SALEM
SALEM STUDY SYSTEM
Systems > Pressurizer & PRT

Pressurizer & PRT

⚠️ DRAFT

Pressurizer & PRT

Function

The pressurizer provides a point in the RCS where liquid and vapor are maintained in equilibrium under saturated conditions for pressure control. It accommodates positive and negative surges caused by load transients. (UFSAR 5.1, 5.5.10)

Key Design Parameters

ParameterValueSource
Design/Operating Pressure2485 / 2235 psigUFSAR T5.2-4
Hydrostatic Test Pressure (cold)3107 psigUFSAR T5.2-4
Design/Operating Temperature680 / 653°FUFSAR T5.2-4
Shell ID84 inUFSAR T5.2-4
Water Volume (full power)1080 ft³ (60% of net internal volume)UFSAR T5.2-4
Steam Volume (full power)720 ft³UFSAR T5.2-4
Electric Heater Capacity1800 kWUFSAR T5.2-4
Heatup Rate (heaters only)~55°F/hrUFSAR T5.2-4
Maximum Spray Rate800 gpmUFSAR T5.2-4
Surge Line Nozzle Diameter14 inUFSAR T5.2-4

Construction

  • Vertical, cylindrical vessel with hemispherical top and bottom heads
  • Carbon steel construction with austenitic stainless steel cladding on all surfaces exposed to reactor coolant
  • Electrical heaters installed through the bottom head (removable for maintenance)
  • Spray nozzle, relief and safety valve connections on top head
  • Surge line attached to bottom, connects to hot leg of one RCS loop
  • (UFSAR 5.1)

Pressurizer Relief Tank

ParameterValueSource
Design Pressure100 psigUFSAR T5.2-4
Rupture Disc Release Pressure100 psigUFSAR T5.2-4
Design Temperature340°FUFSAR T5.2-4
Normal Water TemperatureContainment ambient (120°F max)UFSAR T5.2-4
Total Volume1800 ft³UFSAR T5.2-4
Total Rupture Disc Relief Capacity1.60 x 10⁶ lb/hrUFSAR T5.2-4
  • Carbon steel with corrosion-resistant coating on wetted surfaces
  • Normally contains water in a predominantly nitrogen atmosphere
  • Steam enters through sparger pipe under water level
  • Two rupture discs discharge to reactor containment
  • Internal spray and drain for cooling after a discharge
  • (UFSAR 5.1)
Exam — 2018 Q6
PRT cooling: accomplished by a manual-only feed and bleed process — feed via 2WR82 (Primary Water supply) and bleed via 2PR14 (PRT drain). There is NO automatic PRT cooling function. During PRT cooling, the PRT drains directly to the RCDT pump suction header (NOT the RCDT tank itself). Trap: many other plant processes have automatic functions, but PRT cooling is entirely manual. Also, the drain path is to the RCDT pump suction header — a distinction from draining into the RCDT tank.
Exam — 2018 Q8
PZR saturation determination using steam tables: at PZR Pressure 2005 psig (2020 psia), saturation temperature is 637°F. With PZR liquid temperature at 635°F, the PZR is subcooled (NOT water saturated). Per 1-EOP-TRIP-6, the reason for establishing and maintaining saturation conditions in the PZR before RCP restart is to limit the PZR pressure DECREASE upon RCP restart. Trap: steam tables are listed in psia, not psig — must add ~15 psi to convert. Also: the concern is pressure DECREASE (not increase) — pressure decrease occurs because cold water from the loop enters the PZR surge line when forced circulation is established.
Exam — 2019 Q6
Reactor head vents drain to the PRT and will cause PRT temperature to rise when the reactor is at power. Reactor Flange Leakoff is directed to the RCDT, NOT the PRT. Per S2.OP-SO.PZR-0003 Section 5.3 ("Reducing PRT Temperature by Feed and Bleed"), the liquid in the PRT will be pumped to the HUT (Hold-Up Tank) using an RCDT Pump. The PRT drain is physically connected to the RCDT via piping with a check valve, but the PRT liquid is pumped to the HUT, not kept in the RCDT.
Exam — 2019 Q7
Per LCO 3.4.10.2, maximum allowable PZR heatup rate is 100°F/hr. Maximum PZR cooldown rate is 200°F/hr (common distractor — heatup and cooldown limits are different). Per S2.OP-SO.RC-0002 Section 5.4, during PZR degassing via 2PR1 (PZR PORV), maintain PRT pressure less than 10 psig.
Exam — 2019 Q10
PORV leak-by is a constant enthalpy (throttling) expansion process. At PZR pressure 415 psig (430 psia) with PRT pressure 0 psig, hg ≈ 1205 BTU/lbm. Following the constant enthalpy line on a Mollier diagram from 415 psig to 0 psig yields tailpipe temperature of approximately 330°F. 212°F is the boiling point at 0 psig and 450°F is for ~515 psig — both are plausible distractors but do not account for the throttling process.
Exam — 2022 Q34
PRT has a rupture disc (NOT a relief valve) rated at 100 psig. 2PR15 (PRT Vent to RCDT) cannot be opened if PRT pressure ≥ 10 psig — interlock prevents opening. Per S2.OP-SO.PZR-0003, if PRT pressure ≥ 10 psig: drain PRT first via 2PR14 to lower level and pressure, then open 2PR15 to vent PRT to 3 psig. 2PR15 is NOT available for venting when PRT pressure is above 10 psig — must drain first to clear the interlock.
Exam — 2023 Q32
PRT drain path per S2.OP-SO.PZR-0003: open 2PR14 to drain PRT to RCDT, which automatically opens 2WL12 and starts the RCDT pump (defeats low level cutoff). RCDT pump discharge destinations: RWST, CVCS Hold-Up Tanks, or Waste Hold-Up Tanks. PRT does NOT gravity drain — the RCDT pump is required.
Exam — 2023 Q76
PZR vapor space leak (SBLOCA): at RCS pressure 1450 psig stable with subcooling 10°F and PZR level 30% rising, both charging and SI pumps are injecting. SI termination criteria in EOP-LOCA-1 are met — transition to EOP-TRIP-3, not directly to EOP-LOCA-2. Ultimately: LOCA-1 → TRIP-3 → LOCA-2.
Exam — 2020 Q2
PORV discharge temperature is determined by a constant enthalpy (throttling) process from RCS pressure to PRT pressure (Mollier Diagram). Key relationships: lowering PRT pressure → lower discharge temperature; raising PRT pressure → higher discharge temperature. Changes in RCS pressure or PORV leak rate do NOT directly lower the indicated discharge temperature. A leaking PRT rupture disk lowers PRT pressure, thereby lowering discharge temperature.
Exam — 2022 Q2
PZR safety valve leak is a throttling/constant enthalpy process. Tailpipe temperature determined by following the enthalpy line on a Mollier diagram to PRT pressure. At RCS 1900 psig (1915 psia, hg ~1140 BTU/lb), throttling to PRT 35 psig (50 psia) yields tailpipe temperature of approximately 282°F.

PORV Accumulators

Exam — 2018 Q25
Each PZR PORV has 2 accumulators sized for 100 opening/closing cycles (50 per accumulator). With both CA330 (Containment Supply Inlet Valves) closed (e.g., on loss of control air), the PORVs CAN still be operated using their accumulators. Trap: loss of containment air supply does NOT prevent PORV operation — the accumulators provide a self-contained air supply independent of the plant air headers.

Tech Spec LCOs

  • TS 3/4.4 — Reactor Coolant System|TS 3/4.4.4 — Pressurizer (level and heater requirements)
  • TS 3/4.4 — Reactor Coolant System|TS 3/4.4.3 — PORVs and Block Valves
JPM — 2023 Sim-c
EOP-LOCA-2 Step 20 depressurization via Auxiliary Spray: open 2CV75 (RCS Aux Spray Valve), close 2CV77/2CV79 (charging to loops). Stop when PZR level >77% (74% adverse) or subcooling <10F.
JPM — 2023 Sim-d
EOP-FRHS-1 Bleed and Feed: if PORV 2PR2 fails to open, open reactor head vent valves 2RC40 through 2RC43 (key-locked on 2RP2 backpanel) as alternate bleed path. 2PR1 must already be open for the "bleed" portion.
JPM — 2022 IP-i
Transfer of 22 Backup Group PZR heaters to emergency power (2A 460V Vital Bus) per S2.OP-SO.PZR-0010 Section 5.3: place 11 of 14 disconnects in OFF (only 3 remain ON to limit load within emergency bus capacity), place 2EP PZR HTR BUS EMERGENCY FEED DISCONNECT SWITCH in ON using JAM key, then insert interlock key and UNLOCK breaker 2AX1AX14X.
Scenario — 2022 #4
PZR spray valve 2PS3 fails to close during SGTR-1 RCS depressurization. Both spray valves opened for depressurization per Table D criteria. When termination criteria met, RO closes both valves — 2PS3 fails to close. Recovery: stop 21 and 23 RCPs to eliminate spray flow path (spray valves are in the RCP seal injection lines from the cold legs of loops 1 and 3). Also: earlier in scenario, 2PR2 PORV seat leakage diagnosed via tailpipe temperature and isolated by closing block valve 2PR7.
Scenario — 2020 #4
During SGTR-1 depressurization, normal PZR spray is NOT available (23 RCP stopped). RCS depressurization uses PZR PORVs IAW Table E criteria. After depressurization termination criteria met, RO attempts to close PORV — PORV fails to close (stuck open). Recovery: close associated PZR PORV block valve (CT-10). Creates a small-break LOCA in addition to tube rupture if not promptly isolated.
JPM — 2020 Sim-a
PZR pressure channel 1 fails high causing both spray valves to open fully and rapid RCS pressure decrease. Operator places MPC in manual and lowers demand. Alternate path: 2PS1 spray valve fails to close when MPC demand is zeroed. Operator places 2PS1 in MANUAL and closes. If 2PS1 cannot be closed, CAS at 2000 psig directs reactor trip and stopping 21 and 23 RCPs (spray is fed from Loops 1 and 3 cold legs).
Scenario — 2018 #1
During startup at 3% power, controlling PZR Pressure Channel I fails high — de-energizes PZR heaters and fully opens both spray valves. RO places Master Pressure Controller (MPC) in manual, lowers demand to close spray valves, selects Channel III for control. RO closes 2PR6 and places 2PR1 in Manual, WCC removes control power from 2PR6. Channel removed from service IAW S2.OP-SO.RPS-0003. Tech Specs entered: 3.3.1.1 Action 6, 3.3.2.1.b Action 19, 3.4.5 Action b (1 hr LCO), 3.2.5 DNB (2 hr LCO).

Connections