Loss of 2B VIB impact on ESFAS: Containment Spray Hi-Hi Containment Pressure bistables are energized to actuate. Loss of the 2B VIB causes the associated Hi-Hi Containment Pressure bistable to remain de-energized, so the coincidence logic goes from 2/4 to 2/3 (the de-energized channel cannot actuate). Per TS 3.3.2.1, the inoperable channel is placed in BYPASS (not tripped) to reduce the possibility of spurious Containment Spray actuation. Trap: most ESF bistables are de-energized to trip and TS requires tripping the inoperable channel. Containment Spray is the opposite — energized to actuate, so the inoperable channel is bypassed.

Loss of 2B VIB makes RVLIS Train A Microprocessor Panel inoperable. Combined with Wide Range Loop 22 THOT failed low (also Train A RVLIS input), only Train A RVLIS is affected. Train B RVLIS remains available. During EOP-TRIP-4, crew transitions to EOP-TRIP-6 (with RVLIS) since at least one RVLIS train is available.