AB.4KV-0002 — Loss of 2B 4KV Vital Bus
Purpose
Provides operator actions for response to a loss of the 2B 4KV vital bus. Entry conditions include loss of voltage on the 2B 4KV vital bus.
Key Actions / Information
Scenario — 2020 #5
2B 4KV Vital Bus de-energizes on bus differential protection during EOP-TRIP-1 following reactor trip. Key impacts: loss of 22 MDAFW Pump, loss of 2B 460/230 VAC buses (several SI and feedwater isolation valves lose power — redundant valves remain in safeguards position). CRS directs assistance restoring 2B 4KV bus while continuing EOP actions. 2CV284 loses power but backup valve 2CV116 is closed. 21BF13 valve position indication lost due to loss of 2B 460/230 VAC bus.
Scenario — 2019 #4
Loss of 2B 4KV Vital Bus occurs after reactor trip (Event 5). Key impacts: 22 AFW pump lost (powered from 2B 4KV). With 21 AFW pump C/T and 23 AFW pump tripping on overspeed after manual start, results in total loss of all AFW — CFST RED path on Heat Sink. Crew transitions to EOP-FRHS-1 and performs Prompt SGFP Recovery.
Connections
- Related systems: 4KV, AFW, 460/230V AC
- Related scenarios: 2019 Scenario 4 — SGFP Trip / Loss of Heat Sink, 2020 Scenario 5 — Loss of Heat Sink / Condensate Recovery
- Related exam: 2019 NRC Operating Exam, 2020 NRC Operating Exam