SALEM
SALEM STUDY SYSTEM
Systems > Pressurizer Level & Press Control

Pressurizer Level & Press Control

⚠️ DRAFT

Pressurizer Level & Press Control

Pressure Control

  • Pressure increase: Spray valves open, condensing steam in the pressurizer steam space
    • Spray valves begin to open at 2260 psig
    • Spray valves full open at 2310 psig
  • Pressure decrease: Heaters energize, generating steam
    • Proportional heaters begin at 2250 psig
    • Proportional heaters full at 2220 psig
    • Backup heaters on at 2210 psig
  • Overpressure protection:
    • PORVs lift at 2335 psig (reset 2315 psig)
    • Safety valves lift at 2485 psig
  • (UFSAR T5.2-1)
Exam — 2018 Q5
PZR heaters de-energize based on PZR low level (at 17%), NOT on an SI signal. Although the SI signal causes many automatic actions, PZR heater de-energization is NOT one of them. Trap: candidates may confuse this with the many SI-actuated functions and incorrectly believe SI directly de-energizes the heaters.
Exam — 2018 Q9
PZR pressure control sequence during a rising pressure transient: spray valves begin opening at 2260 psig, spray valves fully open at 2310 psig. PORVs close setpoint is 2315 psig. PORVs open at 2335 psig. MPC at 100% output when PZR pressure reaches 2355 psig. At 2312 psig: spray valves fully open. At 2340 psig: PORVs open. Trap: 2315 psig is the PORV CLOSE setpoint (not the spray full-open setpoint). Candidates may confuse the 2315 psig value.
Exam — 2018 Q55
PORV open logic requires 2 of 2 coincidence: 2PR1 requires PT-455 AND PT-457 both > 2335 psig; 2PR2 requires PT-456 AND PT-474 both > 2335 psig. With only PT-455 (Channel I) failing high, NO PORVs open — neither PORV has both input channels reading high. Trap: PORVs are NOT controlled by the Master Pressure Controller (MPC). Each PORV has a dedicated 2/2 pressure coincidence circuit independent of the MPC. A single channel failure high cannot open any PORV.

Pressurizer Heater Power Supplies

Exam — 2023 Q7
PZR Backup Heater Group power supplies:
- Group 1 (21): Normal — 2G 4KV Group Bus. Emergency backup — 2C 460V Vital Bus.
- Group 2 (22): Normal — 2E 4KV Group Bus. Emergency backup — 2A 460V Vital Bus.
Transfer to emergency backup source is MANUAL (not automatic). EOP-LOSC-2 step 26 directs restoring normal power or transferring to emergency backup.
Exam — 2023 Q14
Following a reactor trip + SI with instrument air to containment isolated, PORVs cycle on accumulators. When air is restored (accumulators automatically isolate and realign to normal containment control air when pressure is restored — above 90 psig normal supply vs. below 85 psig accumulator). No manual action is required for accumulator realignment. Pressurizer spray valves reopen when air is restored because the Master Pressure Controller (MPC) will have demand to open spray valves post-trip.
Exam — 2023 Q34
MPC fails low (0% output): spray valves close (controlled by MPC) and backup heaters energize → RCS pressure rises → PORVs open at 2335 psig. PORVs are interlocked directly from PZR pressure, NOT from MPC output — MPC failure does not prevent PORV actuation.
Exam — 2023 Q87
EOP-TRIP-4 CAS: if PZR level cannot be maintained > 4% (with 2CV55 and 2CV71 fully open and level still lowering), actuate SI and return to EOP-TRIP-1. PZR heaters will NOT energize with level < 17% — operating heaters to maintain saturated conditions is not possible when level is at 10% and lowering.
Exam -- 2023 Q92
PZR pressure channel failure reportability: with one PZR pressure channel already tripped and a second failing LOW, the 2/4 low PZR pressure trip coincidence is met causing a reactor trip and SI. The SI is NOT valid (pressure was not actually low) and NOT reportable under RAL 11.3.1. The RPS actuation is reportable under RAL 11.3.2 as a 4-hour report.
Exam — 2022 Q37
PZR pressure channel fails HIGH: MPC output rises to 100% (spray valves open, heaters de-energize). To restore RCS pressure, operator must manually LOWER MPC demand (close spray valves, energize heaters). TS 3.2.5 DNB Parameters: minimum DNBR limit is RCS pressure ≥ 2200 psia = ≥2185 psig. 2200 psia ≠ 2200 psig. The TS limit is 2200 psia which equals 2185 psig (subtract ~15 psi for atmospheric).
Exam — 2022 Q9
AB.PZR-0001 directs manual reactor trip when RCS pressure reaches 2000 psig and lowering (spray valve failed open scenario). Reason: prevent challenging the automatic reactor trip on OT Delta-T. Not low PZR pressure — the auto trip on low PZR pressure is 1865 psig (rate-compensated), which is well below 2000 psig. OT Delta-T trips first as pressure lowers because the OT Delta-T setpoint has a +K3*P pressure input.
Exam — 2020 Q7
Confirms 2022 Q9: AB.PZR-0001 PORV failed open sequence: 1) attempt to close PORV in manual, 2) close the associated block valve, 3) if block valve fails to close THEN open control power breaker. CAS: trip reactor at 2000 psig and lowering. Procedure bases: simulator showed auto trip at 1950 psig on OTΔT — this is why 2000 psig was chosen.
Exam — 2022 Q21
PZR reference leg leak causes indicated level to read HIGHER (lower reference leg head → lower DP across transmitter → controller interprets as higher level). Master Flow Controller responds by lowering charging flow, so actual PZR level LOWERS while indication rises — a divergence between actual and indicated level.
Exam — 2022 Q88
Loss of all control air impact on PZR level: with a centrifugal charging pump in service, CV55 fails OPEN and CV71 fails CLOSED. With letdown isolated (no letdown path), higher charging flow to RCP seals causes PZR level to RISE. Per AB.CA-0001: locally adjust CV54 (Centrifugal Charging Pump Flow Control Valve) OR transfer to 23 PDP charging pump (speed controller fails at low speed stop → minimizes RCP seal flow → extends time before PZR reaches 90%).
JPM — 2022 IP-i
During LOOP, PZR backup heaters are transferred to emergency power per S2.OP-SO.PZR-0010 Section 5.3. Transfer is MANUAL (not automatic). Group 22 transfers to 2A 460V Vital Bus. Only 3 of 14 heater disconnects remain ON to limit load within the emergency bus capacity.
Exam — 2019 Q50
PZR Safety Valve seat leakage response: PZR level lowers below program level → master flow controller automatically RAISES charging flow. Trap: PZR safety valves are located on top of the PZR, so candidates may think level rises. In reality, steam leaking out reduces steam space pressure AND inventory → level drops. As RCS pressure lowers from the leak, the OTΔT reactor trip setpoint automatically lowers (K3 pressure coefficient) and trips the reactor before the fixed low PZR pressure setpoint of 1865 psig is reached. OPΔT setpoint varies with AFD, NOT pressure — do not confuse OTΔT (pressure-dependent) with OPΔT (AFD-dependent).
Exam — 2019 Q9
2LT-459 (Channel I PZR Level) variable leg leak: the variable leg is the low side of the D/P cell and is connected to the pressurizer liquid space. A leak causes D/P to increase → indicated PZR level goes off scale LOW. Actual PZR level and pressure also lower (inventory loss). PZR B/U heaters will NOT energize because indicated level is below the 17% low level B/U heater cutoff setpoint. Common misconception: D/P = 0 psid = hi pressurizer level (maximum indicated level), not D/P = maximum = hi level. A variable leg leak INCREASES D/P, indicating LOW.
Exam — 2020 Q57
PZR Level Channel I (controlling channel) fails HIGH: charging flow reduces to minimum (controller sees high level, reduces charging). Actual PZR level drops slowly. At 17% actual level, the alarm channel (Channel II) triggers letdown isolation and PZR heaters off. With minimum charging and no letdown, level eventually rises and a Rx Trip on high PZR level occurs at 92% (2/3 channels II & III). Key distinction: controlling channel fails HIGH = sequential events (charging min → level drops → letdown isolates → level eventually rises → trip). Controlling channel fails LOW = charging rises immediately AND letdown isolates immediately — NOT in the sequential order. Auctioneered Tavg failed high only shifts program level to ~59%.
Exam — 2020 Q36
PORV channel assignments: 2PR1 is controlled by Channel I (2PT-455). 2PR2 is controlled by Channels II & IV. If Channel I fails LOW, 2PR1 AUTO operation is blocked (failed channel prevents PORV from seeing actual high pressure). 2PR2 remains functional on Channels II & IV and will open as pressure rises to the open setpoint. PZR spray valves only function in AUTO via the controlling channel — if the controlling channel fails low, spray valves will NOT open to control pressure rise.
JPM — 2019 Sim-c
EOP-SGTR-1 Step 19 RCS depressurization using normal spray. Open 2PS1 and 2PS3 spray valves. When Table D conditions met (RCS pressure < ruptured SG pressure AND PZR level > 11%), Step 19.1 CAS directs closing spray valves. 2PS3 fails to close — alternate path. Corrective action: STOP 21 and 23 RCPs to eliminate spray flow path. 2PS3 spray valve is supplied by 21 and 23 RCP discharge; stopping these pumps removes the driving head for spray.
Exam — 2018 Q82
2LT-459 (Channel I PZR Level) fails HIGH while controlling: 22 Backup Heaters automatically energize due to +5% PZR level deviation (LACTUAL - LREF). 21 Backup Heaters are already ON in manual. Trap: candidates may incorrectly think B/U heaters will de-energize because PZR pressure (2235 psig) is > 2210 psig (the pressure-based B/U heater auto-energize setpoint). The level deviation logic is a separate, independent auto-energize path for the backup heaters. TS action: per LCO 3.3.1.1, 2LT-459 must be placed in the tripped condition within 6 hours (not 1 hour).

Connections