Steam Generator Water Level Control

Question 1

LCO 3.3.7 “Post Accident Monitoring (PAM) Instrumentation” requirement

Answer 1

The PAM instrumentation for each S/G Wide Range Level shall be operable

Question 2

LCO 3.3.7 “Post Accident Monitoring (PAM) Instrumentation” applicability

Answer 2

Modes 1-3

Question 3

LCO 3.3.8 “Alternate Shutdown System” requirement

Answer 3

The Alternate Shutdown System Function for S/G Wide Range Level shall be operable

Question 4

LCO 3.3.8 “Alternate Shutdown System” applicability

Answer 4

Modes 1-3

Question 5

What power level are the S/G LICs used?

Answer 5

15-100%

Question 6

What S/G levels are maintained by the S/G LICs?

Answer 6

60-70%

Normally 65%

Question 7

What are the power supplies for the S/G LICs?

Answer 7

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

Question 8

How do the S/G LICs fail?

Answer 8

Closed on loss of power

Question 9

How do the S/G LICs respond on a turbine trip?

Answer 9

Controller swaps to manual, so the MFRVs stay at whatever position they were in before the trip

Question 10

What are the modes of operation for the S/G LICs?

Answer 10

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.

Question 11

What is a requirement for placing the S/G LICs in AUTO?

Answer 11

“Green” PF light must be flashing. Light starts flashing when S/G level is within 5% of the controller setpoint

Question 12

How does SGWLC respond on CHP?

Answer 12

• 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)

Question 13

How does SGWLC respond on S/G Low Pressure?

Answer 13

• 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.

Question 14

What is the function of the high level override?

Answer 14

• 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.

Question 15

What is the function of the MFP Combined Speed Controller?

Answer 15

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.

Question 16

What is the power supply for the MFP Combined Speed Controller?

Answer 16

Y-01

Loss of Y-01 causes MFPs to go to minimum speed

Question 17

What is a requirement for swapping MFP Combined Speed Controller from MANUAL to CASCADE?

Answer 17

“Green” PF light needs to be flashing. Light starts flashing when the controller’s output signal is within 0.5% of the input signal.

Question 18

What are the power supplies for the MFP Individual Speed Controllers?

Answer 18

Both from Y-01

Loss of Y-01 causes MFPs to go to minimum speed

Question 19

What is the speed range controlled by the MFP Individual Speed Controllers?

Answer 19

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)

Question 20

What are the modes of operation of the MFP Individual Speed Controllers?

Answer 20

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

Question 21

What are the power supplies for the MFRV Bypass Valve LICs?

Answer 21

Both from Y-01

Valves fail closed on loss of power

Question 22

When are the MFRV Bypass Valves used?

Answer 22

Used to control S/G level at low power (< 15% reactor power).
Smaller valves, so they give finer level control at lower power

Question 23

What are the modes of operation for the MFRV Bypass Valve LICs?

Answer 23

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.

Question 24

What is a requirement to transfer MFRV Bypass Valve LICs from MANUAL to AUTO?

Answer 24

“Green” PF light needs to be flashing. Light starts flashing when S/G level is within 5% of the setpoint

Question 25

How do MFRV Bypass Valve LICs respond to a trip?

Answer 25

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.

Question 26

What are the power supplies for the Wide Range S/G Level Transmitters?

Answer 26

Each S/G has 1 LT powered from Y-10, and 1 from Y-20

Question 27

What are the power supplies for the AFAS S/G Level Transmitters?

Answer 27

Each S/G has 4 LTs, 1 powered from each preferred AC bus (Y-10, 20, 30, 40)

Question 28

What are the power supplies for the MFP Recirc Control Valves?

Answer 28

P-1A - Y-10

P-1B - Y-20

Question 29

How do the MFP Recirc Control Valves fail?

Answer 29

Valves fail open, causing MFPs to trip on low suction pressure.

Question 30

How does shrink and swell impact operation of the SGWLC System?

Answer 30

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.