Manual Reactor Trip Due to Inadequate Feedwater Flow
On October 29, 2018 at 1317 EDT, with St. Lucie Unit 1 in Mode 1 at 100% power, the reactor was manually tripped due to inadequate feedwater flow to both 1A and 1B Steam Generators (S/Gs). The trip was uncomplicated with all systems responding normally post-trip. (All control rods fully inserted and there were no specified system actuations.) Operators responded and stabilized the plant in Mode 3. The cause of the inadequate feed flow to the 1A and 1B Steam Generators is currently under investigation.
Decay Heat removal is being accomplished through forced circulation with stable conditions from Main Feedwater and the Steam Bypass Control System to the Main Condenser. Currently maintaining Pressurizer pressure at 2250 psia and Reactor Coolant System temperature at 532 degrees F.
St. Lucie Unit 2 was unaffected and remains in Mode 1 at 100% power.
This report is submitted in accordance with 10CFR50.72(b)(2)(iv)(B) for the reactor trip.
The NRC Senior Resident Inspector has been notified."
On October 12, 2018 at 1353 EDT, St. Lucie Unit 2 experienced an automatic RPS actuation and Reactor Trip due to a fault on the 2A1 6.9kv bus during a transfer of the bus power supply from the 2A Auxiliary Transformer to the 2A Startup Transformer. The bus fault caused a fire in the 2A1 6.9kv switchgear that has been extinguished. Offsite support was not required to extinguish the fire. The specific cause of the fault is currently under investigation.
Following the reactor trip, both Steam Generators are being supplied by main feedwater. All (Control Element Assemblies) (CEAs) fully inserted into the core. Decay Heat removal is being accomplished through forced circulation. Main Feedwater and Steam Bypass Control Systems are maintaining stable conditions in Mode 3.
St. Lucie Unit 1 was unaffected and remains in Mode 1 at 100 percent power.
This report is submitted in accordance with 10 CFR 50.72(b)(2)(iv)(B) for the Reactor Trip.
The fire was extinguished within 28 minutes. Plant loads are being supplied by the 2B Auxiliary Transformer.