This 60-Day telephone notification is being made per the reporting requirements specified in 10 CFR 50.73(a)(2)(iv)(A) to describe an invalid actuation of containment isolation signal affecting more than one system. On May 13, 2021, during the restoration of the Unit 2 Refuel Floor High Radiation Isolation Logic an invalid isolation signal was received. The condition requiring an isolation signal was verified not to be present prior to restoring the logic; however, it was not recognized that a previous isolation signal was latched in and had not been reset. When the isolation logic was restored, the Primary Containment Isolation System (PCIS) isolated on the invalid signal. The systems successfully completed the isolation per the plant design and plant configuration.
The following systems actuated due to the Unit 2 PCIS Group 6C Isolation:
- Isolation of Containment Hydrogen and Oxygen Sampling Valves,
- Start of the 2A Reactor Enclosure Recirculation System,
- Trip of the Units 1 and 2 Refuel Floor HVAC,
- Start of the A and B Trains of Standby Gas Treatment Systems.