SALEM
SALEM STUDY SYSTEM
Systems > AFW

AFW

⚠️ DRAFT

AFW

Function

Provides feedwater to steam generators when the main feedwater system is unavailable. Ensures decay heat removal via the steam generators following reactor trip, loss of main feedwater, or loss of offsite power. Safety-related. (UFSAR 10.4.9)

Pumps

ParameterMotor-Driven (2)Turbine-Driven (1)
Number21
Power SourceVital buses (EDG-backed)Main steam (no AC required)
SG SupplyEach can supply 2 SGsCan supply all 4 SGs
DC Control PowerVital DCVital DC

Actuation Signals

PumpActuation SignalsSource
Turbine-Driven2/3 Lo-Lo level in any 2 SGs; OR RCP bus undervoltage (1/2 twice); OR manual (local and remote)UFSAR T7.2-1
Motor-Driven2/3 Lo level in any SG; OR trip of both main FW pumps; OR safeguards sequence signal; OR blackout sequence signal; OR manual (local and remote)UFSAR T7.2-1
Exam — 2019 Q16
AFW pump start behavior with controllers in LOCAL MANUAL: LOCAL MANUAL disables all automatic AFW starts EXCEPT those initiated by the SECs. On SI (SEC Mode 1), the SECs send automatic start signals to ONLY 21 and 22 MDAFW pumps (not 23 TDAFW). Consequently, with all controllers in LOCAL MANUAL, a Reactor Trip + SI will start ONLY 21 and 22 AFW pumps. 23 TDAFW does NOT receive an SEC start signal — it starts on 2/3 Lo-Lo level in 2/4 SGs, RCP bus undervoltage, or manual only.
Exam — 2019 Q19
MDAFW pump power supply and SEC Mode 2 start: 22 AFW Pump is powered from 2B 4KV Vital Bus. When 2B bus de-energizes and 2B SEC actuates in Mode 2 (blackout), the SEC starts 22 AFW Pump after bus restoration. At 15% power with 21 SGFP still running, SG levels drop but none reach the Lo-Lo 14% setpoint for automatic MDAFW start. Only 22 AFW is running (from the SEC Mode 2 start on 2B bus). 21 AFW Pump is powered from the A bus (NOT the B bus) — 21 AFW does NOT start because the 2A SEC has no blackout signal.
Exam — 2019 Q20
AFW Pressure Override Runout Protection: with PRESSURE OVERRIDE NORMAL light illuminated, runout protection is enabled. When 21 AFW Pump trips, discharge pressure goes to 0 psig → 23AF21 and 24AF21 AUTOMATICALLY close (runout protection closes AF21 valves when discharge pressure < 1085 psig). AFW flow to 23 and 24 SGs goes to 0 LBM/HR. If PRESSURE OVERRIDE DEFEAT had been selected, the AF21 valves would NOT have auto-closed — they would remain in position and AFW flow would still drop to zero (no pump running) but the valves would stay open. Trip of a MDAFW pump does NOT cause automatic start of 23 TDAFW.
Exam — 2020 Q44
Trip of both SGFPs generates an automatic start of ONLY the MDAFW pumps. The TDAFW pump does NOT start on trip of both SGFPs — the TDAFW pump starts on 2/3 Lo-Lo level in any 2/4 SGs (14% NR), RCP bus undervoltage, or manual actuation. Common trap: believing all AFW pumps start on both SGFPs trip, or that the TDAFW pump starts on 1/4 SGs at 14% — it requires 2/4 SGs at 14%. Per S2.OP-SO.CN-0002, a removed-from-service SGFP is placed in the tripped condition, so the "trip of both SGFPs" interlock is already half-satisfied.
Exam — 2019 Q31
AMSAC AFW pump start mapping: AMSAC Train A starts 21 AFW pump (motor-driven). AMSAC Train B starts 22 AFW pump (motor-driven). Either train starts 23 AFW pump (turbine-driven). A spurious actuation of ONLY Train A starts 21 and 23 AFW pumps. Trap: 22 AFW does NOT start on Train A — it only starts on Train B. The turbine-driven pump (23) starts on either train.

Water Sources

  • Primary: Condensate storage tank
  • Backup: Service water system (safety-related, unlimited supply from Delaware River)
Exam — 2023 Q41
23 AFW Turbine-Driven pump governor maintains constant turbine speed as SG pressure lowers (designed to operate with SG pressures as low as 100 psig). As SG pressure decreases, the differential pressure across the feedpump discharge and the SG increases, so AFW flow RISES even though turbine speed remains constant.
Exam — 2023 Q43
Instrument air supply line rupture to 2MS132 (23 AFW Turbine Steam Inlet Valve) causes the valve to fail OPEN. This starts the 23 AFW pump, injecting cold feedwater into the SGs at power. Reactor power increases above 100% RTP due to cooler feedwater (positive MTC). The digital FW system automatically adjusts MFW Reg Valves — no manual FW control needed. Operator should reduce reactor power per S2.OP-IO.ZZ-0004 (Power Operation). Maximum power level: 3459 MWt (100% RTP).
Exam — 2023 Q44
2DR6 (AFW Tank Makeup Valve) fails OPEN on loss of air. This causes the AFW storage tank level to rise and potentially overflow. Per S2.OP-AB.CA-0001, Attachment 2, the 2DR6 can be manually operated from the field to control tank level.
Exam — 2022 Q46
2PA-3450 (AFW pump discharge pressure transmitter) fails to zero: runout protection circuit closes AF21 valves (flow control) to protect pump from runout. To recover: place PRESS OVERRIDE DEFEAT switch to DEFEAT to bypass the runout protection circuit and allow operator control of AF21s. LOCAL MANUAL is indication only in the control room (no auto-start signals) — it does NOT allow manual control of the AF21 valves. PRESS OVERRIDE DEFEAT is the correct recovery action.

Pump-to-SG Alignment

Exam — 2020 Q46
21 AFW Pump (motor-driven) feeds 23 and 24 SGs. 23 AFW Pump (turbine-driven) feeds all 4 SGs. Pressure override runout protection closes AF21 valves when discharge pressure is < 1085 psig, preventing pump runout. With pressure override active on 21 AFW and 23 AFW running, 23 and 24 SG levels rise SLOWER than 21 and 22 SG levels (only turbine-driven pump feeding them vs. turbine-driven feeding all 4). Common trap: believing 21 AFW feeds 21 and 22 SGs (pump number does NOT match SG number). 23 AFW auto-starts on LOOP due to 4KV Group Bus Undervoltage.

Key Design Points

  • Turbine-driven pump is available during station blackout (no AC power required)
  • Motor-driven pumps auto-start on lower SG level setpoint than turbine-driven pump
  • Turbine-driven pump requires steam pressure >680 psig for IST testing

Tech Spec LCOs

  • TS 3/4.7 — Plant Systems — TS 3.7.1.2 requires three independent AFW pumps OPERABLE in Modes 1, 2, and 3
  • 1 pump inoperable: 72 hours to restore
  • 2 pumps inoperable: Hot Standby in 6 hours
  • 3 pumps inoperable: immediately restore at least one
JPM — 2023 SRO-A4
ICMF during SGTR: TD AFW pump (23 AFW) takes steam from 21 and 23 SGs. With 23 SG ruptured and 23MS45 not yet closed, primary-to-secondary leakage exits through the TD AFW pump steam supply — constitutes an unmonitored release in progress.
Exam — 2022 Q79
2MS132 (23 AFP Turbine Steam Inlet Valve) air supply line rupture: valve fails OPEN on loss of air, causing 23 AFW pump to start at power. Cold AFW injection causes reactor thermal overpower (exceeds 3459 MWt). Per S2.OP-IO.ZZ-0004 (Power Operation): reduce turbine load to lower reactor power below the administrative limit. AB.CA-0001 Attachment 12 provides local control of 23 AFP governor and AF21s but does NOT direct shutting down 23 AFW pump. The overpower condition must be addressed first by reducing turbine load.
Scenario — 2022 #3
Loss of all AFW: 21 AFP C/T for oil bubbler replacement (initial condition). 23 AFP fails to auto start on SI — PO manually starts. 22 AFP trips on overcurrent. 23 AFP trips on overspeed. No SG NR levels > 9% (15% adverse), total AFW flow < 22E4 lbm/hr. CFST Heat Sink Red Path → transition to EOP-FRHS-1. CT#2 (CT-43): Establish feed flow to one SG before bleed and feed is required. Recovery via condensate system (MS10 depressurization + BF40/BF19 bypass).
Scenario — 2020 #4
At 2% power during startup, 21 SGFP trips — AFW pumps fail to auto-start (both motor-driven AFW pump auto-start signals failed). PO manually starts 21 and 22 AFW pumps, sets 21-24 AF21 demands to 0% first, then throttles AF21s to maintain SG levels between +/-5% of program. PO throttles AFW flow to no less than 22E4 lbm/hr after reactor trip.
Scenario — 2020 #5
Complete loss of all AFW following reactor trip: 21 AFP trips on overcurrent (overcurrent relay flag up), 22 MDAFW pump lost with 2B 4KV bus (bus differential protection), 23 AFP trips on overspeed, MSPI AFW pump fails on overspeed. No SG NR levels >9% (15% adverse), total AFW flow <22E4 lbm/hr → transition to EOP-FRHS-1. CT-43: establish condensate feed flow before bleed and feed required. Bleed and feed criteria: 3 WR levels <20% (25% adverse). Caution: steam 21 and 23 SGs last to maximize 23 AFW pump steam supply availability.
Exam — 2018 Q18
AFW backleakage (S2.OP-PT.AF-0002): monitoring required 30 to 60 minutes after an AFW Pump is shutdown in Modes 1-3 (P&L 3.1). Backleakage of hot feedwater can disable motor-driven AFW pumps by causing vapor binding (steam binding) — per SOER 84-3. Trap: backward rotation is a concern for RCPs (which have anti-reverse-rotation devices), not AFW pumps. The AFW failure mode is steam/vapor binding from hot feedwater backing into the pump suction piping.
Exam — 2018 Q66
MDAFW pump power supply confirmation: 11 AFW Pump is powered from 1A 4KV Vital Bus. With 1A 4KV de-energized, 11 AFW is lost. Per EOP-LOSC-2 Step 1: if the 13 AFW Pump (TDAFW) is the ONLY source of AFW flow (both MDAFWs unavailable), steam must NOT be isolated to the 13 AFW Pump. Must trace 4KV bus to AFW pump mapping: 1A 4KV → 11 AFP, 1B 4KV → 12 AFP. With both MDAFWs unavailable, the TDAFW pump is the only remaining source and must be preserved.

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