Pzr Pressure and Lvl Control Flashcards
What is the normal Lvl, temp, and # of the PRT? **
- 100°F
- 83%
- 3#
When will the PRT vent valve not open?
- If # is > 10#
What is the max # of the PRT?
- 100# (Rupture Disk)
What is the PRT designed to do?
- Condenses 110% of Pzr steam space
- Protects the Rx Vessel against brittle fracture during LTOP conditons
- Provides overpressure Protection
What are the inputs to the PRT?
- Pressurizer Safeties and PORVs
- Seal Water Return Safety
- CCP Suction Safeties
- ECCS Safeties
- RHR Suction Safety
- RHR Hot Leg Discharge Safety
- RHR hx Safeties
- PW and N2
What is the design of the Pzr Lvl and # Ctrl?
Designed to accommodate:
- unit load change @ 5% / minute.
- Instant load changes @ 10% w/ auto rod control.
- step load reduction @ 50% w/ auto rods and dumps
What is the lvl per percent in the Pzr?
- 75gal/1% **
What is the Pzr Lvl Program based on?
- Based on Auctioneered High Tave
- Unit 1 - 22% to 50% (28% diff)
- Unit 2 - 22% to 55% (33% diff)
- Both Units Trip at 92% (2/3)
What are the Pressure inputs for the Pzr # Ctrl?
- NPP-151/152/153 NPS-153
- NPP-151 input to QMO-225 (East CCP ELO)
- NPP-153 input to QMO-226 (West CCP ELO)
- If Channel III (NPP-153) is controlling channel and it fails low all PORVs are Inoperable
At what pressure do the Pzr Safeties lift?
- 2485# (SV-45A/B/C)
At what pressure do the Pzr PORVs open?
- 2335# (NRV-151/152/153) **
Which Pzr PORVs have backup air bottles?
- NRV-152/153
What supplies the PRT with water if it needs to be filled or if it gets > 126°F during normal ops?
- PW
Which Safeties and PORVs have acoustic monitors?
- Safeties- 1 monitor for each safety valve (3 total)
- PORVs- 1 monitor total (combined)
What are the Lvl inputs for the Pzr Lvl Ctrl?
- NLP-151 (Ctrl Channel)
- NLP-152 (Bistable)
- NLP-153 (Either Ctrl or Bi)
- NLI-151 (cold cal)
What is the Pressurizer Lvl Rx Trip?
- 92% Pzr Lvl
What are the Pzr Spray Bypass valves for?
Allow continuous flow for:
- PZR boron concentration same as RCS
- Minimize PZR temp stratification
- keep spray lines equilibrium with RCS loops.
What are the Pzr Cycling Heater trips?
- Loadshed on same train
- Pzr Low Level @ 17%
- Overcurrent
- Both trains of Supply Breakers closed
- Load Con
- interlock- can’t close both feeder breakers
What is the interlock associated with the Pzr Cycling Htrs?
- can’t close both feeder breakers (Protects EDGs from overloading)
What provides Cold Overpressure protection with the Pzr PORVs?
- NRV-152 controlled by NPS-122 (Loop 1 WR)
- NRV-153 controlled by NPS-121 (Loop 2 WR)
If there is a leaking PORV, what can it affect?
- could lead to PRT rupture disk failure
What are the Pzr backup Heater trips?
- Loadshed on same train
- Pzr Low Level at 17%
- Overcurrent
What are the important pressure setpoints for the Pzr?
2735# - Max Limit 2485# - Safeties Open 2385# - Rx Trip 2335# - PORVS open 2235# - Normal Ops 2200# - DNB 1950# - Rx Trip 1910# - P11 Block 1775# - SI
What can happen if Channel III (NPP-153) is controlling channel for Pzr # Ctrl and it fails low?
- all Pzr PORVs will be Inoperable and the only protection for Overpressure on the Pzr will be the safeties
What are the Pzr PORV block Valves for?
- Isolate the PORV line in case of PORV leakage or if they fail to close
Where does the PRT drain to?
- RCDT pump Suction
The following plant conditions exist:
Unit 1 is at 100% power
Pressurizer level channel NLP-151 is selected for control and fails LOW.
Which ONE of the following describes the plant response to the pressurizer level channel failure? ASSUME no operator action is taken.
a. Charging flow decreases, actual level decreases, orifice isolation valves close, letdown isolates, and VCT level increases.
b. Charging flow remains the same, letdown isolates, and backup heaters turn on if actual level increases 5% above program.
c. Letdown isolates, charging flow increases, seal flow increases, actual level increases, and VCT level decreases.
d. Letdown isolates and heaters energize to restore pressurizer pressure.
- c. Letdown isolates, charging flow increases, seal flow increases, actual level increases, and VCT level decreases.
Given the following indications on Unit 2:
- Reactor Power 97 percent
- RCS pressure 2260#
- PRZ level channel select switch in position 1 (Channel 3 control, Channel 2 bistable)
- PRZ level 53 percent
- PRZ level recorder select switch in position 1 (Channel 1)
- PRZ liquid level transmitter NLP-152 (Channel 2) fails low
WHAT is the immediate effect on the plant?
a. Recorder indicates level < level Ref., charging flow control valve QRV-251 opens fully, all backup heaters on.
b. Recorder indicates level = level Ref., charging flow is unchanged, all heaters are off, all orifice isolation valves shut, QRV-111 shut.
c. Recorder indicates level < level Ref., charging flow control valve QRV-251 closes, all heaters are off, all orifice isolation valves shut, QRV-112 shut.
d. Recorder indicates level = level Ref., charging flow control valve QRV-251 opens fully, all backup heaters on, all orifice isolation valves shut, QRV-112 shut.
- b. Recorder indicates level = level Ref., charging flow is unchanged, all heaters are off, all orifice isolation valves shut, QRV-111 shut.
The following initial conditions exist:
- Reactor power 99%
- Pressurizer level 33%
- Letdown flow 40 gpm
- Pressurizer level control in manual
Which ONE of the following describes the plant response to a 20 gpm charging line leak outside containment? (Assume NO operator action.)
Pressurizer drops to 17%, …
a. backup heaters turn on, and the reactor trips on low level.
b. all heaters turn on, reactor trips on high pressure.
c. letdown isolates and heaters turn off, reactor trips on low pressure.
d. letdown isolates and heaters turn off, reactor trips on high level.
- d. letdown isolates and heaters turn off, reactor trips on high level.
Unit 1 Reactor power is at 50%. The following conditions exist: - PRZ level is stable at program level - QRV-251 Charging Flow - Controller is in MANUAL - Charging and letdown are balanced.
Which ONE of the following describes the effect on the plant if QRV-251 Charging Flow Controller remains in MANUAL and power is increased to 100%?
A. Charging flow will RISE.
B. Charging flow will LOWER.
C. PRZ level will LOWER.
D. PRZ level will RISE.
- D. PRZ level will RISE.
Unit 2 was operating at 95% power when a load rejection occurred.
Shortly after the load rejection the following plant conditions exist:
RCS Tavg is 572°F
Pressurizer Level is 54%
Pressurizer vapor temperature is 650°F
Pressurizer liquid temperature is 649°F
Which ONE of the following is the current status of the pressurizer based on these conditions?
(Reference the steam tables)
A. Pressurizer PORVs and Spray valves are full OPEN.
B. Pressurizer Spray valves are modulated OPEN.
C. Pressurizer proportional heaters are modulated ON.
D. Pressurizer Backup and proportional heaters are fully ON.
- D. Pressurizer Backup and proportional heaters are fully ON.
ANSWER:
Pressurizer vapor space of 650°F equates to 2193 psig (2208 psia). This is below the 2210 psig setpoint to fully energize the backup heaters.
If PORV was leaking by and could not be isolated and the PRT rupture disk blows, what would be the ROs indication?
- PORV outlet temp will lower
