SALEM
SALEM STUDY SYSTEM
Systems > CFCUs

CFCUs

⚠️ DRAFT

CFCUs

Function

Recirculate and cool the containment atmosphere during normal operation and following a LOCA. (UFSAR 6.2.2.2)

Key Design Parameters

ParameterValueSource
Number5 per unitUFSAR 6.2.2.2.2
TypeCentrifugal fan with plate fintube cooling coilsUFSAR 6.2.2.2.2
Normal Operation Airflow110000 cfm eachUFSAR 6.2.2.2.2
Accident Operation Airflow40000 cfm eachUFSAR 6.2.2.2.2
Heat Removal (accident, per unit)≥44 x 10⁶ Btu/hr eachUFSAR 6.2.2.2.2
Heat Removal (3 units, cumulative)132 x 10⁶ Btu/hrUFSAR 6.2.2.2.2
Service Water Flow (per unit, accident)Minimum 1300 gpmUFSAR 6.2.2.2.2
LocationOperating floor, between containment wall and polar crane wallUFSAR 6.2.2.2.2
Seismic ClassificationClass IUFSAR 6.2.2.2.2

Components

Each fan-cooler unit includes: motor, fan, motor heat exchanger, cooling coils, roughing filters, dampers, duct distribution system, instrumentation, and controls. Cooled by service water. (UFSAR 6.2.2.2.2)

Key Design Points

  • 5 units installed, 3 required OPERABLE by Tech Specs
  • 3 units provide sufficient post-LOCA heat removal capacity
  • Normal operation: recirculate and cool containment atmosphere
  • Accident operation: reduced airflow but higher heat removal due to elevated containment temperature
Exam — 2020 Q52
CFCU service water header supply: with 21SW22 (Nuclear Header Inlet Valve) closed to isolate a leak, 23 CFCU can be supplied from EITHER 21 or 22 SW Header based on check valve locations. The remaining CFCUs (21, 22, 24, 25) are supplied from only one header. Result with 21 Nuclear Header isolated: only 3 CFCUs available via 22 SW Header (plus 23 CFCU from cross-connect). Not all 5 CFCUs have dual-header supply capability — only 23 CFCU has check valve placement allowing cross-header feed.
Exam — 2023 Q25
In LOW speed, CFCU dampers realign flow through HEPA filters (bypassing roughing filters) to reduce radioactivity inside containment. In HIGH speed (normal), flow goes through roughing filters. EOP-FRCE-3 directs placing all CFCUs in LOW speed for containment atmosphere cleanup.
Exam — 2023 Q13
R13 radiation monitors monitor CFCU service water DISCHARGE for radioactivity from containment into the SW system. CFCU SW flow discharges into the OPPOSITE unit's Circulating Water system. Loss of the opposite unit's CW flow prevents monitoring of this effluent pathway.
Exam — 2023 Q24
Service water to CFCUs is NOT isolated by Phase A or Phase B containment isolation signals. Following a LOCA with both Phase A and B actuated, SW from CFCUs is the only source of water into containment that remains unisolated (Fire Protection isolated on Phase A, CCW on Phase B, Primary Water on Phase A).
Exam — 2018 Q27
Confirms SEC Mode 1 CFCU behavior: with 21-24 CFCUs running in high speed and 25 CFCU stopped at time of RT/SI, at 10 minutes post-event ALL five CFCUs (including previously-stopped 25 CFCU) are running in LOW speed. SEC Mode 1 stops the running CFCUs, then starts ALL five in low speed. Trap: the SEC does not skip stopped CFCUs — it starts ALL five. Standby/stopped CFCUs receive the same low-speed start command as previously-running ones.
Exam — 2023 Q38
SEC Mode 1 (SI only): running CFCUs are tripped, then all five auto-start in LOW speed after a 20-second delay (coastdown period before restart). To restore manual HIGH speed control: must reset BOTH trains of SI AND all SECs. Resetting SI alone is NOT sufficient. EOP-TRIP-3 step 1 accomplishes this.
Exam — 2019 Q13
Unit 1 CFCU power distribution: with 1A 4KV Vital Bus de-energized, ONLY 11 CFCU is stopped. Confirms that 11 CFCU is powered from the A bus (consistent with Unit 2 pattern: 21 CFCU on A bus). 5 CFCUs powered from 3 vital buses — knowing the bus-to-CFCU mapping is critical for determining available cooling capacity following bus losses.
Exam — 2023 Q39
CFCU power distribution from 4KV Vital Buses: 21 CFCU (A bus), 22 CFCU (B bus), 23 CFCU (B bus, CIT), 24 CFCU (B bus), 25 CFCU (C bus). Loss of 2B 4KV Vital Bus = 22 and 24 CFCUs unavailable. Only 21 (A bus) and 25 (C bus) remain available. Note: 23 CFCU is normally on C bus but was CIT (Connected In Test) to B bus in the 2023 Q39 scenario. Per 2020 Q9, normal alignment has 23 on C bus.
Exam — 2022 Q41
CFCU SW flow via 2SW223: mechanical stop limits valve travel to ~50%. SW223 opens to the mechanical stop when the CFCU is in service and closes when the CFCU is out of service. SW flow is the same in both HIGH and LOW speed fan operation — the SW223 valve position does not change with fan speed. SW flow does NOT increase in LOW speed (accident) mode. The fixed-resistance flow scheme (inlet/outlet orifices + mechanical stop) ensures constant SW flow regardless of fan speed.
Exam — 2020 Q9
MSLB + LOOP with 2C 4KV Vital Bus lost (OHA J-3, 2C 4KV VTL BUS DIFF PROT): 23 and 25 CFCUs unavailable (both normally on C bus). 21 CFCU failed independently (OHA C-5 indicates 21SW223 outlet flow control valve closed; BEZEL 1-2 low air flow — even with SW58/SW72 open, CFCU is inoperable). Only 22 & 24 CFCUs (B bus) and 21 CS Pump (A bus) available. Containment cooling design bases require 3 CFCUs and 1 CS pump — with only 2 CFCUs, design bases NOT met. 22 CS Pump is on C bus (unavailable), NOT B bus. Both CS pumps are NOT available — only 21 CS Pump (A bus) is running.

Tech Spec LCOs

  • TS 3/4.6 — Containment — TS 3.6.2.3 requires at least 3 CFCUs OPERABLE
  • 1 inoperable (of required 3): 7 days to restore
  • 2 inoperable: 72 hours to restore
JPM — 2023 Sim-f
CFCU surveillance (S2.OP-ST.CBV-0003): if measured SW header DP is between Exhibit 1 values, per P&L 3.4 select minimum flow for the next HIGHER DP value. At 106 psi DP (between 105 and 110), required minimum is 1811 gpm (at 110 psi). Actual ~1785 gpm = UNSAT / inoperable. Also: CFCU SW flow must be >=1465 gpm in all cases (P&L 3.3).
Exam — 2022 Q55
SEC Mode 1 (SI only, no LOOP) CFCU response: SEC trips ALL high-speed 460V breakers (including standby CFCUs), then after a 20-second time delay, starts ALL five CFCUs in low speed. The SEC does NOT use load sequencers in Mode 1. A CFCU in standby receives the same treatment — high-speed breaker trips, then low-speed breaker closes after 20 seconds. There is NO immediate start for standby CFCUs — ALL CFCUs (running and standby) start in low speed after the same 20-second delay.
JPM — 2022 RO-A4
Containment entry for 22 CFCU tagging (Mode 1, 100% power): at the 22 CFCU area on 130' elevation, survey map shows gamma dose rate = 5 mrem/hr, neutron dose rate = 40 mrem/hr. With RP-imposed limits of 0.002 REM gamma / 0.008 REM neutron, the neutron dose is the most limiting factor at 12 minutes (shorter than gamma 24 min and heat stress 15 min).
Scenario — 2022 #4
21 CFCU fails to start in LOW speed on SEC signal following reactor trip/SI for SGTR. 21 CFCU is powered from 2A 4KV bus. Recovery: PO blocks 2A SEC, PO resets 2A SEC, RO manually starts 21 CFCU in LOW speed. This demonstrates the SEC block/reset/manual start sequence tested across multiple 2022 scenarios.
Exam — 2020 Q17
During a DBA LBLOCA with 2B EDG tripped (LOOP conditions), 22 and 24 CFCUs are NOT available — they are powered from the 2B 4KV Vital Bus. The LOCA-5 mitigation strategy to "Run All CFCUs in High Speed" is therefore not implementable under these conditions.
JPM — 2020 RO-A3
SW leak isolation using P&ID 205342: leak on drain valve 21SW268 downstream of 21SW76 (21 CFCU SW Outlet Valve) in SW Valve Room, Auxiliary Building. Requires closing valves on multiple P&ID sheets including cross-connected header valves 22SW76 and 22SW646. Demonstrates P&ID reading skill for SW piping through CFCU cooling coil path.
Exam — 2020 Q89
CFCU service water isolation per AB.SW-0001 Attachment 5: close SW72 (Outlet Water Valve) FIRST, then SW58 (Inlet Water Valve). Basis: minimize the possibility of water hammer following restoration. After the MOVs are closed, field manual isolation valves (SW54 CFCU SW Inlet and SW76 CFCU SW Outlet on 78' elevation) are closed to fully isolate.
Exam — 2020 Q40
Factors affecting CFCU heat removal and containment temperature:
- LOW speed = 47000 cfm vs HIGH speed = 110000 cfm — lower airflow reduces heat transfer across cooling coils → containment temp RISES.
- Increase in SW temperature → reduced delta-T across cooling coils → heat transfer decreases → containment temp RISES.
- Starting additional SW pumps INCREASES SW header pressure and flow across the orifice → INCREASES heat transfer → containment temp LOWERS (not rises).
- Erosion of the flow orifice upstream of SW223 INCREASES SW flow → INCREASES heat transfer → containment temp LOWERS (not rises).
Scenario — 2020 #3
21 SW Accumulator Tank pressure drops below operable band (138-157 psig) — 21 and 22 CFCUs declared inoperable. PO stops 21 and 22 CFCUs and isolates from field by closing 21/22 SW76 and 21/22 SW54. CRS enters TS 3.6.1.1 (1 hour) for containment integrity and TS 3.6.2.3 (14 days) for two CFCUs inoperable.
Scenario — 2020 #4
25 CFCU trips in low speed on overcurrent protection (low speed breaker open, overcurrent flag up at 84 ft switchgear room). CRS directs starting 23 CFCU in high speed. TS entries: TS 3.6.2.3 Action a (14 days) and TS 3.6.1.1 (1 hour containment integrity until control power removed). CRS directs WCC to open control power for 25 CFCU high and low speed breakers to satisfy containment integrity requirements.
JPM — 2019 Sim-f
22 CFCU surveillance test IAW S2.OP-ST.CBV-0003. Shift from high speed to low speed using S2.OP-SO.CBV-0001 (HIGH SPEED STOP → wait 25 seconds → LOW SPEED START). After 15 minutes, record SW flow (~1787 gpm) and SW header DP (106 psi). Per P&L 3.4, measured DP of 106 psi rounds up to next higher value (110 psid = 1811 gpm minimum). Actual flow less than minimum → test result UNSAT, 22 CFCU inoperable. P&L 3.3: both >= 1465 gpm AND >= Exhibit 1 minimum required for operability.
JPM — 2018 Sim-f
22 CFCU surveillance test (S2.OP-ST.CBV-0003): shift from high speed to low speed via S2.OP-SO.CBV-0001 (HIGH SPEED STOP → wait 25 seconds → LOW SPEED START). Verify damper positions (ROUGH FLT DAMPER CLOSED, HEPA INLET/OUTLET OPEN). Verify SW flow >= 1465 gpm. After 15 minutes, record SW flow (~1786 gpm) and SW header DP (106 psi). Per P&L 3.4, measured DP of 106 psi rounds up to 110 psid = 1811 gpm minimum required. Actual flow 1786 gpm < 1811 gpm → test result UNSAT, 22 CFCU inoperable. Same discriminating concept as 2019 and 2023 CFCU JPMs.
JPM — 2018 SRO-A5
Emergency classification with degraded CFCUs: 21 CFCU C/T for cooler leak, 22 and 23 CFCUs failed to start in LOW SPEED — only 24 CFCU running. Combined with containment pressure 35 psi and one CS pump in service → meets CB8.P (containment barrier potential loss, 2 pts): containment pressure > 15 psig AND one CS train in service AND < 3 CFCUs running in low speed.
Exam — 2018 Q12
Minimum containment cooling configurations that maintain Containment Pressure, Temperature and Humidity within design limits with a DBA: 2 CS Pumps, OR 1 CS Pump + 3 CFCUs, OR 5 CFCUs. Trap: 1 CS Pump alone or 1 CS Pump + 2 CFCUs are NOT sufficient for DBA containment cooling. Only 5 CFCUs (without any CS Pump) is sufficient.

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