Transition to APPX-7 vs LOCA-5 during cold leg recirculation transfer: cavitation indications (oscillating RHR pump amps, flows, and discharge pressures) after sump valves are open indicate containment sump blockage → enter EOP-APPX-7. EOP-LOCA-5 would be entered instead only if loss of recirculation was due to mechanical or electrical component failures (not sump blockage). Minimum ECCS flow from Figure A (same figure in both LOCA-5 and APPX-7): at T+16 minutes post-trip, minimum ECCS flow is approximately 550 gpm. Trap: the Figure A x-axis is a LOG scale — incorrectly reading 16 minutes gives 500 gpm, which is the wrong answer.

Step 43, MAINTAINING RCS HEAT REMOVAL: when all RCPs are stopped and sump recirculation has failed, the crew dumps steam from intact SGs to promote Core Reflux Cooling. Reflux cooling is the mechanism by which steam generated in the RCS enters SG tubes and is condensed by cold water on the SG secondary side — this liquid remains in the primary system and promotes cooling. It is especially important to keep the secondary system adequately full of water.

Transition to APPX-7 from LOCA-3: erratic flow and pressure on both trains of ECCS pumps after alignment to containment sump = cavitation = sump blockage indication. Per LOCA-3 CAS, crew IMMEDIATELY transitions to APPX-7. LOCA-5 is the wrong procedure — it applies only when recirculation is lost for reasons NOT related to sump blockage.