IR 05000445/2024003

Integrated Inspection Report 05000445/2024003 and 05000446/2024003

ML24298A116
Person / Time
Site:	Comanche Peak
Issue date:	10/30/2024
From:	Ami Agrawal NRC/RGN-IV/DORS/PBB
To:	Peters K Vistra Operations Company
References
IR 2024003
Download: ML24298A116 (19)

Text

October 30, 2024

SUBJECT:

COMANCHE PEAK NUCLEAR POWER PLANT, UNITS 1 AND 2 -

INTEGRATED INSPECTION REPORT 05000445/2024003 AND 05000446/2024003

Dear Ken Peters:

On September 30, 2024, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at Comanche Peak Nuclear Power Plant, Units 1 and 2. On October 10, 2024, the NRC inspectors discussed the results of this inspection with Heather Winn, Plant Manager, and other members of your staff. The results of this inspection are documented in the enclosed report.

Two findings of very low safety significance (Green) are documented in this report. None of these findings involved a violation of NRC requirements.

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 IV; and the NRC Resident Inspector at Comanche Peak Nuclear Power Plant, 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 K. Peters 2

Room in accordance with Title 10 of the Code of Federal Regulations 2.390, Public Inspections, Exemptions, Requests for Withholding.

Sincerely, Signed by Agrawal, Ami on 10/30/24

Ami N. Agrawal, Chief Reactor Projects Branch B Division of Operating Reactor Safety

Docket Nos. 05000445, 05000446 License Nos. NPF-87, NPF-89

Enclosure:

As stated

Inspection Report

Docket Numbers: 05000445, 05000446

License Numbers: NPF-87, NPF-89

Report Numbers: 05000445/2024003 and 05000446/2024003

Licensee: Vistra Operations Company LLC

Facility: Comanche Peak Nuclear Power Plant, Units 1 and 2

Location: Glen Rose, TX 76043

Inspection Dates: July 1 to September 30, 2024

Inspectors: J. Ellegood, Senior Resident Inspector S. Hedger, Senior Emergency Preparedness Inspector P. Nwafor, Project Engineer H. Strittmatter, Resident Inspector

Approved By: Ami N. Agrawal, Chief Reactor Projects Branch B 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 Comanche Peak Nuclear Power Plant, 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 Identify Post-Maintenance Testing for a Modification Cornerstone Significance Cross-Cutting Report Aspect Section Initiating Events Green [P.2] - 71152A FIN 05000445,05000446/2024003-01 Evaluation Open/Closed The inspectors reviewed a self-revealed Green finding without a violation that occurred on September 4, 2020, when the licensee approved a modification to the main feed pump control system. Specifically, the licensee approved a modification to transition from the Mark V control system to the T3000 control system that did not include dynamic testing of the modification. This omission led to acceptance of a control system that was not able to control pump speed to preclude a reactor trip on the loss of a main feed pump.

Failure to Translate Design Input Requirements into the Final Design Cornerstone Significance Cross-Cutting Report Aspect Section Initiating Events Green [H.12] - Avoid 71152A FIN 05000445,05000446/2024003-02 Complacency Open/Closed The inspectors reviewed a self-revealed Green finding without a violation that occurred on September 4, 2020, and March 14, 2024, when the licensee failed to identify and incorporate design inputs into the final design. Specifically, the design modification for the T3000 did not incorporate power requirements for the servo valve and the amplifier addition mod did not incorporate vendor requirements for shielded cabling and ground separation.

Additional Tracking Items

None.

PLANT STATUS

Units 1 and 2 remained at or near 100 percent 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 onsite portions of IPs. The inspectors reviewed selected procedures and records, observed activities, and interviewed personnel to assess licensee performance and compliance with Commission rules and regulations, license conditions, site procedures, and standards.

REACTOR SAFETY

71111.04 - Equipment Alignment

Partial Walkdown Sample (IP Section 03.01) (1 Sample)

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

(1) Unit 1, train A motor-driven auxiliary feedwater pump on August 27, 2024

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

(1) The inspectors evaluated system configurations during a complete walkdown of the Units 1 and 2 battery/UPS systems on August 14-15, 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) component cooling water on September 23, 2024 (2) Unit 1 main feed and steam enclosures on September 23, 2024 (3) Unit 2 main feed and steam enclosures on September 23, 2024 (4) Unit 1 train B switch gear on September 27, 2024 (5) Unit 2 train B switchgear on September 27, 2024

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

(1) The inspectors evaluated the onsite fire brigade training and performance during an unannounced fire drill on September 17, 2024.

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 high trip risk activity switching Unit 1 circulating water lube water to a temporary strainer on July 24, 2024.

Licensed Operator Requalification Training/Examinations (IP Section 03.02) (1 Sample)

(1) The inspectors observed and evaluated a licensed operator requalification training simulator exam session on July 24, 2024.

71111.12 - Maintenance Effectiveness

Maintenance Effectiveness (IP Section 03.01) (2 Samples)

The inspectors evaluated the effectiveness of maintenance to ensure the following structures, systems, and components remain capable of performing their intended function:

(1) instrument air system following entry into a(1) status (2) Unit 1, chemical and volume control system filter housing leaks

71111.13 - Maintenance Risk Assessments and Emergent Work Control

Risk Assessment and Management Sample (IP Section 03.01) (1 Sample)

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) unplanned safety chiller inoperability and planned yellow risk for emergency diesel generator testing for the week of September 9, 2024

71111.15 - Operability Determinations and Functionality Assessments

Operability Determination or Functionality Assessment (IP Section 03.01) (4 Samples)

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

(1) service water with electrical box secured by ratchet straps (2) untested thermal relief valves on safety-related equipment (3) inverter IV1EC1 current fluctuations (4) Unit 2, channel 1 N-16 with high voltage out of specification

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) (9 Samples)

(1) turbine-driven auxiliary feed water pump discharge to SG 2-01 flow control valve elastomer replacement on July 10, 2024 (2) fire panel power supply replacement on July 11, 2024 (3) containment spray pumps 1-01 and 1-03 bearing cooler clean/inspection and oil replacement on July 30, 2024 (4) Unit 2, train B switchgear fire protection deluge valve diaphragm replacement on August 15, 2024 (5) diesel generator annunciator power supply replacement on August 21, 2024 (6) Unit 1, IV1EC1 static switch control board replacement on August 28, 2024, under Work Order 22-527489 (7) Unit 2, locked high radiation area ladder barrier on September 17, 2024 (8) Unit 2, train C non-safeguards 125 VDC battery charger, BC2D2, component replacement, testing, and calibration on September 9 - 10, 2024 (9) Unit 1, circulating water lube water strainer replacement on September 14, 2024

Surveillance Testing (IP Section 03.01) (1 Sample)

(1) Unit 2, visual examination (VT-2) of the residual heat exchanger on August 13, 2024

Inservice Testing (IST) (IP Section 03.01) (1 Sample)

(1) safety injection pump 2-02 inservice test on August 6, 2024

Diverse and Flexible Coping Strategies (FLEX) Testing (IP Section 03.02) (1 Sample)

(1) observed quarterly inspection of multipurpose high flow flex pumps on July 18 and 22, 2024

71114.02 - Alert and Notification System Testing

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

(1) The inspectors evaluated the maintenance and testing of the alert and notification system between November 12, 2022, and September 14, 2024.

71114.03 - Emergency Response Organization Staffing and Augmentation System

Inspection Review (IP Section 02.01-02.02) (1 Sample)

(1) The inspectors evaluated the readiness of the Emergency Preparedness Organization between November 12, 2022, and September 14, 2024. Inspectors also evaluated the licensee's ability to staff their emergency response facilities in accordance with emergency plan commitments.

71114.04 - Emergency Action Level and Emergency Plan Changes

Inspection Review (IP Section 02.01-02.03) (1 Sample)

(1) The inspectors evaluated the 10 CFR 50.54(q) emergency plan change process and practices between November 12, 2022, and September 14, 2024. The evaluation reviewed screenings and evaluations documenting implementation of the process. The reviews of the change process documentation do not constitute NRC approval.

71114.05 - Maintenance of Emergency Preparedness

Inspection Review (IP Section 02.01 - 02.11) (1 Sample)

(1) The inspectors evaluated the maintenance of the emergency preparedness program between November 12, 2022, and September 14, 2024. The evaluation reviewed evidence of completing various emergency plan commitments, the conduct of drills and exercises, licensee audits and assessments; and the maintenance of equipment important to emergency preparedness.

71114.06 - Drill Evaluation

Additional Drill and/or Training Evolution (1 Sample)

The inspectors evaluated:

(1) a drill involving a steam generator tube rupture on August 7, 2024

OTHER ACTIVITIES - BASELINE

71151 - Performance Indicator Verification

The inspectors verified licensee performance indicators submittals listed below:

MS06: Emergency AC Power Systems (IP Section 02.05) (2 Samples)

(1) Unit 1 (July 1, 2023, through June 30, 2024)

(2) Unit 2 (July 1, 2023, through June 30, 2024)

MS07: High Pressure Injection Systems (IP Section 02.06) (2 Samples)

(1) Unit 1 (July 1, 2023, through June 30, 2024)

(2) Unit 2 (July 1, 2023, through June 30, 2024)

MS09: Residual Heat Removal Systems (IP Section 02.08) (2 Samples)

(1) Unit 1 (July 1, 2023, through June 30, 2024)

(2) Unit 2 (July 1, 2023, through June 30, 2024)

BI02: RCS Leak Rate Sample (IP Section 02.11) (2 Samples)

(1) Unit 1 (July 1, 2023, through June 30, 2024)

(2) Unit 2 (July 1, 2023, through June 30, 2024)

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

(1) July 1, 2023, through June 30, 2024

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

(1) July 1, 2023, through June 30, 2024

EP03: Alert And Notification System Reliability Sample (IP Section 02.14) (1 Sample)

(1) July 1, 2023, through June 30, 2024

71152A - Annual Follow-up Problem Identification and Resolution

Annual Follow-up of Selected Issues (Section 03.03) (2 Samples)

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

(1) emergency operating procedure 3.0 adequacy to prevent overfilling of the pressurizer (2) plant trip due to loss of main feedwater pump

71152S - Semiannual Trend Problem Identification and Resolution

Semiannual Trend Review (Section 03.02) (1 Sample)

(1) The inspectors reviewed the licensees corrective action program to identify potential trends in the licensee's review and implementation of nuclear safety advisory letters from Westinghouse on September 13 and 16, 2024.

INSPECTION RESULTS

Failure to Identify Post-Maintenance Testing for a Modification Cornerstone Significance Cross-Cutting Report Aspect Section Initiating Events Green[P.2] - 71152A FIN 05000445,05000446/2024003-01 Evaluation Open/Closed The inspectors reviewed a self-revealed Green finding without a violation that occurred on September 4, 2020, when the licensee approved a modification to the main feed pump control system. Specifically, the licensee approved a modification to transition from the Mark V control system to the T3000 control system that did not include dynamic testing of the modification. This omission led to acceptance of a control system that was not able to control pump speed to preclude a reactor trip on the loss of a main feed pump.

Description: The licensee contracted with Siemens to develop a modification to the main feed pump control system in 2016. The licensee, with vendor support, installed the system for Unit 1 during 1RF22 (May 2022) and for Unit 2 during 2RF20 (May 2023). The new control system was designated the T3000. Following installation of the modification, the site experienced degraded performance of all four main feed pumps. Issues included feed pump speed oscillations, poor servo valve performance requiring replacements, and feed pump trips. These issues led to a Unit 1 trip on June 16, 2023, and a Unit 2 trip on March 12 and 17, 2024. In addition to control system issues, the pumps have a history of water intrusion into the lubricating/control oil system. The water intrusion has resulted in corrosion products inhibiting proper operation of the mechanical portion of the main feed pump.

During the design process, the licensee relied heavily on the vendor, Siemens, to provide the necessary expertise in designing system controls. In addition, the licensee contracted a third-party reviewer to provide a critical review of the design. Although the third-party reviewer identified that the bases to conclude the T3000 would behave as the predecessor Mark V system was weak, the comments were not addressed prior to site acceptance of the design nor before acceptance of the as-installed modification. Part of the third-party comments addressed the quality and detail of the site's acceptance testing procedure. However, these comments were not addressed. Licensee Procedure IP-ENG-001, Standard Design Process, states post-maintenance testing should validate performance through testing or demonstration.

In January 2024, engineering identified degraded performance of the Unit 2 A main feed pump. On February 2, the licensee reduced power on Unit 2 and replaced the servo valve. At the time of the replacement, the licensee attributed the performance to water intrusion and the impacts of corrosion products on servo performance. However, inspection of the servo did not support this attribution. Further investigation by the licensee revealed that the T3000 generated a +/- 30 mA signal but the servo had an operating range of +/- 250 mA. On March 12, 2024, the licensee performed a servo valve oil filter swap for the Unit 2 A main feed pump. Following the swap, the feed pump performance degraded. Control room operators initiated a manual runback to 700 MWe. The B main feed pump did not ramp up speed as designed. As steam generator level lowered to the Lo/Lo set point, operators determined a manual trip was required; however, an automatic trip occurred prior to insertion of the manual trip.

During the forced outage, the licensee installed amplifiers to match T3000 output to servo capabilities. However, this modification also led to a plant trip which is addressed as a separate finding in this report.

Corrective Actions: The licensee added current amplifiers to address the incompatibility between the T3000 output amperage and required amperage for the servo controlling feed pump speed. The licensee performed dynamic testing following amplifier addition.

Corrective Action References: CR-2024-1805 Performance Assessment:

Performance Deficiency: The licensee's failure to establish a post-maintenance test that would ensure affected equipment was not adversely affected was a performance deficiency. Licensee Procedure ECE-5.08, Standard Design Process, revision 3, appendix 5, step 5.9, states the installer/operations/engineer should ensure that specified post-modification testing will verify that affected equipment has not been adversely affected

by the modification. However, the design failed to specify dynamic testing that would validate system response. Weaknesses in specified post-modification testing were identified by the third-party reviewer but not addressed.

Screening: The inspectors determined the performance deficiency was more than minor because it was associated with the Design Control attribute of the Initiating Events cornerstone and adversely affected the cornerstone objective to limit the likelihood of events that upset plant stability and challenge critical safety functions during shutdown as well as power operations. Specifically, the inadequate post-maintenance test did not validate that the design would control the main feed pumps as required. This led to multiple plant trips.

Significance: The inspectors assessed the significance of the finding using IMC 0609 Appendix A, The Significance Determination Process (SDP) for Findings At-Power. The finding screened as Green in accordance with exhibit 1 of Appendix A to IMC 0609 question B. The issue caused a reactor trip but did not cause a loss of mitigating equipment.

Cross-Cutting Aspect: P.2 - Evaluation: The organization thoroughly evaluates issues to ensure that resolutions address causes and extent of conditions commensurate with their safety significance. Specifically, following installation of the T3000 modification, there were precursor indications of degraded main feed pump performance. These indications were not evaluated thoroughly to determine the cause.

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

Failure to Translate Design Input Requirements into the Final Design Cornerstone Significance Cross-Cutting Report Aspect Section Initiating Events Green[H.12] - Avoid 71152A FIN 05000445,05000446/2024003-02 Complacency Open/Closed The inspectors reviewed a self-revealed Green finding without a violation that occurred on September 4, 2020, and on March 14, 2024, when the licensee failed to identify and incorporate design inputs into the final design. Specifically, the design modification for the T3000 did not incorporate power requirements for the servo valve and the amplifier addition mod did not incorporate vendor requirements for shielded cabling and ground separation.

Description: The licensee contracted with Siemens to develop a modification to the main feed pump control system in 2016. The licensee, with vendor support, installed the system for Unit 1 during 1RF22 (May 2022) and for Unit 2 during 2RF20 (May 2023). The new control system was designated the T3000. Following installation of the modification, the site experienced degraded performance of all four main feed pumps. Issues included feed pump speed oscillations, poor servo valve performance, and feed pump trips. These issues led to a Unit 1 trip on June 16, 2023, and a Unit 2 trip on March 12 and 17, 2024. In addition to control system issues, the pumps have a history of water intrusion into the lubricating/control oil system. The water intrusion has resulted in corrosion products inhibiting proper operation of the mechanical portion of the main feed pump. Following the plant trip on March 12, 2024, the licensee installed an amplifier on the output of the T3000 to address a design issue.

However, the modification also included a design error.

The original design for the T3000 did not include adequate current output from the T3000 to drive the servo. In February 2024, the licensee determined that the T3000 generated a

+/- 30 mA signal but the servo had an operating range of +/- 250 mA. The licensee determined in a root cause analysis that the T3000 design neglected to address the critical design parameter related to servo current requirements. The analysis documented that although the servo was included as a design input, critical characteristics related to the operating current range were not included. In addition, the third-party review identified technical rigor issues; however, these issues were not addressed.

With respect to modification to install a current amplifier, the licensee did not address amplifier vendor specifications to use shielded cabling and to use a star grounding pattern.

These omissions led to noise on the output signal and diagnostic alarms. Ultimately, the Unit 2 B main feed pump tripped causing a subsequent insertion of a manual trip. In the root cause, the licensee documented the omission of these specifications from the design and that these omissions led to pump trip and subsequent unit trip.

Corrective Actions: The licensee added current amplifiers to address the omissions in the T3000 modifications. For the amplifier error, the licensee required the grounding system for the amplifiers prior to unit restart.

Corrective Action References: CR-2024-1805 Performance Assessment:

Performance Deficiency: The licensee's failure to ensure design inputs and bounding technical requirements were properly translated into design was a performance deficiency. Licensee Procedure ECE 5.08, Standard Design Process, revisions 3 and 4, require the design to meet design inputs and technical requirements. For both the T3000 design and amplifier addition, the licensee failed to do so.

Screening: The inspectors determined the performance deficiency was more than minor because it was associated with the Design Control attribute of the Initiating Events cornerstone and adversely affected the cornerstone objective to limit the likelihood of events that upset plant stability and challenge critical safety functions during shutdown as well as power operations. Specifically, the designers did not ensure design inputs and technical requirements were properly translated into the final design.

Significance: The inspectors assessed the significance of the finding using IMC 0609 Appendix A, The Significance Determination Process (SDP) for Findings At-Power. The finding screened as Green in accordance with exhibit 1 of Appendix A to IMC 0609 question B. The issue caused a reactor trip but did not cause a loss of mitigating equipment.

Cross-Cutting Aspect: H.12 - Avoid Complacency: Individuals recognize and plan for the possibility of mistakes, latent issues, and inherent risk, even while expecting successful outcomes. Individuals implement appropriate error reduction tools. As documented in the root cause, the licensee made assumptions regarding the adequacy of the design.

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

EXIT MEETINGS AND DEBRIEFS

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

• On October 8, 2024, the inspectors presented the emergency preparedness program inspection results to Charles O'Dell, Director, Organizational Effectiveness, and other members of the licensee staff.

• On October 10, 2024, the inspectors presented the integrated inspection results to Heather Winn, Plant Manager, and other members of the licensee staff.

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