AOP-3 Main Feedwater Transients Flashcards
What is the purpose of AOP-3, MAIN FEEDWATER TRANSIENTS?
Provides instructions to mitigate Main Feed Water transients and associated system malfunctions.
Combines the actions from the following Main Feedwater event procedures:
- Loss of Main Feedwater
- Excessive Feedwater Flow
What are the Initiating events for a loss of normal feedwater flow? What does it result in?
Initiating events
Trip of the Main Feedwater (MFW) pumps or a malfunction in the feedwater control
valves.
Results in decreased subcooling in the secondary side downcomer leading to an increase in the primary coolant system (PCS) temperature. As the PCS temperature increases, the coolant expands into the pressurizer which increases the pressure by compressing the steam volume.
What are the AOP-3 Entry conditions?
AOP-3 Entry conditions
- EK-0143, “FW PUMP P1A TURBINE K7A TRIP”
- EK-0146, “FW PUMP LO SUCTION PRESS CHANNEL TRIP” (250 psig)
- EK-0148, “FW PUMP P1A LO SUCTION FLOW OR LO DISCH PRESS” (2500 gpm or 800 psig)
- EK-0149, “FW PUMP P1B TURBINE K7B TRIP”
- EK-0154, “FW PUMP P1B LO SUCTION FLOW OR LO DISCH PRESS” (2500 gpm or 800 psig)
- EK-0155, “CONDENSATE PUMP TRIP”
- EK-0157, “CONDENSATE PUMP P2A DISCHARGE LO PRESS” (390 psig)
- EK-0160, “FDWTR PUMP LO SUCTION” (305 psig)
- EK-0163, “CONDENSATE PUMP P2B DISCHARGE LO PRESS” (390 psig)
- EK-0170, “HEATER DRAIN PUMP TRIP”
- EK-0961, “STEAM GENERATOR E-50A HI LEVEL” (84.7%)
- EK-0962, “STEAM GENERATOR E-50A LO LEVEL” (55%)
- EK-0963, “STEAM GENERATOR E-50B HI LEVEL” (84.7%)
- EK-0964, “STEAM GENERATOR E-50B LO LEVEL” (55%)
- Indications of a Main Feedwater transient in progress
- Condensate Cleanup System Leak
- Main Feedwater Piping Rupture
- Heater Drain Pump Malfunction
What are the AOP-3, Main Feedwater Transients, automatic actions?
Auto Actions
- CV-0608, Moisture Separator Drain Tank T-5 Level Control fully opens (Low Feedwater suction pressure 270 psig)
- Main Feed Pumps, trips (Low Feedwater Pump suction pressure 250 psig after a 3 second time delay).
- AFAS initiation (Steam Generator level of 30%)
- Reactor trip (Steam Generator level of 28%)
- CV-0701, E-50A Feed Regulating Valve, closes by high level override (84.7%).
- CV-0703, E-50B Feed Regulating Valve, closes by high level override (84.7%).
What are the Reactor Trip Criteria of AOP-3, Main Feedwater Transients under any power levels?
Reactor Trip Criteria under any Reactor Power
- Either Steam Generator level lowers to 30%
- No Main Feedwater Pump operating
- EK-0961, STEAM GENERATOR E-50A HIGH LEVEL is alarming, AND SG level(s) are less than 60% and lowering (e.g. fault in high level override circuit)
- EK-0963, STEAM GENERATOR E-50B HIGH LEVEL is alarming, AND SG level(s) are less than 60% and lowering (e.g. fault in high level override circuit)
What are the Reactor Trip Criteria of AOP-3, Main Feedwater Transients, at greater than 80% power?
Reactor Trip Criteria at greater than 80% power?
Any operating Main Feedwater Pump trips
CV-0711, Feed Pump P-1A Recirculation Valve fails open
CV-0710, Feed Pump P-1B Recirculation Valve fails open
What are the Reactor Trip Criteria of AOP-3, Main Feedwater Transients, at greater than or equal to 15% power?
Reactor Trip >=15% Power
- Either Steam Generator level is greater than 90% AND the high level override has not lowered feedwater flow
- Either Steam Generator level is greater than 95%
What are the turbine trip criteria of AOP-3, Main Feedwater Transients, at less than 15% reactor power?
Turbine Trip criteria at < 15% reactor power.
- Either Steam Generator level is greater than 90% AND the high level override has not lowered feedwater flow
- Either Steam Generator level is greater than 95%
If malfunctioning is diagnosed, what controllers does the operator take manual control to restore/stabilize Steam Generator level(s)?
Items for Manual Control to restore/stabilize Steam Generator level(s):
- CV-0701, E-50A Feed Regulating Valve
- CV-0703, E-50B Feed Regulating Valve
- CV-0735, E-50B Feed Reg Bypass
- CV-0734, E-50B Feed Reg Bypass
- HIC-0525, Combined Feed Pump Speed Control
- HIC-0526, P-1A Turbine Driver K-7A Speed Control
- HIC-0529, P-1B Turbine Driver K-7B Speed Control
What must be considered if a failed FW Flow input is recognized?
A failed Feedwater flow input results in HP_PWR being inoperable. Use highest of
NI/Delta-T power for monitoring reactor power.
What are the Feed Reg and Bypass Feed Reg valves failure modes?
Feed Reg and Bypass Failures
- Fails “as is” on loss of air
- Fails closed on loss of signal to the valve.
- Feedback failure on the Valve positioner– Valve will oscillate open and closed
Feed Regulating Valves Only
- Valve positioner failure – variable positions possible
How does a loss of the Main Feed Pump driver show itself?
Feed Pump Failure
- On loss of Air or Loss of Y-01
- Feed pump fails to 3250 rpm.
As steam generator pressure rises and falls, how does feedwater level initially react?
SG Pressure and Level
Rising pressure - loss or reduction in steam flow
- Level goes down
- “Bubbles” compress
Lowering pressure - rise in steam flow
- Level goes up
- “Bubbles” expand
How will a failed steam pressure instrument feeding the SGWL controls impact the system?
Instrument fails high
- Seen as a rise in density and therefore steam flow
Instrument fails low
- Seen as a lowering of density and therefore steam flow
What does it mean when a controller’s yellow alarm light is lit?
Yellow alarm light lit
- Indicates a failure in an input or an output.
- Take manual control of controller and control system (bumpless transfer).
Yellow alarm light flashing indicates low voltage condition in battery
