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The following information was provided by the licensee via email: Notification per 10 CFR 50.72 (b)(3)(v)(A) and (v)(D) At time 1630 CDT on 4/18/23, Comanche Peak Unit 1 entered TS (Technical Specification) 3.0.3 for 11 minutes due to declaring Train A component cooling water (CCW) inoperable in conjunction with a Train B centrifugal charging pump (CCP) inoperable for scheduled maintenance. This resulted in an event or condition that could have prevented fulfillment of a safety function, high head injection of the emergency core cooling system. CCP 1-02 and fan cooler were tagged out of service at 0400 CDT on 4/18/23 due to scheduled maintenance activities. Containment spray (CT) pump 1-03 seal oil cooler CCW leak was found by a watchstander at 0930 CDT on 4/18/23. Engineering determined that leakage was CCW from a pipe flange weld after insulation removal and could not (determine) operability and notified control room at 1630 CDT on 4/18/23. This placed unit 1 in a TS 3.0.3 condition from 1630 to 1641 CDT for approximately 11 minutes until CCP 1-02 was restored back to operable status. CCW was declared operable at 1912 after CT pump 1-03 seal oil cooler was isolated. CT pump 1-03 remained inoperable until weld repair completed. Train A CT pump 1-03 declared operable at 1211 CDT 4/19/23. ENS notification should have been made by 0030 CDT on 4/19/23. This report restores compliance. The NRC Resident Inspector has been notified.

• * * RETRACTION ON 6/7/2023 AT 1000 EDT FROM CASEY DAVIES TO BILL GOTT * * *

The following information was provided by the licensee via phone and email: Although Comanche Peak Unit 1 conservatively entered a limiting condition for operation action statement and performed repairs immediately, further engineering inspection and evaluation concluded that the CCW system was fully able to provide the needed flow to the 1-03 CT pump seal coolers from the time of discovery (0930 CDT) until which time the piping was isolated for repairs. During this period, structural integrity of the joint was maintained, CCW inventory loss remained within acceptable limits, and CCW could perform its intended design and safety functions. Based on this revised operability determination, train A CCW was always operable, and TS 3.0.3 did not apply. Therefore, reportability requirements per 10 CFR 50.72 (b)(3)(v)(A) and (v)(D) did not apply, and a 60 day LER will not be submitted. The licensee notified the NRC Resident Inspector. Notified R4DO (Young)

This report describes an invalid actuation of the Unit 2 Turbine Driven Auxiliary Feedwater Pump that occurred on October 31, 2019. This report is being made in accordance with 10CFR50.73(a)(1), which states, in part, 'In the case of an invalid actuation reported under 10CFR50.73(a)(2)(iv), other than actuation of the Reactor Protection System (RPS) when the reactor is critical, the licensee may, at its option, provide a telephone notification to the NRC Operations Center within 60 days after discovery of the event instead of submitting a written LER.'

On October 31, 2019, Comanche Peak Nuclear Power Plant Unit 2 was in Mode 1 operating at 100% power. At 1919 CDT, the Main Steam Line 2-01 steam supply valve to the TDAFWP opened due to a loss of continuity between the fuse supplying control power to the valve positioner and the fuse clips. Operators initiated a 50MW load reduction to maintain power less than 100%. The steam supply to the TDAFWP was closed, the TDAFWP was stopped, and the fuse clips were tightened. Unit 2 was returned to full power at 2055 CDT.

The specific train and system that actuated was the third AFW train on Unit 2. The train actuation was complete and during the TDAFWP start the system started and functioned correctly. The NRC Resident Inspector was notified.

On March 28, 2017 at approximately 1957 CDT, a condition was discovered whereby a postulated moderate-energy line break (MELB) involving three fire protection (FP) pipe segments in the Safeguards Building did not contain MELB shielding. It was subsequently determined a postulated crack in one of the affected FP piping sections could adversely affect circuitry associated with the cooling support system for the train A RHR (Residual Heat Removal) pump room, potentially causing the ventilation system to be unavailable to support operation of the train A RHR pump. This condition is not consistent with the CPNPP licensing basis for the protection of essential safe shutdown RHR equipment. At approximately 1957 CDT train A RHR was declared inoperable but available and the unit entered a seventy-two hour LCO (Limiting Condition for Operation) Action Statement per Technical Specification 3.5.2 B pending completion of mitigative actions. Since Unit 1 train B RHR system components and related supporting equipment have been periodically declared inoperable at various times in the last three years for surveillance testing or maintenance, given the MELB condition, both trains of RHR and or support equipment could have been inoperable and this represents an unanalyzed condition per 10 CFR 50.72(b)(3)(ii)(B). At the time of discovery, train B RHR and support equipment were operable. Therefore, the identified condition is not reportable as a loss of safety function per 10 CFR 50.72(b)(3)(v). The Senior NRC Resident Inspector has been notified. Compensatory actions will include installing a spray shield on the affected cable trays.

• * * RETRACTION FROM JOHN ALEXANDER TO VINCE KLCO ON 5/23/17 AT 1720 EDT * * *

On 03/29/2017 Comanche Peak reported an ENS Report (no. 52646) related to the identification of potential moderate-energy line break (MELB) considerations in the Safeguards Building and the potential for adverse interaction with specified Unit 1 electrical equipment. The specific interactions of concern were related to ventilation equipment which would support operation of the Unit 1 A RHR train and several segments of fire protection piping. Subsequent investigations by Engineering have determined: (1) all but one of the suspected potential interactions were determined to not be credible, i.e., the potential MELB would not result in an adverse interaction with the 'target' equipment, and (2) for the remaining potential interaction, an assessment of piping stresses determined there was not a credible MELB source in the affected piping segment and therefore there was not a potential for adverse interaction with the ventilation support equipment. Based on the above, the condition described in ENS report no. 52646 is not considered to be an un-analyzed condition as described in 10 CFR 50.72(b)(3)(ii)(B). The licensee informed the NRC Resident Inspector. Notified the R4DO (Groom).

Based on a walk down in the Service Water Intake Structure (SWIS) with the NRC Resident (Inspector), it was observed that a vertical section of 4 inch Fire Protection pipe that provides a normally pressurized source of fire water supply to the overhead sprinkler system in the SWIS is not Moderate Energy Line Break (MELB) shielded similar to the horizontal segment of the same line near the ceiling. In the event of a MELB crack along any portion of the unshielded pipe, the MELB has a potential impact to the function of any one of the 4 Service Water pumps. Only one train at a time would be affected during the event. This is due to the physical characteristics of the postulated MELB and the configuration/separation relative to the source line and target pumps and/or associated Motor Control Centers (MCCs) that support pump operation. Since the Service Water trains have been periodically declared inoperable at various times in the last three years for surveillance testing or maintenance, if the MELB were to have occurred during these times and affected the opposite train, then two Service Water trains could have been inoperable and this represents an unanalyzed condition. At the time of discovery, all four Service Water trains were operable, therefore, this condition is not reportable as a loss of safety function per 10 CFR 50.72(b)(3)(vi). Currently, Service Water Train B on each Unit has been declared inoperable per Technical Specification (TS) 3.7.8. This condition will be corrected within the 72-hour Completion Time of TS 3.7.8. Currently, Emergency Diesel Generator B on each Unit has been declared inoperable per Technical Specification (TS) 3.8.1. This condition will be corrected within the 72-hour Completion Time of TS 3.8.1. The NRC Resident Inspector was informed.

• * * UPDATE ON 10/6/2016 AT 2009 EDT FROM DAMON SCHROEDER TO DONG PARK * * *

This is an update to Event Number 52239. On September 13, 2016 at 2228 EDT, Comanche Peak reported an unanalyzed condition involving station service water trains per 10CFR50.72(b)(3)(ii)(B). Specifically, the reported condition involved a vertical section of 4 inch Fire Protection pipe in the SWIS that was not adequately shielded for a Moderate Energy Line Break (MELB). In the event of a MELB crack along any portion of the unshielded pipe, the MELB had a potential impact to the function of any one of the 4 Service Water pumps. On October 6, 2016 at 1410 hours CDT, a section of eyewash station pipe in the Unit 2 Safeguards Building was identified as a result of extent of condition walkdowns that was not adequately shielded for a Moderate Energy Line Break (MELB). In the event of a MELB crack along any portion of this unshielded pipe, the MELB had the potential to impact Unit 2 Train B 480V Motor Control Center (MCC) 2EB2-1. This MCC provides power to Unit 2 Train B Emergency Core Cooling, Battery Charger, Containment Spray, and Containment Isolation Valve equipment. The affected eyewash station pipe was isolated shortly after it was discovered to not be adequately shielded for a MELB. Since 480V MCC 2EB1-1 and the Unit 2 Train A Emergency Core Cooling, Battery Charger, Containment Spray, and Containment Isolation Valve equipment trains have been periodically declared inoperable at various times in the last three years for surveillance testing or maintenance, if the MELB were to have occurred during these times and affected the opposite train, then 2EB1-1, 2EB2-1 and both trains of the Unit 2 Emergency Core Cooling, Battery Charger, Containment Spray, and Containment Isolation Valve equipment could have been inoperable and this represents an unanalyzed condition. At the time of discovery, 2EB1-1 and the Unit 2 Train A Emergency Core Cooling, Battery Charger, Containment Spray, and Containment Isolation Valve equipment was operable. Therefore, this condition is not reportable as a loss of safety function per 10 CFR 50.72(b)(3)(vi). The NRC Resident Inspector was informed. Notified R4DO (Werner).

• * * UPDATE FROM ROBERT DANIELS TO DONALD NORWOOD AT 2233 EDT ON 10/10/2016 * * *

This is an additional update to Event Number 52239. On September 13, 2016 at 2228 EDT and again on October 6, 2016 at 2009 EDT, Comanche Peak reported unanalyzed conditions involving Station Service Water System trains and a 480V Motor Control Center (MCC) per 10 CFR 50.72(b)(3)(ii)(B). The reported conditions involved sections of piping that were not adequately shielded for a Moderate Energy Line Break (MELB). In the event of a MELB crack along any portion of the unshielded piping, the MELB had a potential impact to the function of safety-related equipment in the Service Water Intake Structure and the Unit 2 Safeguards Building. On October 10, 2016 at 1708 CDT, as a result of ongoing extent of condition walkdowns, a section of fire protection pipe in the Unit 1 Safeguards Building was identified that was not adequately shielded for a MELB. In the event of a MELB crack along any portion of this unshielded pipe, the MELB had the potential to impact Unit 1 Train B Switchgear 1EA2, Unit 1 Train B 480V MCC 1EB4-2, and Unit 1 Train B Distribution Panel 1ED2-2. Only one of these power supplies at a time would be affected. 1EA2 provides 6.9KV electrical power to various Unit 1 Train B safety-related pumps, panels, sequencer, and transformers. 1EB4-2 provides 480V electrical power to various Unit 1 Train B safety-related pumps, valves, fans, panels, and transformers. 1ED2-2 provides 125VDC electrical power to EDG 1-02 channel 1 starting circuit. The affected fire protection pipe was isolated shortly after it was discovered to not be adequately shielded for a MELB. Since Unit 1 Train A Switchgear 1EA1, Unit 1 Train A 480V MCC 1EB3-2, and Unit 1 Train A Distribution Panel 1ED1-2 have been periodically declared inoperable at various times in the last three years for surveillance testing or maintenance, if the MELB were to have occurred during these times and affected the opposite train, then both trains of Unit 1 6.9KV power (1EA2 and 1EA1), both trains of Unit 1 480V power (1EB4-2 and 1EB3-2), and both trains of Unit 1 125VDC power (1ED2-2 and 1ED1-2) along with the safety-related equipment they supply could potentially have been inoperable and this represents an unanalyzed condition per 10 CFR 50.72(b)(3)(ii)(B). At the time of discovery, none of the affected Train A equipment was inoperable. Therefore, this condition is not reportable as a loss of safety function per 10 CFR 50.72(b)(3)(v). The NRC Resident Inspector was informed. Notified R4DO (Werner).

• * * UPDATE FROM HUNTER SCHILL TO DONALD NORWOOD AT 1457 EST ON 11/7/2016 * * *

This is an update to Event Number 52239. On November 17, 2016 at 0730 CST, during ongoing extent of condition walkdowns in the Boric Acid Transfer Pump Area of the Auxiliary Building, two pressurized fire protection pipe segments were identified that did not contain Moderate Energy Line Break (MELB) shielding. In the event of a MELB crack along the unshielded portion of these pipes, the MELB had the potential to impact Unit 1 Train B 480V Motor Control Center (MCC) 1 EB4-1. This MCC provides 480V electrical power to various Unit 1 Train B safety-related pumps, valves, fans, battery chargers, and transformers. At 0743 CST, Technical Specification 3.8.9 Condition A was entered for one AC electrical power distribution subsystem inoperable. At 1021 CST, MCC 1 EB4-1 was declared Operable after MELB shielding was installed on the affected fire protection lines. Since Unit 1 Train A 480V MCC 1 EB3-1 and the associated Unit 1 Train A safety-related pumps, valves, fans, battery chargers, and transformers have been periodically declared inoperable at various times in the last three years for surveillance testing or maintenance, given the MELB condition, 1 EB4-1, 1 EB3-1 and both trains of the Unit 1 safety-related pumps, valves, fans, battery chargers, and transformers they supply could have been inoperable and this represents an unanalyzed condition. At the time of discovery, 1 EB3-1 and the associated Unit 1 Train A safety-related pumps, valves, fans, battery chargers, and transformers were operable. Therefore, this condition is not reportable as a loss of safety function per 10 CFR 50.72(b)(3)(v). The NRC Resident Inspector was informed. Notified R4DO (Azua).

• * * UPDATE ON 12/05/2016 AT 1730 EST FROM HUNTER SCHILL TO STEVEN VITTO * * *

This is an update to Event Number 52239. On December 5, 2016 during ongoing extent of condition walk downs in the Auxiliary Building, pressurized fire protection pipe segments (a flange and a pipe elbow) were identified which did not contain Moderate Energy Line Break (MELB) shielding. In the event of a MELB crack along the un-shielded portion of the pipes, a MELB had the potential to impact Unit 2 Train B 480V Motor Control Center (MCC) 2EB4-1. This MCC provides 480V electrical power to various Unit 2 Train B safety-related pumps, valves, fans, battery chargers, and transformers. At approximately 1355 CST Technical Specification 3.8.9 Condition A was entered for one AC electrical power distribution subsystem inoperable. At 1459 CST, MCC 2EB4-1 was declared Operable after MELB shielding was installed on the affected fire protection line locations. Since Unit 2 Train A 480V MCC 2EB3-1 and the associated Unit 2 Train A safety-related pumps, valves, fans, battery chargers, and transformers have been periodically declared inoperable at various times in the last three years for surveillance testing or maintenance, given the MELB condition, 2EB4-1 , 2EB3-1 and both trains of the Unit 2 safety-related pumps, valves, fans, battery chargers, and transformers they supply could have been inoperable and this represents an un-analyzed condition. At the time of discovery, 2EB3-1 and the associated Unit 2 Train A safety-related pumps, valves, fans, battery chargers, and transformers were operable. Therefore, this condition is not reportable as a loss of safety function per 10CFR 50.72(b)(3)(v). The NRC Resident Inspector was informed. Notified R4DO (Gaddy).

• * * UPDATE ON 12/22/2016 AT 1649 EST FROM HUNTER SCHILL TO DONG PARK * * *

This is an update to Event Number 52239. On December 22, 2016 at approximately 1046 (CST) during ongoing extent of condition walk downs in the common Auxiliary Building (AB) corridor room (X-179), several normally pressurized Waste Processing (WP) pipe segments and one Vent & Drain (VD) segment which are greater than 1" nominal pipe diameter, did not contain MELB shielding. In the event of a MELB crack along the unshielded portion of these pipes, a MELB could have had the potential to impact Unit 1, Train B 480V Motor Control Center (MCC) 1EB4-1. This MCC provides 480V electrical power to various Unit 1 Train B safety-related pumps, valves, fans, battery chargers, and transformers. Prior to the field walkdown, the subject WP and VD line segments were either isolated and depressurized (WP lines) and/or the AB sump discharges realigned (VD) such that the subject lines would pose no threat to the MCC 1EB4-1 if confirmed that shielding is required. As such, the identified condition does not adversely affect operability of 1EB4-1 and entry into a Technical Specification action statement was not required. Field activities continue to install MELB shielding in the affected locations. Since Unit 1 Train A 480V MCC 1EB3-1 and the associated Unit 1 Train A safety-related pumps, valves, fans, battery chargers, and transformers have been periodically declared inoperable at various times in the last three years for surveillance testing or maintenance, given the MELB condition, 1EB4-1, 1EB3-1 and both trains of the Unit 1 safety-related pumps, valves, fans, battery chargers, and transformers they supply could have been inoperable and this represents an unanalyzed condition. At the time of discovery, 1EB3-1 and the associated Unit 1 Train A safety-related pumps, valves, fans, battery chargers, and transformers were operable. Therefore, this condition is not reportable as a loss of safety function per 10CFR 50.72(b)(3)(v). The NRC Resident Inspector was informed. Notified R4DO (Hay).

CPNPP (Comanche Peak Nuclear Power Plant) experienced an unplanned loss of the seismic monitoring instrument on May 24, 2016 at 1022 (CDT). The unplanned loss of the seismic monitor resulted in a loss of assessment capability for the HA1.1 (seismic event greater than operating basis earthquake) Alert emergency classification. The seismic monitor was restored to service on May 24, 2016 at 1043. This loss of assessment capability is reportable to the NRC within 8 hours of discovery in accordance with 10 CFR 50.72(b)(3)(xiii). The NRC Resident Inspector has been notified.

• * * UPDATE ON 6/2/16 AT 1630 EDT FROM ANTHONY PATE TO DONG PARK * * *

On May 24, 2016 at 1748 (EDT), Comanche Peak reported an unplanned loss of emergency assessment capability per 10 CFR 50.72(b)(3)(xiii) (EN# 51955). Specifically, Comanche Peak reported an unplanned loss of the seismic monitoring instrument. The unplanned loss of the seismic monitor would have resulted in a loss of assessment capability for the HA 1.1 (seismic event greater than operating basis earthquake) Alert emergency classification. The seismic monitor was restored to service on May 24, 2016 at 1043 (CDT). The engineering review determined that the alarms displayed on the seismic monitoring screen provides Operations awareness of the system status. Signals were still being received from the sensor and if there was an OBE (Operating Basis Earthquake) during the time the alarms were in, it would have displayed on the monitoring screen and on the Main Control Board by providing an OBE Exceedance alarm, maintaining emergency assessment capability. Therefore, Comanche Peak requests that the May 24, 2016, 10 CFR 50.72(b)(3)(xiii) reportable event for Units 1 & 2 be retracted. The licensee will notify the NRC Resident Inspector. Notified R4DO (Deese).

At CPNPP (Comanche Peak Nuclear Power Plant), eyewash stations are located just outside of the Class 1E battery rooms. The battery room doors are normally open and if a MELB (Moderate Energy Line Break) occurred on the demineralized water line connected to the eyewash station, the water could potentially spray onto the Class 1E safety related batteries. If this occurred, an electrical short could potentially cause a loss of both the batteries and the associated battery chargers. This condition has been conservatively determined to be reportable per 10 CFR 50.72(b)(3)(ii)(B) as an unanalyzed condition. Currently, the demineralized water lines on the battery room eyewash stations for both Units 1 and 2 have been isolated, therefore, all safety related equipment is currently operable. Comanche Peak Engineering is performing a past operability review of this condition. The NRC Resident Inspector has been notified.

• * * RETRACTION AT 1821 EST ON 02/27/2016 FROM DANNY BRADFORD TO JEFF HERRERA * * *

On February 23, 2016 at 2045 (EST), Comanche Peak reported an unanalyzed condition per 10 CFR 50.72(b)(3)(ii)(B). Specifically, the reported condition involved eyewash stations that are located just outside of the Class 1E battery rooms. The battery room doors are normally open and if a Moderate Energy Line Break (MELB) occurred on the demineralized water line connected to the eyewash station, the water could potentially spray onto the Class 1E safety related batteries. If this occurred, an electrical short could have potentially caused a loss of both the batteries and the associated battery chargers. This condition was conservatively determined to be reportable per 10 CFR 50.72(b)(3)(ii)(B) as an unanalyzed condition. The demineralized water lines on the battery room eyewash stations for both Units 1 and 2 were isolated, and Comanche Peak Engineering initiated a past operability evaluation of this condition. The past operability evaluation has been completed and shows that there are no operability concerns regarding a MELB impact on the Class 1E batteries, DC bus or Class 1E battery chargers. Therefore, Comanche Peak requests that the February 23, 2016, 10 CFR 50.72(b)(3)(ii)(B) reportable event for Units 1 & 2 be retracted. The NRC Resident Inspector has been notified. Notified the R4DO (Whitten).