On February 28, 2019, at 2217
CST, LaSalle Unit 2 experienced a trip of the 241Y Safety Related Bus during surveillance testing resulting in a valid
undervoltage actuation signal to the Common
Emergency Diesel Generator ('O'
EDG), causing it to start and load to Bus 241Y. The purpose of the surveillance testing was to demonstrate the operability of the breakers necessary to provide the second off site source to Unit 2. This event is reportable in accordance with 10 CFR 50.72(b)(3)(iv)(A), as an event that results in a valid actuation of the emergency
AC electrical power system. In addition to the 241Y bus trip and 'O'
EDG actuation signal, the following plant responses occurred as designed due to the momentary loss of this
AC Bus: "A"
RPS de-energized due to the loss of the 2A
Reactor Protection System Motor-Generator Set, and the running Unit 2 Fuel Pool Cooling pump tripped. The Non-Safety Related Bus 241X de-energized resulting in a trip of the Unit 2 Station Air Compressor. All systems have been restored and troubleshooting is currently in progress. Unit 1 remained in MODE 1 during this event.
The NRC Senior Resident Inspector has been notified.
