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The following information was provided by the licensee via email: On January 18, 2024, at 0030 PST, diesel generator 2 (DG2) was shut down following a monthly surveillance run. Subsequently, a leak was discovered in the DG2 building. Service water pump '1B' was secured at 0117, effectively stopping the leak. The leak was determined to be service water coming from a diesel generator mixed air cooling coil. Service water system 'B' and DG2 were subsequently declared inoperable at 0135. After discussion with engineering, it was identified that the amount of service water leakage from the cooling coil was assumed to be greater than the leakage allowed by the calculation to assure adequate water in the ultimate heat sink to meet the required mission time of 30 days. At 1204, it was determined that entry into Technical Specification 3.7.1 condition D was warranted since the assumed leakage from the cooling coil could exceed the calculated allowed value. At 1238, the control power fuses for service water pump '1B' were removed. DG2 and service water system 'B' were declared unavailable, and the technical specification condition for the inoperable ultimate heat sink was exited. With the control power fuses removed, the pump is kept from auto starting, effectively preventing the leak and ensuring the safety function of the ultimate heat sink is maintained while the cooling coil is repaired or replaced. Due to the leakage assumed greater than the calculated allowable value this condition is reportable per 10 CFR 50.72(b)(3)(ii)(B) as an unanalyzed condition and per 10 CFR 50.72(b)(3)(v)(B) as an event or condition that could have prevented fulfillment of the safety function of structures or systems that are needed to remove residual heat. There was no impact to the health and safety of the public. The NRC Resident has been notified.

• * * RETRACTION ON 3/18/24 AT 1923 FROM VALERIE LAGEN TO KAREN COTTON * * *

The following information was provided by the licensee via email: On January 18, 2024 at 2138 EST, Columbia Generating Station notified the NRC under 10 CFR 50.72(b)(3)(ii)(B) of an unanalyzed condition on the available capacity of the ultimate heat sink (UHS) and under 10 CFR 50.72(b)(3)(v)(B) of an event or condition that could have prevented fulfillment of the safety function of structures or systems needed to remove residual heat. On January 18, 2024, following monthly surveillance of the diesel generator DG2, a DG2 room cooler flow alarm was received at 0115. A leak was discovered in the diesel mixed air (DMA) air handler unit. Service Water Pump '1B' was secured and the leakage was stopped at 0117. The service water system 'B' and diesel generator system 'B' were declared inoperable at 0135. The leak was assumed to be greater than that allowed to ensure adequate water in the UHS required to meet the 30-day mission time, and the UHS was declared inoperable at 1204. Control power fuses for the service water pump '1B' were removed to fully eliminate the leakage path from the cooler, and the UHS was declared operable at 1238. Following the event, engineering performed an analysis based on the size and location of the leak, and concluded it would have taken 1.4 days to deplete the available excess water in the UHS to below the minimum technical specification required water level of the spray pond. Operations were able to secure the service water subsystem of the UHS prior to exceeding the volumetric margins in the spray ponds to ensure the 30-day mission time was met. The condition did not represent a safety significant unanalyzed condition nor a loss of safety function. The NRC Resident Inspector has been notified. Notified R4DO (Gepford).

The following information was provided by the licensee via email: At 1545 CST on November 10, 2023, personnel at Waterford Steam Electric Station Unit 3 determined that 19 conduits in the engineered safety features actuation system (ESFAS) auxiliary relay cabinets A and B did not have the required fire seals for bay separation. This condition meets the criteria involving an unanalyzed condition that significantly affects plant safety. The plant is currently defueled. Decay heat is being removed by normal spent fuel cooling system operations. ESFAS is not required to be operable in the current plant mode. This event is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(ii)(B) as an unanalyzed condition that significantly degrades plant safety. There was no impact to the health and safety of the public or plant personnel. The NRC Region 4 Branch Chief (Dixon) has been notified.

• * * RETRACTION ON 1/8/2024 AT 1222 EST FROM PETER RAMON TO ERNEST WEST * * *

On November 10, 2023, Waterford Steam Electric Station Unit 3 reported in EN 56849 that 19 conduits in engineered safety features actuation system (ESFAS) auxiliary relay cabinets A and B did not have the required fire seals for bay separation. This condition met the criteria involving an unanalyzed condition that significantly affects plant safety. Waterford 3 has determined that the ESFAS auxiliary relay cabinets A and B jumper conduits do not require fire seals based on review of an engineering specification that specifies the size and length of conduits which require fire seals to be installed. None of the nineteen affected conduits meet the size and length criteria that would necessitate installation of a fire seal. Based on this, the condition described in EN 56849 is not considered to be an unanalyzed condition that significantly affects plant safety as described in 10 CFR 50.72(b)(3)(ii)(B) and therefore is not reportable. The licensee notified the NRC Resident Inspector. Notified R4DO (Gaddy)

EN Revision Imported Date : 8/18/2020 EMERGENCY PROCEDURE ERROR POTENTIALLY PREVENTING TIMELY COMPLETION OF EMERGENCY CORE COOLING SYSTEM RECIRCULATION ALIGNMENT At 0815 CDT on 7/30/2020, it was determined that a procedural error in emergency procedure ES1.3, Transfer to Cold Leg Recirculation, could delay realignment from emergency core cooling system (ECCS) injection phase to recirculation phase under lower plant operational modes. It is noted this scenario is postulated to occur only when the boron dilution mitigation system is operable in lower modes of operation as per Technical Specification 3.3.9 (required operable in Mode 2 (below P-6), 3, 4 and 5). Current plant conditions require this feature nonfunctional so this issue does not impact current plant conditions. This condition is not bounded by existing design and licensing documents; however, it poses no current impact to the health and safety of the public or plant personnel. Therefore, this event is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(ii)(B). The NRC Resident Inspector has been notified.

• * * RETRACTION ON 8/17/2020 AT 1603 EDT FROM JOSH COPELAND TO KERBY SCALES * * *

Event Notification (EN) 54806, made on 7/30/2020, is being retracted because re-evaluation performed subsequent to the notification has demonstrated that the error in Emergency Operating Procedure ES1.3 would not have resulted in a condition outside of the current licensing basis analyses of record for the Callaway Plant. This re-evaluation addressed core effects, containment pressure-temperature and radiological consequences analyses, documented in the plant's corrective action program. The re-evaluation has led to the conclusion that the procedural error in ES1.3 would not have prevented any system required to be OPERABLE by the Technical Specifications from performing its specified safety functions. With all systems capable of performing their specified safety functions, the current licensing basis analyses of record for Callaway Plant remain valid and bounding. Based on these considerations, it has been determined that the condition reported in EN 54806 did not result in the plant being in an unanalyzed condition that significantly degraded plant safety. Consequently the condition did not meet the criteria for an 8-hour notification per 10 CFR 50.72(b)(3)(ii)(B) for an unanalyzed condition that significantly degrades safety. The NRC Resident Inspector has been notified of this Event Notification retraction. Notified R4DO (Taylor)

EN Revision Imported Date : 2/21/2020 CONTAINMENT RELIEF VALVES INOPERABLE At 22:18 (EST) on 1/21/20, it was discovered that all Unit 1 containment vacuum relief isolation valves were closed and all vacuum relief lines were simultaneously inoperable; therefore, this condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v). The isolation valves were opened and the vacuum relief valves were restored to operable. There is no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified.

• * * UPDATE ON 02/20/2020 AT 1626 EST FROM FRANK SCHULTE TO BRIAN P. SMITH * * *

At 1549 (EST), February 20, 2020, a completed engineering evaluation of the condition initially reported on January 22, 2020 determined that the inoperability of the Sequoyah Unit 1 Containment Vacuum Relief System affected the ability to protect containment against an external pressure event. This condition is not bounded by existing design and licensing documents; however, it poses no impact to the health and safety of the public or plant personnel. The condition was resolved when isolation valves were opened on January 21, 2020 and the vacuum relief lines were restored to an operable status. Therefore, this event is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(ii)(B), "an unanalyzed condition that significantly degrades plant safety. Subsequent to the initial notification, continued evaluation of the reported condition has concluded that the isolation of the containment vacuum relief function did not prevent the fulfillment of a safety function that is needed to control the release of radioactive material; nor mitigate the consequences of an accident therefore this event is not reportable under 10 CFR 50.72(b)(3)(v), "Event or Condition that could have prevented fulfillment of a safety function. The NRC Resident has been notified. Notified R2DO (Musser)

EN Revision Text: CONTAINMENT PENETRATION DISCOVERED NOT ISOLATED At 2115 CDT on 9/5/2019, an inside containment test connection and inoperable outside containment isolation valve were discovered to be open for a containment air sample penetration. This resulted in the containment penetration not being isolated. The inside containment test connection was closed at 2322 CDT on 9/5/2019.

This event is being reported under 10 CFR 50.72(b)(3)(v)(C) and (D) and 10 CFR 50.72(b)(3)(ii)(B).

There was no impact to the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified.

• * * UPDATE FROM PAUL BURTON TO HOWIE CROUCH AT 1342 EST ON 11/7/19 * * *

This event was originally reported on September 6, 2019 under 10 CFR 50.72(b)(3)(v)(C) and (D) and 10 CFR 50.72(b)(3)(ii)(B). Upon completion of the investigation of the event, it was determined that the event had insignificant safety consequences because the containment breach was disconnected from the Reactor Coolant System by a series of closed valves for the duration of the event. Additionally, the lines to the inside containment connection and the outside inoperable containment isolation valve that was found to be open as well as the main line connecting and passing through the penetration were one-inch diameter lines. Analysis determined that containment breaches that are less than a three-inch diameter do not lead to a large radiation release. The event did not place the plant in an unanalyzed condition that significantly degrades plant safety. Therefore, 10 CFR 50.72(b)(3)(ii)(B) did not apply to this event and this notification is to retract reporting under that criterion. The licensee notified the NRC Resident Inspector. Notified R4DO (Drake).

At 2006 (MST), on 3/31/2019, the Palo Verde Nuclear Generating Station Unit 1 Shift Manager was informed that leakage was measured from the Train A Emergency Core Cooling System (ECCS) piping at approximately 100 ml/minute through a High Pressure Safety Injection (HPSI) A drain valve. This value exceeds the assumed 3000 ml/hour ECCS leakage for a large break loss of coolant accident analysis. At 0230 (MST) on April 1, 2019, the valve was flushed and the leakage reduced to 10 ml/minute (600 ml/hour) and was no longer above the limit of the safety analysis. This condition is being reported as an unanalyzed condition per 10 CFR 50.72(b)3)(ii)(B) and a condition that could have prevented the fulfillment of a safety function to the control the release of radioactive material per 10 CFR 50.72(b)(3)(v)(C). This event did not result in an abnormal release of radioactive material. Notification received by Caty Nolan and emailed to HOO.HOC@NRC.GOV The NRC asked a followup question: Why was the criterion for Control of Radioactive Material selected? per the PVNGS Unit 1 Shift Manager, this criterion was selected due to the potential of exceeding offsite dose projections, post recirculation, following a Design Basis Accident. The resident inspector has been notified.

• * * UPDATE ON 05/15/19 AT 1417 EDT FROM SEAN DORNSEIF TO BETHANY CECERE * * *

An engineering evaluation concluded that the as-found ECCS leakage would not have degraded the performance of the Pump Room Exhaust Air Cleanup system; therefore, it remained operable. The evaluation also concluded that the as-found leakage was within the analysis margins for HPSI pump hydraulic performance and containment flood level following a Large Break Loss of Coolant Accident; therefore, the ECCS also remained operable. Based on the above information, the condition identified on March 31, 2019, was an unanalyzed condition per 10 CFR 50.72(b)(3)(ii)(B), but did not prevent the fulfillment of the safety function of the structures or systems that are needed to control the release of radioactive material per 10 CFR 50.72(b)(3)(v)(C). The NRC resident inspectors have been informed. Notified R4DO (Proulx).

EN Revision Text: UNANALYZED CONDITION DUE TO MODIFICATION NOT ADDED TO PROCEDURE On November 1, 2018, at approximately 1300 EDT, Fermi 2 identified that a Station Blackout (SBO) procedure was deficient as a result of a modification installed during a recent refueling outage. A review identified that the performance of the SBO procedure could have resulted in a challenge to having an alternate AC source available within one hour as outlined in the Updated Final Safety Analysis Report (UFSAR) 8.4.2. The alternate AC source was always available to be manually aligned in accordance with other standard operating procedures. The modification did not affect the function for Appendix R alternative shutdown. Immediate actions are underway to revise the impacted procedure. The health and safety of the public was not affected as offsite power has remained available since the modification was installed. Investigation into the cause and corrective actions is ongoing. Fermi 2 is reporting this event as an unanalyzed condition pursuant to the requirements of 10 CFR 50.72(b)(3)(ii)(B). The licensee notified the NRC Resident Inspector.

• * * RETRACTION ON 12/28/18 AT 1228 EST FROM JEFFREY MYERS TO JEFFREY WHITED * * *

The purpose of this notification is to retract a previous report made on November 1, 2018 (EN 53712) under 10 CFR 50.72(b)(3)(ii)(B). Subsequent to the initial notification, the event, site procedures, and the NRC guidance in NUREG-1022 pertaining to 10 CFR 50.72(b)(3)(ii)(B) were reviewed further. The evaluation determined that at the time of the event, there were multiple methods defined in existing station procedures to establish an available alternate AC source within one hour as outlined in the Updated Final Safety Analysis Report (UFSAR) 8.4.2. Under these circumstances, the event does not represent an unanalyzed condition under 10 CFR 50.72(b)(3)(ii)(B). Therefore, EN 53712 can be retracted and no Licensee Event Report (LER) under 10 CFR 50.73(a)(2)(ii)(B) is required to be submitted. The licensee has notified the NRC Resident Inspector. Notified R3DO (Riemer).

EN Revision Text: DISCOVERY OF AN UNANALYZED CONDITION THAT SIGNIFICANTLY DEGRADES PLANT SAFETY On July 3, 2018, while performing a review of Emergency Operating Procedures, a concern was identified regarding the potential for excessive loss of ultimate heat sink inventory (UHS) through the auxiliary feedwater (AFW) system mini-flow recirculation pathway. This condition would have the potential to prevent the ultimate heat sink from providing an adequate inventory of water for a 30-day mission time.

The normal water supply for the Callaway AFW system is the condensate storage tank (CST). The CST is a non-safety grade component. The safety-grade supply for AFW is the essential service water (ESW) system. The ESW system is supplied by the UHS. The UHS thermal performance analysis accounts for a loss of UHS inventory to the AFW system up until the point of the accident sequence that the AFW pumps would be secured. The analysis did not include an allowance for loss of UHS inventory through the AFW mini-flow recirculation pathway following the AFW pumps being secured. The EOP guidance that secures the AFW pumps does not isolate the mini-flow recirculation pathway.

Initial estimates indicate that loss of UHS inventory through the mini-flow recirculation pathway, if not isolated, would preclude the UHS from completing its 30-day mission time. This potential for depletion of the UHS placed the plant in an unanalyzed condition that significantly degraded safety.

Callaway has issued interim guidance to the on-shift personnel regarding this concern to ensure that the ultimate heat sink water level is maintained at a level that will be adequate to mitigate the potential loss of inventory.

This condition is reportable per 10 CFR 50.72(b)(3)(ii)(B) for an unanalyzed condition that significantly degrades safety. The NRC Resident Inspectors have been notified of this condition.

• * * RETRACTION ON 07/31/2018 AT 1430 EDT FROM LEE YOUNG TO ANDREW WAUGH * * *

Event Notification (EN) 53485, made on July 3, 2018, is being retracted because re-evaluation performed subsequent to the notification has demonstrated, based on actual plant equipment and environmental conditions, that the unanalyzed inventory losses previously reported by EN 53485 would not have depleted the UHS inventory to an unacceptable level during its 30-day mission time. The re-evaluation has led to the conclusion that the previously unanalyzed losses of UHS inventory would not have prevented the UHS from performing its specified safety functions and meeting its 30-day mission time requirements. With the UHS capable of performing its specified safety functions and meeting its 30-day mission time requirements, the systems supported by the UHS would have remained capable of performing their specified safety functions. Based on these considerations, it has been determined that the condition reported in EN 53485 did not result in the plant being in an unanalyzed condition that significantly degraded safety. Consequently, the condition did not meet the criteria for an 8-hour notification per 10 CFR 50.72(b)(3)(ii)(B) for an unanalyzed condition that significantly degrades safety. The NRC Resident Inspector has been notified of the Event Notification retraction. Notified R4DO (Gaddy).

EN Revision Text: GAS VOIDS DISCOVERED IN BOTH TRAINS OF LOW HEAD SAFETY INJECTION On 5/22/2018, while operating at approximately 100 percent power, Ultrasonic Testing of the Beaver Valley Power Station (BVPS) Unit 1 Low Head Safety Injection (LHSI) pump suction piping identified gas voids in excess of the acceptable limit for void volume. Both trains of LHSI were declared inoperable. Technical Specification (TS) 3.5.2 for both trains of the LHSI system was entered along with TS 3.0.3 which requires the initiation of a plant shutdown. Time of TS entry was 12:56 (EDT). Plant shutdown was commenced at 15:56 (EDT) in accordance with plant procedures. At 15:59 (EDT) Train 'A' LHSI was restored to operable status, TS 3.0.3 Action was exited and the power reduction was stopped at approximately 99 percent. At 17:43 (EDT) Train 'B' LHSI was restored to operable status, TS 3.5.2 Actions were exited. This is reportable per 10 CFR 50.72(b)(3)(ii) Unanalyzed Condition, 10 CFR 50.72(b)(3)(v) Event or Condition that Could Have Prevented the Fulfillment of a Safety Function and 10 CFR 50. 72(b )(2)(i) TS Required Shutdown. The NRC Resident Inspector has been notified.

• * * RETRACTION ON 6/21/18 AT 1535 EDT FROM SHAWN KEENER TO RICHARD SMITH * * *

Further engineering evaluation has determined that the gas voids that existed at the time of discovery would not have rendered the LHSI (Low Head Safety Injection) system inoperable if it were required to actuate. The engineering evaluation concluded that filling of the containment sump during a Design Basis Accident would result in a void volume reduction such that the void in the LHSI suction piping would not be large enough to significantly impact the operability of the system. Therefore, the system remained operable but degraded. No TSs (Technical Specifications) were required to be entered and no shutdown was required. As such, all three reporting criteria do not apply and are being retracted. The NRC Resident Inspector has been notified. Notified R1DO (Burritt).