EOP-LOSC-1 — Loss of Secondary Coolant
Purpose
Referenced in 2023 NRC Operating Exam simulator scenarios. Details to be backfilled from source documents.
Key Actions / Information
Exam — 2020 Q9
Referenced as 2-LOSC-1 for design bases MSLB + LOOP event. Containment cooling design bases configuration requires 3 CFCUs and 1 CS pump. With 2C 4KV Vital Bus lost and 21 CFCU failed independently, design bases are NOT met (only 22 & 24 CFCUs and 21 CS pump available).
Scenario — 2020 #3
Entered from EOP-TRIP-1 on 21 SG pressure dropping in uncontrolled manner (feedwater line break inside containment). MSLI previously initiated. PO closes/verifies closed: 21BF13, 21BF40, 21MS7, 21MS10, 21MS18, 21MS167, and 21GB4 to isolate faulted 21 SG (CT-17 Part 2). Trips and stops 23 AFW pump. Dispatches operator to close 21MS45. PO reports 21 SG is faulted, other SGs NOT depressurizing. RCS temperature rising — PO adjusts MS10s to stabilize. Transition to EOP-TRIP-3 when RCS subcooling >0 F, PZR level >11%, RCS pressure stable/rising.
Connections
- Related systems: CFCUs, Containment Spray, Main Steam, Feed & Condensate, AFW, Steam Generator & Blowdown
- Related EOPs: EOP-TRIP-1 — Reactor Trip or Safety Injection, EOP-TRIP-3 — SI Termination
- Related exam questions: 2020 Q9
- Related scenarios: 2020 Scenario 3 — ATWS / Feedwater Line Break
- Related exam: 2020 NRC Written Exam, 2023 NRC Operating Exam, 2020 NRC Operating Exam