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 Start dateSiteRegionReactor typeEvent description
ENS 5703317 March 2024 20:15:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopThe following information was provided by the licensee via phone and email: On March 17, 2024, at 1515 CDT, the Comanche Peak Unit 2 reactor was manually tripped due to an anticipated automatic trip due to lo-lo steam generator (SG) water levels. Prior to the trip, main feedwater pump '2B' tripped and an auto runback to 700 MW (60 percent power) was in progress. Both motor driven auxiliary feedwater pumps and the turbine driven auxiliary feedwater pump started due to lo-lo level in all SGs. Unit 2 is being maintained in hot standby (Mode 3) in accordance with integrated plant operating procedures IPO-007B. The emergency response guideline network has been exited. Decay heat is being rejected to the main condenser via the steam dump valves. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: The cause of the '2B' main feed pump trip was due to loss of primary and redundant power to the servo control valve. The loss of power to the servo control valve is under investigation.
ENS 5702412 March 2024 13:16:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopThe following information was provided by the licensee via phone and email: On March 12, 2024, at 0816 CDT, Comanche Peak Unit 2 reactor automatically tripped on lo-lo level in the 2-03 steam generator (SG). Prior to the trip, main feedwater pump (MFP) 2A speed reduced and a manual runback to 700 MW (60 percent) was in progress. Both motor driven auxiliary feedwater pumps and the turbine driven auxiliary feedwater pump started due to lo-lo level in all SGs. Concurrent with the loss of speed on MFP 2A, a servo filter swap was in progress on MFP 2A. Unit 2 is being maintained in hot standby (Mode 3) in accordance with integrated plant operating procedure IPO-007A. The emergency response guideline network has been exited. Decay heat is being rejected to the main condenser via the steam dump valves. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: The cause of the loss of the MFP is under investigation. Unit 1 was unaffected.
ENS 570105 March 2024 13:20:00Comanche PeakNRC Region 4Westinghouse PWR 4-Loop

The following information was provided by the licensee via email:

      • 8 Hour Notification was due at 1520 CST *** Follow up discussion of conditions after recovery determined that a report is required. This report restores reporting compliance.

On March 5, 2024, at 0720 CST, the X-02 118V uninterruptible power supply air conditioning (UPS A/C) unit tripped with the associated emergency fan coil units (EFCUs) shut down for planned maintenance in the area. The X-01 UPS A/C unit was declared inoperable upon discovery due to a scheduled outage of support systems (Unit 1 station service water) via the safety function determination process. This placed the site in technical specification 3.7.20 condition A, B, and C to restore the UPS A/C system within one hour. The EFCUs were restarted at 0729 which satisfied condition B and C, and X-01 UPS A/C unit was aligned to Unit 2 cooling water at 0801, exiting condition A. The condition that could have prevented the fulfillment of the safety function lasted for approximately nine minutes. Area temperatures had no notable change based on field observations during the condition. The UPS HVAC system provides temperature control for the safety related UPS and distribution rooms during all normal and accident conditions. The UPS HVAC system consists of (a) a dedicated UPS room EFCU in each safety-related UPS and distribution room, and (b) two electrically independent and redundant A/C trains either of which can support all four safety related UPS and distribution rooms; each train consists of an air conditioning unit, ductwork, dampers, and instrumentation. The NRC Resident Inspector has been notified.

ENS 568324 November 2023 03:31:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopThe following information was provided by the licensee via email: On 11/03/2023 at 2231 CDT, a security officer found 2 bottles of vanilla extract in the protected area. One bottle was a 1.5 ounce size with a trace amount of vanilla in the bottle, the other bottle was a 4.5 ounce size with approximately 1 ounce of vanilla. Alcohol was identified as an ingredient on the label. It was determined the vanilla extract is 35 percent alcohol by volume (ABV), above the 0.5 percent ABV considered low alcohol content. Security personnel took custody of the bottles of vanilla extract. The NRC Resident Inspector has been notified.
ENS 567155 September 2023 14:52:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopThe following information was provided by the licensee via email: A supplemental contract manager had a confirmed positive for an illegal substance during a random fitness-for-duty test. The employee's access to the plant has been terminated.
ENS 567025 July 2023 06:30:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopThe following information was provided by the licensee via email: On 07/05/2023, at 0130 hours, a security officer found a 1 ounce bottle of vanilla extract in the protected area. Alcohol was identified as an ingredient on the ingredients label. It was determined the alcohol by volume (ABV) for vanilla extract is 35 percent ABV, above the 0.5 percent ABV considered low alcohol content. Vanilla extract is not listed as a prohibited item within Comanche Peak procedures. The initial reporting assessment of not reportable has been questioned during an in-process security access inspection and reassessed as a reportable condition. Emergency Notification System notification should have been made by 0130 CDT on 07/06/2023. This report restores compliance. The NRC Resident will be notified.
ENS 5658016 June 2023 23:32:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopThe following information was provided by the licensee via email: (On June 16, 2023,) at 1832 CDT, Unit 1 reactor automatically tripped on lo-lo level in the '1-04' steam generator (SG). Prior to the trip, the 1B (main feedwater pump) (MFP) tripped due to speed oscillations and a runback to 700MW was in progress. Both motor driven auxiliary feedwater pumps started due to the lo-lo level in SG '1-04'. Unit 1 is being maintained in hot standby (Mode 3) in accordance with Integrated Plant Operating Procedure IPO-007A. The Emergency Response Guideline network has been exited. Decay heat is being rejected to the main condenser via the steam dump valves. The licensee notified the NRC Resident Inspector. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: Unit 1 is in a normal post-trip electrical line-up. There was no effect on Unit 2 due to the Unit 1 trip.
ENS 5648018 April 2023 21:30:00Comanche PeakNRC Region 4Westinghouse PWR 4-Loop

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)

ENS 560916 September 2022 04:45:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopThe following information was provided by the licensee via email: At 2345 CDT, Unit 1 Reactor tripped due to a turbine trip. All auxiliary feedwater pumps started due to steam generator Lo Lo levels. Unit 1 is being maintained in Hot Standby (Mode 3) in accordance with Integrated Plant Operating Procedure IPO-007A. The Emergency Response Guideline procedure has been exited. Decay heat is being rejected to the main condenser via steam dump valves. The cause of the Turbine Trip is currently under investigation. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: NRC Resident Inspector has been notified. Unit 2 is unaffected by this event.
ENS 556947 January 2022 07:20:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopThe following information was provided by the licensee via fax or email: At 0120 (CST) on 01/07/2022, a partial loss of the 25KV Power Distribution System caused a loss of both the Primary and Backup Meteorological Towers at the Comanche Peak Nuclear Power Plant. This resulted in a loss of emergency assessment capability with regard to meteorological conditions. A backup diesel generator for the primary Meteorological Tower did not start due to a dead battery. After the battery issue was resolved, the diesel generator started but it subsequently tripped due to a loose fuse. The 25 KV Plant Support Power Loop feeds certain non-safety-related equipment and does not affect plant operation. Power was restored to both Meteorological Towers at 0305 (CST) on 01/07/2022 and proper operation was verified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: The NRC Resident Inspector was notified.
ENS 5561024 November 2021 13:00:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopA violation occurred concerning Comanche's Peak's Fitness-For-Duty Program. Two empty mini-bottles of alcohol were discovered in a trash can within the protected area. The event has been documented in the corrective action program. The resident inspector has been notified.
ENS 5530513 June 2021 03:27:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopAt time 2227 CDT on 06/12/21, Main Steam Line 2-01 Radiation Monitor 2-RE-2325 was declared to be non-functional. With this radiation monitor non-functional, all of the emergency action levels for a steam generator tube rupture in Steam Generator 2-01 could neither be evaluated nor monitored. This unplanned condition is reportable as a loss of assessment capability per 10 CFR 50.72(b)(3)(xiii). Comanche Peak Nuclear Power Plant (CPNPP) has assurance of steam generator integrity and fuel cladding integrity. Compensatory measures are in place to assure adequate monitoring capability. Radiation Protection technicians have been briefed on taking local readings with a Geiger-Mueller tube on MSL 2-01. Corrective actions are being pursued to restore 2-RE-2325 to functional status. The NRC Resident Inspector has been notified.
ENS 5530412 June 2021 22:25:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopAt time 1725 CDT on 06/12/21, Main Steam Line 2-03 Radiation Monitor 2-RE-2327 was declared to be non-functional. With this radiation monitor non-functional, all of the emergency action levels for a steam generator tube rupture in Steam Generator 2-03 could neither be evaluated nor monitored. This unplanned condition is reportable as a loss of assessment capability per 10 CFR 50.72(b)(3)(xiii). Comanche Peak Nuclear Power Plant (CPNPP) has assurance of steam generator integrity and fuel cladding integrity. Compensatory measures are in place to assure adequate monitoring capability. Radiation Protection technicians have been briefed on taking local readings with a Geiger-Mueller tube on MSL 2-03. Corrective actions are being pursued to restore 2-RE-2327 to functional status. The NRC Resident Inspector has been notified.
ENS 552957 June 2021 20:27:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopAt 1527 (Central Standard Time) Unit 2 Reactor tripped caused by a turbine trip due to a fault and fire on Unit 2 Main Transformer #1. All Aux Feedwater Pumps started due to steam generator Lo-Lo levels. Unit 2 is being maintained in Hot Standby (Mode 3) in accordance with Integrated Plant Operating Procedure IPO-007B. The Emergency Response Guideline Network has been exited. Decay heat is being rejected to the Main Condenser via the steam dump valves. Fire was extinguished at 1546 without offsite assistance. No major injuries reported and no personnel transported offsite for medical attention. Cause of the fault and fire are under investigation. NRC Resident Inspector has been notified. All rods inserted into the core during the trip. There were no relief valves or safety valves lifted during the transient. The plant is stable in its normal shutdown electrical lineup via the auxiliary transformer with all safety equipment available. Unit 1 was not affected by the transient.
ENS 5492930 September 2020 13:15:00Comanche PeakNRC Region 4At time 0815 (CDT) on 09/30/20, Main Steamline Radiation Monitor 2-RUK-2325/2327 (Main Steam Line 2-01/2-03 Radiation Monitor) was removed from service for planned maintenance. Compensatory measures were in place prior to removing the monitor from service to assure adequate monitoring capability available to implement the CPNPP (Comanche Peak Nuclear Power Plant) emergency plan in the unlikely event of challenges to the steam generator or fuel cladding. The N16 radiation monitor serves as a backup with alarm function and Radiation Protection technicians have been briefed on taking local readings with a Geiger-Mueller tube on MSL 2-01 and MSL 2-03. With this radiation monitor non-functional, compensatory measures in place and the monitor not restored to service within 72 hours, the condition is reportable as a loss of assessment capability per 10CFR50.72(b)(3)(xiii). Comanche Peak Nuclear Power Plant (CPNPP) has assurance of steam generator integrity and fuel cladding integrity and there is negligible safety significance to the current condition with respect to the public health and safety perspective. Corrective actions are being pursued to complete maintenance and restore 2-RUK-2325/2327 to functional status. The NRC Resident Inspector has been notified.
ENS 544601 January 2020 18:53:00Comanche PeakNRC Region 4At 1253 (CST) Unit 2 Reactor was manually tripped due to a trip of both Main Feed Pumps. During an evolution to secure Circulating Water Pump 2-01, vacuum was reduced in the auxiliary condensers for both Main Feed Pumps causing both Main Feed Pumps to trip. Both Motor Driven and the Turbine Driven Auxiliary Feedwater Pumps started due to steam generator Lo-Lo levels. Unit 2 is being maintained in Hot Standby (Mode 3) in accordance with Integrated Plant Operating Procedure IPO-0078. The Emergency Response Guideline Network has been exited. Decay heat is being rejected to the Main Condenser via the Steam Dump Valves. The licensee notified the NRC Resident Inspector.
ENS 5443310 December 2019 15:20:00Comanche PeakNRC Region 4

At 0920 CST on December 10, 2019, Comanche Peak began a planned modification on the Unit 1 Plant Computer System. During this modification, the ability to perform emergency assessment in the Technical Support Center (TSC) and the Emergency Operations Facility (EOF) will be impacted. Since the ability to perform emergency assessment is not expected to be restored within 72 hours, this is reportable per 10CFR50.72(b)(3)(xiii) as an event that results in a loss of emergency assessment capability. During this modification, the Control Room will continue to have the ability to perform emergency assessment. If an Alert, Site Area Emergency, or General Emergency is declared during this modification, communicators dedicated to performing emergency assessment will be stationed in the Control Room, TSC, and EOF. The Plant Computer System modification is scheduled to be completed on December 22, 2019, and a follow-up ENS notification will be made once the Unit 1 Plant Computer System is declared functional. The NRC Resident Inspector has been informed.

  • * * UPDATE ON 1/24/20 AT 1034 EST FROM THOMAS BOWDEN TO RODNEY CLAGG * * *

Licensee provided an update to inform that as of 0853 CST on 1/24/20, the modification is complete and the emergency assessment capabilities of the TSC and EOF have been restored. Notified R4DO (Silva)

ENS 5443010 December 2019 03:26:00Comanche PeakNRC Region 41-RE-2328 Main Steam Line #1-04 MSL181 received an operate failure on loss of counts. At time 2126 (CDT), the radiation monitor was declared non-functional. With this radiation monitor non-functional, all of the emergency action levels for a steam generator tube rupture in steam generator 1-04 could neither be evaluated nor monitored. This unplanned condition is reportable as a loss of assessment capability per 10 CFR 50.72(b)(3)(xiii). Comanche Peak Nuclear Power Plant (CPNPP) has assurance of steam generator integrity and fuel cladding integrity. There is a negligible safety significance to the current condition from a public health and safety perspective. Additionally, compensatory measures are in place to assure adequate monitoring capability is available to implement the CPNPP emergency plan in the unlikely event of challenges to the steam generator or fuel cladding. The N16 radiation monitor serves as a backup with alarm function and additionally Radiation Protection technicians have been briefed on taking local readings with a Geiger-Mueller tube on MSL 1-04. Corrective actions are being pursued to restore 1-RE-2328 to functional status. The NRC Resident Inspector has been notified.
ENS 543673 November 2019 14:00:00Comanche PeakNRC Region 4

EN Revision Text: PLANNED LOSS OF EMERGENCY RESPONSE FACILITIES AND EQUIPMENT At 0800 CST on November 3, 2019, Comanche Peak began a planned modification on the Unit 2 Plant Computer System. During this modification, the ability to perform emergency assessment in the Technical Support Center (TSC) and the Emergency Operations Facility (EOF) will be impacted. Since the ability to perform emergency assessment is not expected to be restored within 72 hours, this is reportable per 10 CFR 50.72(b)(3)(xiii) as an event that results in a loss of emergency assessment capability. During this modification, the Control Room will continue to have the ability to perform emergency assessment. If an Alert, Site Area Emergency, or General Emergency is declared during this modification, communicators dedicated to performing emergency assessment will be stationed in the Control Room, TSC, and EOF. The Plant Computer System modification is scheduled to be completed on November 24, 2019 and a follow-up ENS notification will be made once the Unit 2 Plant Computer System is declared functional. The NRC Resident Inspector has been informed.

  • * * UPDATE FROM MATT KARL TO HOWIE CROUCH AT 1104 EST ON 12/10/19 * * *

Unit 2 Plant Computer System has returned to service at 0756 CST on 12/10/19. The NRC Resident Inspector has been notified. Notified R4DO (Groom).

ENS 544311 November 2019 00:19:00Comanche PeakNRC Region 4

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.

ENS 5432914 October 2019 14:11:00Comanche PeakNRC Region 4At time 0911 (CDT), Main Steamline Radiation Monitor 2-RUK-2325/2327 (MAIN STEAM LINE 2-01/2-03 RADIATION MONITOR) was removed from service for planned maintenance. Compensatory measures were in place prior to removing the monitor from service to assure adequate monitoring capability available to implement the CPNPP emergency plan in the unlikely event of challenges to the steam generator or fuel cladding. The N16 radiation monitor serves as a backup with alarm function and Radiation Protection technicians have been briefed on taking local readings with a Geiger-Mueller tube on MSL (Main Steam Line) 2-01 and MSL 2-03. With this radiation monitor non-functional, with compensatory measures in place, and the monitor NOT expected to be returned to service within 72 hours, the condition is reportable as a loss of assessment capability per 10CFR50.72(b)(3)(xiii). Comanche Peak Nuclear Power Plant (CPNPP) has assurance of steam generator integrity and fuel cladding integrity and there is negligible safety significance to the current condition with respect to the public health and safety perspective. Corrective actions are being pursued to complete maintenance and restore 2-RUK-2325/2327 to functional status. The NRC Resident Inspector has been notified.
ENS 5406415 May 2019 02:51:00Comanche PeakNRC Region 4At 2151 CDT, on 14 May 2019, Comanche Peak Nuclear Power Plant (CPNPP) experienced a voltage transient within the onsite 138kV switchyard due to the loss of one of the offsite switchyards supplying power to the CPNPP 138kV switchyard. The reduction in safeguards bus voltage due to the transient caused the Unit 2 safeguard busses to load shed and perform a slow transfer to power supplied from 345kV transformer XST2A. Unit 2 was subjected to actuation of both blackout sequencers causing an automatic start of both motor driven Auxiliary Feedwater (AFW) pumps as well as the turbine-driven AFW pump. No emergency diesel generators started by design. All AFW pumps have been returned to standby status. All other safety systems functioned as designed. Unit 1 is currently defueled, and was unaffected by this event. The licensee has notified the NRC resident inspector.
ENS 539062 March 2019 09:17:00Comanche PeakNRC Region 4At 0317 CST, the Unit 2 Reactor tripped due to Feedwater Isolation Valve (FWIV) 2-04 going closed. All Auxiliary Feedwater Pumps started due to steam generator Lo-Lo levels. Unit 2 is being maintained in Hot Standby (Mode 3) in accordance with Integrated Plant Operating Procedure IPO-007B. The Emergency Response Guideline Procedure Network has been exited. Decay heat is being rejected to the Main Condenser via the Steam Dump Valves. The cause of the FWIV going closed is currently under investigation. All control rods fully inserted and the reactor trip was uncomplicated. Unit 2 is in a normal post-trip electrical line-up. There was no impact on Unit 1 due to the Unit 2 reactor trip. The licensee notified the NRC Resident Inspector.
ENS 537673 December 2018 06:00:00Comanche PeakNRC Region 4At 0315 (CST) on 12/3/18, the Comanche Peak Nuclear Power Plant experienced a loss of 138 KV transformer XST1. Unit 1 is currently at 100% power. Unit 2 was subjected to actuation of both blackout sequencers causing an automatic start of both motor driven Auxiliary Feedwater (AFW) pumps as well as the turbine driven AFW pump. No emergency diesel generators started as per design. Train A and B motor driven and the turbine driven AFW pumps have been returned to automatic. All other safety systems functioned per design. The loss of power to 138 KV transformer XST1 resulted in loss of power to both safeguards busses on Unit 2. The busses performed a load-shed and slow transfer to power supplied from 345 KV transformer XST2A as designed and were re-energized and loads sequenced back onto the busses. The emergency diesel generators are not required to start unless the busses are not re-energized by the alternate offsite transformer. All electrical power related actuations functioned as designed. There was no impact on Unit 1. The licensee has notified the NRC Resident Inspector.
ENS 5355013 August 2018 05:00:00Comanche PeakNRC Region 4At 23:58 (Central Daylight Time) Unit 2 Reactor Tripped (automatic reactor trip) due to a Turbine Trip/ Generator Lock Out. All Auxiliary Feedwater Pumps started due to steam generator Lo Lo levels. Unit 2 is being maintained in Hot Standby (Mode 3) in accordance with Integrated Plant Operating Procedure IP0-007B. The Emergency Response Guideline Procedure Network has been exited. Decay heat is being rejected to the Main Condenser via Steam Dump Valves. The cause of the Generator Lockout is currently under investigation. All control rods fully inserted in response to the automatic reactor trip. The licensee notified the NRC resident.
ENS 5347226 June 2018 05:00:00Comanche PeakNRC Region 4At time 0003 (CDT), Main Steamline Radiation Monitor 2-RE-2326 (Main Steam line 2-02) reading spiked and (was) declared non-functional. With this radiation monitor non-functional, all of the emergency action levels for a steam generator tube rupture in steam generator 2-02 could neither be evaluated nor monitored. This unplanned condition is reportable as a loss of assessment capability per 10CFR50.72(b)(3)(xiii). Comanche Peak Nuclear Power Plant (CPNPP) has assurance of steam generator integrity and fuel cladding integrity and there is negligible safety significance to the current condition (with respect to the) public health and safety perspective. Additionally, compensatory measures are in place to assure adequate monitoring capability is available to implement the CPNPP emergency plan in the unlikely event of challenges to the steam generator or fuel cladding. The N16 radiation monitor serves as a backup with alarm function and Radiation Protection technicians have been briefed on taking local readings with a Geiger-Mueller tube on MSL 2-02. Corrective actions are being pursued to restore 2-RE-2326 to functional status. The NRC Resident Inspector has been notified.
ENS 5342323 May 2018 13:48:00Comanche PeakNRC Region 4Westinghouse PWR 4-Loop

At time 0848 (CDT), Main Steamline Radiation Monitor 2-RE-2328 (Main Steamline 2-04) lost communications and was declared non-functional.

With this radiation monitor non-functional, all of the emergency action levels for a steam generator tube rupture in steam generator 2-04 could neither be evaluated nor monitored. This unplanned condition is reportable as a loss of assessment capability per 10CFR50.72(b)(3)(xiii). Comanche Peak Nuclear Power Plant (CPNPP) has assurance of steam generator integrity and fuel cladding integrity and there is a negligible safety significance to the current condition from a public health and safety perspective. Additionally, compensatory measures are in place to assure adequate monitoring capability is available to implement the CPNPP emergency plan in the unlikely event of challenges to the steam generator or fuel cladding. The N16 radiation monitor serves as a backup with alarm function and Radiation Protection technicians have been briefed on taking local readings with a Geiger-Mueller tube on MSL 2-04. Corrective actions are being pursued to restore 2-RE-2328 to a functional status. The NRC Resident Inspector has been notified.

ENS 533803 May 2018 17:20:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopDuring planned maintenance on Unit 2 Radiation Monitor 2-RE-4270 (Service Water Train B to Discharge Canal Rad Monitor), at 1220 CDT, several other Unit 2 Radiation Monitors that are used for Emergency Action Level evaluation became nonfunctional for about 1 hour. With these radiation monitors non-functional, all of the Emergency Action Levels associated with these monitors could neither be evaluated nor monitored. This unplanned condition is reportable as a loss of assessment capability per 10 CFR 50.72(b)(3)(xiii). A PC11 computer reboot restored the affected radiation monitors to a functional status. The NRC Resident Inspector has been notified.
ENS 5321215 February 2018 09:06:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopAt time 0306 (CST), Main Steamline Radiation Monitor 2-RE-2326 (Main Steamline 2-02) reading spiked and declared non-functional. With this radiation monitor non-functional, all of the emergency action levels for a steam generator tube rupture in steam generator 2-02 could neither be evaluated nor monitored. This unplanned condition is reportable as a loss of assessment capability per 10CFR50.72(b)(3)(xiii). Comanche Peak Nuclear Power Plant (CPNPP) has assurance of steam generator integrity and fuel cladding integrity and there is a negligible safety significance to the current condition from a public health and safety perspective. Additionally, compensatory measures are in place to assure adequate monitoring capability is available to implement the CPNPP emergency plan in the unlikely event of challenges to the steam generator or fuel cladding. The N16 radiation monitor serves as a backup with alarm function and Radiation Protection technicians have been briefed on taking local readings with a Geiger-Mueller tube on MSL 2-02. Corrective actions are being pursued to restore 2-RE-2326 to functional status. The NRC Resident Inspector has been notified.
ENS 531546 January 2018 17:26:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopAt 1126 (CST), main steamline radiation monitor 2-RE-2326 (Main Steamline 2-02) reading was determined to be erratic and was declared non-functional. With this radiation monitor non-functional, all of the emergency action levels for a steam generator tube rupture in steam generator 2-02 could neither be evaluated nor monitored. This unplanned condition is reportable as a loss of assessment capability per 10 CFR 50.72(b)(3)(xiii). Comanche Peak Nuclear Power Plant (CPNPP) has assurance of steam generator integrity and fuel cladding integrity and there is a negligible safety significance to the current condition from a public health and safety perspective. Additionally, compensatory measures are in place to assure adequate monitoring capability is available to implement the CPNPP emergency plan in the unlikely event of challenges to the steam generator or fuel cladding. The N16 (Nitrogen-16) radiation monitor serves as a backup with alarm function and Radiation Protection technicians have been briefed on taking local readings with a Geiger-Mueller tube on MSL (Main Steam Line) 2-02. Corrective actions are being pursued to restore 2-RE-2326 to functional status. The NRC Resident Inspector has been notified.
ENS 531432 January 2018 17:37:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopAt 1137 CST on January 2, 2018, Comanche Peak Nuclear Power Plant (CPNPP) Unit 2 experienced an unplanned loss of the Plant Computer System (PCS). The loss of the Unit 2 PCS resulted in a loss of emergency assessment capability to the CPNPP Technical Support Center (TSC) and Emergency Operations Facility (EOF) for greater than 60 minutes. This report is being made pursuant to 10 CFR 50.72(b)(3)(xiii), any event that results in a loss of emergency assessment capability, off-site response capability, or off-site communications ability. The NRC Resident Inspector has been informed. Repairs are on-going.
ENS 531056 December 2017 02:00:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopAt 2000 (CST), Comanche Peak experienced a failure of SCADA B of the PC11 Radiation Monitor System. This failure caused a loss of Unit 1 Main Steam Line 1-01 and 1-03 Radiation Monitors (1-RE-2325 and 1-RE-2327) and Train A and Train B Station Service Water Radiation Monitors (1-RE-4269 and 1-RE-4270). With the Main Steam Line Radiation Monitors nonfunctional, all of the emergency action levels for a steam generator tube rupture in steam generators 1-01 and 1-03 could neither be evaluated nor monitored. With the Station Service Water Radiation Monitors non-functional, all of the emergency action levels for a radioactive release through station service water could neither be evaluated nor monitored. This unplanned condition is reportable as a loss of assessment capability per 10 CFR 50.72(b)(3)(xiii). Comanche Peak Nuclear Power Plant (CPNPP) has assurance of steam generator integrity, reactor coolant system integrity, and fuel cladding integrity and there is a negligible safety significance to condition from a public health and safety perspective. Additionally, compensatory measures are in place to assure adequate monitoring capability is available to implement the CPNPP emergency plan in the unlikely event of challenges to the steam generator, reactor coolant system, or the fuel cladding. Until these radiation monitors were restored, Operations implemented compensatory measures to monitor the Condenser Off Gas Radiation Monitor for early signs of a steam generator tube leak/rupture and Radiation Technicians were briefed on taking local readings with a Geiger-Mueller tube on the Main Steam Lines. Chemistry Technicians were performing hourly samples of Station Service Water and reporting results to the Control Room. Corrective actions were pursued to restore the non-functional radiation monitors back to service. Those actions are complete and all radiation monitors have been restored to service. The NRC Resident Inspector has been notified. PC11 is a computer common to both Units. The failure happened during radiation monitor maintenance to a single monitor, which unexpectedly affected multiple monitors.
ENS 5309126 November 2017 02:25:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopAt time 2025 (CST) on 11/25/17, Unit 2 reactor was manually tripped due to a loss of all Main Feedwater. Operators observed both Main Feed Pumps tripped and SG (Steam Generator) levels decreasing, resulting in the direction for a manual reactor trip. The reactor trip actuated a turbine trip, both Motor Driven Auxiliary Feedwater Pumps started on the loss of both Main Feed Pumps, and Steam Generator Lo Lo levels started the Turbine Driven Auxiliary Feedwater Pump. All systems responded as expected. There was no work in progress at the time of the incident. Currently Unit 2 is being maintained in Hot Standby (Mode 3) in accordance with Integrated Plant Operating Procedure IP0-0078 and the Emergency Response Guideline Procedure Network has been exited. Decay Heat is being rejected to the Main Condenser via Steam Dump Valves. The licensee has notified the NRC Resident Inspector.
ENS 529452 September 2017 02:40:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopAt time 2140 (CDT) on September 1, 2017, CPNPP (Comanche Peak Nuclear Power Plant) Unit 2 experienced two (2) dropped rods, one control, one shutdown. The reactor was then manually tripped. This event is being reported in accordance with 10CFR50.72(b)(2)(iv)(B) for reactor trip and 10CFR 50.72(b)(3)(iv)(A) for an actuation of auxiliary feedwater. Currently Unit 2 is being maintained in Hot Standby (Mode 3) in accordance with Integrated Plant Operating Procedure IP0-007B, Emergency Response Guideline Procedure Network has been exited. Decay Heat is being rejected to the Main Condenser via Steam Dump Valves (Turbine Bypass Valves). The NRC Resident Inspector has been notified. All rods inserted into the core during the trip. No relief or safety valves actuated during the plant transient. The electrical grid is stable and supplying plant loads. Unit 1 was not affected by the transient.
ENS 5293730 August 2017 07:10:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopAt 0210 CDT on August 30, 2017, Comanche Peak Nuclear Power Plant (CPNPP) Unit 2 experienced an unplanned loss of the Plant Computer System (PCS). The loss of the Unit 2 PCS resulted in a loss of emergency assessment capability to the CPNPP Technical Support Center (TSC) and Emergency Operations Facility (EOF) for greater than 60 minutes. As of 0530 CDT the Unit 2 PCS has been restored. Assessment capability has been verified to be available in the TSC and EOF. This report is being made pursuant to 10CFR50.72(b)(3)(xiii), any event that results in a loss of emergency assessment capability, off site response capability, or off site communications ability. The NRC Resident Inspector has been informed.
ENS 5289811 August 2017 16:24:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopAt 1124 CDT on 11 August 2017, CPNPP (Comanche Peak Nuclear Power Plant) Unit 2 experienced an automatic turbine trip and trip of both main feedwater pumps on high steam generator water level (P-14, 81.5 percent level) in steam generator 2-02. Following the turbine trip, the auxiliary feedwater system actuated as required. The plant was stabilized at 2-3 percent reactor power with auxiliary feedwater feeding all steam generators with all levels within their normal bands. The cause of the high steam generator level appears to be a mechanical malfunction of steam generator 2-02 flow control valve bypass valve 2-LV-2163 (SG 2-02 FW BYP CTRL VLV) to close when demanded. Troubleshooting and repair of 2-LV-2163 is in progress. This event is being reported in accordance with 10 CFR 50.72(b)(3)(iv)(A) for an actuation of auxiliary feedwater. The NRC Resident Inspector has been notified.
ENS 5281721 June 2017 15:00:00Comanche PeakNRC Region 4Westinghouse PWR 4-Loop

During the review of an electrical circuit coordination calculation to support an ongoing revision of the Fire Safe Shutdown Analysis (FSSA), a lack of appropriate circuit protection coordination was identified in the coordination of electrical protective devices on 118 VAC electrical panels operating in bypass mode of operation. One or more of these electrical panels could be lost for various 10 CFR Appendix R III.G.2 fires outside the Control Room at CPNPP (Comanche Peak Nuclear Power Plant) due to circuit coordination issues. This could adversely affect safe shutdown equipment and potentially cause the loss of the ability to conduct a safe shutdown as required by 10 CFR 50 Appendix R. Immediate compensatory actions are being taken to establish (or confirm already existing) fire watches in the Fire Areas containing the associate circuits which can potentially jeopardize the FSSA. This condition is reportable in accordance with 10 CFR 50.72(b)(3)(ii)(B) as an unanalyzed condition. The NRC Resident Inspector has been notified.

  • * * RETRACTION ON 8/2/17 AT 1638 EDT FROM BRIAN MITCHELL TO BETHANY CECERE * * *

On 06/21/2017 Comanche Peak reported an ENS Report (no. 52817) related to the potential loss of 118 VAC electrical panels operating in bypass mode of operation for various 10 CFR (50) Appendix R III.G.2 fires outside the Control Room due to circuit coordination issues. This could adversely affect safe shutdown equipment and potentially cause the loss of the ability to conduct a safe shutdown as required by 10 CFR 50 Appendix R. Subsequent analysis by Engineering has determined that the affected panels remain coordinated for fire generated faults and can be credited as available by the Fire Safe Shutdown Analysis for a fire outside of the Control Room. Based on the above, the condition described in the ENS report no. 52817 is not considered to be an unanalyzed condition as described in 10 CFR 50.72(b)(3)(ii)(B). The licensee notified the NRC Resident Inspector. Notified R4DO (Azua).

ENS 5264629 March 2017 00:57:00Comanche PeakNRC Region 4Westinghouse PWR 4-Loop

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).

ENS 5248411 January 2017 21:00:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopOn September 16, 2016, Comanche Peak reported an unanalyzed condition and potential loss of safety function per 10 CFR 50.72(b)(3)(ii)(B) and 10 CFR 50.72(b)(3)(v) related to Teflon (PTFE) installed in the pressure gauge diaphragm seal assemblies for all four of the Centrifugal Charging Pumps and both of the Positive Displacement Charging Pumps on Units 1 and 2 (EN#52244). On November 14, 2016, this event was subsequently retracted. On December 12, 2016, during the ongoing extent of condition review, Teflon was also found to be installed in the suction and discharge pressure gauge diaphragm seal assemblies for the Unit 1 and 2 Containment Spray Pumps. On January 11, 2017 at approximately 1500 CDT, the reportability evaluation determined that reasonable assurance did not exist that the Containment Spray system would have been able to fulfill its design function of removing heat from the containment environment without impacting the applicable dose limits. Teflon (PTFE) is a restricted material normally prohibited from use in contact with reactor coolant or in radiation environments. Teflon (PTFE) is not radiation tolerant and degrades in a radiation environment. The Teflon (PTFE) used in these diaphragm seal assemblies could fail during a postulated Loss of Coolant Accident (LOCA) which could cause the Containment Spray Pumps on Units 1 and 2 to be inoperable, and exceed system leakage limits. This could challenge dose limits and in plant post-accident accessibility. This represents an unanalyzed condition. The pressure gauges and diaphragm seals for all of the Unit 1 and 2 Containment Spray Pumps have been isolated and the Unit 1 and 2 Containment Spray Pumps are operable. The Teflon (PTFE) has likely existed in these diaphragm seals since initial plant licensing. Luminant Power is continuing to investigate the extent of this condition and potential repair techniques. The NRC Resident Inspector has been notified.
ENS 5236313 November 2016 16:12:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopAt 1012 (CST), Unit 1 Main Steam Line 1-01 Radiation Monitor (1-RE-2325) failed high. With this radiation monitor non-functional, all of the emergency action levels for a steam generator tube rupture in steam generator 1-01 could neither be evaluated nor monitored. This unplanned condition is reportable as a loss of assessment capability per 10 CFR 50.72(b)(3)(xiii). Comanche Peak Nuclear Power Plant (CPNPP) has assurance of steam generator integrity and fuel cladding integrity and there is a negligible safety significance to the current condition from a public health and safety perspective. Additionally, compensatory measures are in place to assure adequate monitoring capability is available to implement the CPNPP emergency plan in the unlikely event of challenges to the steam generator or fuel cladding. Until this radiation monitor can be restored, Operations has implemented compensatory measures to monitor the main steamline 1-01 N-16 (Nitrogen-16) radiation monitor for early signs of a steam generator tube leak/rupture and pre-brief radiation protection technicians on taking local readings with a Geiger-Muller tube on Main Steam Line 1-01 and reporting the reading to the Control Room. Corrective actions are being pursued to restore 1-RE-2325 to functional status. The NRC Resident Inspector has been notified. Radiation monitor 1-RE-2325 is not in the plant technical specifications but is important to safety and the Emergency Plan.
ENS 5224415 September 2016 20:40:00Comanche PeakNRC Region 4Westinghouse PWR 4-Loop

During a review of commercial grade dedication records for a Unit 1 (Emergency Core Cooling System ECCS) Centrifugal Charging Pump discharge pressure gauge, it was identified that the process side of the diaphragm seal utilizes a Teflon (PTFE) gasket. Further review found Teflon (PTFE) to be installed in the pressure gauge seal assembly for all four of the Centrifugal Charging Pumps and both of the Positive Displacement Charging Pumps on Units 1 and 2. Teflon (PTFE) is a restricted material normally prohibited from use in contact with reactor coolant or in radiation environments. Teflon (PTFE) is not radiation tolerant and significantly degrades in a radiation environment. The Teflon (PTFE) used in these pressure gauges could fail during a LOCA (Loss of Coolant Accident) which could cause the (ECCS) Centrifugal Charging Pumps and both of the Positive Displacement Charging Pumps on Units 1 and 2 to be inoperable, and exceed system leakage limits. Excessive leakage from systems which would contain post-LOCA recirculation fluid would challenge onsite and offsite dose estimates and in-plant post-accident accessibility. This represents an unanalyzed condition. Currently, the pressure gauges for all four of the (ECCS) Centrifugal Charging Pumps and both of the Positive Displacement Charging Pumps on Units 1 and 2 have been isolated until this issue can be further evaluated. Luminant Power believes that the Teflon (PTFE) has existed in the pressure gauges since initial plant licensing. Luminant Power is currently investigating the extent of the condition and repair techniques. The NRC Resident Inspector has been notified.

  • * * RETRACTION AT 1634 EST ON 11/14/16 FROM DANNY BRADFORD TO JEFF HERRERA * * *

On 09/16/2016, Comanche Peak reported an ENS Report (no. 52244) related to the identification of teflon-containing pressure-seal assemblies installed on the suction and discharge sides of the centrifugal charging pumps and on the suction side of the positive displacement pump. The technical concern was the potential for the teflon-containing assemblies to leak if subjected to post-LOCA recirculation fluid and associated radiation levels. Subsequent investigations by Engineering have determined: (1) the centrifugal charging pumps were operable for all postulated non-LOCA design bases events which required their operation and (2) for postulated LOCA scenarios which would involve radiation levels sufficient as to call into question the ability of the teflon-containing assemblies to maintain system pressure boundary, the ECCS function would be fulfilled in the event one or all of the charging pumps had to be removed from service (due to system leakage) and limiting (control room) doses would have remained below applicable regulatory limits. Based on the above, the condition described in ENS report no. 52244 is not considered to be an un-analyzed condition as described in10 CFR 50.72(b)(3)(ii)(B), nor is it considered to be a condition which could have led to a potential uncontrolled radiation release per 10CFR 50.72(b)(3)(v)(C), nor is it considered to be a condition which could have prevented fulfillment of a safety function under 10 CFR 50.72.(b)(3)(v)(D). The NRC Resident Inspector has been notified. Notified the R4DO (Azua).

ENS 5223913 September 2016 22:30:00Comanche PeakNRC Region 4Westinghouse PWR 4-Loop

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).

ENS 522171 September 2016 15:25:00Comanche PeakNRC Region 4Westinghouse PWR 4-Loop

During a review of ongoing analyses related to postulated tornado missiles, a question was raised about the sentinel valve on the turbine driven auxiliary feedwater pump (TDAFW). The sentinel valve is designed as a warning system on steam equipment to warn personnel of increased back pressure. The valve is not an ASME component and its operation is not required to support TDAFW operation. The draft analysis predicts the TDAFW exhaust stack could be partially crimped by a tornado missile and the resultant back pressure on the turbine would increase to approximately 40 psi. This is higher than the set point for the sentinel valve (nominally 27 and 29 psi for Units 1 and 2, respectively). Therefore, in a design basis tornado with a design basis tornado missile striking the TDAFW exhaust stack, and in a condition where the TDAFW is demanded to run, the sentinel valve is expected to lift and allow steam to flow into the room. Vendor correspondence indicates that at approximately 40 psi the sentinel valve will conservatively pass 600 lbm/hr. Thus, it is conservatively considered operation of the TDAFW under such conditions would create an adverse steam environment which would be beyond that which the TDAFW pump has been analyzed to operate. Actions planned to alleviate the above condition would eliminate the potential for adverse environmental conditions. The steam supplies to the TDAFW have been isolated to affect repairs, which are expected to be limited to removal of the sentinel valve from each Unit and installation of a plug. Said activities are expected to be completed within the Allowed Out-of-Service Time (AOT) of the TDAFW of seventy-two hours per Technical Specification 3.7.5. NRC Resident Inspector has been informed.

  • * * RETRACTION ON 10/27/2016 AT 1353 EDT FROM DANNY BRADFORD TO BETHANY CECERE * * *

On 09/01/2016 Comanche Peak reported an ENS Report (no. 52217) related to unanalyzed conditions related to the sentinel valve on the turbine driven auxiliary feedwater pump (TDAFW) during postulated tornado-based scenarios and non-tornado based scenarios. The technical concern was the potential for the sentinel valve to release steam into the TDAFW room and result in adverse environmental conditions within the room and potentially external to the TDAFW room for both tornado-based and non-tornado based scenarios. Subsequent investigations by Engineering have determined the sentinel valve would not be demanded to open during tornado based scenarios and would not result in adverse environmental conditions internal or external to the TDAFW room in any design bases scenario. The licensee has notified the NRC Resident Inspector. Notified the R4DO (Farnholtz).

ENS 5195524 May 2016 15:22:00Comanche PeakNRC Region 4Westinghouse PWR 4-Loop

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).

ENS 5187119 April 2016 18:43:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopWhile performing a monthly check source on radiation monitor 1-RE-2328 (Main Steamline 1-04 Radiation Detector), the monitor was determined to be non-functional. With this radiation monitor non-functional, all of the emergency action levels for a steam generator tube rupture in steam generator 1-04 could neither be evaluated nor monitored. This unplanned condition is reportable as a major loss of assessment capability per 10 CFR 50.72(b)(3)(xiii). Comanche Peak Nuclear Power Plant (CPNPP) has assurance of steam generator integrity and fuel cladding integrity and there is a negligible safety significance to the current condition from a public health and safety perspective. Additionally, compensatory measures are in place to assure adequate monitoring capability is available to implement the CPNPP emergency plan in the unlikely event of challenges to the steam generator or fuel cladding. Until this radiation monitor can be restored, Operations has implemented compensatory measures to monitor main steamline 1-04 N16 Radiation Monitor for early signs of a steam generator tube leak/rupture, pre-brief radiation protection technicians on taking local readings with a geiger-mueller tube on main steam line 1-04 and reporting the reading to the Control Room. Corrective actions are being pursued to restore 1-RE-2328 to functional status. The NRC Resident Inspector has been notified.
ENS 5175123 February 2016 23:00:00Comanche PeakNRC Region 4Westinghouse PWR 4-Loop

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).

ENS 517179 February 2016 14:12:00Comanche PeakNRC Region 4Westinghouse PWR 4-Loop

Planned maintenance of the Plant Computer System (PCS) will cause a loss of emergency assessment capability. Beginning February 9, 2016, PCS data will not be available to the following Comanche Peak Nuclear Power Plant (CPNPP) facilities due to planned PCS software modifications: -Emergency Operations Facility (EOF) -Backup EOF -Operations Support Center The Emergency Response Data System (ERDS) will also be unavailable. The planned maintenance of the PCS is being reported as a loss of assessment capability in accordance with 10 CFR 50.72(b)(3)(xiii) because the duration is expected to be more than 72 hours and the data to the Backup EOF is also affected. CPNPP has compensatory measures in place to ensure timely emergency classification, protective action recommendation and emergency notification, as needed. The PCS modification is expected to be complete by February 18, 2016. A follow-up ENS (Emergency Notification System) communication will be made when the EOF assessment capability is restored. The Licensee has notified the NRC Resident Inspector.

  • * * UPDATE FROM RAUL MARTINEZ TO STEVEN VITTO ON 02/18/2016 AT 1541 EST * * *

The planned maintenance of the Comanche Peak Plant Computer System (PCS) that began on February 9, 2016 is complete. Assessment capability in the following facilities was restored effective 1300 (CST) February 18, 2016: -Emergency Operations Facility (EOF) -Backup EOF -Operations Support Center The Emergency Response Data System availability has also been restored. The Licensee has notified the NRC Resident Inspector. Notified the R4DO(Werner).

ENS 516397 January 2016 13:59:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopAt 0759 CST on 01/07/2016, a partial loss of the 25kV Plant Support Power Distribution System caused an unplanned loss of both primary and backup meteorological towers at Comanche Peak Nuclear Power Plant. Loss of both meteorological towers constitutes a major loss of emergency assessment capabilities in regard to meteorological conditions. During the power loss, the National Weather Service was available to compensate for the on-site data loss. The 25kV system and both meteorological towers were restored at 0923 CST on 01/07/2016. The 25kV Plant Support Power Distribution System feeds non-safety related equipment and does not affect plant operation, with the exception already described. The fault occurred due to an aged stress cone and faulty lightning arrestor. The fault was isolated and power was restored. The licensee notified the NRC Resident Inspector.
ENS 514443 October 2015 15:00:00Comanche PeakNRC Region 4Westinghouse PWR 4-Loop

During the scheduled Unit 2 down power to start 2RF15, Steam Generator 3 Feed Control Valve failed to control in Automatic or Manual resulting in excessive feedwater flow. Control Room Operators manually tripped the reactor and aligned Auxiliary Feedwater. No automatic RPS or ESF actuations occurred. Plant conditions are stable. All control rods fully inserted on the trip and no safety or relief valves lifted. The plant is supplying water to the steam generators with auxiliary feedwater and removing decay heat through the main condenser. The unit is in its normal shutdown electrical lineup. There was no effect on unit-1. The licensee informed the NRC Resident Inspector.

  • * * UPDATE AT 1848 EDT ON 10/05/15 FROM JOHN RASMUSSEN TO JEFF HERRERA * * *

The licensee added 10 CFR 50.72(b)(3)(iv)(A) to the 10 CFR codes reporting section. No other text was modified. Notified the R4DO (Taylor).

ENS 509657 April 2015 16:00:00Comanche PeakNRC Region 4Westinghouse PWR 4-LoopLuminant Generation Company LLC (Luminant Power) has completed a review of seismic monitor performance at the Comanche Peak Nuclear Power Plant (CPNPP) over the last three years. The CPNPP emergency preparedness plan requires seismic monitoring instruments to diagnose an earthquake for emergency action levels (EAL) HA1.1 (seismic event greater than OBE (operating basis earthquake) and HU1.1 (identified seismic event that is less than the OBE). The seismic monitor performance review identified one unplanned instance of monitor unavailability and three instances when planned monitor outage durations exceeded 24 hours. Any loss of seismic monitoring capability results in a major loss of assessment capability for the Alert (HA1.1) and a degraded assessment capability for the Unusual Event (HU1.1) emergency classification. The seismic monitor is currently functional, however it was determined to be non-functional on the following dates: Unplanned out-of-service: 12/4/2013 through 12/1 0/2013 Planned out-of-service lasting greater than 24 hours: 5/16/2012 through 5/24/2012 3/20/2013 through 3/27/2013 9/29/2014 through 10/1/2014 The loss of assessment capability is reportable to the NRC within 8 hours of discovery in accordance with 10 CFR50.72(b)(3)(xiii). This report is required per 10 CFR50.72(a)(1)(ii) as an event that occurred within 3 years of the date of discovery. The seismic monitor issues and the missed reporting of the loss of assessment capability have been documented in the CPNPP corrective action program. This review was prompted by the licensee's evaluation of industry's operating experience. A similar report was received from Limerick Generating Station - EN # 50951. The licensee informed the NRC Resident Inspector.