Pressurizer Pressure and Level Control System Flashcards

Question

Discuss RTGB switches for Pressurizer Heaters.

Answer 1

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

Answer 2

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

Answer 3

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

Answer 4

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

Answer 5

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)

Answer 6

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%)

Answer 7

* 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

Answer 8

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

Answer 9

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

Answer 10

* 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

Answer 11

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

Answer 12

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

Answer 13

~ 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%

Answer 14

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

Answer 15

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%]

Answer 16

* 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.

Answer 17

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

Answer 18

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}

Answer 19

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

Answer 20

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]