1/2 Edg Auto Started and Lpci/Core Spray Inoperable Due to Loss of Safety Bus
On October 24, 2018 at 0901 CDT, during performance of the 'Functional Test of Unit 1 Second Level Undervoltage,' a loss of Bus 13-1 and Bus 18 occurred. The 1/2 Emergency Diesel Generator (EDG) automatically started due to a valid actuation on loss of power to Bus 13-1, but did not load due to required testing alignment.
The loss of Bus 13-1 caused the loss of the 1A loop of Core Spray, both loops of Low Pressure Coolant Injection (LPCI), and Bus 18. All equipment responded as expected.
Bus 13-1 and Bus 18 were restored at 0911(CDT) on 10/24/18. Other affected systems are in the process of being restored. An investigation as to the cause of the event has been initiated.
This notification is being made in accordance with 10 CFR 50.72(b)(3)(iv), 'Event or Condition that results in valid actuation of any of the systems listed in paragraph (b)(3)(iv)(B),' because the 1/2 EDG auto started due to the loss of power condition.
This notification is also being made in accordance with 10 CFR 50.72(b)(3)(v)(B), 'Event or Condition that Could Have Prevented Fulfillment of a Safety Function,' because both loops of LPCI were inoperable for a short time period.
During the ten minutes where LPCI was unavailable, Unit 1 was in Technical Specification LCO 3.0.3. Unit 1 is currently in LCO 3.8.1(b) until the EDG is restored. Unit 2 was not affected by this event.
The licensee will notify the NRC Resident Inspector.
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