SALEM
SALEM STUDY SYSTEM
Systems > RHR

RHR

⚠️ DRAFT

RHR

Function

The Residual Heat Removal (RHR) system removes decay heat from the reactor core during plant shutdown and cooldown. It reduces RCS temperature from 350°F to 140°F (cold shutdown/refueling). During a LOCA, the RHR pumps function as low-head safety injection pumps for the ECCS. (UFSAR 5.5.7)

Key Design Parameters

ParameterValueSource
RCS Temperature at RHR Startup350°FUFSAR T5.5-1
Time to Cool from 350°F to 140°F (design, 2 trains)16 hr (original); 18 hr (with 1.4% uprate)UFSAR T5.5-1
Time to Cool (single train requirement)72 hrUFSAR T5.5-1
Decay Heat at 20 hr After Shutdown72.1 x 10⁶ Btu/hr (original design)UFSAR T5.5-1
CCW Supply Temperature (design)95°FUFSAR T5.5-1
RWST Boron Concentration~2000 ppmUFSAR T5.5-1
Plant Design Life40 yearsUFSAR T5.5-1

Heat Exchangers

ParameterShell SideTube SideSource
Number2 per unit—UFSAR T5.5-1
Design Heat Transfer—34.15 x 10⁶ Btu/hrUFSAR T5.5-1
Design Pressure150 psig600 psigUFSAR T5.5-1
Design Temperature200°F400°FUFSAR T5.5-1
Design Flow Rate2.475 x 10⁶ lb/hr1.48 x 10⁶ lb/hrUFSAR T5.5-1
Design Outlet Temperature108.8°F114°FUFSAR T5.5-1
Design Inlet Temperature95°F137°FUFSAR T5.5-1
FluidCCWReactor coolant (borated demin water)UFSAR T5.5-1
MaterialCarbon steelAustenitic stainless steelUFSAR T5.5-1

Pumps

ParameterValueSource
Number2 per unitUFSAR T5.5-1
TypeVertical centrifugalUFSAR T5.5-1
Design Pressure600 psigUFSAR T5.5-1
Design Temperature400°FUFSAR T5.5-1
Shutoff Head170 psiUFSAR T5.5-1
Design Flow Rate3000 gpmUFSAR T5.5-1
Design Head350 ftUFSAR T5.5-1
Available NPSH at Design Flow25 ftUFSAR T5.5-1
Fluid Temperature Range40–350°FUFSAR T5.5-1
MaterialAustenitic stainless steelUFSAR T5.5-1

Piping Design

SectionPressureTemperatureSource
Pump Suction (isolated loop)450 psig*400°FUFSAR T5.5-1
Pump Discharge (isolated loop)600 psig400°FUFSAR T5.5-1
Isolation Valves and Piping (RCS boundary)2485 psig650°FUFSAR T5.5-1

*Unit 2 piping downstream of 2RH75 & 76 designed to 600 psig.

Exam — 2018 Q3
RHR system physical connections: RHR Pumps take suction from the 21 Hot Leg and can be aligned to discharge into the 23 and 24 Hot Legs. The suction and discharge connections are NOT on the same loops — suction is from Loop 1, discharge is to Loops 3 and 4.
Exam — 2019 Q4
During solid plant operations in MODE 5, throttling 22RH18 (RHR HX Outlet Valve) more CLOSED and 2RH20 (RHR HX Bypass Valve) more OPEN reduces flow through the RHR HX → RCS temperature rises → RCS pressure rises (water is incompressible in solid plant conditions). To restore pressure: throttle 2CV18 (Low Pressure Letdown Control Valve) more OPEN to increase letdown flow. Solid plant pressure control is maintained by adjusting letdown (not charging). Throttling CV18 more closed would RAISE RCS pressure, not lower it.
Exam — 2023 Q30
To LOWER the cooldown rate while maintaining constant RHR flow: lower RH18 demand (closes HX flow control valves, reducing flow through the RHR HX) and raise RH20 demand (opens HX bypass valve, routing more flow around the HX). Total RHR flow stays constant but less passes through the heat exchanger. Reverse actions (raise RH18 / lower RH20) would increase cooldown rate.
Exam — 2020 Q31
RHR HX tube blockage from foreign material reduces heat transfer, lowering cooldown rate. To RESTORE the cooldown rate: raise 21RH18 demand (increases flow through the partially blocked RHR HX to compensate) and lower 2RH20 demand (decreases HX bypass flow, forcing more total flow through the HX). Per S2.OP-SO.RHR-0001. Trap: "raise demand" on RH18 OPENS the valve (more HX flow); "lower demand" on RH20 CLOSES the bypass (less bypass flow). Both actions increase heat removal through the HX.

Valve Failure Modes

Exam — 2022 Q31
21RH18 (RHR HX Outlet Valve) fails OPEN on loss of 2A VIB (115V Vital Instrument Bus) — increases flow through RHR HX, RCS temperature lowers. 2RH20 (RHR HX Bypass Valve) fails OPEN on loss of 2D VIB — independent power supply from 21RH18. Loss of 2A VIB only affects 21RH18, NOT 2RH20. 2RH20 remains as-is unless 2D VIB is lost.
Exam — 2022 Q32
Solid plant ops with RHR pump trip: RCS pressure rises (charging continues adding inventory with no RHR pump to provide letdown path). Letdown line pressure lowers (loss of RHR discharge pressure). 2CV18 throttles closed attempting to maintain letdown pressure at setpoint. 2CV6 (Letdown Relief Valve) opens at 600 psig to protect downstream piping if pressure not controlled.
Exam — 2019 Q12
RHR pump power supply: 22 RHR Pump is powered from 2B 4KV Vital Bus (NOT 2C). During a Reactor Trip + SI coincident with LOOP and EDG 2C unavailable, 22 RHR Pump is running because 2B bus is powered by EDG 2B. Common confusion: 22 SI Pump is on 2C bus, but 22 RHR Pump is on 2B bus — pump number does not indicate bus assignment.

RCS Isolation

The RHR system is isolated from the RCS by two normally closed motor-operated valves in each suction line. These valves are interlocked to prevent opening when RCS pressure is above the RHR system design pressure. (UFSAR 5.5.7.3.2)

Exam — 2022 Q7
2RH1 and 2RH2 (RHR Suction Isolation Valves) are interlocked to PREVENT OPENING until PT-403 and PT-405 < 375 psig — they do NOT auto-close on high RCS pressure. Must be manually closed during RCS heatup. Design pressures: suction piping 450 psig, discharge piping 600 psig (design temp 400°F). Suction relief valve lifts at 350 psig. POPs actuates at RCS > 375 psig opening both PZR PORVs.

LOCA Recirculation Mode

During LOCA recirculation, the RHR pumps take suction from the containment sump and pump radioactive borated water (with H₂ and NaOH in solution) through the RHR heat exchangers and into the RCS. (UFSAR T5.5-1)

Exam — 2020 Q6
Shutdown LOCA in Mode 4 (RCS temp 325°F, pressure 300 psig): enter AB.LOCA-0001 (Shutdown LOCA) for any uncontrolled reduction in PZR level in Mode 4. CAS directs if PZR level <11%: stop the operating RHR Pump aligned for Shutdown Cooling and close 2RH1 and 2RH2 (RHR Common Suction). AB.RHR-0001 redirects to AB.LOCA-0001 in Mode 4. AB.RHR-0001 actions (isolate letdown, start SI/charging, maintain PZR level 5-50%) apply only to Modes 5 or 6.

Tech Spec LCOs

  • TS 3/4.5 — ECCS — RHR subsystems as part of ECCS
  • TS 3/4.9 — Refueling Operations|TS 3/4.9 — RHR requirements during refueling
Exam — 2023 Q79
Loss of RHR breaker reclosure: per OP-SA-108-106-1001 step 4.2.2, during an emergency condition the Shift Manager can authorize one attempt at reclosing a failed breaker without an investigation, if the equipment is essential for plant stability. Does NOT require Plant Manager authorization or STA concurrence. In the exam scenario, Time to Core Boiling <15 minutes with both RHR pumps lost constitutes an emergency condition.
JPM — 2023 Sim-b
EOP-LOCA-4 hot leg recirculation with 21 RHR pump C/T: Step 4.0 directs CLOSE 22CS36 (RHR Supply to CS Valve) and OPEN 22SJ49 (Cold Leg Isolation Valve) for the running 22 RHR pump alignment.
Scenario — 2022 #1
21 RHR pump C/T for motor bearing inspection. During LBLOCA, 22 RHR pump fails to start on 2B SEC signal (CT#2, CT-5). PO blocks and resets 2B SEC, RO manually starts 22 RHR. Later in EOP-LOCA-1, 22 RHR pump trips on overcurrent — no RHR pumps available for emergency recirculation. CRS transitions to EOP-LOCA-5, Loss of Emergency Recirculation. Loss of both RHR pumps is the driver for CT#3 (RWST conservation actions).
Scenario — 2020 #2
21 RHR Pump C/T for motor bearing replacement (initial condition). During LBLOCA in EOP-TRIP-1, 22 RHR pump fails to start on 2B SEC signal — PO blocks and resets 2B SEC, RO manually starts 22 RHR (CT-5). Later in EOP-LOCA-1, 22 RHR pump trips on overcurrent (relay flag dropped). No RHR pumps available — transition to EOP-LOCA-5.
Exam — 2020 Q25
LOCA outside containment indication from RHR piping: OHA C-34 (22 RHR SUMP OVRFLO) and 23/24 RHR Sump Pump starts indicate a leak in the RHR system outside containment. During SI termination (EOP-TRIP-3), these alarms combined with 2R41D Plant Vent alarm and inability to recover PZR level trigger the CAS to restart ECCS pumps and transition to EOP-LOCA-1, then to EOP-LOCA-6.
JPM — 2020 Sim-b
Loss of both RHR pumps in Mode 5 with RCS depressurized and vented (2PS59). 21 RHR Pump trips on electrical fault. Alternate path: 22 RHR Pump trips shortly after starting. With both pumps lost, navigate AB.RHR-0001 to Step 3.32 and select Attachment 8, Cold Leg Injection (preferred when core exit TCs <200°F). Valve lineup: open RWST outlet (2SJ1/2SJ2), close VCT outlet (2CV40/2CV41), open BIT inlet/outlet (2SJ4/2SJ5, 2SJ12/2SJ13), close charging discharge (2CV68/2CV69) — establishing borated injection from RWST through BIT to cold legs via the running charging pump.
Exam — 2019 Q63
During LOCA outside containment (EOP-LOCA-6), the crew is MOST concerned with RHR piping connecting to the RCS because it is only rated to 600 psig (vs RCS piping rated to 2500 psig). This is the basis for the leak isolation strategy in LOCA-6.
Exam — 2018 Q84
AB.CONT-0001 (Containment Closure) response during Loss of RHR: Containment Closure should be established prior to Core Boiling (not within 4 hours — that applies to other initiating events). Outage Equipment Hatch may be closed using 4 corner bolts per AB.CONT-0001 (expedited closure for time-critical RHR loss), versus ALL 10 bolts per SC.MD-FR.CAN-0001 for non-RHR events.
Exam — 2018 Q87
AB.RHR-0001 CAS routing for loss of RCS inventory by MODE: In MODE 5 with inventory loss (PZR level lowering, containment particulate monitor rising), the CAS directs: START SI and Charging Pumps as required AND CONTROL PZR level between 5% and 50% while maintaining RHR System in service. Do NOT go to AB.LOCA-0001 (Mode 4 only), AB.RHR-0002 (reduced inventory only), or Attachment 9 (loss of all vital buses only).
Exam — 2018 Q63
RH19 (RHR Discharge X-CONN Valves): per EOP-LOCA-6 Step 2, the crew WILL close 11RH19 and 12RH19 to separate the 11 and 12 RHR discharge lines during LOCA outside containment leak isolation. This enhances the ability to diagnose which train has the leak. Successful isolation confirmed by rising RCS pressure.
Scenario — 2018 #2
During LBLOCA cold leg recirculation transfer (EOP-LOCA-3): RHR suction aligned to containment sump via 21SJ44 and 22SJ44 (sump auto arm pushbuttons depressed when >62% lights lit). Both RHR pumps running. Close 21 and 22RH19s (discharge cross-connect valves) to separate trains. Close 2SJ67 and 2SJ68. Open 22SJ45 then 21SJ45 (RHR injection to cold legs). Place 21RH29 and 22RH29 in manual and ensure closed (Step 15 — CT#2 Part 3, within 11.2 min of RWST lo alarm).

Connections