RCP restart priority order: 23, 21+22 or 21+24, 21 (to provide normal PZR spray). Single pump operation preferred in the loop providing best spray. Primary reason for starting RCPs: forced convection permits faster cooldown with less potential for upper head voiding. Note N1-1 allows two RCPs for better spray if 23 unavailable.

Borating during natural circulation cooldown to Cold Shutdown: more time is required for complete boron mixing due to significantly lower RCS flow rate without RCPs. Once mixing is complete, the reactivity effect per ppm boron change is equal to what it would be during forced circulation. The key distinction is mixing time, not reactivity worth.

EOP-TRIP-4 CAS (foldout page): if subcooling is 0 degrees F OR PZR level cannot be maintained > 4%, then actuate SI and go to EOP-TRIP-1. With 2CV55 and 2CV71 fully open and PZR level at 10% and lowering, PZR level cannot be maintained — actuate SI. Trap: PZR heaters will NOT energize with level < 17%; aligning charging to RWST/BIT and going to EOP-LOCA-1 is plausible but TRIP-4 does not direct entry into LOCA-1.

EOP-TRIP-4 rapid cooldown transition: if RVLIS is available, crew transitions to EOP-TRIP-6 (NATURAL CIRCULATION RAPID COOLDOWN WITH RVLIS) when required RCS cooldown rate exceeds 25 °F/hr. Key RVLIS power supply detail: Loop 22 THOT provides input to Train A RVLIS. 2B Vital Instrument Bus powers RVLIS Train A Microprocessor Panel. Loss of 2B VIB makes Train A RVLIS inoperable, but Train B is unaffected — therefore RVLIS is still available and TRIP-6 (with RVLIS) applies. Trap: Loop 22 THOT failed low does NOT affect Train B RVLIS, and 2B VIB loss affects only Train A RVLIS microprocessor — not Train B. Both failures affect the same train.