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• 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.

This 60-day telephone notification is being made under 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 any of the equipment specified in paragraph 50.73(a)(2)(iv)(B). In this case, the equipment actuated was the four Unit 1 and 2 emergency diesel generators (EDG) A, B, C, and D. These EDGs are common equipment for Browns Ferry Units 1 and 2. On November 10, 2006, personnel were performing surveillance requirement (SR) test 0-SR-3.8.1.6, Common Accident Signal Logic. At this time Browns Ferry Unit 1 was shutdown and defueled, and Unit 2 was operating at 100% thermal power. During conduct of this testing, at 0010 hours CST, all four of the common U1/2 EDGs were inadvertently started. This occurred when test personnel (non-licensed) inadvertently placed a keylock switch in the wrong position during the equipment restoration portion of the testing. The SR test step being performed was correct, but it was incorrectly implemented. All affected equipment operated per the plant design in response to the switch manipulation, with each of the four EDGs properly starting and running in response to the invalid start signal. No loss of normal plant electrical power occurred, and none of the EDGs connected to its associated 4-Kv shutdown board. The EDGs were shutdown in accordance with plant operating procedures approximately 13 minutes after their start.

Since no actual plant condition existed which required the EDGs to start, and since the starts occurred inadvertently as a result of a human error during a test performance, this event is classified as invalid.

There were no safety consequences or impacts on the health and safety of the public. The event was entered into TVA's corrective action program for evaluation and resolution. (Reference BFN corrective action document PER 114498). The NRC Senior Resident Inspector has been notified.

• * *UPDATED ON 3/13/07 BY KOZAL TO EXPORT TO NRC INTERNAL WEBSITE* * *

This 60-day telephone notification is being made under reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) to describe an invalid actuation of general containment isolation signals affecting more than one system. On November 15, 2005, while operating at 100% thermal power, at 08:05 hours CST, Browns Ferry Unit 2 incurred an inadvertent, invalid actuation of the PCIS Group 6 logic. One reactor zone ventilation exhaust radiation monitor (the B channel) was indicating downscale due to a pre-existing maintenance issue, and, during activities to formally place the channel in a tripped status in accordance with the applicable Technical Specifications, the PCIS logic fuse for the opposite (A channel) radiation monitor was inadvertently removed rather than the fuse for the B channel. The PCIS logic responded as designed to the condition of both radiation monitors being downscale, and a Group 6 logic actuation resulted. The actuation was invalid because it resulted from an error related to an equipment tagging activity; there were no actual plant conditions which required the associated equipment actuations/isolations to occur. The following equipment actuations/isolations occurred: Unit 2 Group 6

• Initiation of the Standby Gas Treatment System
• Initiation of Control Room Emergency Ventilation
• Isolation of the following equipment:

  * reactor zone and refuel zone normal ventilation systems
  * drywell-torus differential pressure compressor
  * drywell-torus Hydrogen/Oxygen analyzers
  * drywell radiation continuous air particulate monitor

All equipment responded in accordance with the plant design. There were no safety consequences or impacts on the health and safety of the public. The event was entered into TVA's corrective action program for resolution. The NRC senior resident inspector has been notified.

This 60-day telephone notification is being made under reporting requirements specified by 10 CFR 50.73 (a)(2)(iv)(A) to describe an invalid actuation of general containment isolation signals affecting more than one system.

On September 25, 2004, with Unit 3 operating at 100% thermal power, at 1814 hours CDT, a voltage regulator problem occurred on RPS motor-generator (MG) set 3B. The associated RPS circuit protectors sensed an undervoltage condition and opened, thereby de-energizing RPS bus 3B. Primary Containment Isolation System (PCIS) logic circuits powered from this bus lost power, and PCIS logic Groups 2, 3, 6, and 8 were actuated. 

The following actuations/isolations occurred: Group 2: Isolation of the Pressure Suppression Chamber head tank pumps, Drywell Floor and Equipment Drains Isolation. Group 3: Isolation of the reactor water clean-up system. Group 6: Initiation of the Standby Gas Treatment System, Initiation of Control Room Emergency Ventilation, Isolation of the reactor zone and refuel zone normal ventilation systems. Group 8: This logic isolates the Traversing Incore Probes (TIP) if they are inserted. The TIPs were not inserted at the time of this event. All equipment responded in accordance with the plant design, with the exception that Unit 2 refuel zone ventilation system supply inboard isolation damper 2-DMP-064-0006 failed to close. The series damper, 2-DMP-064-0005, fully closed, therefore there would have been no impact to secondary containment integrity had this been an actual event. The damper's failure to close resulted from a sticking solenoid valve which was subsequently replaced. There were no safety consequences or impacts on the health and safety of the public. The event was entered into TVA's corrective action program for resolution.

The NRC senior resident inspector has been notified.