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The following information was provided by the licensee via email: During thermography of a reactor protection system (RPS) distribution panel, a circuit breaker (RPS-CB-7B) was inadvertently opened. This resulted in a partial loss of power to RPS Division B, which caused containment isolations to occur in multiple systems (Reactor Water Clean Up, Equipment Drains Radioactive, Floor Drains Radioactive, Reactor Recirculation, and Traversing lncore Probe). Specifically, RWCU-V-1, FDR-V-3, EDR-V-19, RRC-V-19, and TIP-V-15 all closed. All actuations occurred as designed upon the partial loss of RPS power. This event is being reported pursuant to 10 CFR 50.72(b)(3)(iv)(A) due to an unplanned valid actuation of a system pursuant to 10 CFR 50.72(b)(3)(iv)(B)(2). Additionally, this is being reported pursuant to 10 CFR 50.72 (b)(3)(xiii) for a major loss of emergency assessment capability due to the inability to assess primary containment identified and unidentified leakage rates. Emergency assessment capability was restored at 1008 PDT upon system restoration. The NRC resident was notified by the licensee.

• * * UPDATE FROM SIMEON MORALES TO DONALD NORWOOD AT 1547 EDT ON 6/16/2022 * * *

The following information was received via email: This event is being reported pursuant to 10 CFR 50.72 (b)(3)(xiii) only for a major loss of emergency assessment capability due to the inability to assess primary containment identified and unidentified leakage rates. The containment isolation was not due to actual plant conditions or parameters meeting design criteria for containment isolation. Therefore, this is considered an invalid actuation. Updated ENS Text: During thermography of a reactor protection system (RPS) distribution panel, a circuit breaker (RPS-CB-7B) was inadvertently opened. This resulted in a partial loss of power to RPS Division B, which caused containment isolations to occur in multiple systems (Reactor Water Clean Up, Equipment Drains Radioactive, Floor Drains Radioactive, Reactor Recirculation, and Traversing Incore Probe). Specifically, RWCU-V-1, FDR-V-3, EDR-V-19, RRC-V-19, and TIP-V-15 all closed. All actuations occurred as designed upon the partial loss of RPS power. This is being reported pursuant to 10 CFR 50.72 (b)(3)(xiii) for a major loss of emergency assessment capability due to the inability to assess primary containment identified and unidentified leakage rates. Emergency assessment capability was restored at 1008 PDT upon system restoration. The plant is stable, and all effected systems have been restored. There was no impact to the health and safety of the public or plant personnel. The NRC resident has been notified. Notified R4DO (Azua).

• * * UPDATE FROM TRACY HOWARD TO ERNEST WEST AT 1853 EDT ON 8/10/2022 * * *

The following information was received via email: At 0923 (PDT) on June 13, 2022, a partial loss of power to the Reactor Protection System (RPS) 'B' occurred due to the inadvertent opening of circuit breaker RPS-CB-7B during thermography of RPS-PP-C72/P001. The partial loss of RPS 'B' resulted in closure of primary containment isolation valves (PCIVs) in multiple systems. No plant parameters existed which would cause the opening of RPS-CB-7B or actuation of the primary containment isolation; therefore, this is considered to be an invalid actuation of a system listed in 10 CFR 50.73(a)(iv)(B). The closure of PCIVs were expected responses to the partial loss of RPS 'B'. Circuit breaker RPS-CB-7B was closed lo restore energy lo RPS 'B' at 1008 (PDT), containment isolation valves were opened, and the affected systems were returned to normal operating conditions for the current configuration per plant procedures. As indicated in 10 CFR 50.73(a)(1), in the case of an invalid actuation reported under 10 CFR 50.73(a)(2)(iv)(A), the licensee may, at its option, provide a telephonic notification lo the NRC Operations Center within 60 days of discovery of the event instead of submitting a written Licensee Event Report. This 60-day telephone notification is being made in accordance with 10 CFR 50.73(a)(1) for invalid actuations reported under 10 CFR 50.73 (a)(2)(iv)(A). This actuation was invalid since it was caused by maintenance activities and not the result of actual plant conditions warranting containment isolation. The following additional information is provided as specified in NUREG-1022: The following inboard containment isolation valves were actuated when personnel inadvertently bumped into RPS-CB-7B during the removal of a panel � RWCU-V-1 Reactor Water Cleanup Suction Inboard Isolation Valve � EDR-V-19 Drywell Equipment Drain Inboard Isolation Valve � FDR-V-3 Drywell Floor Drain Inboard Isolation Valve � RRC-V-19 Reactor Water Sample Inboard Isolation Valve � TIP-V-15 Traversing In-Core Probe Purge Isolation Valve All actuations occurred as designed upon the partial loss of RPS power. There were no actual safety consequences associated with this event since all affected equipment responded as designed. The NRG Residents have been notified. Notified R4DO (O'Keefe).

• 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 2307 EDT on April 21, 2019, in Mode 1 at approximately 100 percent reactor power, Unit 1 automatically tripped due to a Main Turbine Trip. The Main Turbine Trip was a result of two out of three level instruments sensing a false high reactor water level. All control rods inserted as expected during the scram. Safety Relief Valves G and K lifted per design. The same level instruments that failed also tripped both Reactor Feed Pumps. As a result, reactor water level dropped below the Low Level 1 and 2 actuation setpoints. Per design, the Low Level 1 signal resulted in Group 2 (i.e., floor and equipment drain isolation valves), Group 6 (i.e., monitoring and sampling isolation valves) and Group 8 (i.e., shutdown cooling isolation valves) isolations. The Low Level 2 signals resulted in Group 3 (i.e. Reactor Water Cleanup) isolation, a secondary containment isolation signal, and an auto start of Standby Gas Treatment and Control Room Emergency Ventilation. Also, the Low Level 2 resulted in (high pressure coolant injection) HPCI and (reactor core isolation cooling system) RCIC automatically starting and injecting into the vessel. All systems responded as designed. This event is being reported in accordance with 10 CFR 50.72(b)(2)(iv)(B) for RPS actuation and 10 CFR 50.72(b)(3)(iv)(A) as an event that results in valid actuations of the Primary Containment Isolation System. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. Decay heat is currently being removed via the turbine bypass valves. Condensate and feed water are maintaining water level. The reactor is still at saturation temperature and 475 psi, lowering slowly. The reactor is still in a normal electrical lineup. There was no impact to Unit 2 as a result of this event.

• * * UPDATE ON 04/22/19 AT 0220 EDT FROM ALAN SCHULTZ TO JEFFREY WHITED * * *

The licensee updated the event report to include a 4-Hr Non-Emergency Notification in accordance with 10 CFR 50.72(b)(2)(iv)(A) for Emergency Core Cooling System, HPCI, Discharge to the Reactor Coolant System. Notified R2DO (Dickson), NRR EO (Miller) and IR MOC (Gott).

This 60-day report, as allowed by 10 CFR 50.73(a)(1), is being made pursuant to 10 CFR 50.73(a)(2)(iv)(A) to describe an unplanned, invalid actuation of containment isolation valves in more than one system. On 3/28/16, at approximately 1320 (EDT), a loss of power occurred on the Unit 2 E124 480 volt load center due to an equipment operator inadvertently opening the main feed breaker during the process of applying a clearance to de-energize the E124-P-A motor control center for planned maintenance. Loss of the E124 load center resulted in Group II and Group III primary containment isolations due to an invalid ESF actuation signal. Systems impacted by the containment isolations included containment instrument nitrogen, containment atmospheric monitoring, reactor water cleanup, and secondary containment. Balance of plant impacts included partial loss of feedwater heating and a reduced condenser vacuum. Reactor power lowered to 86% as a result of the event and further decreased to approximately 80 percent when re-establishing the 3A, 4A and 5A feedwater heaters.

Following direction from the control room, the E124 main feed breaker was promptly re-closed by equipment operators. Affected equipment was restored to its normal or planned configuration and containment isolations were reset at 1406. The containment isolation signal was generated as a result of the loss of power to the E124 load center and was not due to actual plant conditions or parameters meeting design criteria for containment isolation. Therefore, this is considered to be an invalid actuation. The licensee has notified the NRC Resident Inspector.

At 1313 (EDT) on 7/26/14, the plant experienced an electrical transient on bus EK-1-B1 (safety-related 120 volt AC distribution panel) that resulted in partial Balance of Plant Division 2 isolation signals and alarms received in the Control Room. The following component actuations occurred: valve 1P50F140 closed, resulting in a trip of Containment Vessel Chilled Water C; valve 1G41F140 closed, isolating the Fuel Pool Cooling and Clean-up return from the containment building upper pools; valve 1B33F019 closed, isolating Reactor Water sampling; valve 1D17F071B closed, isolating the Drywell Atmosphere Radiation Monitor; valve 1D17F081B closed, isolating the Containment Atmosphere Radiation Monitor; valves 1G61-F030, 1G61-F150, 1G61-F075, and 1G61-F165 closed, isolating the Containment and Drywell Floor and Equipment drain sumps; valve 1G50-F272 closed isolating the Reactor Water Cleanup Backwash Receiving Tank: 1M25F020B, Control Room HVAC Inboard supply damper, closed and Division 2 indicated an auto initiation (M25-S12, Auto Initiate Active amber light was on). This event is considered an invalid system actuation reportable under 10 CFR 50.73(a)(2)(iv)(A).

The isolation was not initiated in response to actual plant conditions or parameters, and was not a manual initiation. Therefore, this notification is provided via a 60 day optional phone call in accordance with 10 CFR 50.73(a)(1) instead of submitting a written Licensee Event Report. The event meets reporting criteria specified in 10 CFR 50.73(a)(2)(iv)(B)(2) as a general containment isolation valve signal affecting containment isolation valves in more than one system. All affected systems functioned as expected in response to the electrical transient on bus EK-1-B1 that resulted in the partial Balance of Plant Division 2 isolation signals. The valves were reopened in accordance with plant procedures. The failure mechanism that caused the electrical transient was a failed capacitor in regulating transformer EFB1B2. The capacitor was replaced and tested with satisfactory results. The NRC Resident Inspector has been notified.

At 0754 on 8/23/13, a loss of power to the Reactor Protection System (RPS) 'B' occurred due to the unexpected opening of the circuit breaker (RPS-CB-MG2) for the RPS 'B' motor generator due to a failure of the voltage regulator circuit card. The loss of RPS 'B' resulted in a half scram signal, closure of Primary Containment Isolation Valves (PCIVs) from multiple systems and loss of power to main steam line radiation monitors (MS-RIS-610B & MS-RIS-610D). No plant parameters or maintenance activities existed which would cause the opening of RPS-CB-MG2 or actuation of the primary containment isolation; therefore, this is considered to be an invalid actuation of a system listed in 10CFR50.73(a)(2)(iv). The half scram signal, closure of Primary Containment Isolation Valves (PCIVs) from multiple systems, and loss of power to main steam line radiation monitors were an expected response to the loss of RPS 'B'. RPS 'B' was repowered from an alternate power supply. The half scram signal was reset, the containment isolation valves were opened and the affected systems were returned to normal operation. The voltage regulator circuit card was replaced and RPS 'B' was returned to its normal power supply. As indicated in 10CFR50.73(a)(1), in the case of an invalid actuation reported under 10CFR50.73(a)(2)(iv)(A), the licensee may, at its option, provide a telephonic notification to the NRC Operations Center within 60 days of discovery of the event instead of submitting a written LER. This 60-day telephone notification is being made to meet the reporting requirements instead of submitting an LER since the actuation was invalid. The following additional information is provided as specified in NUREG-1022: The specific train(s) and system(s) that were actuated: PCIVs in multiple systems

    EDR-V-19 Drywell Equipment Drain Inboard Isolation Valve
    EDR-V-20 Drywell Equipment Drain Outboard Isolation Valve
    FDR-V-3 Drywell Floor Drain Inboard Isolation Valve
    FDR-V-4 Drywell Floor Drain Outboard Isolation Valve
    RWCU-V-1 Reactor Water Cleanup Suction Inboard Isolation Valve
    RWCU-V-4 Reactor Water Cleanup Suction Outboard Isolation Valve
    RRC-V-19 Reactor Water Sample Inboard Isolation Valve
    RRC-V-20 Reactor Water Sample Outboard Isolation Valve
    TIP-V-15 Traversing In-Core Probe Purge Isolation Valve
    CRD-V-11 Control Rod Drive Scram Discharge Volume Drain Valve

Whether each train actuation was complete or partial:

    All PCIVs actuations for a loss of RPS 'B' were complete.
    The reactor half scram for a loss of RPS 'B' was a partial activation.

Whether or not the system started and functioned successfully:

    All PCIVs functioned successfully.

The licensee notified the NRC Resident Inspector.