SALEM
SALEM STUDY SYSTEM
Systems > 115V AC

115V AC

⚠️ DRAFT

115V AC

Function

Vital instrument buses provide regulated AC power to protection system instrumentation. Fed from inverters under normal operation with automatic transfer to regulated AC supply as backup. (UFSAR 8.3.1.4)

115V AC Instrumentation Power

  • Vital instrument buses provide power to protection system instrumentation
  • Fed from inverters (normal) with automatic transfer to regulated AC supply (backup) (UFSAR 8.3.1.4)
Exam — 2020 Q12
Loss of 2A 115V Vital Instrument Bus affects VCT level instrument LT-112 (loss of indication, alarms, and auto makeup). LT-114 remains available but only via the plant computer in the control room (NOT on the control console) and at Panel 216 in charging pump alley.
Exam — 2020 Q88
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 bistable to remain de-energized → logic goes from 2/4 to 2/3. Per TS 3.3.2.1, the inoperable channel is BYPASSED (not tripped) to prevent spurious CS actuation. Most ESF bistables are de-energized to trip → tripped on inoperability. CS bistables are the exception — energized to actuate → bypassed on inoperability.
Exam — 2019 Q34
Steam Dump I/P converters are powered by C/D 115 VAC Instrument Bus. Loss of 115 VAC to the I/P converters causes steam dumps to fail closed.
Exam — 2019 Q89
LCO 3.8.2.1 with 2 inverters inoperable: LCO 3.8.2.1 addresses only one inverter inoperable (Required Action A). With 2 inverters inoperable, there is no applicable Required Action → LCO 3.0.3 applies. From the time the 2nd inverter becomes inoperable, the crew has 1 hour to begin + 6 hours to reach Hot Standby = 7 hours maximum. Trap: do not use the 30-hour restoration time from Required Action B — that applies only to one inoperable inverter. With two, LCO 3.0.3 is the default.

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