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EOPs > EOP-LOCA-1 — Loss of Reactor or Secondary Coolant

EOP-LOCA-1 — Loss of Reactor or Secondary Coolant

⚠️ DRAFT

EOP-LOCA-1 — Loss of Reactor or Secondary Coolant

Purpose

Primary EOP for response to a loss of reactor coolant or secondary coolant accident. Entered from EOP-TRIP-1 when RCS or secondary leak conditions are identified.

Key Actions / Information

Exam — 2023 Q37
After performing actions in EOP-LOCA-1 including SI reset and SEC reset, if a subsequent LOOP occurs, EDGs will auto-start in SEC Mode 2 (Blackout only). Only charging pumps are auto-sequenced — other safeguard loads (SI pumps, RHR pumps, CFCUs) must be manually started since SI/SECs were previously reset.
Exam — 2023 Q58
Step 17 — Containment Hydrogen Concentration: only one hydrogen recombiner may be placed in service when H2 concentration is between >0.5% and <4%. Operation of both recombiners is not permitted. If H2 >4% (6.0% in dry air = upper limit of recombiner operability), consult TSC for additional recovery actions. Purpose: prevent flammable mixture that could cause pressure excursion challenging containment integrity.
Exam — 2020 Q92
Step 24 — Containment Hydrogen Concentration decision points: between 0.5% and 4.0% → start ONLY one hydrogen recombiner. ≥ 4.0% → consult TSC for additional recovery actions. Trap: the normal operating procedure (S2.OP-SO.CAN-0001) starts two recombiners if concentration is 2.0% and rising — but EOP-LOCA-1 limits operation to only ONE recombiner below 4%. Do not confuse OP procedure guidance with EOP guidance.
Exam — 2019 Q91
Step 24 — Containment Hydrogen Concentration Verification (SRO question): with H2 at 0.7% (greater than 0.5%), crew starts ONLY ONE hydrogen recombiner by performing S1.OP-SO.CAN-0001 CONCURRENTLY with EOP-LOCA-1. Trap: starting BOTH recombiners is wrong below 4%. Consulting TSC is wrong below 4%. Waiting until 4.0% before acting is wrong (action threshold is 0.5%).
Exam — 2023 Q76
PZR vapor space leak (SBLOCA) with RCS at 1450 psig: both charging pumps AND SI pumps are injecting (1450 psig is below the shutoff head of both charging pumps at 2670 psig and SI pumps at 1520 psig). With subcooling at 10°F, PZR level 30% and rising, and RCS pressure stable — SI termination criteria in EOP-LOCA-1 are met, so the next procedure transition is to EOP-TRIP-3 (SI Termination), not directly to EOP-LOCA-2.
Exam — 2023 Q77
Step 7.4 (stopping containment spray pumps) is a continuous action step. Per OP-SA-108-101-2002 step 2.16.2: continuous action steps should NOT be performed when a Red or Purple path FRP is in progress. Even though containment pressure is below 13 psig and conditions for stopping CS pumps are met, a valid PURPLE path on Thermal Shock takes priority — transition to the FRP, do NOT perform Step 7.4.
JPM — 2022 Sim-c
Step 14 — accumulator isolation: when at least two RCS T-Hots < 405F, remove lockout from 21-24 SJ54 and close all. If 24SJ54 fails to close (alternate path), vent the unisolated accumulator: open 2NT35 (N2 HDR Valve) and 24SJ93 (N2 Supply Valve), verify accumulator pressure reaches zero.
Scenario — 2022 #1
Entered from EOP-TRIP-1 following LBLOCA based on containment pressure >4 psig (or two or more Table J channels not normal). In LOCA-1: RO confirms all RCPs stopped, PO maintains AFW flow. RO resets Phase A, opens 21 and 22 CA330s. RO resets both trains of SI, PO resets SECs. PO stops unloaded EDGs. 22 RHR pump trips during LOCA-1 — CRS determines no RHR pumps available and transitions to EOP-LOCA-5 (loss of emergency recirculation). Possible CFST Purple Path on Thermal Shock (FRTS-1) during LOCA-1 — enter/exit with no actions performed.
Scenario — 2020 #2
Entered from EOP-TRIP-1 following LBLOCA based on containment pressure >4 psig. In LOCA-1: RO resets SI and Phase A, opens 21 and 22 CA330s. PO resets all SECs, stops unloaded EDGs. RO reports subcooling NOT >0 F, RHR not aligned for cold leg recirc, RHR flow >300 gpm. 22 RHR Pump trips (overcurrent) — no RHR pumps available (21 RHR C/T). CRS transitions to EOP-LOCA-5 based on no RHR pumps available at Step 16.
Exam — 2019 Q77
RWST LEVEL LO alarm actuation during EOP-LOCA-1: crew transitions to EOP-LOCA-3 (TRANSFER TO COLD LEG RECIRCULATION). Trap: LOCA-3 is cold leg recirc, LOCA-4 is hot leg recirc. The RWST LO alarm drives the transition to LOCA-3, not remaining in LOCA-1 until LO-LO or performing concurrent RWST makeup.
Exam — 2019 Q14
Containment Spray reset per EOP-LOCA-1 (after AUTOMATIC actuation without manual backup): the NCO resets one train of Containment Spray by depressing bezel button B ONLY. Key switches A and C are NOT required when resetting after an automatic-only actuation. Bezel button B is the reset mechanism. Key switches would be involved only if a manual backup actuation had been performed.
Exam — 2020 Q25
LOCA outside containment recognition from EOP-LOCA-1: alarms indicating a LOCA outside containment include 2R41D (Plant Vent) in alarm, RHR sump overflow (OHA C-34), and RHR sump pump starts. Combined with inability to recover PZR level, the transition path is from EOP-LOCA-1 to EOP-LOCA-6. Key recognition: the crew arrives at LOCA-1 via the TRIP-3 CAS (PZR level cannot be maintained > 11%).
Exam — 2018 Q77
Hydrogen recombiner and hot leg recirculation timing: start ONLY one hydrogen recombiner when containment H2 concentration > 0.5%. Transfer to Hot Leg Recirculation (EOP-LOCA-4) is required 14 hours after SI actuation (not 12 hours). Trap: 12 hours is the requirement to start PREPARATIONS for hot leg recirc. The actual performance of LOCA-4 is at 14 hours. Also: there are two hydrogen recombiners on site, but EOP-LOCA-1 only starts ONE below 4% H2.
Exam — 2019 Q51
EOP-LOCA-1 Step 3 feed flow requirement: "MAINTAIN TOTAL FEED FLOW GREATER THAN 22E04 LB/HR UNTIL AT LEAST ONE SG NR IS GREATER THAN 9% (15% ADVERSE)". Containment pressure at 2.5 psig is NOT adverse — adverse containment threshold has not been reached. Therefore the non-adverse SG NR level limit of 9% applies, and the requirement is AT LEAST ONE SG (not all SGs). Trap: "ALL SGs" vs "AT LEAST ONE SG" — the step requires only ONE SG to exceed the limit. Also, 15% is the adverse containment limit, not the normal limit.
Scenario — 2018 #2
EOP-LOCA-1 entered from EOP-TRIP-1 after LBLOCA. STA reports RED path for Thermal Shock — CRS transitions to EOP-FRTS-1 (enter/exit: RCS pressure <300 psig and RHR flow >300 gpm). Returns to LOCA-1. RO resets SI, Phase A, Phase B. Resets SECs (2A and 2C reset, 2B de-energized). When RWST level lo alarm actuates at 15.2 feet, CRS transitions to EOP-LOCA-3 for cold leg recirculation transfer (CT#2: CT-36).

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