(b)(3)(v) impedes/impacts the regulatory process. The violation was processed using traditional enforcement and determined to be a Severity Level IV violation consistent with NRC's Enforcement Policy, Section 6.9.d.9, Inaccurate and Incomplete Information or Failure to Make a Required Report.

Corrective Action References: CR1276108

EXIT MEETINGS AND DEBRIEFS

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

• On January 29, 2025, the inspectors presented the integrated inspection results to James Petty, Site Vice President, and other members of the licensee staff.

• On October 11, 2024, the inspectors presented the radiological hazards inspection results to Michael O'Connor, Site Vice President, and other members of the licensee staff.

• On October 18, 2024, the inspectors presented the inservice inspection results to Michael O'Connor, Site Vice President, and other members of the licensee staff.

THIRD PARTY REVIEWS

Inspectors reviewed Institute of Nuclear Power Operations reports that were issued during the inspection period.

DOCUMENTS REVIEWED

Inspection

Procedure

Type

Designation

Description or Title

Revision or

Date

71111.04

Corrective Action

Documents

Resulting from

Inspection

CR1272622

CR1275560

CR1276950

CR1277214

71111.05

Corrective Action

Documents

Resulting from

Inspection

CR1271031

CR1276600

CR1277021

Procedures

SFP 17

Fire Penetration Seal and Barrier Inspections

Revision 5

71111.08P Corrective Action

Documents

265348

271216

271984

273004

273007

Corrective Action

Documents

Resulting from

Inspection

272292

272770

Drawings

203-11004

Area 'A' of Paving Drainage and Fencing Drawing

03/27/1974

203-11017

Miscellaneous Yard Foundation, Sht. 4

04/18/1997

203-20158

Aux, Feedwater Large Bore Piping, Main Feedwater System Revision 3

203-LR26005

License Renewal Diagram Condensate Storage and Aux

Feed

Revision 11

Engineering

Evaluations

ETE-CEP-2024-

1008

Millstone Unit 2 Steam Generator Integrity Condition

Monitoring and Operational Assessment Refueling Outage

(2R29)

10/31/2024

ETE-MP-2024-

1045

Venting Containment Liner Leak Chase for One Fuel Cycle

Revision 0

Procedures

ER-AA-NDE-UT-

816

Procedure for Manual Phased Array Ultrasonic Examination

of Weld Overlaid Similar and Dissimilar Metal Welds

Revision 0

71111.12

Corrective Action

Documents

CR1268172

Inspection

Procedure

Type

Designation

Description or Title

Revision or

Date

Resulting from

Inspection

Engineering

Evaluations

ETE-MP-2024-

1107

Millstone Unit 2 Condensate Storage Tank Trench Piping

Reportability Evaluation

Revision 0

Procedures

ER-AA-BPM-101

Underground Piping and Tank Integrity Program

Revision 19

71111.13

Corrective Action

Documents

CR1273169

CR1273439

Corrective Action

Documents

Resulting from

Inspection

CR1273172

Procedures

C MP 702A

Freeze Sealing

Revision 3

71111.15

Corrective Action

Documents

CR1269315

CR1270048

CR1270050

Corrective Action

Documents

Resulting from

Inspection

CR1273611

Miscellaneous

CEM-0347

Millstone 2 - Pipe Stress Analysis of the Return Line from

Cooling Coil X-54B to Pump Suction P-122B (2*-JDB-61)

and Pump Discharge to Chiller X-169B (2"-JBD-64) and

Chilled Water PMP Bypass Line (1/2" & 3/4"-JBD-57)

ETE-CEM-2024-

0010

Unit 2 Functionality Assessment of Chilled Water Pump P-

2B Support and Associated Piping with Degraded Pump

Support Conditions Identified in CR1269315, CR1270048,

and CR1270050

Revision 0

Work Orders

WO532439190

71111.18

Calculations

MP-CALC-ENG-

405269

Millstone Point Unit 2 Hanger Design Calculations - Restraint

Design Calculation

Revision 1

Engineering

Changes

MP2-24-01040

Unit 2 CST Pipe Trench Support Modifications

Revision 1

Procedures

C MP 702A

Freeze Sealing

Revision 3

FCR-DOM-2024-

Additional Weld Information for Construction Installation

Revision 0

Inspection

Procedure

Type

Designation

Description or Title

Revision or

Date

1043

Sketch M2HGR-405269/405270

Work Orders

WO53203440824

WO53203440825

WO53203440997

WO53203440999

71111.20

Corrective Action

Documents

CR1271372

CR1271744

CR1271889

CR1272255

CR1273216

Corrective Action

Documents

Resulting from

Inspection

CR1273397

CR1274206

CR1274390

Procedures

ETE-NAF-2024-

0094

Implementation of Reduced In-Core Hold time Requirement

Prior to Offload for Millstone 2R29

Revision 0

MA-AA-102

Foreign Material Exclusion

Revision 27

OP 2205

Plant Shutdown

Revision 22

OP 2206

Reactor Shutdown

Revision 19

OP 2209A

Refueling Operations

Revision 38

OP 2209B

RCS Inventory Tracking

Revision 2

OP 2301E

Draining the RCS (ICCE)

Revision 38

71111.24

Corrective Action

Documents

CR1275064

Procedures

C MP 780A

GE Model AM Magne-Blast Circuit Breaker PM

Revision 12

ER-AA-IST-CKV-

104

ASME IST Program - Check Valve Condition Monitoring

Program Implementation

Revision 6

SP 2401BA

Wide Range Monitor Functional Test

Revision 2-

SP 2610G-001

PORV Stroke Time IST

10/06/2024

SP 2610M-001

PORV Hot Functional Test

11/04/2024

Work Orders

WO53203335776

71152A

Corrective Action

Documents

CR1168977