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What is the maximum pressurizer level?
- When operating in Mode 1-3, level shall be <62.8%
- -permits pressure control equipment to function as designed
- -preserves steam space during normal operations, thus making spray and heaters available for pressure control
- -pressure control during normal operation maintains subcooled reactor coolant
What are the inputs to the pressurizer level controllers (LIC-0101A/B)?
- Recieves level signal from
- -Pzr level transmitters LT-0101A/B
- -Tave signal from either TYT-0100 or TYT-0200 (Tave/Tref calculators)
What is the normal pressurizer level band?
- Function of PCS average temperature
- -Tave=532oF(0%pwr)=42% level
- -Tave=560oF(100%pwr)=57% level
What instruments are used for PZR level when cold calibrated instruments are used?
- Calibrated at Patm and 100oF
- -provides 0-100% level indication in the control room (LIA-0102A)
- -high level alarm set at 49%
- -0-100% level indication at the aux hot shutdown panel (C-150) on LI-0102B
- -provides 0-100% level indication at C-12 (LI-0103A)
- -LI-0103B is on panel C-33
PZR safety valves
- 3 back pressure compensated spring loaded code safety valves
- Sized to limit PCS overpressure to 110% of design pressure (2750 psig) following a complete loss of load with out a reactor trip
- 230,000 lbm/hr each
- -2500 psia
- -2540 psia
- -2580 psia
What is the pressurizer pressure control system designed to do?
Designed to maintain PCS pressure between 2010 psia to 2100 psia during power operation.
- 120 sheath type immersion heaters
- -12 proportional (150kw)
- -108 backup (1350kw)
- -1500kw total (12.5kw each)
- Powered from 15 and 16 (bus 1E and 1D)
- -emergency power from bus 1C dilution water pump breaker
- All heaters deenergize on PZR LO-LO level (36%)
What is the problem with operating with pressurizer level >62.8%?
- If in Modes 1,2,3 you will violate T.S. 3.4.9
- Must restore level <62.8% in 6 hours or be in Mode 3 with the reactor tripped
What are the 2 types of PZR level control?
- -operates when in cascade, a deviation from setpoint controls charging pumps and letdown orifices
- -overrides the normal output signal
- -always uses Tave to control PZR level
What are the 3 modes of operation of the PZR level controllers LIC-0101A/B?
- -uses Tave to calculate setpoint
- -you must go through auto to get to cascade
- -allows operator to control PZR level by changing the setpoint
- -allows operator to control PZR level by changing controller output
What are the consequences of operating the PZR outside of the 2010 to 2100 psia?
Operation outside of the range is an entry into T.S. 3.4.1 and is a 2 hour action
Which PZR level transmitters are hot calibrated?
- -sends level signal to LIC-0101A on C-02
- -sends signal to LIC-0101AL on the back of C-11
- -sends signal to the PPC
- -level signal to PZR level controller LIC-0101B on C-02
- -sigma type indicator LIC-0101BL located on the back of panel C-11
How do the PICs control PZR spray valves and the PZR heaters?
- Proportional heaters vary from full on to off as the PIC output varies from 0-33.3% of scale
- Spray valves are controlled from shut to full open from 66.6% to 100%
- When PIC output is between 33.3% to 66.6%, the proportional heaters are off and the spray valves are closed
How do the PICs for the pressurizer fail?
Fails to all heaters on.
What heater capacity (PZR HTRS) is needed for natural circulation?
One half of the total heater capacity (750kw)
What happens to the PCS if the PT fails low?
- PIC output goes to 0%. Both spray valves close and proportional heaters go to full on.
- PCS pressure will rise
- RX trip on high PCS pressure
- If PIC is not in service then you just get an alarm
What is the purpose of the PZR level control system?
- Maintains the PCS operating pressure and compensates for changes in the coolant volume during load changes.
- Pzr is sized to accomodate power increases and decreases without filling the pressurizer solid and lifting the safeties, or conversely emptying the pressurizer and uncovering heaters.
How is the not in service PZR level controller maintained?
- The out of service controller is in manual at 50% to prevent the controller from getting a 0% or 100% signal due to being saturated
- -this allows it to be available for immediate use
What is the pressurizer level heater trip?
All pressurizer heaters deenergize on low-low pressurizer level of 36% to prevent the heaters from burning up
ORM 3.1.2 PZR heatup and cooldown rates
- PZR C/D rate shall be </= 200oF/hr
- PZR H/U rate shall be </= 100oF/hr
- When SDC isolation valves, MO-3015/3016, are open, PZR H/U rate shall be </=60oF
APP: at all times
- Actions: Requirements not met
- -restore to withing limits within 30 minutes
What is the purpose of the spray valve bypass valves?
- Throttled to approximately 1 gpm flow
- Reduces the thermal shock to the PZR spray lines and surge line.
- Also helps to minimize differences in boron concentration between the PZR and the PCS.
What is the mode of operation for the non selected PZR PIC?
- Normally in manual at 50%
- -prevents the controller from saturating itself due to it not reading exactly what the other PIC does.
What is the function of the pressurizer heaters?
To maintain thermal equilibrium at approximately 640oF during normal operations and to limit the pressure drop and restore pressure to controller setpoint during transient and normal operations.
What are the power supplies for PZR level controllers LIC-0101A/0101B?
What are the PIC-0101A and PIC-0101B power supplies?
What is the impact on PZR level control with charging pumps and letdown orifices in manual mode?
- Charging pump P-55B or P-55C
- -in manual, P-55B and C are not available for auto start/trip in response to PZR level
- -if P-55B and/or 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 determines P-55A response
- Letdown orifices stop valves (CV-2003/2004/2005)
- -in manual they don't respond to the PZR level control program
- -letdown flow would be determined by the number of stop valves open
How are the backup PZR heaters normally operated?
- All are normally on (manual)
- -by placing in manual, enough heat is added to keep PZR at 2060 psia
- -this eliminates pressure cycling
- -quicker spray response
- --this results in little pressure cycling of PZR pressure
- -Better boron mixing or less boron concentration difference between the PZR and PCS
What is the normal sequence of operation on increasing PZR level?
- Trip P-55C
- Trip P-55B
- P-55A speed lowers to required speed
- CV-2003 is open
- CV-2004 opens
- P-55A is at minimum speed
- CV-2005 opens
What are the Tave/Tref controllers (TYT-0100/0200) power supplies?
- Th, Tc, and TYT-0100 for loop 1
- Th, Tc, and TYT-0200 for loop 2
PZR spray control valves (CV-1057, CV-1059)
- Sized to use the D/P between the PCP discharge and the PZR
- 2 parallel 3" diaphram air operated spray control valves.
- Close/auto control switch
- When in auto controlled by PIC output from 66.6% to 100%.
What happens to the PCS pressure if the PT fails high?
- PIC output goes to 100%, both spray valves fully open and the proportional heaters turn off
- PCS pressure will lower
- Rx trip and SIS on low PCS pressure
- If PIC channel is not selected, then you just get an alarm
Backup pressurizer heaters
- 108 heaters divided into 4 groups
- -1 and 3 have 24 heaters (300kw/group)
- -2 and 4 have 30 heaters (375kw/group)
- Operated by OFF/AUTO/MANUAL switch at C-02
- -we do not use auto
What is the normal sequence of operation on a decreasing pressurizer level?
- CV-2005 closes
- CV-2004 closes
- P-55A goes to req'd capacity
- CV-2003 is open
- P-55B starts
- P-55A goes to max speed
- P-55C starts
What are the effects of 1E/1D bus undervoltage on PZR pressure control system?
- Results in a loss of half of the PZR heaters
- Should have no effect on PCS pressure if the other bus is available
Aux spray control valve (CV-2117)
- 2 position air operated valve
- Fails closed on a loss of air
- Aux spray is supplied by the charging pumps
- Used during startups/shutdowns and natural circulation
Why do the PZR heater breakers on D bus not automatically reclose after PZR level returns to >36%?
This prevents overloading of the diesel if the diesel is being loaded by the sequencer.
- 2 groups with 6 heaters/group
- Full power is supplied to the heaters at 0% output from the PIC, and 0% power when PIC output is 33.3%
- Only ON(auto)/OFF control at C-02
- When in on, heter is controlled by the PIC
What is the purpose of the pressurizer level control channel selector switch HS1/LRC-0101?
- It passes the normal and backup level signals from LIC-0101A and B to P-55A/B/C and orifices #2, #3
- Also activates the high/low level alarm and energizes the backup heaters if in auto based on a deviation from program level setpoint
What is the effect of a loss of AC bus Y-01 on the PZR pressure control system?
- You will lose your protective trip function of the PZR heaters on a 36% PZR level
- PZR temperature indications are lost
- PZR spray line, surge line, and PORV discharge temperatures are lost.
What is the function of PZR level control channel 1/2-LIC-0101AL/0101BL?
- Recieves level input from LT-0101A/B level transmitters and activates the channel PZR low-low level alarm at 36%
- Sends the low low signal to HS1/LIC-0101 to trip all pressurizer heaters and to HS-2003 to close letdown orifice CV-2003, letdown stop valve (if in auto)
What is the effect on the pressurizer level control system on a loss of Y-10 or Y-20?
- Pressurizer level control channel A LIC-0101A (B LIC-0101B) loses power
- -loss of power to the controller results in maximum charging and minimum letdown
- -manual control of PLCS is available or the other controller
- -to restore letdown
- --must take the switch to the other channels controller
- TYT-0100(TYT-0200) Tave loop 1(2) input to LIC-0101A/B are lost
- -programmed level will go to 42% (0% power program level)
- -letdown and charging will respond as if level is high
What effect does a loss of Y-01 have on the pressurizer level control system?
- Results in a PZR low low signal and results in maximum charging and zero letdown
- -P-55A goes to max speed, P-55B/C start
- -CV-2001 (letdown stop valve) closes when HS-2001 is in auto
What does the PZR heater control select switch HS1/LIC-0101 do?
- Passes a signal from LIC-0101AL(LIC-0101BL) to trip pressurizer heaters and close CV-2003, letdown stop valve (if in auto) on a low pressurizer level of 36%
- 3 position handswitch
- -Channel A
- -Channel B
- -Channel A+B