05000446/LER-2025-001, (Cpnpp), Containment Spray Pump Declared Inoperable Due to Misaligned Breaker

(Cpnpp), Containment Spray Pump Declared Inoperable Due to Misaligned Breaker

ML25286A003
Person / Time
Site:	Comanche Peak
Issue date:	10/13/2025
From:	Christopher Jackson Vistra Operations Company
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
CP-202500314, TXX-25054 LER 2025-001-00
Download: ML25286A003 (1)

LER-2025-001, (Cpnpp), Containment Spray Pump Declared Inoperable Due to Misaligned Breaker

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
4462025001R00 - NRC Website

text

COMANCHE PEAK NUCLEAR POWER PLANT CP-202500314 TXX-25054 October 13, 2025 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

Subject:

Comanche Peak Nuclear Power Plant (CPNPP)

Docket No. 50-446 Comanche Peak Nuclear Power Plant Christopher J Jackson Nuclear Site Vice President Vistra Operations Company LLC P.O. Box 1002 6322 North FM 56 Glen Rose, TX 76043 Office: 254.897.6411 Ref 10 CFR 50.73 Containment Spray Pump Declared Inoperable due to Misaligned Breaker License Event Report 2-25-001-00

Dear Sir or Madam:

Attached is a Licensee Event Report (LER) 2-25-001-00, "Containment Spray Pump Declared Inoperable due to Misaligned Breaker for Comanche Peak Nuclear Power Plant (CPNPP) Unit 2.

This communication contains no new commitments regarding CPNPP Units 1 or 2.

Should you have any questions, please contact Kassie Mandrell at (254)897-6987 or Kassie.Mandrell@vistracorp.com.

Sincerely, Christopher Jackson

Abstract

Phone Number (Include area code) 254-897-6987 Manufacturer Reportable to IRIS Month Day Year On August 12, 2025, the Unit 2, train B containment spray pump 2-04(CSP) failed to start in support of a refueling water storage tank (RWST) recirculation for a weekly chemistry sample. A field walkdown by Operations following the event identified that the Unit 2, 2-04 CSP breaker trip pushbutton was not flush with the front of the breaker face and the position locking collar was not fully engaged. The breaker was racked out and then restored to connect and retested satisfactorily. The past operability evaluation determined that the last time the breaker was racked in was March 25, 2025 resulting in a partially racked in position until the pump failed to start. Although the pump was successfully operated during the period from March 25,2025 to August 12,2025, the integrity of the partially racked in breaker condition could not be reasonably relied upon during a seismic event, leading to a failure to meet Technical Specification (TS) Limiting Condition of Operation (LCO) 3.6.6.

The cause of this error was determined to be a failure of Nuclear Equipment Operators to appropriately utilize human performance tools for procedure use and adherence when racking in breakers. Corrective actions implemented include verification of related breaker connections, coaching of the responsible individuals and breaker training for Nuclear Equipment Operators (NEO).

I. DESCRIPTION OF THE REPORTABLE EVENT

A

REPORTABLE EVENT CLASSIFICATION

050 052

2. DOCKET NUMBER

3. LER NUMBER I

00446 D

NUMBER NO.

I YEAR SEQUENTIAL REV

~-I 001 1-0 This event is reportable under 10 CFR 50.73(a)(2)(i)(B) for a condition prohibited by TS LCO 3.6.6, "Containment Spray System," which was not met from March 25, 2025 to August 12, 2025. TS LCO 3.6.6 condition A was not met, where condition A is restore to operable within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and condition B requires a shutdown to MODE 3 in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, if condition A is not met.

A subsequent evaluation of performed planned maintenance was completed on Unit 2 Train A safety systems during the inoperable period. The evaluation concluded that this event is also reportable under 10 CFR 50. 73(a)(2)(v)(C) and (D) as an event which could have prevented fulfillment of a safety function during the concurrent planned maintenance. Details of the safety system train inoperability periods are provided in section 111.B.

B.

PLANT CONDITION PRIOR TO EVENT Comanche Peak Nuclear Power Plant (CPNPP) Unit 2 was in MODE 1, operating at approximately 100% power at time of discovery.

C.

STATUS OF STRUCTURES, SYSTEMS, OR COMPONENTS THAT WERE INOPERABLE AT THE START OF THE EVENT AND THAT CONTRIBUTED TO THE EVENT There were no structures, systems, or components that were inoperable prior to the event that contributed to the event.

D.

NARRATIVE SUMMARY OF THE EVENT, INCLUDING DATES AND APPROXIMATE TIMES On August 12, 2025, the Unit 2 Train B containment spray pump 2-04 (CSP) [EIIS: (BE)(P)] failed to start. TS LCO 3.6.6.A, for one containment spray train inoperable, was entered on August 12, 2025 at 2028.

A Nuclear Equipment Operator (NEO) performed a walkdown of the system and reported that there was no trip indication on the Unit 2 Train B 6.9 kV electrical bus or on the CSP breaker [EIIS: (BE)(BKR)] but that the breaker trip pushbutton was not flush with the front of the breaker face and the position locking collar was not fully engaged. Maintenance reviewed the system and found no additional signs of why the breaker did not operate. The breaker was racked out and then restored to connect and retested satisfactorily. TS LCO 3.6.6.A was exited on August 12, 2025 at 2211.

On August 28, 2025, a past operability evaluation was completed for this condition. The evaluation determined that the CSP breaker was last racked in on March 25, 2025. Although the pump and breaker were successfully operated three times during the period from March 25,2025 to August 12,2025, the integrity of the partially racked in breaker condition could not be reasonably relied upon during a seismic event. The Unit 2 Train B containment spray system was determined to be inoperable for a period greater than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

I

2. DOCKET NUMBER

3. LER NUMBER IYEAR SEQUENTIAL REV NUMBER NO.

00446 l202sl -I 1-0 001 E.

THE METHOD OF DISCOVERY OF EACH COMPONENT OR SYSTEM FAILURE, OR PROCEDURAL PERSONNEL ERROR The initial walkdown following the CSP failure identified the partially racked in status of the breaker. A subsequent past operability evaluation determined that on March 25, 2025, the NEO failed to properly rack in and verify the CSP breaker connection in accordance with the System Operating Procedure (SOP). As a result of the misalignment, the breaker auxilliary contacts failed to remain connected following several cycles.

II. COMPONENT OR SYSTEM FAILURES A.

CAUSE OF EACH COMPONENT OR SYSTEM FAILURE The CSP breaker was left partially racked in and not fully connected. This status can allow for initial connection of the auxiliary contacts and operation of the breaker. However, with subsequent cycling, those contacts can become disconnected.

B.

FAILURE MODE, MECHANISM, AND EFFECTS OF EACH FAILED COMPONENT Inadequate procedure use and adherence led to the inoperable condition of the containment spray system.

C.

SYSTEMS OR SECONDARY FUNCTIONS THAT WERE AFFECTED BY FAILURE OF COMPONENTS WITH MULTIPLE FUNCTIONS This event did not involve systems or secondary functions that were impacted by the CSP failure.

D.

FAILED COMPONENT INFORMATION

The function of the CSP 2-04 motor breaker is to provide electrical power to the containment spray 2-04 motor. The secondary function of the breaker is to provide electrical protection from faults and trip on detection of faults.

The Containment Spray system provides containment atmosphere cooling to limit post accident pressure and temperature in containment to less than the design values. Reduction of containment pressure and the iodine removal capability of the spray reduces the release of fission product radioactivity from containment to the environment, in the event of a Design Basis Accident (OBA), to within limits.

Ill.

ANALYSIS OF THE EVENT

A.

SAFETY SYSTEM RESONSES THAT OCCURRED No safety system responses occurred due to this event.

I

2. DOCKET NUMBER

3. LER NUMBER IYEAR SEQUENTIAL REV NUMBER NO.

00446 l202sl -I 1-0 001 B.

DURATION OF SAFETY SYSTEM TRAIN INOPERABILITY The past operability evaluation determined the Unit 2 Train B CSP was inoperable from March 25, 2025 at 1052 until August 12, 2025 at 2211, approximately 140 days. An additional evaluation of planned performed maintenance was performed on related Unit 2, Train A safety systems during the same period. The following periods were identified when both trains of Containment Spray were unable to perform their specified safety function.

Containment Spray Unit 2, Train A April 1, 2025 - 6.1 hours1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> May 27, 2025 - 9.43 hours4.976852e-4 days <br />0.0119 hours <br />7.109788e-5 weeks <br />1.63615e-5 months <br /> May 29, 2025 - 0.37 hours4.282407e-4 days <br />0.0103 hours <br />6.117725e-5 weeks <br />1.40785e-5 months <br /> Component Cooling Water Unit 2, Train A April 26, 2025 - 0.2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> May 7, 2025 - 0.87 hours0.00101 days <br />0.0242 hours <br />1.438492e-4 weeks <br />3.31035e-5 months <br /> July 20, 2025 - 0.18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> July 22, 2025 - 0.53 hours6.134259e-4 days <br />0.0147 hours <br />8.763227e-5 weeks <br />2.01665e-5 months <br /> Safety Chilled Water Unit 2, Train A May 28, 2025-1.9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> Emergency Diesel Generator Unit 2, Train A March 30, 2025 - 0.63 hours7.291667e-4 days <br />0.0175 hours <br />1.041667e-4 weeks <br />2.39715e-5 months <br /> April 9, 2025 - 6. 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> April 10, 2025 - 0.53 hours6.134259e-4 days <br />0.0147 hours <br />8.763227e-5 weeks <br />2.01665e-5 months <br /> May 8, 2025 - 1.17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br /> May 9, 2025 - 0.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> May 10, 2025 - 0.87 hours0.00101 days <br />0.0242 hours <br />1.438492e-4 weeks <br />3.31035e-5 months <br /> June 4, 2025 - 0.73 hours8.449074e-4 days <br />0.0203 hours <br />1.207011e-4 weeks <br />2.77765e-5 months <br /> June 4, 2024 - 0.63 hours7.291667e-4 days <br />0.0175 hours <br />1.041667e-4 weeks <br />2.39715e-5 months <br /> June 5, 2025 - 0.8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> June 23, 2025 - 0.52 hours6.018519e-4 days <br />0.0144 hours <br />8.597884e-5 weeks <br />1.9786e-5 months <br /> July 2, 2025 - 8.4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> July 3, 2025 - 1.4 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> July 30, 2025 - 2.53 hours6.134259e-4 days <br />0.0147 hours <br />8.763227e-5 weeks <br />2.01665e-5 months <br /> July 31, 2025 - 0.58 hours6.712963e-4 days <br />0.0161 hours <br />9.589947e-5 weeks <br />2.2069e-5 months <br /> Solid State Protection System Unit 2, Train A April 7, 2025 - 2.67 hours7.75463e-4 days <br />0.0186 hours <br />1.107804e-4 weeks <br />2.54935e-5 months <br /> Total loss of safety function duration was approximately 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> and 8 minutes.

I

2. DOCKET NUMBER

3. LER NUMBER IYEAR SEQUENTIAL REV NUMBER NO.

00446 l202sl -I 1-0 001 C.

SAFETY CONSEQUENCES AND IMPLICATIONS OF THE EVENT There were no actual nuclear, radiological or personnel safety consequences associated with this event. The containment spray system limits the temperature, pressure and radiological impact that could be experienced following a OBA The station lost the safety function to mitigate these consequences for a loss of coolant accident (LOCA) or steam line break (SLB) during the periods identified in section 111.B. If during a OBA this specific condition were to occur, CPNPP processes provide for manual operator action to restore the breaker and mitigate the consequences of the failed CSP. An assessment of Core Damage Probability and Large Early Release Probability resulted in a small change in risk that remains within Region Ill of Regulatory Guide 1.174. Therefore, this event is not considered to have any significant effect on the health and safety of the public, nuclear safety, reactor safety, radiological safety or environmental safety.

IV.

CAUSE OF THE EVENT

The cause of this error was determined to be a failure of NEOs to appropriately utilize human performance tools for procedure use and adherence when racking in breakers. Interviews with the responsible operations personnel identified that although all indications of the breaker being fully racked in were checked, the attention to detail regarding indications of the breaker being fully racked in was less than adequate.

V.

CORRECTIVE ACTIONS

Corrective Actions include the following completed and planned items:

- Immediate actions were taken for an extent of condition verification of all safety related 6.9kV breakers to ensure locking collar was in the correct position. No exceptions were noted.

- Operations provided coaching to responsible individuals to reinforce expectations

- Planned NEO requalification training of breaker racking in the onsite breaker laboratory.

VI.

PREVIOUS SIMILAR EVENTS

Based on a review of events from the last three years, there have been no previous, similar events related to misalignment of a 6.9kV breaker or with inoperability of the CSP as a result of a human performance event. Page 5

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