Pressurizer Level Control

Question 1

LCO 3.4.9 “Pressurizer” requirements

Answer 1

The pressurizer shall be operable with:

• Pressurizer water level <62.8% (not applicable in Mode 3 until after a bubble has been established in the pressurizer and pressurizer water level has been lowered to within its normal operating band)
• > = 375 kW of pressurizer heater capacity available from bus 1D
• > = 375 kW of pressurizer heater capacity available from bus 1E with the capability of being powered from an emergency power supply (‘A’ dilution water pump breaker on bus 1C)

Question 2

LCO 3.4.9 “Pressurizer” applicability

Answer 2

Modes 1-3

Question 3

What is the purpose of the PZR level control system?

Answer 3

Maintains PCS pressure and compensates for changes in volume during load changes.

Question 4

What is the relationship between power level, Tave, and PZR level?

Answer 4

0% power = 532 F Tave = 42% PZR level

100% power = 560 F Tave = 57% PZR level

Question 5

How does the PZR level control system control PZR level?

Answer 5

• Opening/closing letdown orifice stop valves
• Starting/stopping P-55B/C, Charging Pumps
• Controlling the speed of P-55A, Charging Pump

Question 6

What are the power supplies for the PZR level controllers?

Answer 6

LIC-0101A from Y-10

LIC-0101B from Y-20

Question 7

How does the PZR level control system respond to a lowering PZR level?

Answer 7

Sends a signal for more charging (raising P-55A speed or starting P-55B and/or P-55C) and less letdown (closing letdown orifice stop valves)

Question 8

How does the PZR level control system respond to a rising PZR level?

Answer 8

Sends a signal for less charging (lowering P-55A speed or stopping P-55B and/or P-55C) and more letdown (opening letdown orifice stop valves)

Question 9

What are the modes of operation of the PZR level controllers?

Answer 9

CASCADE - receives a signal from selected Tave controller and generates a PZR level setpoint
AUTO - operator selects a PZR level setpoint for the controller to maintain
MANUAL - operator controls output signal with slide bar on the controller

Question 10

How does the PZR backup level control work?

Answer 10

• Still controls level through the same in service level controller as the normal level control program.
• Separate on/off control signals independent of normal level control signals.
• Only controls P-55B/C, and CV-2004/2005, Letdown Orifice Stop Valves.
• Backup level control signals override the normal level control signals in all modes of operation (cascade/auto/manual).

Question 11

How is the out of service PZR level controller maintained and why?

Answer 11

Maintained in MANUAL with output set to 50%. This is to keep the controller immediately available for use, and to prevent it from becoming “saturated” due to “fighting” the in service controller if setpoints are slightly different.

Question 12

What is indicated on the PZR level recorders?

Answer 12

• PZR pressure
• Actual PZR level
• PZR level setpoint (either the auto generated setpoint while in CASCADE, or the setpoint that is manually set by the operator when in AUTO)

Question 13

How many gallons/% in the PZR?

Answer 13

66

Question 14

How many gallons/% in the VCT?

Answer 14

34

Question 15

What is the PZR Hi/Lo level alarm setpoint?

Answer 15

5.75% deviation from setpoint

Question 16

What is the PZR Lo-Lo level alarm setpoint?

Answer 16

36%

Question 17

What is the PZR High level alarm setpoint?

Answer 17

49% cold calibrated level (equivalent to approximately 75% hot calibrated level)

Question 18

What is the order of equipment operation as PZR level lowers, if PZR level is initially high with all letdown orifice stop valves open, and only the ‘A’ Charging Pump is running?

Answer 18

• Close CV-2005, Letdown Orifice Stop Valve
• Close CV-2004, Letdown Orifice Stop Valve
• Start P-55B, Charging Pump
• Start P-55C, Charging Pump

Question 19

What is the order of equipment operation as PZR level rises, if PZR level is initially low with all letdown orifice stop valves closed, and all 3 charging pumps running?

Answer 19

• Stop P-55C, Charging Pump
• Stop P-55B, Charging Pump
• Open CV-2004, Letdown Orifice Stop Valve
• Open CV-2005, Letdown Orifice Stop Valve

Question 20

How can the PZR level control system be operated manually without the backup PZR level control overriding?

Answer 20

• AUTO/MANUAL handswitches for P-55B and P-55C on C-12 must be taken to MANUAL
• Letdown Orifice Stop Valves taken to OPEN or CLOSE (taken out of AUTO) with their respective handswitches

Question 21

How is PZR level control affected by a loss of Y-10?

Answer 21

• ‘A’ PZR level controller loses power, causing a 0 output (max charging) if the ‘A’ controller is in service.
• PZR heaters trip off (if the heater control selector switch is in ‘A-B’ or ‘A’) due to sensed low PZR level on the ‘A’ channel. Can re-energize heaters by taking the heater control selector switch to ‘B’, but the breaker on D bus must be manually closed (doesn’t re-close automatically to ensure EDG is not overloaded when running)

Question 22

How is PZR level control affected by a loss of Y-20?

Answer 22

• ‘B’ PZR level controller loses power, causing a 0 output (max charging) if the ‘B’ controller is in service.
• PZR heaters trip off (if the heater control selector switch is in ‘A-B’ or ‘B’) due to sensed low PZR level on the ‘B’ channel. Can re-energize heaters by taking the heater control selector switch to ‘A’, but the breaker on D bus must be manually closed (doesn’t re-close automatically to ensure EDG is not overloaded when running)

Question 23

How is PZR level control affected by a loss of Y-01?

Answer 23

PZR level controllers have power, but the switches that receive signals from the normal and backup level control programs don’t have power. This causes MAX charging and ZERO letdown.