Steam Generator Water Level Control Flashcards
LCO 3.3.7 “Post Accident Monitoring (PAM) Instrumentation” requirement
The PAM instrumentation for each S/G Wide Range Level shall be operable
LCO 3.3.7 “Post Accident Monitoring (PAM) Instrumentation” applicability
Modes 1-3
LCO 3.3.8 “Alternate Shutdown System” requirement
The Alternate Shutdown System Function for S/G Wide Range Level shall be operable
LCO 3.3.8 “Alternate Shutdown System” applicability
Modes 1-3
What power level are the S/G LICs used?
15-100%
What S/G levels are maintained by the S/G LICs?
60-70%
Normally 65%
What are the power supplies for the S/G LICs?
LIC-0701 (A S/G) - Y-10, auto swaps to Y-30 on loss of Y-10
LIC-0703 (B S/G) - Y-20, auto swaps to Y-40 on loss of Y-20
How do the S/G LICs fail?
Closed on loss of power
How do the S/G LICs respond on a turbine trip?
Controller swaps to manual, so the MFRVs stay at whatever position they were in before the trip
What are the modes of operation for the S/G LICs?
MANUAL - output is directly input by the operator
AUTO - operator sets the set point (blue pointer), and the controllers maintain S/G level at that setpoint.
What is a requirement for placing the S/G LICs in AUTO?
“Green” PF light must be flashing. Light starts flashing when S/G level is within 5% of the controller setpoint
How does SGWLC respond on CHP?
- Controller is grounded, which gives a zero output signal, closing the MFRV.
- If only 1 channel of CHP comes in, only that train of SGWLC is affected (left train - A S/G, right train - B S/G)
How does SGWLC respond on S/G Low Pressure?
- At 500 psia, controller is grounded, which gives a zero output signal, closing the MFRV.
- Only the controller/MFRV associated with the affected S/G.
What is the function of the high level override?
- 84.7% S/G level, controller is grounded, which gives a zero output signa, closing the MFRV.
- Only the controller/MFRV associated with the affected S/G.
What is the function of the MFP Combined Speed Controller?
When in CASCADE, receives signal from both S/G LICs. Auctioneers the highest of the 2 signals, and passes this signal on to the individual MFP Speed Controllers. Lowest S/G level dictates the speed of both MFPs, and MFRVs adjust accordingly.
What is the power supply for the MFP Combined Speed Controller?
Y-01
Loss of Y-01 causes MFPs to go to minimum speed
What is a requirement for swapping MFP Combined Speed Controller from MANUAL to CASCADE?
“Green” PF light needs to be flashing. Light starts flashing when the controller’s output signal is within 0.5% of the input signal.
What are the power supplies for the MFP Individual Speed Controllers?
Both from Y-01
Loss of Y-01 causes MFPs to go to minimum speed
What is the speed range controlled by the MFP Individual Speed Controllers?
Min - 3250 rpm (54% input from combined speed controller, 0% output on individual speed controller)
Max - 5250 rpm (88% input from combined speed controller, 100% output on individual speed controller)
What are the modes of operation of the MFP Individual Speed Controllers?
AUTO - auto button doesn’t work, but on a turbine trip, controllers will automatically swap to auto and ramp to minimum speed (3250 rpm), if controller was in CASCADE
CASCADE - controls MFP speed based on input signal from MFP Combined Speed Controller
MANUAL - control speed manually with the slide bar. Provides much faster speed change
What are the power supplies for the MFRV Bypass Valve LICs?
Both from Y-01
Valves fail closed on loss of power
When are the MFRV Bypass Valves used?
Used to control S/G level at low power (< 15% reactor power).
Smaller valves, so they give finer level control at lower power
What are the modes of operation for the MFRV Bypass Valve LICs?
AUTO - receives signal from the same input as the MFRV LICs. Controls S/G level at setpoint that is set by the operator (normally 65%)
MANUAL (normal) - output is set by the slide bar. During normal power operations, these controllers are in MANUAL and set to CLOSE.
What is a requirement to transfer MFRV Bypass Valve LICs from MANUAL to AUTO?
“Green” PF light needs to be flashing. Light starts flashing when S/G level is within 5% of the setpoint
How do MFRV Bypass Valve LICs respond to a trip?
They remain in the mode they were in (MANUAL/AUTO) before the trip. If they were in AUTO, they continue to try to maintain S/G levels at the setpoint.
What are the power supplies for the Wide Range S/G Level Transmitters?
Each S/G has 1 LT powered from Y-10, and 1 from Y-20
What are the power supplies for the AFAS S/G Level Transmitters?
Each S/G has 4 LTs, 1 powered from each preferred AC bus (Y-10, 20, 30, 40)
What are the power supplies for the MFP Recirc Control Valves?
P-1A - Y-10
P-1B - Y-20
How do the MFP Recirc Control Valves fail?
Valves fail open, causing MFPs to trip on low suction pressure.
How does shrink and swell impact operation of the SGWLC System?
Shrink occurs when a decrease in steam demand causes steam pressure and temperature to rise, which results in less boiling occurring, and compression of steam bubbles cause a level drop.
Swell occurs when an increase in steam demand results in a pressure reduction. This causes increased boiling and expansion of steam bubbles, which causes a level rise.
