IR 05000352/2022004

Integrated Inspection Report 05000352/2022004 and 05000353/2022004

ML23041A388
Person / Time
Site:	Limerick
Issue date:	02/13/2023
From:	Jon Greives NRC/RGN-I/DORS
To:	Rhoades D Constellation Energy Generation, Constellation Nuclear
References
IR 2022004
Download: ML23041A388 (1)

Text

February 13, 2023

SUBJECT:

LIMERICK GENERATING STATION, UNITS 1 AND 2 - INTEGRATED INSPECTION REPORT 05000352/2022004 AND 05000353/2022004

Dear David Rhoades:

On December 31, 2022, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at Limerick Generating Station, Units 1 and 2. On February 10, 2023, the NRC inspectors discussed the results of this inspection with Michael Gillin, Site Vice President, and other members of your staff. The results of this inspection are documented in the enclosed report.

Three findings of very low safety significance (Green) are documented in this report. One of these findings involved a violation of NRC requirements. We are treating this violation as a non-cited violation (NCV) consistent with Section 2.3.2 of the Enforcement Policy.

If you contest the violation or the significance or severity of the violation documented in this inspection report, you should provide a response within 30 days of the date of this inspection report, with the basis for your denial, to the U.S. Nuclear Regulatory Commission, ATTN:

Document Control Desk, Washington, DC 20555-0001; with copies to the Regional Administrator, Region I; the Director, Office of Enforcement; and the NRC Resident Inspector at Limerick Generating Station, Units 1 and 2.

If you disagree with a cross-cutting aspect assignment or a finding not associated with a regulatory requirement 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 Limerick Generating Station, Units 1 and 2. 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, Digitally signed by Jonathan E.

Jonathan E. Greives Date: 2023.02.13 08:00:37 Greives -05'00'

Jonathan E. Greives, Chief Projects Branch 4 Division of Operating Reactor Safety Docket Nos. 05000352 and 05000353 License Nos. NPF-39 and NPF-85

Enclosure:

As stated

Inspection Report

Docket Numbers: 05000352 and 05000353 License Numbers: NPF-39 and NPF-85 Report Numbers: 05000352/2022004 and 05000353/2022004 Enterprise Identifier: I-2022-004-0035 Licensee: Constellation Energy Generation, LLC Facility: Limerick Generating Station, Units 1 and 2 Location: Sanatoga, PA 19464 Inspection Dates: October 1, 2022 to December 31, 2022 Inspectors: A. Ziedonis, Senior Resident Inspector L. Grimes, Resident Inspector M. Henrion, Health Physicist B. Edwards, Health Physicist Approved By: Jonathan E. Greives, Chief Projects Branch 4 Division of Operating Reactor Safety Enclosure

SUMMARY The U.S. Nuclear Regulatory Commission (NRC) continued monitoring the licensees performance by conducting an integrated inspection at Limerick Generating Station, Units 1 and 2, 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 Failure to use engineering controls in accordance with Radiation Work Permit (RWP)

Cornerstone Significance Cross-Cutting Report Aspect Section Occupational Green [H.8] - 71124.03 Radiation Safety NCV 05000352,05000353/2022004-01 Procedure Open/Closed Adherence A finding of very low safety significance (Green) and associated non-cited violation (NCV) of Title 10 of the Code of Federal Regulations (10 CFR) 20.1701, Use of process or other engineering controls, was self-revealed on April 9, 2022, when Constellation workers failed to use, to the extent practical, process or other engineering controls (e.g., containment, decontamination, or ventilation) to control the concentration of radioactive material in air meet the requirements of 10 CFR 20.1701. Specifically, on April 9, 2022, during a refuel outage at Limerick Generating Station, Constellation failed to use process or other engineering controls (e.g., high-efficiency particulate air (HEPA) ventilation unit and maintain the work in a wetted condition) prior to engaging in aggressive work activities on the main steam isolation valve (MSIV) in the Unit 1 drywell. This resulted in airborne radioactivity in the immediate work area and one worker received an unplanned exposure of 49 millirem committed effective dose equivalent.

Inadequate maintenance procedure results in electrohydraulic (EHC) fluid leak from main turbine bypass valve (BPV)

Cornerstone Significance Cross-Cutting Report Aspect Section Mitigating Green None (NPP) 71152A Systems FIN 05000352,05000353/2022004-02 Open/Closed The inspectors determined there was a Green, self-revealing finding because maintenance procedure MA-LG-763-473, Disassemble and Assemble Main Steam BPV Actuator/Spring Can, Revision 0, did not include adequate steps to effectively reassemble BPV number 1 (BPV-1) actuator following the performance of preventive maintenance activities, which resulted in an EHC fluid leak on May 14, 2022, and adversely impacted the reliability of the main turbine bypass system.

Inadequate performance monitoring and margin management associated with MSIV local leak rate testing (LLRT)

Cornerstone Significance Cross-Cutting Report Aspect Section Barrier Integrity Green [H.6] - Design 71152A FIN 05000352,05000353/2022004-03 Margins Open/Closed The inspectors identified a Green finding against procedure ER-AA-2003, System Performance Monitoring and Analysis, Revision 8, because Constellation did not perform adequate performance monitoring and analysis of MSIV LLRT results to ensure that degrading trends were identified prior to challenging required limits during the operating cycle.

Additional Tracking Items Type Issue Number Title Report Section Status URI 05000352,05000353/ Failure to follow 71152A Open 2022004-04 maintenance procedure results in emergency diesel generator (EDG) jacket water (JW) leak

PLANT STATUS Unit 1 began the inspection period at rated thermal power (RTP). On November 26, 2022, the unit was down-powered to approximately 75 percent thermal power for a control rod sequence exchange. The unit was returned to full power on November 27, 2022, and remained at or near RTP for the remainder of the inspection period.

Unit 2 began the inspection period at RTP. On November 19, 2022, the unit was down-powered to approximately 75 percent thermal power for a control rod sequence exchange. The unit was returned to full power on November 20, 2022, and remained at or near RTP 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 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 during the week of December 12, 2022:

• Unit 1 and 2 hardened vent remote operation control system batteries

• Unit 1 and 2 residual heat removal (RHR) systems

• Unit 1 and 2 control rod hydraulic control units and scram discharge volumes Impending Severe Weather Sample (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 associated with a winter weather advisory during the week of December 12, 2022

71111.04 - Equipment Alignment Partial Walkdown Sample (IP Section 03.01) (3 Samples)

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

(1) Unit 1 'A' drywell chiller following 'B' chiller trip on October 11, 2022 (2) Unit common off-site power alignment during period of elevated voltage on the 20 regulating transformer on October 20, 2022 (3) Unit 2 safeguard battery divisions 1, 2, and 4, during troubleshooting of Division 3 on December 13, 2022 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 common fire area 25, auxiliary equipment room 542 with area fire panel non-functional due to heat detection trouble on October 28, 2022 (2) Unit 2 fire area 16, D24 emergency 4KV switchgear room on November 10, 2022 (3) Unit common FLEX diesel generator storage building on November 15, 2022 (4) Unit 2 fire area 64, reactor enclosure cooling water heat exchanger area rooms 284 and 286 on December 9, 2022 (5) Unit 1 fire area 31, 'B' and 'D' RHR heat exchanger and pump room, rooms 103 and 204 on December 16, 2022 71111.07A - Heat Exchanger/Sink Performance Annual Review (IP Section 03.01) (1 Sample)

The inspectors evaluated readiness and performance of:

(1) Unit common, RT-1-011-391-0, main control room chiller heat transfer performance calculation test on December 15, 2022 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 annual requalification results for the annual operating exams completed on November 17, 2022.

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 a Unit 2 planned power reduction for a rod pattern adjustment on November 19 and 20, 2022; and during near-rated rod notching on Unit 2 on December 11, 2022 Licensed Operator Requalification Training/Examinations (IP Section 03.02) (1 Sample)

(1) The inspectors observed and evaluated licensed operator requalification training scenarios in the simulator on November 8, 2022 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 'B' primary containment instrument gas subsystem on November 10, 2022 (2) Unit 1 EDG D12 following speed switch failure on December 20 and 21, 2022 (3) Unit 2 EDG D22 following output breaker trip on reverse power trip during the week December 19, 2022 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 1 implementation of risk informed completion time with the average power range monitor (APRM) voter number 1 inoperable on October 14, 2022 (2) Unit 1 high-pressure coolant injection (HPCI) emergent work on October 14, 15, and 16 (3) Unit 2 EDG D22 emergent work following surveillance test (ST) failure on October 15 and 16, 2022 (4) Unit 2 EDG D21 emergent work following ST failure on November 3, 2022 (5) Unit 1 risk assessment during planned testing with select nuclear steam supply shutoff system valves inoperable on December 19, 2022

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 1 APRM ST results evaluation on October 14, 2022 (2) Unit 2 EDG D22 following ST failure on October 14, 17, and 18, 2022 (3) Unit 1 'A' adjustable speed drive functionality with the runback feature placed in bypass on October 31, 2022 (4) Unit 1 EDG D12 after unexpected 'EDG running' alarms received in main control room November 1 and 2, 2022 (5) Unit 2 EDG D22 following receipt of motor control center shunt trip coil undervoltage alarm during the week of November 14, 2022 (6) Unit 1 'L' safety relief valve following step increase in tailpipe temperature on November 28 and 29, 2022 71111.18 - Plant Modifications Temporary Modifications and/or Permanent Modifications (IP Section 03.01 and/or 03.02)

(1 Sample)

The inspectors evaluated the following temporary or permanent modifications:

(1) Unit common third off-site source transfer switch on October 3 and 4, 2022 71111.19 - Post-Maintenance Testing Post-Maintenance Test Sample (IP Section 03.01) (7 Samples)

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

(1) Unit common 101 safeguard transformer load tap changer following transformer replacement on October 4, 5, and 6, 2022 (2) Unit 2 EDG D21 following speed switch replacement on November 4, 2022 (3) Unit 2 reactor core isolation cooling following planned maintenance on November 16, 2022 (4) Unit common 'A' emergency service water system following motor replacement on November 22, 2022 (5) Unit 1 'A' RHR following planned maintenance on November 30, 2022 (6) Unit common 'A' RHR service water pump following planned maintenance on December 14 and 15, 2022 (7) Unit 2 'B' core spray system unit cooler following corrective maintenance on December 22, 2022

71111.22 - Surveillance Testing The inspectors evaluated the following surveillance testing activities to verify system operability and/or functionality:

Surveillance Tests (other) (IP Section 03.01) (2 Samples)

(1) ST-6-092-312-2, Unit 2 D22 diesel generator slow start operability test run, with additional instrumentation, on November 7, 2022 (2) ST-6-055-230-2, Unit 2 HPCI pump, valve, and flow test on December 21, 2022 Reactor Coolant System (RCS) Leakage Detection Testing (IP Section 03.01) (1 Sample)

(1) ST-6-107-590-2, Unit 2 daily surveillance log with elevated RCS unidentified leakage on December 16, 2022 71114.06 - Drill Evaluation Drill/Training Evolution Observation (IP Section 03.02) (1 Sample)

The inspectors evaluated:

(1) An emergency preparedness training evolution on November 17, 2022 RADIATION SAFETY 71124.03 - In-Plant Airborne Radioactivity Control and Mitigation Permanent Ventilation Systems (IP Section 03.01) (1 Sample)

The inspectors evaluated the configuration of the following permanently installed ventilation systems:

(1) Unit common spent fuel pool ventilation system Temporary Ventilation Systems (IP Section 03.02) (1 Sample)

The inspectors evaluated the configuration of the following temporary ventilation system:

(1) Walked down HEPA vacuum and unit storage locations and reviewed inventory procedures Use of Respiratory Protection Devices (IP Section 03.03) (1 Sample)

(1) The inspectors evaluated the licensees use of respiratory protection devices Self-Contained Breathing Apparatus for Emergency Use (IP Section 03.04) (1 Sample)

(1) The inspectors evaluated the licensees use and maintenance of self-contained breathing apparatuses

71124.04 - Occupational Dose Assessment Source Term Characterization (IP Section 03.01) (1 Sample)

(1) The inspectors evaluated licensee performance as it pertains to radioactive source term characterization External Dosimetry (IP Section 03.02) (1 Sample)

(1) The inspectors evaluated how the licensee processes, stores, and uses external dosimetry Internal Dosimetry (IP Section 03.03) (2 Samples)

The inspectors evaluated the following internal dose assessments:

(1) Reviewed Accuscan of worker with internal contamination (2) Reviewed Fastscan of worker with internal contamination Special Dosimetric Situations (IP Section 03.04) (2 Samples)

The inspectors evaluated the following special dosimetric situations:

(1) Reviewed evaluation of a declared pregnant worker (2) Reviewed procedure for special increased exposures 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 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:

MS10: Cooling Water Support Systems (IP Section 02.09) (2 Samples)

(1) Unit 1 for the period of October 1, 2021, through September 30, 2022 (2) Unit 2 for the period of October 1, 2021, through September 30, 2022 BI01: RCS Specific Activity Sample (IP Section 02.10) (2 Samples)

(1) Unit 1 for the period of October 1, 2021, through September 30, 2022 (2) Unit 2 for the period of October 1, 2021, through September 30, 2022 BI02: RCS Leak Rate Sample (IP Section 02.11) (2 Samples)

(1) Unit 1 for the period of October 1, 2021, through September 30, 2022 (2) Unit 2 for the period of October 1, 2021, through September 30, 2022 OR01: Occupational Exposure Control Effectiveness Sample (IP Section 02.15) (1 Sample)

(1) December 2021 through October 2022 PR01: Radiological Effluent Technical Specifications (TSs)/Offsite Dose Calculation Manual Radiological Effluent Occurrences (RETS/ODCM) Radiological Effluent Occurrences Sample (IP Section 02.16) (1 Sample)

(1) December 2021 through October 2022 71152A - Annual Follow-up Problem Identification and Resolution Annual Follow-up of Selected Issues (Section 03.03) (3 Samples)

The inspectors reviewed the licensees implementation of its corrective action program (CAP) related to the following issues:

(1) Potential adverse trends associated with MSIV LLRT on November 17, 18, 21, and 30, 2022 (2) Evaluation and corrective actions associated with Unit 1 BPV #1 EHC fluid leakage, and associated work group evaluation (WGE) 4499745 on November 21 and December 12, 2022 (3) Evaluation and corrective actions associated with Unit 2 EDG D21 jacket water leakage, and associated WGE 4514473 on December 9, 12, and 21, 2022

71152S - Semiannual Trend Problem Identification and Resolution Semiannual Trend Review (Section 03.02) (1 Sample)

(1) The inspectors reviewed Constellations CAP for potential adverse trends that might be indicative of a more significant safety issue. The inspectors determined that Constellation was appropriately identifying, evaluating, and resolving adverse trends.

INSPECTION RESULTS Failure to use engineering controls in accordance with RWP Cornerstone Significance Cross-Cutting Report Aspect Section Occupational Green [H.8] - 71124.03 Radiation Safety NCV 05000352,05000353/2022004-01 Procedure Open/Closed Adherence A finding of very low safety significance (Green) and associated NCV of 10 CFR 20.1701, Use of process or other engineering controls, was self-revealed on April 9, 2022, when Constellation workers failed to use, to the extent practical, process or other engineering controls (e.g., containment, decontamination, or ventilation) to control the concentration of radioactive material in air meet the requirements on of 10 CFR 20.1701. Specifically, on April 9, 2022, during a refuel outage at Limerick Generating Station, Constellation failed to use process or other engineering controls (e.g., HEPA ventilation unit and maintain the work in a wetted condition) prior to engaging in aggressive work activities on the MSIV in the Unit 1 drywell. This resulted in airborne radioactivity in the immediate work area and one worker received an unplanned exposure of 49 millirem committed effective dose equivalent.

Description: On April 9, 2022, two workers entered the Unit 1 drywell under RWP (LG-0-22-00509) to complete machining work of MSIV valves 'B' and 'D'. The individuals alarmed the personnel contamination monitor (PM-12) at the radiologically controlled area (RCA) exit.

One worker was machining in the drywell on the B MSIV. The other individual was setting up on the D MSIV nearby. The individual machining on the B MSIV had assumed the work after receiving turnover from the previous crew who had set the machine in the valve. The B MSIV did not have the required HEPA ventilation, and the valve seat was not properly maintained wet during the evolution as required by the RWP and the as low as reasonably achievable (ALARA) plan. The worker at the B MSIV also reported hearing a loud banging noise above where they were working and that the pipe and valve vibrated with the banging.

The vibrations were determined to be from power tool ratcheting to loosen the main steam relief valve (MSRV) bolts on the same line nearby. This vibration is thought to have contributed to an airborne event in the work area from the valve. The lack of proper HEPA ventilation and maintaining the work wet caused one worker to receive 49 millirem (mrem)

committed effective dose equivalent (internal dose).

The licensee evaluated the event and found that contributing factors which led to these degraded conditions were as follows:

• The workers did not understand ALARA plan requirements and were not aware of the requirements due to only being discussed verbally well in advance of the work.

• The ALARA brief was not discussed by radiation protection (RP) staff and the workers during the radiological conditions briefing provided before the workers entered to perform the work on the MSIVs. Workers stated that the briefing was focused on the

dose rates in the area and did not include the contamination control aspects of the ALARA plan. In addition, the ALARA plan was not reviewed in detail as the RP technician thought the initial ALARA brief was adequate.

• Various roles and responsibilities were not made clear at the initial ALARA brief, as RP staff assumed that the workers would set up the HEPA and the workers thought that a HEPA vacuum in the valve was adequate.

• RP did not provide adequate oversite of the work area. The RP brief should have identified the need for the workers to contact RP to verify the engineering controls (HEPA placement and wetting of surfaces) were adequate prior to aggressive work. This did not occur due to the key ALARA plan requirements not being reviewed during subsequent briefs.

Corrective Actions:

• Performed a training performance analysis

• Define which jobs will require oversight/observations to ensure RP/ALARA plan compliance and invite corporate oversight to those activities

• Identify critical jobs using the RP manpower sheet for on-line and schedule review for outages and assign the responsible oversight Supervisor/Manager

• Benchmark industry leader for education of outage supplemental workforce on basic RP fundamentals including engineering controls and site operating experience

• Implement actions from the benchmark

• Review and validate the use of engineering controls Corrective Action References: Issue Report (IR) 04491897 Performance Assessment:

Performance Deficiency: The improper use of engineering controls (HEPA unit and maintaining work wet) was reasonably within Constellations ability to foresee and correct and should have been prevented and therefore was a performance deficiency.

Screening: The inspectors determined the performance deficiency was more than minor because it was associated with the Program and Process attribute of the Occupational Radiation Safety cornerstone and adversely affected the cornerstone objective to ensure the adequate protection of the worker health and safety from exposure to radiation from radioactive material during routine civilian nuclear reactor operation. In addition, it is similar to example 6.h of IMC 0612, Appendix E. Specifically, the worker failed to use a HEPA and keep work wet during the duration of the valve work per the RWP ALARA Plan, which resulted in an unplanned exposure of 49 mrem committed effective dose equivalent (internal dose).

Significance: The inspectors assessed the significance of the finding using IMC 0609, Appendix C, Occupational Radiation Safety Significance Determination Process (SDP). The finding was of very low safety significance (Green) because: 1) it was not ALARA finding, 2)

there was no overexposure, 3) there was no substantial potential for an overexposure, and 4)

the ability to assess dose was not compromised.

Cross-Cutting Aspect: H.8 - Procedure Adherence: Individuals follow processes, procedures, and work instructions. The inspectors determined that this finding had a cross-cutting aspect

in the area of Human Performance, Procedure Adherence, because the individuals failed to follow verbal and written work instructions.

Enforcement:

Violation: Title 10 of the CFR 20.1701, Use of process or other engineering controls, states that, The licensee shall use, to the extent practical, process or other engineering controls (e.g., containment, decontamination, or ventilation) to control the concentration of radioactive material in air." Contrary to the above, on April 9, 2022, Constellation failed to use process or other engineering controls (e.g., HEPA ventilation unit and maintain the work in a wetted condition), in violation of 10 CFR 20.1701; resulting in airborne radioactivity and unplanned dose of 49 mrem committed effective dose equivalent to one worker.

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

Inadequate maintenance procedure results in EHC fluid leak from main turbine BPV Cornerstone Significance Cross-Cutting Report Aspect Section Mitigating Green None (NPP) 71152A Systems FIN 05000352,05000353/2022004-02 Open/Closed The inspectors determined there was a Green, self-revealing finding because maintenance procedure MA-LG-763-473, Disassemble and Assemble Main Steam BPV Actuator/Spring Can, Revision 0, did not include adequate steps to effectively reassemble BPV number 1 (BPV-1) actuator following the performance of preventive maintenance activities, which resulted in an EHC fluid leak on May 14, 2022, and adversely impacted the reliability of the main turbine bypass system.

Description: The main turbine steam bypass system is designed to control steam pressure when reactor steam generation exceeds turbine requirements during unit startup, sudden load reduction, and cooldown. It allows excess steam flow from the reactor to the condenser without going through the turbine. The system is comprised of nine valves that have a total bypass capacity of approximately 25 percent of the nuclear steam supply system rated steam flow. The main turbine bypass system is designed to limit the peak pressure in the main steam lines and maintain reactor pressure within acceptable limits during events that cause rapid pressurization such that the safety limit minimum critical power ration is not exceeded.

Each of the nine BPVs consist of a dual-acting actuator that uses EHC fluid flow both over and under an actuator piston to allow for precise control in both the open and close direction of the valve. EHC fluid is directed to the top and bottom of the actuator piston using an electronic servo. When a BPV is closed, the servo directs EHC fluid to the top of the actuator piston at full EHC system pressure (approximately 1600 pounder per square inch) to maintain the valve closed, with some residual amount of fluid maintained at the bottom of the piston to support a fast opening function. For the BPV to open, the servo repositions to increase the volume of fluid at the bottom of the actuator piston.

On May 14, 2022, during Unit 1 shutdown for a planned maintenance outage, operators received a low-level alarm for the EHC fluid reservoir. Operators entered the abnormal operating procedure for response to EHC leaks, and dispatched operators into the plant in an attempt to identify the leak location. After approximately 24 minutes, operators in the main control room decided to secure the in-service EHC pump, based on the leak location not

being identified, and the fact that Unit 1 had entered OPCON 4 (Cold Shutdown)

approximately 8 minutes prior to receipt of the alarm with shutdown cooling already placed in-service following closure of the final BPV (BPV-1) during the plant cooldown. Trending of plant data for EHC level estimated the leak was approximately 6.5 gallons per minute (gpm).

Subsequent operator entry into the main condenser bay identified the leak location was from BPV-1. Upon disassembly of the BPV-1 for repairs, it was identified that there was a loose mounting bolt and deteriorated o-ring from one of four bolts that secure the actuator assembly to the servo mounting plate, which is referred to as the tombstone. The tombstone is designed with internal fluid ports that direct EHC fluid flow from the servo to the actuator. The loose mounting bolt was therefore determined to have allowed pressurized EHC fluid to leak from the mating surface between the tombstone and the actuator following closure of BPV-1, which is the last BPV to close during unit cooldown.

Constellation performed a WGE under IR 4499745, and determined that the loose mounting bolt was most likely caused by an o-ring extruding through a clearance gap between the tombstone and actuator, as a result of inadequate procedural guidance that omitted any steps to check for clearance gaps to ensure for proper alignment between mating surfaces.

Specifically, Limerick procedure MA-LG-763-473, Disassemble and Assemble Main Steam BPV Actuator/Spring Can, was used during the previous reassembly of the BPV-1 actuator and tombstone following the completion of preventive maintenance activities in 2012, under work order (WO) R1130130. Procedure step 4.6.17 specified a torque value of 95 foot-pounds, applied over 3 torque passes, but did not include a step to check clearance gaps to ensure proper alignment between mating surfaces.

The inspectors reviewed WGE 4499745, as well as the completed WO R1130130 from 2012, and verified that step 4.6.17 of MA-LG-763-473 was signed off as completed with the specified torque value of 95 foot-pounds. The inspectors also reviewed procedure MA-LG-763-473, Revision 0, and noted that it was issued in 2012, just prior to performance of WO R1130130. The inspectors subsequently reviewed Constellation procedure MA-AA-736-600, Torquing and Tightening of Bolted Connections, Revision 14, issued in 2022, and noted that Section 4.2, Connection Reassembly, included steps to remove all clearance gaps during application of torque passes, and contained clearance gap criteria for misaligned joints. The inspectors subsequently reviewed the equivalent Limerick maintenance procedure in effect in 2012, MA-LG-716-1017, Control of Bolting / Torquing / Tensioning, Revision 0 (issued in 2010), and noted that section 7.2.5 covered torque sequencing and contained steps to ensure uniform surface alignment, including steps to ensure uniform gap checks for misaligned flanges. Based on this procedure review, the inspectors determined that it was reasonably within Limericks ability to foresee and correct the inadequate instructions for BPV reassembly contained in maintenance procedure MA-LG-763-473 that was issued in 2012, and the inspectors therefore determined that uneven clearance gaps between the tombstone and actuator should have been prevented to ensure reliable BPV operation.

Corrective Actions: Constellation replaced the failed BPV-1 actuator and verified all four of the tombstone-to-actuator mounting bolts were adequately torqued to the required values and performed an extent of condition torque check on all the remaining BPV accessible bolts to verify as-found values of 95 foot-pounds. Constellation assigned WGE action 4499745-14 to add a step to procedure MA-LG-763-473 to ensure that clearance values were less than 0.0015 inches between the tombstone and the actuator. WGE action 4499745-15 was created to scope torque checks of all remaining BPV bolts into the next refueling outages for Unit 1 (1R20) and Unit 2 (2R17), and action 4499745-16 was created to evaluate creating a

new preventive maintenance task to perform torque checks, in between actuator inspection preventive maintenance activities, if additional bolts are found loose under action 4499745-15.

Corrective Action References: IRs 4499745, 4499944, 4499968, 4537024 Performance Assessment:

Performance Deficiency: The inspectors determined that Constellations inadequate maintenance procedure instructions for BPV reassembly was reasonably within Constellations ability to foresee and correct, and should have been prevented, and therefore constituted a performance deficiency. Specifically, procedure MA-LG-763-473, Disassemble and Assemble Main Steam BPV Actuator/Spring Can, Revision 0, did not contain adequate instructions to ensure the BPV actuator and tombstone mounting surfaces were properly aligned with consistent clearance gaps to prevent o-ring extrusion and EHC fluid leakage.

Screening: The inspectors determined the performance deficiency was more than minor because it was associated with the Equipment Performance attribute of the Mitigating Systems cornerstone and adversely affected the cornerstone objective to ensure the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. Specifically, failure to ensure properly assembly of the BPV-1 actuator resulted in a significant EHC fluid leak from the valve and challenged reliable operation of the main turbine bypass system.

Significance: The inspectors assessed the significance of the finding using IMC 0609 Appendix A, The SDP for Findings At-Power. This finding was screened to Green using the Mitigating Systems screening questions because it did not involve a design deficiency, did not represent the loss of a train of TS equipment for longer than its allowed outage time, and did not represent loss of a probabilistic risk analysis system or function.

Cross-Cutting Aspect: Not Present Performance. No cross-cutting aspect was assigned to this finding because the inspectors determined the finding did not reflect present licensee performance. Specifically, the BPV-1 maintenance utilizing the deficient preventive maintenance procedure was performed in 2012, and no maintenance was performed on the actuator and tombstone of any other BPVs on either unit in the last three years using the deficient preventive maintenance procedure.

Enforcement: Inspectors did not identify a violation of regulatory requirements associated with this finding.

Inadequate performance monitoring and margin management associated with MSIV LLRT Cornerstone Significance Cross-Cutting Report Aspect Section Barrier Integrity Green [H.6] - Design 71152A FIN 05000352,05000353/2022004-03 Margins Open/Closed The inspectors identified a Green finding against procedure ER-AA-2003, System Performance Monitoring and Analysis, Revision 8, because Constellation did not perform adequate performance monitoring and analysis of MSIV LLRT results to ensure that degrading trends were identified prior to challenging required limits during the operating cycle.

Description: The inspectors performed a historical review of MSIV as-found LLRT data on Unit 1, and noted in refueling outage 1R18 (spring of 2020) three of the eight MSIVs exceeded the TS limit of 100 standard cubic foot per hour (scfh): specifically, outboard valves 28B, 28C and 28D. TS 3.6.1.2 requires each MSIV leak rate to be less than or equal to 100 scfh, and the total leak rate through all four main steam lines to be less than or equal to 200 scfh, in operational conditions 1, 2 and 3. Constellation determined the 200 scfh total as-found limit through all four main steam lines was not exceeded, because the leakage values through the A main steam line, as well as the B, C, and D inboard MSIVs, were all sufficiently low enough to ensure the total leakage was less than 200 scfh, when considering the performance of the redundant inboard valve in each line. Two of the MSIVs (28C and 28D) were repaired in 1R18 to restore leakage below the 100 scfh single MSIV limit. For the third MSIV (28D), an emergency license amendment was approved (ML20098C922) to allow for a one-time TS change from 100 scfh to 105 scfh, due to challenges related to the COVID-19 public health emergency.

The inspectors reviewed the LLRT performance data for the 28C and 28D MSIVs and noted progressively increasing trends from 1R15 through 1R18. As a result, inspectors determined that further review was warranted to understand whether appropriate MSIV LLRT performance monitoring and margin management was being performed to ensure leak rates were maintained below required limits during plant operation.

The inspectors reviewed MSIV maintenance history, and noted MSIVs did not have regularly scheduled in-body preventive maintenance activities to proactively limit valve seat leakage, and further noted that no in-body maintenance was performed on the 28C or 28D during the time period from 1R15 until 1R18, when as-found results exceeded TS limits. The inspectors noted that MSIVs at Limerick were exempt from 10 CFR Part 50, Appendix J, Primary Containment Leakage Testing, and were therefore not subject to overall allowable containment leakage limits required under Appendix J. The inspectors reviewed design analysis LM-0646, Re-analysis of loss of coolant accident (LOCA) Using Alternate Source Terms, Revision 6, and noted the TS 3.6.1.2 total MSIV leakage limit of 200 scfh was used as an analytical input to validate the radiological consequences of a LOCA remained below regulatory limits. The inspectors subsequently reviewed ST-4-LLR-001-1, The Local Leak Rate (LLR) Program an Accountability Test, Revision 18, and ST-4-LLR-03/4/5/61-001, Main Steam Line A/B/C/D LLR STs, Revisions 16, 15, 15, and 16, respectively, and noted the acceptance criteria were established at the TS 3.6.1.2 limits. The inspectors noted that there was no established margin between the LLRT ST limits, the LM-0646 analysis of record, and the TS 3.6.1.2 limits.

The inspectors reviewed Constellation procedure ER-AA-2003, System Performance Monitoring and Analysis, Revision 8, and noted that performance monitoring plans were required for Tier 1 systems, which included the main steam system. Step 4.1.5 requires establishment of alert levels and action levels. An alert level is described as a parameter level that when exceeded is indicative of equipment degradation and requires IR initiation. An action level is described as the threshold where action is required to prevent a consequential event, though consequential events are undefined. Attachment 2 further describes monitoring alert level considerations, and states that monitoring bands and frequencies should be sufficient to identify degrading trends before design, operating, or licensing requirements are challenged. In addition, Attachment 1 lists items to consider for trending, and refers to ER-AA-2007, Management of Design and Operating Margins, Revision 8, which discusses how to identify and control design and analytical margins. The inspectors reviewed the main steam performance monitoring plan, and noted MSIV LLR STs were included in the plan, but

the alert and action levels were each established at the TS limits. The inspectors further noted the MSIV LLR STs did not establish any administrative limits. The inspectors therefore concluded that Constellation did not adequately perform step 4.1.5 of ER-AA-2003 to conduct performance monitoring of MSIV LLRT data, because alert levels were not established to indicate equipment degradation, and IRs were not initiated until TS limits were exceeded.

Corrective Actions: Constellation performed industry benchmarking and captured the performance deficiency under IR 4553559, to evaluate the issue and develop appropriate corrective actions. There were no violations of regulatory requirements that warranted immediate corrective action, because both C and D outboard MSIVs had been repaired in 1R18 and there were no existing MSIVs with adverse trends.

Corrective Action References: IRs 4553559, 4331517, 4331518, 4331519 Performance Assessment:

Performance Deficiency: The inspectors determined that Constellations inadequate performance monitoring and analysis in accordance with station procedures was reasonably within Constellations ability to foresee and correct, should have been prevented, and was therefore determined to be a performance deficiency.

Screening: The inspectors determined the performance deficiency was more than minor because if left uncorrected, it would have the potential to lead to a more significant safety concern. Specifically, the inspectors determined that if no additional actions were taken to monitor MSIV leakage performance, then TS and analytical limits could be exceeded during the operating cycle.

Significance: The inspectors assessed the significance of the finding using IMC 0609, Appendix A, The SDP for Findings At-Power. The inspectors utilized IMC 0609, Appendix A, Exhibit 3, Barrier Integrity Screening Questions, to determine this finding was of very low safety significance (Green) because it did not represent an actual open pathway in the reactor containment barrier, and did not involve a failure of the any one of the following: the containment isolation system, containment pressure control equipment, containment heat removal components, or severe accident mitigation features.

Cross-Cutting Aspect: H.6 - Design Margins: The organization operates and maintains equipment within design margins. Margins are carefully guarded and changed only through a systematic and rigorous process. Special attention is placed on maintaining fission product barriers, defense-in-depth, and safety-related equipment. Specifically, Constellation did not perform adequate performance monitoring of MSIV LLRT results to guard and maintain design margins to the allowable limits and did not place special attention on maintaining containment barrier margins below analyzed limits.

Enforcement: Inspectors did not identify a violation of regulatory requirements associated with this finding.

Unresolved Item Failure to follow maintenance procedure results in EDG JW 71152A (Open) leak URI 05000352,05000353/2022004-04 Description: On August 2, 2022, during a monthly ST of D21 EDG at full load, equipment operators discovered a JW leak from a threaded fitting connection on a 0.25-inch diameter tubing instrument root valve connection to the five-inch JW piping header. At approximately

30 minutes into the loaded run, operators measure leakage at 0.37 ounces per minute. Just prior to completion of the two-hour loaded run, operators measure leakage at 0.78 ounces per minute. Operators subsequently declared D21 EDG inoperable, because leakage was measured above the pre-determined operability limit of 0.5 ounces per minute, as calculated in Technical Evaluation (TE) 202873-01. The inspectors noted the 0.5 ounce per minute limit supported successful operation of the EDG over the seven-day mission time required for TS operability, without credit for inventory make-up to the closed-loop JW sub-system. The inspectors further noted that Updated Final Safety Analysis Report section 9.5.5.2.1, stated that normal maintenance of system components will ensure that leakage rates will be kept below the amount requiring tank makeup within a seven-day period. Operators determined that D21 EDG remained available, because leakage was not expected to exceed the 24-hour probabilistic risk assessment mission time limit of 3.5 ounces per minute, based on no visible cracks observed in the fitting connection, and no evidence that there was a risk of complete fitting failure. In addition, the downstream (JW outlet) side of the instrument root valve was noted to consist of a second, leak-tight, threaded connection to a pressure switch and small diameter hard pipe tubing, such that complete unthreading of the upstream (JW inlet)

threaded connection to the JW header was determined by Constellation to be very unlikely.

On August 3, 2022, Constellation performed corrective maintenance repairs that consisted of tagging out D21 EDG, draining the JW system, disassembling the two fittings on either side of the instrument root valve, replacing a reducer coupling at the threaded connection between the instrument root valve and JW header, re-installing the threaded fittings on either side of the instrument root valve one at a time, and performing an unloaded EDG run with no JW leakage observed from the re-assembled threaded connections.

Following corrective maintenance, Constellation performed WGE 4514473-12, to determine the cause of the leaking fitting that resulted in D21 EDG inoperability. Constellation determined that the cause was attributed to inadequately tightening the instrument root valve fitting connection to the JW header during D21 EDG planned maintenance that was completed on June 18, 2022. The WGE further stated that the instrument root valve fitting was re-assembled under maintenance procedure M-020-002, Fairbanks Morse Opposed Piston Diesel Generator Major Examination and General Maintenance. In addition, while no leakage was noted during multiple post-maintenance test runs that were conducted on June 17 and 18, Constellation noted that IR 4508586 was generated on June 30, during equipment operator rounds with D21 EDG in a standby condition, which documented minor weepage at the instrument root valve threaded connection to the JW piping header. The inspectors noted that no observations of leakage were documented during the July 5, 2022, monthly ST. As part of the WGE, Constellation sent the reducer coupling, which was removed during the August 3 corrective maintenance, off-site for a failure analysis. No presence of cracks, galling, or cross-threading were noted in the reducer coupling.

The inspectors reviewed the WGE, and discussed the D21 EDG JW leak with maintenance technicians, operators, and engineers. The inspectors agreed with Constellations causal determination in the WGE. In addition, the inspectors noted that after the D21 EDG instrument root valve fitting connection was not properly tightened during planned maintenance that completed on June 18, minor leakage from the fitting was subsequently discovered on June 30 that progressively degraded to 0.78 ounces per minute on August 2, after accruing approximately 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> of run time during post-maintenance test runs and ST. Based on this information, the inspectors questioned Constellation as to whether the D21 EDG was inoperable for greater than the allowed outage time of 30 days, and whether it therefore constituted a violation of TS Limiting Condition for Operation 3.8.1. At the close of

the inspection period, Constellation was re-evaluating the assumptions and inherent margin in TE 202873-01, with respect to the allowable JW leakage over the 7-day mission time, in response to the inspectors question.

Planned Closure Actions: The inspectors will review Constellation's re-evaluation of TE 202873-01 to understand the allowable JW leak rate in support of the 7-day mission time of the D21 EDG, and whether the D21 EDG was inoperable from June 18 to August 2, 2021.

Licensee Actions: At the close of the inspection period, Constellation was re-evaluating the assumptions and inherent margin in TE 202873-01, with respect to the allowable JW leakage over the 7-day mission time, in response to the inspectors question.

Corrective Action References: IRs 4514473 and 4508586, and TE 202873 EXIT MEETINGS AND DEBRIEFS The inspectors verified no proprietary information was retained or documented in this report.

• On February 10, 2023, the inspectors presented the integrated inspection results to Michael Gillin, Site Vice President, and other members of the licensee staff.

• On December 15, 2022, the inspectors presented the IP 71124.03 and IP 71124.04 inspection results to Mike Gillin, Site Vice President, and other members of the licensee staff.

• On November 10, 2022, the inspectors presented the IP 71124.07, Radiological Environmental Monitoring Program, inspection results to Matt Bonanno, Plant Manager, and other members of the licensee staff.

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