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BWR Recirculation Pump Modeling

Source

BWR Modeling Guidance — Recirculation Pump Modeling.

Overview

This section provides guidance on modeling BWR recirculation pumps in TRACE. The pump and discharge nozzle are modeled as a PUMP component (IPMPTY=2); the pump suction nozzle is modeled as a separate PIPE component. The guidance is applicable to:

  • GE BWR/3, BWR/4, BWR/5, and BWR/6

Typical BWR plants have two recirculation loops, so two PUMP components and two suction nozzle PIPE components should be created.

Required Inputs

  • Nominal system pressure and core inlet subcooling
  • Change in pressure across the recirculation pump
  • Pump suction and discharge nozzle geometry (ID, length)
  • Pump water volume
  • Height from pump suction to pump discharge mid-plane
  • Pump moment of inertia
  • Pump rated head, torque, volumetric flow, density, and impeller speed
  • Single-phase and degraded homologous pump curves (head and torque)
  • Loop mass flow rate

Pump Suction Nozzle — PIPE (1 cell, 2 edges)


Typical recirculation pump suction nozzle nodalization.

Component Number = (Loop) × 100 + 1025 (pump A) or + 1055 (pump B)

Geometry

Parameter Value
DXcell1 Pump suction nozzle length
VOLcell1 Frustum: π·DX/12·(ID²suction line + ID²pump suction + IDsuction · IDpump)
FAedge1 π/4 · ID²suction line
FAedge2 π/4 · ID²pump suction
HDedge1 IDsuction line
HDedge2 IDpump suction
GRAV +1.0 (vertical upward)

Friction

  • NFFedge1 = 1; NFFedge2 = 0
  • KFAC = 0.0 at all edges — all losses included in manufacturer pump head curves
  • KFACR = 0.0; ICFLG = 0; CCFL not applied

General Inputs

  • ICONC = 0; IPOW = 0; EPSW = plant-specific or 4.572 × 10⁻⁵ m
  • NSIDES = 0; IACC = 0

Recirculation Pump — PUMP (2 cells, 3 edges)


Typical recirculation pump nodalization.

Component Number = (Loop) × 100 + 1030 (pump A) or + 1060 (pump B)

Initialization:

  • IPMPTY = 2 (equation-based rotational speed)
  • NCELLS = 2
  • Total Length = height from suction nozzle to discharge mid-plane + discharge nozzle length

Cell Layout

Cell DX VOL
1 (pump body) 2 × height from suction outlet to discharge mid-plane Pump water volume (from manufacturer)
2 (discharge nozzle) Discharge nozzle length Frustum: π·DX/12·(ID²discharge line + ID²pump discharge + IDline · IDpump)

Cell 1 DX

Half of cell 1 DX must equal the elevation change from pump suction outlet to discharge mid-plane. TRACE assumes zero elevation change across edge 2 in the momentum equation. Otherwise, the net gravitational head calculated for the loop will be incorrect.

Edge Geometry

Edge FA HD GRAV
1 (suction) π/4 · ID²pump suction IDpump suction +1.0 (vertical)
2 (pump-to-discharge) π/4 · ID²pump discharge IDpump discharge 0.0 (horizontal)
3 (discharge outlet) π/4 · ID²discharge line IDdischarge line 0.0 (horizontal)
  • CCFL: not applied; ICFLG = 0 at all edges (impeller choking is in the pump curves)

Friction

  • NFFedges1,2 = 0; NFFedge3 = 1
  • KFAC = 0.0 at all edges — all losses included in manufacturer pump curves
  • KFACR = 0.0

Initial Conditions

  • P = plant-specific suction/discharge pressure, or nominal system pressure
  • TL = plant-specific or Tsat − ΔTsubcooling; TV = Tsat
  • ALPN = 0.0; PA = 0.0
  • VL = ṁloop / (ρ · FAedge); VV = 0.0

Pump Performance Data

All pump performance parameters must be obtained for the specific pump being modeled. No generic recommendations are provided.

Rated Values

Parameter Description
RHEAD Rated head
RTORK Rated torque
RFLOW Rated volumetric flow
RRHO Rated density
ROMEGA Rated impeller speed

Frictional Torque Coefficients

Parameter Description
TFR0–TFR3 Frictional torque polynomial coefficients
TFRB Torque break speed
TFRL0–TFRL3 Low-speed frictional torque coefficients

Speed Values

Parameter Value
OMEGAN (initial speed) Nominal rotational speed (BWR/5-6 constant speed); 0.0 otherwise
OMGOFF (off speed) 0.0 (typical transients don't re-activate pumps)
ROMGMX (max speed change) 10²⁰ (no restriction)
OMGSCL (speed scale factor) 1.0
NPMPSD (off-speed controller) Control block output for variable speed (BWR/3-4); 0 for constant speed

Homologous Pump Curves

Curve Description
HSP Single-phase homologous head curve
HTP Fully degraded homologous head curve
TSP Single-phase homologous torque curve
TTP Fully degraded homologous torque curve
HDM Head degradation multiplier curve
TDM Torque degradation multiplier curve

Pump Curve Option (OPTION)

  • OPTION = 0 — User-specified curves (preferred if plant-specific data available)
  • OPTION = 4 — Built-in Westinghouse curves (fallback if no plant-specific data)

Other General Inputs

Parameter Value
IRP (reverse rotation) Plant-dependent: 0 (No) or 1 (Yes)
IPM (degradation option) 1 (single/two-phase curves) if OPTION ≠ 3,4; 2 (two-phase multipliers) if OPTION = 3,4
EFFMI Manufacturer-specified effective moment of inertia
ETA Pump efficiency (default 85% if not provided)
Use Alternate Inertia False (not recommended for typical BWR modeling)
IPMPTR Trip ID controlling pump speed
IPOW 0 (use PUMPFRICQ namelist for frictional heat)
Use Pipewall False (attach HTSTR to cells 1–2 manually)

Steady-State Checklist

Steady-State Verification

  • Pump ΔP matches plant data
  • Loop flow rate matches target
  • Pump speed is at rated value (constant speed) or target value (variable speed)
  • Pump efficiency is consistent with rated parameters
  • 10:1 adjacent cell volume ratio satisfied (check against adjacent recirc line cells)

Cross-References

This page faithfully extracts recirculation pump modeling guidance from the BWR Modeling Guidance. The pump is modeled as a 2-cell PUMP component (IPMPTY=2) with separate suction nozzle PIPE. All hydraulic losses are assumed included in the manufacturer pump curves — no KFAC values are applied. BWR/3-4 use variable speed control (NPMPSD); BWR/5-6 use constant speed (OMEGAN).