Auxiliary Feedwater System Flashcards
.What is the purpose of the Auxiliary Feedwater System?
Designed to provide a supply of feedwater to the steam generators during start‑up operations and to remove primary system sensible and decay heat during initial stages of shutdown operations.
What is the functional design of the Auxiliary Feedwater System?
Consists of two motor driven pumps and one steam turbine driven pump configured into two trains.
The system is normally aligned for fully automatic operation. When at least 2 S/G level safety channels associated with an S/G reach a pre-determined setpoint (30%), an AFW pump starts and its associated flow control valves open to deliver the required flow (165 gpm) to both Steam Generators.
What quantity of condensate must be available for the Auxiliary Feedwater System?
Total combined capacity between T-2 and T‑81, Primary Makeup Storage Tank, must be greater than 100,000 gallons.
This exceeds the amount needed for 8 hours of auxiliary feedwater pump operation for decay heat removal following a reactor trip.
What is the design/power supplies for P-8A/B?
Horizontal, split case, single suction, double volute, nine-stage centrifugal pumps
Capable of delivering the minimum required flow for decay heat removal up to 1000 psia in the S/Gs with all four PCPs in service.
415 gpm design flow
P-8A is supplied Left channel power from Bus 1C
P-8B turbine driven with steam from E-50A
What is the design/power supplies for P-8C?
Horizontal split case single suction, double volute, seven-stage centrifugal pump.
Design flow of 330 gpm
P-8C is a converted HPSI pump. It will deliver the minimum required flow for decay heat removal if S/G pressure is maintained at or below 900 psia with all four PCPs in service OR if S/G pressure is at or below 1000 psia with all PCPs secured.
Powered from Bus 1-D
What is the low suction pressure trip for P-8A/B?
Trips on low suction pressure (6.7 psig) on 2 of 3 switches.
Reset P-8A
- Take control room handswitch or breaker cubicle switch momentarily to the TRIP position before pump can be restarted.
Reset P-8B
- Take control room handswitch to close for CV-0522B
Power Supplies
Y-10 supplies switches, swaps to Y-30 in normal is lost
What is the P-8C Low Suction Pressure trip?
Trips pump on low suction pressure (8 psig) on 2 out of 3 switches.
Reset P-8C
- Take control room handswitch or breaker cubicle switch momentarily to the TRIP position before pump can be restarted.
Switches powered by Y-20, no backup.
What trips an auxiliary feedwater pump?
P-A/C - Overcurrent
P-8A/B - 6.7 psig low suction pressure
P-8B - 8 psig low suction pressure
P-8B - overspeed at 110%. (3560 rpm rated, 3845-3916 rpm trip)
Motive force for CV-0522B, P-8B Steam Supply Valve
CV-0522B, P-8B Steam Supply Valve
Valve is air operated supplied by instrument air with bottled nitrogen backup supply from Nitrogen Station #2. It is equipped with a manual operator for local control.
What are the left train flow control valves?
AFW Flow Control Valves are associated with left train AFW (P‑8A/B)
CV-0727 and CV-0749,
- Four inch valves
- CV-0727 – ‘B’ Steam Generato
- CV-0749 – ‘A’ Steam Generator
Instrument air operated.
Backed up by bottled nitrogen from Nitrogen station #1.
Equipped with manual operators for local control.
Air to close (fail open on loss of air).
What are the right train flow control valves?
AFW Flow Control Valves are associated with right train AFW (P-8C)
CV-0736A and CV-0737A,
- Four inch valves
- CV-0736A – ‘B’ Steam Generator
- CV-0737A – ‘A’ Steam Generator
Air to close (fail open on loss of air).
Instrument air operated. NO backup nitrogen supply.
Equipped with manual operators
What are the right train flow control bypass valves?
CV-0736A and CV-0737A also contain 1.5” bypass valves:
CV-0736 and CV-0737
- Allow continuous auxiliary feedwater at low flow rates during start-up and hot shutdown conditions.
Air to open (fail closed on loss of air).
Operated by instrument air system. NO backup nitrogen supply
Equipped with manual operators for local control..
What are the FOGG valves?
FOGG – Feed Only Good Generator
Disabled – not used at Palisades
Block valves are locked open with power removed:
- MO‑0743 – P-8A/B to E‑50B S/G
- MO‑0798 – P-8A/B to E‑50B S/G
- MO‑0753 – P-8A/B to E‑50A S/G
- MO‑0760 – P-8A/B to E‑50A S/G
- MO‑0748 – P-8C to E‑50B S/G
- MO‑0755 – P-8C to E‑50B S/G
- MO‑0754 – P-8C to E‑50A S/G
- MO‑0759 – P-8C to E‑50A S/G
What is Auxiliary Feedwater Actuation System (AFAS) C-187?
Auxiliary Feedwater Actuation System (AFAS) C-187
Provides automatic AFW pump starting on low level in either S/G of 30%
4 Sensor Channels with input from S/G safety channel level indication
- SCA, SCB, SCC, and SCD
- Y-10, Y-20, Y-30, Y-40
Sensor Channel Trips
- Level in either S/G is +-30%.
- Preferred AC Bus Trip
- 2 out of 4 sensor channels activate both actuation channels when tripped
Actuation Channels (ACA - Left Train Actuation and ACB - Right Train Actuation)
- Power supplies:
- ACA - D11‑1
- ACB - D21‑2
Loss of power prevents actuation channel from generating an AFAS.
What is required in order to bypass a sensor channel?
To bypass a tripped sensor channel requires power available to the sensor channel. The bypass is not effective if sensor channel power has been lost.
What happens on a loss of Y-10 and Y-30?
Low Suction Pressure Trip (LSPT) on P‑8A/B
Loss of Y-20 results in LSPT on P-8B
What happens on a loss of D-11-1 or D-21-1?
No Channel Actuation
- D-11-1: ACA - Left Train Actuation
- D-21-1: ACB - Right Train Actuation)
CV-0522B opens to modulate supply pressure to ~250#, POC-0522B supplies via CV-0522G and H to run P-8B. Position indication for CV-522B is lost.
How does the P‑8A Auto Start sequence function?
- AFAS signal present (occurs at < 30.0% in either S/G on a 2/4 safety channel logic.)
- P‑8A control room handswitch must be in AUTO.
- 2400V power available
If above conditions are met, a start signal is sent to P‑8A after 2.5 seconds.
Start is delayed 2.5 sec and only in for 5 sec since the anti pump feature requires removal of start signal.
How does the P‑8C Auto Start sequence function?
- AFAS signal present (occurs at < 30.0% in either S/G on a 2/4 safety channel logic.)
- P‑8C control room handswitch must be in AUTO.
- 2400V power available
- P‑8A not running or not delivering flow to A and B S/G.
- Not delivering flow means: At least 1 out of 2 flow switches to A S/G and B S/G sensing less than 100 gpm OR P‑8A breaker contact indicates P‑8A not running.
If, at any time, these permissives are met, a start signal is sent to P‑8C after 30.5 seconds.
How does the P‑8B Auto Start sequence function?
AFAS signal present (occurs at < 30.0% in either S/G on a 2/4 safety channel logic.)
P‑8B control room handswitch must be in AUTO.
P‑8A not running or not delivering flow to A and B S/G. Starts 112.5 sec counter.
If P-8C not delivering flow anytime after 112.5 sec, the P-8B Starts.
Not delivering flow means: At least 1 out of 2 flow switches to A S/G and B S/G sensing less than 100 gpm OR P‑8A breaker contact indicates P‑8A not running.
