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Block 2 > Pressurizer Pressure and Level Control System > Flashcards

Pressurizer Pressure and Level Control System Flashcards

1
Q

Discuss the Design Functions of the Pressurizer and Level Control System.

A
  • Sufficient water volume to prevent draining the PZR as a result of a Rx/Turbine trip
  • Contain total water volume to minimize total mass and energy released to CNMT in LOCA
  • Sufficient water volume to prevent heaters from uncovering during PZR outsurge following 10% step decrease or 5% per minute ramp decrease in rated power. (Ramp 15 – 100% power)
  • Sufficient steam volume to allow an insurge w/o water level reaching Safety or PORV nozzles
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2
Q

Discuss the Pressurizer Surge Line.

A
  • 12” Line - off B Hot Leg

Unit 1
* Low Temp alarm @ 580°F indicative of:
 Insurge (rapid load change - Tave increase)
 Insufficient PZR recirculation flow (spray)

Unit 2
* Low Temp alarm @ 590°F indicative of:
 Insurge (rapid load change - Tave increase)
 Insufficient PZR recirculation flow (spray)

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3
Q

Discuss the Pressurizer Spray Lines.

A
  • Spray from B1 & B2 Cold Legs - flow generated by the DP across the Core
  • Continuous Spray flow: 1 gpm total
    0.75 gpm per bypass line
    0.25 gpm per valve notch
  • Purpose of continuous flow:
     Surge & spray lines stay warm – minimize thermal shock to spray nozzle
     Cools the spray nozzle
     Equalize Boron concentration between PZR and RCS
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4
Q

What are the Pressurizer Pressure Safety Instruments?

A

PT-1102A, PT-1102B, PT-1102C, PT-1102D
Supply RPS and ESFAS

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5
Q

What are the Pressurizer Pressure Control Instruments?

A

PT-1100X & PT-1100Y
Supply PZR pressure control system

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6
Q

Discuss the Pressurizer Pressure Master Controller.

A
  • PIC-1100 X/Y
  • PIC-1100 X/Y output goes to:
     Proportional Heaters; and
     Spray Valves via HIC-1100
    (HIC-1100 must be in Auto in order for PIC-1100 to position the Main Spray Valves)
  • Max Output from PIC-1100 = Spray Valves Full Open / RCS pressure lowers
  • Min Output from PIC-1100 = Proportional Heaters at Maximum / RCS pressure rises
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7
Q

Discuss the Pressurizer Main Spray Valve Controller.
HIC-1100

A
  • In Auto: Receives input from selected Master Pressure Controller (1100X or Y) to positions the Main Spray Valves
  • In Manual: Adjusting output controls the position of the Main Spray Valves
    0% - Spray valve fully closed
    100% - Spray valve fully open
  • Remember, the output of HIC-1100 controls ONLY the spray valve. It does NOT control proportional heaters
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8
Q

Discuss the Pressurizer Main Spray Valve Selector Switch.

A
  • 3 positions – “1100E / BOTH / 1100F”
  • Selects either, or both valves for operation.
    The position of the switch dictates where the output of HIC-1100 goes.
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9
Q

Discuss the Pressurizer Main Spray Valves.

A
  • PCV-1100F – B1 loop
    PCV-1100E – B2 loop
  • Designed to mitigate pressure excursions to avoid PORV operation during 5%/min ramp and 10% step
  • Both valves fail closed on loss of Instrument Air.
  • Auto – Receives input from selected Master Pressure Controller (1100X or Y)
  • Manual – Operator varies output of HIC-1100 which opens / closes spray valves
  • 0% - Full close signal, 100% - full open signal
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10
Q

What are the Pressurizer Main Spray Valve setpoints?

A

Unit 1
Start to open @ 2300 psia
Full open at 2350 psia

Unit 2
Start to open @ 2275 psia
Full open @ 2325 psia

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11
Q

Discuss the Pressurizer Aux Spray Valves.

A
  • SE-02-03, “A” 125 VDC
    SE-02-04, “B” 125 VDC
  • Key operated control switch on RTGB
  • Used during EOP’s when RCP’s are not operating, and align CHG flow directly to the PZR steam space (CHG loop isol valves have to be closed after opening aux spray valves as well)
  • Fail closed on loss of 125 VDC

Unit 1
* Aux spray flow path also used as an alternate Hot Leg Injection path.
Flow comes from upstream of the Regen HX & requires MV-02-1 to be closed to use this path. It is normally de-energized open >1750 psia

Unit 2
Used as an Aux Spray flow path only

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12
Q

Discuss Pressurizer Safety Valves.

A
  • 3 Valves – Lift @ 2500 psia
    Each valve can relieve 200,000 lbm/hr
  • Limits RCS pressure to 110% of design pressure (2750 psia) - Prevents safety limit violation
  • TE in each tailpipe alarms at 280F; 338F Tsat at 115 psia QT, 220F-rupture
  • Acoustic flow monitors in each tailpipe give positive position indication
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13
Q

Discuss Power Operated Relief Valves (PORVs).

A
  • Designed to prevent safety valve actuation during transients
  • Solenoid actuated - 125VDC
  • Requires D/P to operate – needs associated block valve to be open
    If the block valves were closed with valid opening signals present to PORV’s, no steam would be available to operate the valves
  • Does not need steam pressure to close. Steam bleeds off & spring closes valve

Unit 1
V1402 – ‘A’ Train
V1404 – ‘B’ Train

Unit 2
V1474 – ‘A’ Train
V1475 – ‘B’ Train

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14
Q

What is the PORV lift setpoint?

A

Unit 1
2400 psia

Unit 2
2370 psia

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15
Q

What is the PORV capacity?

A

Unit 1
153,000 lbm / hr

Unit 2
306,000 lbm / hr - Double the size of Unit 1

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16
Q

What is the normal PORV configuration?

A

Unit 1
Both valves in service

Unit 2
One valve isolated in Modes 1 & 2

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17
Q

Discuss PORV RTGB Position Indication.

A

Unit 1
Only indicates if Solenoid has power
Positive indication on Unit 1 is only by acoustic monitors - only 1 TE

Unit 2
Reed switches show actual valve position
Backup position indication provided by acoustic monitor

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18
Q

Discuss PORV Tailpipe alarm.

A

Unit 1
280F in the combined discharge

Unit 2
280F in each discharge

19
Q

Discuss PORV Control Switches.

A

Unit 1
One 3-Position Switch
“LOW RANGE / NORMAL / OVERRIDE”
* NORMAL-Allows auto opening of PORV on 2/4 logic from RPS HI Ppzr bistables @ 2400 psia
* LOW RANGE-Allows auto opening of PORV via low range P&T instruments @ 530 / 350 psia
* OVERRIDE- Removes all inputs and will close the PORV

Unit 2
Two switches: PORV & Mode Sel Sw.
PORV: “OFF / OVERRIDE / TEST”
* OFF - Allows auto opening of PORV on 2/4 logic from RPS HI Ppzr bistables @ 2370 psia
* OVERRIDE - Removes all inputs and will close the PORV
* TEST – Allows testing circuitry without opening PORV
MSS: “NORMAL / LTOP”
* NORMAL – Allows auto opening of PORV on 2/4 logic from RPS HI Ppzr bistables @ 2370 psia
* LTOP – Allows auto opening of PORV via low range P&T instruments @ 490 psia

20
Q

Discuss PORV response to a loss of DC.

*Note PORV relay is opposite train of App R buses. Need relay power and PORV power to open.

A

Unit 1
* Each valve needs DC to operate
‘A’ PORV – ‘A’ DC / ‘B’ PORV – ‘B’ DC
* Additionally, there is one RPS relay, 63X/P-1102, which is the output from the RPS to the PORVs for the high PZR pressure signal that must energize for PORVs to open.
* Relay powered from 125VDC Bus ‘A’
* Normally, both PORV’s in-service
* PORV response upon loss of a DC bus:
‘A’ DC Bus lost:
o Neither PORV opens.
‘B’ DC Bus lost:
o ‘A’ PORV opens

Unit 2
* Each valve needs DC to operate
‘A’ PORV – ‘A’ DC / ‘B’ PORV – ‘B’ DC
* Additionally, there is one RPS relay, 63X/P-1102, which is the output from the RPS to the PORVs for the high PZR pressure signal that must energize for PORVs to open.
* Relay powered from 125VDC Bus ‘B’
* Normally, only 1 PORV’s in-service
* PORV response upon loss of a DC bus:
‘A’ DC Bus lost:
o ‘B’ PORV opens (only if in-service).
‘B’ DC Bus lost:
o Neither PORV opens.

21
Q

Discuss LTOP setpoints.

A

Unit 1
Unit 1 – (1/1 Logic)
≤ 530 psia: when Tcold is >200 to < 300 F
≤ 350 psia: when Tcold is < 200 F
Fed from PT-1103 & 1104
PORV’s only for LTOP, not SDC reliefs.

Unit 2
Unit 2 – (2/2 Logic)
490 psia
Fed from PT-1103, 1104, 1105, 1106
Unit 2 can also use their SDC relief valves to meet LTOP TS

22
Q

Discuss Pressurizer Heaters.

A

2 Proportional Heater Banks (P-1 & P-2)
6 Backup Heater Banks (B-1, 2, 3, 4, 5 & 6)

23
Q

What is the power supply for the Pressurizer Heaters?

A

Powered From 4160V Buses A3 and B3 via PZR Heater Transformer

24
Q

Discuss where Pressurizer Heaters can be operated from.

A

Unit 1
Controlled from:
RTGB – all heaters
HSP – all heaters

Unit 2
Controlled from:
RTGB – all heaters
HSP – Backup Heaters only

25
Q

Discuss RTGB switches for Pressurizer Heaters.

A

Proportional HTRS – (OFF/RESET / ON). “ON” allows auto operation of heaters
Backup Heaters – (OFF / AUTO / ON). AUTO allows auto operation.

26
Q

Discuss Pressurizer Proportional Heater Control.

A

Proportional heater setpoint is controlled by the Master Pressure Controller.
The nominal values are set as follows:
* Min output: 2275 psia
* 50% output: 2250 psia
* Max output: 2225 psia
* Proportional Heaters will also energize at max output if PZR level is +3.6% greater than level setpoint

27
Q

Discuss Pressurizer Backup Heater Control.

A

Unit 1
Back-up heaters setpoint is set by a fixed bistable
Heaters in Auto will turn:
ON: @ 2200 psia or +3.6% ∆ level
OFF: @ 2220 psia

Unit 2
Back-up heaters setpoint is set by a fixed bistable
Heaters in Auto will turn:
ON: @ 2200 psia or +3.6% ∆ level (only if pressure is <2275 psia)
OFF: @ 2220 psia

28
Q

Discuss the Interlocks that will automatically deenergize ALL Pressurizer Heaters.

A

Unit 1
PZR Lo- Lo Lvl
* 28%
* Trips all 480V Heater contactors
SIAS
* 1600 psia
* Trips and locks out 4160 V A3 / B3 PZR Heater Xfmr Feeder Breaker
* 480V heater contactors then trip open on UV - Lights turn off
LOOP
* Trips 4160V Breakers on UV, then 480V heater contactors trip on UV
* Can physically get ALL heaters back on Unit 1

Unit 2
PZR Lo- Lo Lvl
* 27%
* Trips associated side 4160V Bkr & opposite side 480V contactors.
SIAS
* 1736 psia
* Trips and locks out 4160 V A3 / B3 PZR Heater Xfmr Feeder Breaker
* 480V heater contactors then trip open on UV - Lights turn off
LOOP
* Trips 4160V Breakers on UV, then 480V heater contactors trip on UV
* Can only get back B1 & B4 BU Heaters due to contactor interlock with 3 to 2 tie breaker
Hi Hi Pressure Shutoff
* ≥ 2340 psia
* Trips all 480V Prop Heater contactors, not breakers

29
Q

Discuss how to reset Pressurizer Heaters.

A

Unit 1
IF HEATERS WERE DE-ENERGIZED DUE TO:

LEVEL (Due to instrument failure of selected or non-selected channel):
* Position the “Low Level Cutout” switch to the good channel
* ALL Proportional and Backup 480V heater contactors may then be reset.

SIAS:
* Reset SIAS signal
Then reset 4160V Feeder breakers and all 480V heater contactors

LOOP
* Reset LOOP (Close 3-2 tie breaker)
Then reset 4160V Feeder breakers and all 480V heater contactors

Unit 2
IF HEATERS WERE DE-ENERGIZED DUE TO:

LEVEL (Due to instrument failure of selected or non-selected channel)
* Position the “PZR Backup Interlock Bypass” key switch” to “LEVEL” position (For instrument failure)
* UNAFFECTED SIDE Proportional and Backup 480V heater contactors may then be reset.

SIAS:
* Reset SIAS signal
Then reset 4160V Feeder breakers and all 480V heater contactors

LOOP
* Reset LOOP (Close 3-2 tie breaker)
Then reset 4160V Feeder breakers and B1 and/or B4 480V heater contactor(s)

30
Q

Discuss Pressurizer Heater 4160V Feeder Breakers.

A

Unit 1
* Breakers open on SIAS & LOOP

Unit 2
* Breakers open on SIAS & LOOP and from a train-related PZR LO-LO level Interlock (27%)

31
Q

Discuss Pressurizer Backup Heater Operation.

A
  • OFF/RESET-AUTO-ON
  • Auto ON @ 2200 psia
    Auto OFF at 2220 psia
    (Won’t clear the DNB T/S: ≥ 2225 psia)

Unit 1
* Backup Heaters in “Auto” will also turn ON if PZR level > Setpoint by +3.6%. (No interlock with PZR pressure)

Unit 2
* RCS Pressure has to be < 2275 psia for Backup Heaters in AUTO to energize on a +3.6% level deviation

32
Q

Why do Pressurizer Heaters turn on for a level deviation?

A

Heaters cycle on when an insurge is indicated due to anticipation of a pressure decrease from the colder water and a subsequent outsurge.

33
Q

Discuss Pressurizer Heater Level Instrument Failure Cutout Switches.

A

Unit 1
Unit 1 PZR Low Level Cutout Switch
* Defeats low level trip signal of the failed low control channel. This allows ALL Proportional and Backup 480V heater contactors to then be reset.
* Positions – “CH X / BOTH / CH Y” – Normally maintained in ‘BOTH”

Unit 2
Unit 2 PZR Backup Interlock Bypass Key Switch
* Defeats low level trip of the failed low control channel. Allows the opposite 4160V Feeder breaker, Proportional and Backup 480V heater contactors to be reset.
* Positions – “LEVEL / PRESSURE / PRESSURE – LEVEL / LOCKED OFF”
LEVEL – Overrides Low Level trip from failed channel by resetting the 480V heater controls on the opposite proportional and backup heaters. Low Level protection still available by good channel which will trip the remaining closed 4160 feeder breaker on actual low level.
PRESSURE – (not used) – Overrides High Pressure trip
PRESSURE-LEVEL – (not used) – overrides Low Level and High Pressure trips
LOCKED OFF – normal position

34
Q

Discuss the Quench Tank

A
  • Normal Quench Tank level ~{60%} [65%]
  • Capable of condensing the steam released from the Pressurizer as a result of a loss of load event, followed immediately by an uncontrolled CEA withdrawal event with no coolant letdown or Pressurizer spray.
  • Designed for 100 psig and 350F;
  • 3 psig of N2 overpressure
  • Overpressure Protection - Relief valve lifts at 70 psig,
  • Rupture Disk - Blows at 85 psig
  • Filled from PMW system, MV-15-1 [HCV-15-1 and HCV-15-2] which isolates on CIS [CIAS]
  • Drains to CNMT drain header (then to RDT), controlled by RTGB switch
  • Vented to the waste gas system by RTGB controlled valve
  • Cooled by draining and filling
  • Hi Level Alarm {65%} [70%] - insufficient gas volume to accept design PZR steam release
  • Lo Level Alarm {55%} [60%] - sparger may be affected, may not condense design release
  • ≤ 40% level – Sparger uncovered
35
Q

What are the inputs to the Quench Tank?

A
  • Safety or PORV discharge
  • Both SDC Hot Leg Suction Relief Valves - 5 gpm
  • RCP CBO (Alternate Path) - 20 gpm
  • Reactor Coolant Gas Vent System
36
Q

Discuss Pressurizer Pressure Setpoints (psia)

A

PZR Safeties Full Open 2575 2575
PZR Safeties Open 2500 2500
ATWS Trip 2437 2437
Safeties Reseat 2400 2400
High Pressure Rx Trip / PORV’s Open 2400 2370
Pre-Trip Alarm 2350 2327
PZR Spray Full Open 2350 (setpoint +100) 2325 (setpoint +75)
High Pressure Alarm 2340 2340
High Pressure 480V trip N/A 2340 [All Heaters Trip]
PZR Spray Full Closed 2300 (setpoint +50) 2275 (setpoint +25)
Proportional Heaters Minimum 2275 2275
Normal Operating Pressure 2250 (Prop heaters 50%) 2250 (Prop heaters 50%)
Proportional Heaters Maximum 2225 or + 3.6% Lvl 2225 or + 3.6% Lvl
Backup Heaters Off 2220 2220
Backup Heaters On 2200 or + 3.6% Lvl 2200 or +3.6% Lvl & <2275#
Low Pressure Alarm 2100 2100
TM/LP Trip Minimum Setpoint 1887 1900
SIAS (Low PZR Press) 1600 1736
SIT Outlet Auto Open 350 500 [& SDC Closes]
Open Permissive to SDC suctions <267 <276

37
Q

Discuss Pressurizer Level Program.

A

~ Tavg PZR Level Rx Power
532 - 538°F 33% 0% - 15%
538 - 570°F 33% - 66 [63] % 15% - 90%
570 – 577.5°F 66 [63] % 90% - 100%

38
Q

Discuss Pressurizer Level Controller (Local/Remote).

A

REMOTE: Setpoint is from RRS based on Tavg (Tave = (Thot + Tcold) / 2)
LOCAL: Setpoint is the Controller Auto setpoint (not used)

39
Q

Discuss Pressurizer Level Setpoints.

A

High Level Alarm [+10%PACB 67% Ind. Level] / RTGB +5%
Max Letdown (128 gpm) +9%
All B/U Heaters ON, Props at Max +3.6% [If Ppzr < 2275 psia]
BU CHG Pump{s} BU Stop Signal__+3.6% {2 pumps}+3.6% [1 pump]
PZR Level Setpoint from RRS 0% Deviation
Min Letdown (29 gpm) - 1%
First BU CHG Pump Stop - 1% rising
Second BU CHG Pump Stop - 2% rising [N/A]
First BU CHG Pump Start - 3%
Second BU CHG Pump Start - 3.6% [N/A]
BU CHG Pump BU Start Signal{s} - 5% {2 Pumps} - 5% [1 Pump]
Low PZR Level Alarm - 5%
All PZR Heaters Off (LO-LO alarm) {<28} [< 27%]

40
Q

Discuss the Letdown Limiter.

A
  • Limits letdown flow to between 29 – 128 GPM
  • “BYPASS” position allows the Letdown Flow Control Valves to be fully opened or closed to facilitate reestablishing Letdown Flow following isolation.
41
Q

Discuss the Letdown Flow Controller.

A

HIC 1110 in AUTOMATIC simply passes the analog control signal provided by LIC 1110X(Y).

42
Q

Discuss the Pressurizer Level Interlock BYPASS Switch.

A

Unit 1 Only
* Two Position Keyswitch (NORMAL/BYPASS) - Defeats the Backup Signal to stop the Backup CHG Pumps
* Allows more than one CHG Pump to run when filling the PZR
* Pressurizer Lvl Control Bypass Unit 1 only and only bypasses Hi level shut down on the back-up charging pumps (allows for faster pressurizer fill for solid ops) the pump that is running in auto does not get a shut down signal on Hi pressurizer level.

Unit 2 CHG Pumps have a “Hard Start” position so the CHG pumps will continue to run regardless of PZR level {Unit 1 switch spring returns to AUTO}

43
Q

Discuss Pressurizer Pressure Channel Failure Scenarios.

A

Controlling Channel Selected Pressure X Fails High (>2340 psia)
* High Pressure alarm (@ 2340 psia)
* Proportional Heaters: {U1: At minimum (>+25 psia over setpoint)} [U2: OFF >2340 psia]
* Backup Heaters: HTRS in AUTO go OFF (>2220 psia) [U2 > 2340 psia all heaters trip]
* Spray valve full Open >+100 [75] psia over setpoint
* Actual pressure decreases, Low pressure alarm on Y channel (2100 psia)
* TM/LP trip at 1887 psia [1900 psia]

Non-Selected Pressure Control Channel X Fails High
* High pressure alarm on channel X - Plant remains stable

Selected Pressure Control Channel X Fails Low
* Low Pressure alarm (2100 psia)
* Proportional Heaters at max (-25 psia under setpoint)
* Backup Heaters in AUTO go on (<2200)
* Spray valves closes (<+50 [25] psia over setpoint)
* Actual pressure increases
* High pressure alarm on Y channel (2340 psia)
* High PZR Pressure trip {2400 psia} [2370 psia]

Non-Selected Pressure Control Channel X Fails Low
* Low pressure alarm on channel X - Plant remains stable

44
Q

Discuss Pressurizer Level Channel Failure Scenarios.

A

Selected Level Control Channel X Fails High
* High Level Alarm (+10% dev) [+5% dev and 67%]
* Max Letdown of 128 gpm (+9% dev)
* All heaters on, secures any backup charging pump running
* Actual Level and pressure decreases
* Low Level alarm on channel Y (-5% dev)
* All heaters off {28%} [27%]
* TM/LP trip at 1887 psia [1900 psia]

Non-selected Level Control Channel X Fails High
* High Level Alarm (+10% dev) [+5% dev and 67%]
* Loss of low level heater cutout protection from channel X, No action required, Plant stable

Selected Level Control Channel X Fails Low (< 28[27] %)
* Low Level Alarm and backup CHG pumps on (-5% dev)
* Min Letdown of 29 gpm (-1% dev)
* All heaters off {28% - all contactors} [27% - one feeder breaker, 4 contactors]

  • Actual Level and pressure increases
  • High Level Alarm (+10% dev) [+5% dev and 67%]
  • Spray valves open on high pressure
  • High PZR pressure trip at 2400 psia [2370 psia]

Non-Selected Level Control Channel X Fails Low (< 28[27] %)
* Low Level Alarm (-5% dev)
* All heaters off {28% - all contactors} [27% - one feeder breaker, 4 contactors]

  • Actual pressure decreases, TM/LP trip at 1887 psia [1900 psia]

Block 2 (8 decks)

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