| ENS 57850 | Browns Ferry | 10 June 2025 23:10:00 | 60-DAY Optional Telephonic Notification for Invalid Containment Isolation | The following information was provided by the licensee via phone and 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 a general containment isolation signal affecting more than one system.
On June 10, 2025, Unit 2 operations personnel received an `A' channel half scram and entered 2-AOI-99-1. Motor generator set 2A was shut down and reactor protection system `A' was swapped to alternate. This resulted in primary containment isolation system (PCIS) groups 2, 3, 6, and 8 isolations, and initiation of standby gas treatment (SGT) trains `A', `B', and `C' and control room emergency ventilation system (CREV) train `A'. All affected safety systems responded as expected.
Plant conditions which initiate PCIS groups 2 and 8 actuations are reactor vessel low water level and high drywell pressure. Plant conditions which initiate PCIS group 3 actuations, are reactor vessel low water level and reactor water cleanup area high temperature.
Plant conditions which initiate PCIS group 6, CREV and SGT actuations, are reactor vessel low water level, high drywell pressure, or reactor building ventilation exhaust high radiation (reactor zone or refuel zone). At the time of the event, these conditions did not exist; the actuation was due to a loss of power and not due to a low reactor water level or drywell pressure. Therefore, the actuation of the PCIS, CREV, and SGT was invalid.
Upon investigation, the 2A2 circuit protector was found to have charred wire on the top right lug. The terminal block was replaced.
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 2019406. |