At 0208 EDT on 05/13/2020, Sequoyah Unit 1 was at 100% power when an
automatic reactor trip signal was received concurrent with a low steam line pressure safety injection signal.
The low steam line pressure safety injection signal was actuated from the steam pressure rate of decrease feature. Main steam isolation valves (MSIVs) automatically closed as designed and steam generator pressures stabilized following the isolation. All other safety-related equipment operated as designed, with the exception of 1-FCV-61-122 Glycol inboard containment isolation valve which failed to automatically isolate on a Phase A containment isolation signal. The corresponding outboard containment isolation valve, 1-FCV-61-110, automatically isolated as designed which isolated penetration X-114.
Safety injection was terminated at 0221 EDT 5/13/20, and Unit 1 is currently being maintained in Mode 3 at normal operating temperature and pressure with auxiliary feedwater supplying the steam generators and decay heat removal via steam generator atmospheric relief valves.
There is no indication of any primary to secondary leakage. The electrical alignment is normal with shutdown power supplied from off-site power. There is no current operational impact to Unit 2.
There is no impact on public health or safety. Post safety injection actuation investigation is in progress.
The NRC Resident Inspector has been notified.
