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The following information was provided by the licensee via fax and email: Fire potentially degrading the level of safety of the plant. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: At 0907 EST, the licensee declared a notification of unusual event, under emergency action level HU.4, due to multiple fire alarms and CO2 discharge in the emergency diesel building. When the plant fire brigade entered the building, there was no indication of fire or damage to any plant equipment. The cause of the multiple alarms is under investigation. State and local authorities were notified and no offsite assistance was requested. Both units remain at 100 percent power. The NRC Resident Inspector has been notified. Notified DHS SWO, FEMA Operations Center, CISA Central, FEMA NWC (email), CWMD Watch Desk (email), DHS NRCC THD Desk (email), and DHS Nuclear SSA (email).

• * * UPDATE FROM TYSON JONES TO KAREN COTTON AT 1007 EDT ON 10/21/23 * * *

At 1007 EDT, Watts Bar terminated the notification of unusual event. The basis for termination was that no fire or damaged plant equipment was found. The NRC Resident Inspector has been notified. Notified R2DO (Miller), IR-MOC (Crouch), NRR-EO (Felts), DHS-SWO, FEMA Ops Center, CISA Central, FEMA NWC (email), CWMD Watch Desk (email), DHS NRCC THD Desk (email), and DHS Nuclear SSA (email).

• * * RETRACTION ON 10/22/23 AT 0925 EDT FROM TYSON JONES TO KAREN COTTON * * *

Watts Bar Nuclear Plant (WBN) is retracting Event Notice 56809, Notice of Unusual Event, based on the following additional information, not available at the time of the initial notification. Specifically, in accordance with the emergency preparedness implementing procedures, WBN reported a condition that was determined to meet emergency action level (EAL) HU4, Initiating criteria number 1, receipt of multiple (more than 1) fire alarms or indicators and the fire was within any Table H2 plant area, which includes the diesel generator building. It was further determined that multiple fire detection zones actuated (spurious and invalid) enabling the discharge of installed fire suppression (CO2) into the space. Upon entry by the site fire brigade, it was determined that no smoke or fire existed and reported to the Shift Manager at 0930 EDT. All fire alarms were reset. Troubleshooting activities are in progress to determine the cause. A fire watch has been established and CO2 has been isolated. The required compensatory measures for the affected areas will remain in place until completion of the investigation, and CO2 suppression is restored to functional. Notified R2DO (Miller), IR-MOC (Crouch), NRR-EO (Felts), DHS-SWO (email), FEMA Ops Center (email), CISA Central (email), FEMA NWC (email), CWMD Watch Desk (email), DHS NRCC THD Desk (email), and DHS Nuclear SSA (email).

The following information is a synopsis of information provided by the licensee via fax and phone: On May 23, 2022, Framatome informed Tennessee Valley Authority (TVA) of a deviation of breakers purchased under contract. On January 23, 2023, TVA determined that a defect of the basic component could create a substantial safety hazard. Framatome Inc. identified a deviation in the Siemens medium voltage vacuum circuit breaker where a failure to electrically charge or electrically close could occur. Framatome Inc. identified this as a departure from the technical requirements included in the procurement document. It is noted that the ability to electrically trip the circuit breaker would not be affected by the condition. TVA was notified by Framatome under 10 CFR 21.21(b) to evaluate the application of the breaker for a substantial safety hazard. The TVA evaluation identified these breakers as intended for use in safety related Class 1E applications where a loss of the closure function would impact mitigation of design basis accidents and transients. During the Framatome dedication testing/inspection of Siemens medium voltage vacuum breakers, a hi-pot test failure on one circuit breaker was encountered. Troubleshooting and inspection found damage to charging motor wiring. It was determined that the cause of the damage was due to the manner in which control wiring was routed and connected to the internal bracket in close proximity to a bracket edge. This edge caused damage to wiring after significant number of cycles were applied to the breaker prior to dedication testing. TVA received nine medium voltage vacuum circuit breakers at an offsite warehouse facility. While located at that facility, TVA, with assistance from Framatome, examined the affected breakers for the wire routing condition. The wiring harnesses of certain breakers were corrected. Framatome is to examine medium voltage vacuum circuit breakers that may be purchased under this contract for the wiring condition and correct as necessary before delivery. The NRC Senior Resident Inspector has been notified. This is a non-emergency notification required by 10 CFR 21.21(d)(3)(i).

• * * UPDATE ON 1/26/23 AT 0916 EST FROM RICARDO MEDINA TO BRIAN P. SMITH * * *

The following information is a synopsis of information provided by the licensee via phone: The Sequoyah site licensing manager requested via phone call to the HOO that the model number for the basic component with the defect be listed in the Part 21 event narrative in addition to the official Part 21 report. The component discussed is a Siemens 6.9kV, 1200A, 125VDC Vacuum Circuit Breaker, Model No.: 7-HKR-50-1200-130. Notified R2DO (Miller) and the Part 21 Reactors Group (Email).

The following information was provided by the licensee via fax: At 1345 CDT, Browns Ferry declared a Notification of Unusual Event due to a fire at the 3B Reactor Feedwater Pump within the Turbine Building which was not extinguished within 15 minutes. Subsequently, the fire was extinguished at 1402 CDT. Unit 3 remains in Mode 1 at approximately 9.5 percent rated thermal power (RTP). Unit 1 and 2 remain at 100 percent RTP and unaffected. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: The fire began at 1332 CDT. It is believed that the fire was in the oil system of the Feedwater Pump. The fire was extinguished by the on-site fire brigade. No off-site assistance was requested. The Unusual Event was declared under Emergency Action Level HU-4. The licensee notified the NRC Resident Inspector and required State and local government agencies. Unit 3 is currently stable. Notified DHS-SWO, FEMA Ops Center, and CISA Central Watch Officer, and FEMA NWC, DHS NRCC THD Desk, and DHS NuclearSSA via email.

• * * UPDATE FROM CHASE HENSLEY TO DONALD NORWOOD AT 1650 EDT ON 4/2/2022 * * *

The Notification of Unusual Event was exited at 1544 CDT. Notified R2DO (Miller), IR-MOC (Kennedy), NRR-EO (Felts), DHS-SWO, FEMA Ops Center, and CISA Central Watch Officer.

• The following information was provided by the licensee via email:

This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of the Reactor Protection System (RPS). On October 20, 2021, at approximately 0705 hours Central Daylight Time (CDT), Browns Ferry, Unit 1, 1B RPS bus unexpectedly lost power. The loss of the bus resulted in a half scram, automatic Primary Containment Isolation System (PCIS) Groups 2, 3, 6, and 8 isolations, and Trains A, B, and C SBGT (Stand-By Gas Treatment) and A CREV (Control Room Emergency Ventilation system) started. All systems responded as expected. At 0720 hours CDT, the bus was placed on the alternate power supply and the half scram and PCIS isolations were reset. Plant conditions which initiate PCIS Group 2 actuations are Reactor Vessel Low Water Level (Level 3) or High Drywell Pressure. The PCIS Group 3 actuations are initiated by Reactor Vessel Low Water Level (Level 3) or Reactor Water Cleanup Area High Temperature. The PCIS Group 6 actuations are initiated by Reactor Vessel Low Water Level (Level 3), High Drywell Pressure, or Reactor Building Ventilation Exhaust High Radiation (Reactor Zone or Refuel Zone). The PCIS Group 8 actuations are initiated by Low Reactor Vessel Water Level (Level 3) or High Drywell Pressure. At the time of the event, these conditions did not exist; therefore, the actuation of the PCIS was invalid. The cause of the RPS bus loss was a trip of the underfrequency relay due to drift of the relay setpoint. The relay was replaced and 1B RPS bus was returned to the normal power supply on October 21, 2021, at 0510 hours CDT. There were no safety consequences or impact to the health and safety of the public as a result of this event. This event was entered into the Corrective Action Program as Condition Report 1729592. The NRC Resident Inspector has been notified of this event.

At 2150 CST on 11/04/2020, it was discovered that Unit 1 High Pressure Coolant Injection System (HPCI) was INOPERABLE; therefore, this condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v), as an event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident. During performance of 1-SR-3.5.1.7, HPCI Main and Booster Pump Set Developed Head and Flow Rate Test at Rated Reactor Pressure, Unit 1 HPCI was manually tripped by the control room operator due to local report of excessive shaking of the cooling water supply from the booster pump line. There was no impact to the safety of the public or plant personnel. The NRC Resident Inspector has been notified. CR 1650042 documents this condition in the Corrective Action Program. The Unit is in a 14-day LCO 3.5.1(c). The RCIC System is operable.

• * * RETRACTION FROM MARK ACKER TO HOWIE CROUCH AT 1607 EST ON 12/29/2020 * * *

ENS Event number 54983, made on 11/05/2020 is being retracted. NRC notification 54983 was made to ensure that the Eight-Hour Non-Emergency reporting requirements of 10 CFR 50.72 were met when Unit 1 HPCI was manually tripped by the control room operator due to a local report for excessive shaking of the cooling water supply from the booster pump line. A subsequent engineering evaluation concluded on 11/06/2020 there was reasonable assurance of operability with no additional intrusive maintenance performed and that the condition was bounded by a previous evaluation documented in (Condition Report) CR 1347736. As such, the circumstances discussed in the report did not result in any condition that at the time of discovery could have prevented the fulfillment of the safety function of structures of the system that are needed to mitigate the consequences of an accident. Therefore, this event is not reportable under 10 CFR 50.72(b)(3)(v). TVA's evaluation of this event is documented in the corrective action program. The licensee has notified the NRC Resident Inspector. Notified R2DO (Miller).