Pressurizer Level Control

Question 1

What is the purpose of the Pressurizer Level Control System

Answer 1

• Provides sufficient water volume to prevent draining the Pressurizer as a result of a reactor trip yet minimizes the water volume to reduce the energy release and resultant containment pressure rise during a Loss of Coolant Accident.
• Method of maintaining the proper water volume is to control the level to a calculated setpoint that is programmed as a function of average primary coolant temperature.

Question 2

What are the inputs to the Pressurizer Level Control system?

Answer 2

• Pressurizer level Hot Calibrated Control Channels, (LT-0101A/B) for actual Pressurizer level
• Tavg signal via TYT-100 (loop 1) or TYT-200 for program Pressurizer level based on PCS temperature which is related to reactor power.

Question 3

What is the pressurizer level control program output?

Answer 3

Controllers establish a Pressurizer level setpoint proportional to Tave.

Normal and Backup signals are then sent to control:

• P-55A speed
• P-55B/C Start and Stop
• CV-2004/2005 Open and Close

Question 4

What are the modes of operation for the level controlers?

Answer 4

Cascade

• Allows internally generated Pressurizer level setpoint to be controlling signal.

Auto

• Allows operator to generate Pressurizer level setpoint.
• Band must be within confines of Backup Level Control Program

Manual

• Allows operator to control output signal of controller.
• Band must be within confines of Backup Level Control Program

Question 5

How is pressurizer level calculated?

Answer 5

Internal programming of LIC-0101A and LIC-0101B calculated it.

• Ramps linearly from 42% Pressurizer level at 0% power to 57% Pressurizer level at 100% power.
  
  • 532ºF equates to 0% power = 42% level
  • 560ºF equates to 100% power = 57% level

Question 6

Describe normal pressurizer level control.

Answer 6

Only Outputs in Cascade mode of operation.

Controller generates an output signal due to a deviation from the calculated setpoint. Controller will continue to raise or lower the output signal based on the amount of deviation from setpoint.

Higher the output signal (vs 50%) - less charging more letdown (signal indicator in output meter moving toward the right).

50% output signal (0 deviation) P-55A at required capacity CV-2003 is Open

Question 7

What actions occur as level rises from setpoint and deviation from setpoint grows larger?

Answer 7

50% output signal start

• P-55A at required capacity and CV-2003 is Open
  69. 3% output signal
• Open CV-2004
  72. 4% output signal
• Min Speed P-55A
  88. 5% output signal
• Open CV-2005

Question 8

What actions occur as level lowers from setpoint and deviation from setpoint grows larger?

Answer 8

50% output signal start

• P-55A at required capacity and CV-2003 is Open
  30. 8% output signal
• Start P-55B
  27. 6% output signal
• P-55A at Max Speed
  24. 3% output signal
• Start P-55C

Question 9

What is the full sequence on rising level from minimum controler output to max?

Answer 9

• Max Speed P-55A
• Trip P-55C
• Trip P-55B
• P-55A at Required Speed and CV-2003 open (zero deviation: 50% output)
• Open CV-2004
• P-55A at Minimum Speed
• Open CV-2005

Question 10

What is the full sequence on lowering level from maximum controler output to min?

Answer 10

• Minimum Speed P-55A
• Close CV-2005
• Close CV-2004
• P-55A at Required Speed and CV-2003 open (zero deviation: 50% output)
• Start P-55B
• P-55A at maximum speed
• Start P-55C

Question 11

What is Backup Level Control?

Answer 11

Backup signals from Controller are separate ON/OFF signals independent of normal output signals.

Backup signal overrides the normal output signal.

Generated within the controller, actions occur based on deviation of Pressurizer level from the internally calculated setpoint as determined by selected Tave signal.

(P-55A has no input from the backup level control)

Question 12

What actions are associated with a +6% deviation via the Backup Level Control?

Answer 12

Hi-Lo Level Alarm (EK-0761)

Question 13

What actions are associated with a +5% deviation via the Backup Level Control?

Answer 13

• Backup Heaters On (Already On)
• Open CV-2004 and CV-2005
• Trip P-55B and P-55C

Question 14

What actions are associated with a +4% deviation via the Backup Level Control?

Answer 14

• Hi-Lo Level Alarm Off (EK-0761)

Question 15

What actions are associated with a +2% deviation via the Backup Level Control?

Answer 15

• Backup Heater Off
• Permit P-55B and P-55C Start
• Permit CV-2004 and CV-2005 Closure

Question 16

What actions are associated with a -4% deviation via the Backup Level Control?

Answer 16

• Hi-Lo Level Alarm Off (EK-0761)
• Permit P-55B & P-55C Stop
• Permit CV-2004 & CV-2005 Open

Question 17

What actions are associated with a -2% deviation via the Backup Level Control?

Answer 17

• Hi-Lo Level Alarm On (EK-0761)
• Start P-55B & P-55C
• Close CV-2004 & CV-2005

Question 18

What supplies power to LIC-0101A and LIC-0101B?

Answer 18

LIC-0101A

• Y-10

LIC-0101B

• Y-20

Question 19

What position is the non-selected controller left in?

Answer 19

Manual - 50% output

If left in Auto/Cascade, slight differences between it and the actual control would have the feedback loop continue to provide a non-zero error signal to the controller. The reset function of the controller would then begin to step in an ever larger (or smaller) output signal to attempt to correct the error.

Controller would become saturated at 100% or 0% output which would require operator to reset before using.

Question 20

What is the function of Pressurizer Level Control Channel Selector Switch - HS 1/LRC-0101?

Answer 20

Passes the normal and backup level signals from LIC‑0101A or B to P-55A/B/C and orifices # 2 and # 3.

Also activates the high/low level alarm and energizes the backup heaters if in auto (backup heater are always on procedurally)

Question 21

What is the function of Pressurizer Level Recorders - LR-0101A/B?

Answer 21

Input for actual and program level indication come from respective Pressurizer Level Controllers LIC‑0101A/B.

• Red is Actual Level
• Blue is Setpoint

Question 22

What is the function of Pressurizer Level Control Channel 1 - LIC-0101AL?

Answer 22

Level indicator controller LIC-0101AL - Input from LT-0101A level transmitter

• Activates the “A” channel Pressurizer low-low level alarm at 36%. (EK‑0763)
• Sends lo-lo level signal to
  
  • HS 1/LIC-0101 Trips all Pressurizer heaters
  • HS-2003 to close letdown orifice CV-2003, Letdown Stop Valve (if in AUTO).

Question 23

What is the function of Pressurizer Level Control Channel 2 - LIC-0101BL?

Answer 23

Level indicator controller LIC-0101BL - input from LT-0101B level transmitter

• Activates the “B” channel Pressurizer low-low level alarm at 36%. (EK‑0764).
• Sends lo-lo level signal to
  
  • HS 1/LIC-0101 to trip all Pressurizer heaters
  • HS-2003 to close letdown orifice CV-2003.

Question 24

What is the function of Pressurizer Heater Control Select Switch - HS 1/LIC 0101

Answer 24

Passes signal from LIC-0101AL and/or LIC-0101BL on a low Pressurizer level of 36%.

• Trips Pressurizer heaters
• Closes CV-2003, Letdown Stop Valve (if in AUTO),
• Would also isolate Letdown flow (if CV-2004 and CV-2005 were in AUTO)

Three Positions

• Channel A
  
  • Passes signal from LIC-0101AL only
• Channel B
  
  • Passes signal from LIC-0101BL only
• Channel A+B
  
  • Passes signal from both

Question 25

What is the function of HS-0102A and where is it?

Answer 25

Located on panel C-150. Selects signal from LT-0102 to read out on either LI-0102B at C-150 or LIA-0102A at C-02

Question 26

What instruments in the Pressurizer Level Control System are hot calibrated and for what temperature?

Answer 26

LT-0101A * Level signal to Pressurizer Level Controller LIC-0101A * Sigma type indicator LIC-0101AL located on back of panel C-11 * PPC input (PT ID LT\_0101A\_D) LT-0101B * Level signal to Pressurizer Level Controller LIC‑0101B on panel C-02 * Sigma type indicator LIC-0101BL located on back of panel C-11 Pressure = 2060 psia Temperature = 640°F (saturation temperature for 2060 psia).

Question 27

What instruments in the Pressurizer Level Control System are cold calibrated and for what temperature?

Answer 27

LT-0102 * Provides 0-100% level indication in the control room on LIA‑0102A. * High level alarm set at 49% on EK-0769, "Pressurizer Level High" * 0-100% level indication at the Auxiliary Hot Shutdown Control Panel C-150 on LI-0102B LT-0103 * Signal to LI-0103A on C-12 * Signal to LI-0103B on panel C-33. Displayed on both indicators at the same time. Pressure = atmospheric Temperature = 100°F

Question 28

What are Correction Curves?

Answer 28

Since Pressurizer level instruments are calibrated at specific PCS conditions, their indicated levels must be compensated due to changes in the PCS and Containment.

Question 29

How do hot and cold calibrated Pressurizer instruments read compared to actual level when not at their calibrated temperature and pressure?

Answer 29

Hot Calibrated: When less than Normal Operating Temperature and Pressure, Hot Cal instrument reads higher than actual DP Cold Calibrated: When the Pressurizer temperature is above 100°F, Cold Cal instrument reads lower than actual DP Key point here is that DP does not change, however the level inside the actual PZR level rises or lowers depending on temperatures. Key is expansion and contraction of the fluid inside the PZR.

Question 30

What happens to indicated pressurizer level on rising containment temperature?

Answer 30

Density of the water inside the Pressurizer reference leg will also change as Containment temperature is changed. As temperature rises in containment this will cause indicated level to be higher than actual level in the Pressurizer (reference leg density lowers and DP will lower).

Question 31

How does the Pressurizer Level Control Program interface with CVCS?

Answer 31

* CVCS responds to changes in Pressurizer level with changes in charging pump P-55A speed control and flow, P-55B/C start and stop, and letdown orifice isolation valve operation (CV-2003, CV-2004, CV 2005) * Charging Pumps starting and stopping and Letdown Orifices opening and closing adds to or reduces heat load on the Letdown Heat Exchanger and causes system pressures to change. Expect CVCS temperature alarms and Charging Pump Seal Cooling Pump alarms as these actions occur. * Changing heat loads on the Letdown Heat Exchanger causes heat loads to change on the CCW System. Expect possible CCW temperature alarms during these changes.

Question 32

How does the Pressurizer Level Control Program interface with PCS?

Answer 32

* Pressurizer level instruments and PCS Tave provide input to the Pressurizer Level Control system. * Changing temperatures and pressures in the PCS can cause the Pressurizer Level Control program to activate components. * Overcooling the PCS greater than Charging Pump ability to maintain Pressurizer level will result in tripping the Pressurizer Heaters and closing the #1 Letdown Orifice Stop on a Pressurizer level \<36%.

Question 33

How does the Pressurizer Level Control Program interface with Pressurizer Pressure Control System?

Answer 33

* Pressurizer level instruments provide input to Pressurizer Heater trip on low level and Backup heaters to energize during a Pressurizer level increase. * Failures or transients in the Pressurizer Pressure Control system may cause Pressurizer level to rise or lower and thus cause the Pressurizer Level Control program to activate components.

Question 34

What is the ramification of operating with Pressurizer level greater than 62.8%

Answer 34

If in Modes 1, 2 or 3 this is a violation of T.S. 3.4.9. Must restore Level to \<62.8% in 6 hours or be in MODE 3 with reactor tripped

Question 35

What is the impact of having the Charging Pumps and Letdown Orifice Stop Valves in manual?

Answer 35

Charging Pump P-55B or P-55C * P-55B/C not available for automatic start/trip in response to Pressurizer level. * P-55B/C are initially OFF, they will remain OFF, if initially ON, they remain ON. * The operating condition of P-55A (AUTO or MANUAL) speed control would determine P-55A response. Letdown Orifice Stop Valve (CV-2003, 2004, or 2005) * CV-2003, 2004, and 2005 are not available for automatic closure/open in response to the Pressurizer Level Control Program. * Letdown flow would be determined by the number of Stop valves open.

Question 36

How many Gallons of water equivalent to 1% change?

Answer 36

66 gallons NOT accurate at other than rated PCS conditions (2060 PSIA, \> 525°F).

Question 37

What happens on loss of Preferred AC Bus Y-10?

Answer 37

PZR Level Control Channel 'A' LIC-0101A loses of power. * Loss of power to controller results in maximum charging and minimum letdown. (0 output). TYT 0100 - Tave Loop 1 input to LIC 0101A/**B** controller is lost. * Programmed level will go to 42% that is 0% power program level. * Letdown and charging will respond as if level is actually high. **When ‘B’ Channel PZR Level Control is in service will have minimum Charging and maximum Letdown**

Question 38

What happens on loss of Preferred AC Bus Y-20?

Answer 38

PZR Level Control Channel 'B' LIC-0101B loses of power. * Loss of power to controller results in maximum charging and minimum letdown. (0 output). TYT 0200 - Tave Loop 2 input to LIC 0101**A**/B controller is lost. * Programmed level will go to 42% that is 0% power program level. * Letdown and charging will respond as if level is actually high **When ‘A’ Channel PZR Level Control is in service will have minimum Charging and maximum Letdown**

Question 39

What happens on loss of Preferred AC Buses Y-30 or 40?

Answer 39

No impact

Question 40

What happens on loss of Instrument AC Bus Y-01?

Answer 40

Loss of Y-01 to the Pressurizer control scheme contact arrangement causes a Pressurizer Lo Lo level signal and results maximum charging and zero letdown. * P-55A Speed Control (goes to maximum speed), P‑55B and P-55C start. * CV 2001 (Letdown Stop Valve) closes when HS 2001 is in AUTO position.

Question 41

What is the impact to CVCS from a loss or malfunction of Pressurizer Level Control including loss of inputs?

Answer 41

Loss of power to Pressurizer Level controller results in maximum charging and minimum letdown. (0 output) Program level input failure from Tave will vary. * If results are a positive deviation of actual versus program then, letdown will be increased and charging will be minimized. (Actual \> Program) * If results are a negative deviation of actual versus program then, letdown will be minimized and charging will be increased. (Program \> Actual) Actual level input failure from Hot Cal instruments will vary. * If results are a positive deviation of actual versus program then, letdown will be increased and charging will be minimized. (Actual \> Program) * If results are a negative deviation of actual versus program then, letdown will be minimized and charging will be increased. (Program \> Actual)

Question 42

What is the impact to PCS from a loss or malfunction of Pressurizer Level Control including loss of inputs?

Answer 42

A malfunction or failure effecting charging/letdown will cause PCS inventory to be raised or reduced accordingly. Pressurizer Pressure Control * Level channel failure can affect Pressurizer Heaters on lo-lo level cutout at 36% on either Hot Cal channels. * Selector switch can remove effected channel from service to restore heaters.

Question 43

What is the impact to Pressurizer Level Control from instrument line losses?

Answer 43

A failure of the wet leg (High side of DP cell) would result in indicated level to rise. * Minimum Charging and Maximum Letdown. * This is also a Vapor space LOCA A failure of the Low side results in a PCS leak! Enter Off Normal procedures. Depending on the size of the failure, this could result in an indicated PZR level of 0%. Maximum Charging and NO Letdown.