AB.4KV-0001 — Loss of 4KV Vital Bus
Purpose
Provides operator actions for response to a loss of a 4KV vital bus (2A or 2B). Entry conditions include loss of voltage on any 4KV vital bus.
Key Actions / Information
JPM — 2022 Sim-g
Loss of 2A 4KV Vital Bus response: A EDG auto-starts and re-energizes the bus. For charging restoration: determine if 23 Charging Pump was providing to Unit 2 (YES) → CLOSE 2CV55 → START 21 Charging Pump. If 21 Charging Pump trips on start (alternate path), START 22 Charging Pump. Note: 2CV55 has a long stroke time (~2 minutes).
Exam — 2020 Q53
Unit 1 — 1A 4KV Bus Differential with #3 SW Bay C/Ted: per step 3.33, 15 and 16 SW Pumps are powered from 1A Bus but are already isolated for #3 SW Bay outage. The 1A Bus Differential has no additional impact on service water system. 13 SW Pump trip (separate event) causes SW header pressure drop → 12 SW Pump auto-starts (C Bus). Correct procedure entry: AB.4KV-0001. Do not confuse with a Loss of All Service Water (AB.SW-0005) — the 1A bus loss does not affect currently-operating SW pumps.
Connections
- Related systems: 4KV, CVCS, EDGs, Service Water
- Related exam questions: 2020 Q53
- Related JPMs: 2022 JPM Sim-g
- Related exam: 2020 NRC Written Exam, 2022 NRC Operating Exam