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BWR Jet Pump Modeling

Source

BWR Modeling Guidance, §9 — Jet Pump Modeling.

Overview

This section provides guidance on modeling BWR jet pumps in TRACE using the JETP component. The guidance is applicable to:

  • GE BWR/3, BWR/4, BWR/5, and BWR/6

Typical BWR plants have two recirculation loops with 10 jet pumps each. Two JETP components should be created, one per recirculation loop, each representing 10 jet pumps.

Required Inputs

  • Nominal system pressure
  • Nominal core inlet subcooling
  • Jet pump throat geometry (ID, length)
  • Jet pump diffuser geometry (discharge ID, diffusing length, discharge length)
  • Driving nozzle geometry (ID, OD, outlet ID, length, radius of curvature)
  • Ram's head driving nozzle assembly geometry (inlet ID, straight section length)
  • Recirculation loop mass flow rate
  • Driving loop flow ratio (compared to total flow out of jet pump)
  • Jet pump material properties (wall roughness)

Component Setup — JETP (7 cells, 9 edges)

Cells 1–4 model the main body (throat + diffuser); cells 5–7 model the driving nozzle assembly.


Figure 9.2-1: Typical jet pump nodalization.

Initialization:

  • Main Tube Length = height from diffuser bottom to suction inlet top
  • Side Tube Length = pipe length from inlet riser top to driving nozzle outlet
  • Main Tube FA = π/4 · ID²diffuser outlet
  • Side Tube FA = π/4 · ID²driving nozzle
  • NCELL1 = 4 (main body), NCELL2 = 3 (driving nozzle)
  • Component Number = (Loop) × 100 + 1030 (pump A) or + 1060 (pump B)

Geometry Inputs


Figure 1.3-1: Typical jet pump schematic showing cell/edge definitions.

Cell Layout

Cell DX VOL
1, 2 ½ throat length π · DX / 8 · ID²throat
3 Diffusing section length π · DX / 12 · (ID²throat + ID²discharge + IDthroat · IDdischarge) — conical frustum
4 Straight-pipe section at diffuser bottom π · DX / 4 · ID²discharge
5 Driving nozzle length π · DX / 12 · (ID²nozzle line + ID²nozzle outlet + IDline · IDoutlet) — conical frustum
6 π · Rcurved section π² / 4 · Rcurve · ID²nozzle line
7 Straight section of ram's head above inlet riser π / 8 · Lstraight · ID²ram's head
  • ILEVcells1-7 = −1 (level tracking off — no distinct liquid/gas interface expected)

Edge Geometry

Edge FA HD
1 (suction inlet) π/4 · (ID²throat − OD²nozzle) (ID²throat − OD²nozzle) / (IDthroat + ODnozzle)
2, 3 π/4 · ID²throat IDthroat
4, 5 π/4 · ID²discharge IDdischarge
6 (nozzle outlet) π/4 · ID²nozzle outlet IDnozzle outlet
7 π/4 · ID²nozzle line IDnozzle line
8 min(FAedge7, π/8 · ID²ram's head) min(IDnozzle line, IDram's head)
9 π/8 · ID²recirc riser IDrecirc riser

Edge 1 Flow Area

FAedge1 may be modified later to obtain the correct ratio of driving to driven flow (M-ratio).

  • CCFL: not applied at any edge (LCCFL = 0 for all edges)

Orientation

Edges GRAV Direction
1–5 (main body) −1.0 Downward (flow descends through throat/diffuser)
6–7 (nozzle) +1.0 Upward (nozzle drives flow down into throat)
8–9 (ram's head) −1.0 Downward

Initial Conditions

Parameter Cells 1–4 (body) Cells 5–7 (nozzle)
P Plant-specific suction/discharge P, or nominal system pressure Plant-specific driving nozzle P, or nominal
TL Plant-specific, or Tsat − ΔTsubcooling Same
TV Plant-specific, or Tsat Same
ALPN 0.0 0.0
PA 0.0 0.0

Initial velocities (if unknown):

\[ VL_{edges\ 1-5} = \frac{\dot{m}_{loop}}{10 \cdot \%_{driving} \cdot \rho \cdot FA_{edge}} \]
\[ VL_{edges\ 6-9} = \frac{\dot{m}_{loop}}{10 \cdot \rho \cdot FA_{edge}} \]

where ṁloop = single recirculation loop flow rate, %driving = fraction of total jet pump outlet flow from driving flow, ρ = liquid density at upstream conditions.

Core Inlet Subcooling

If nominal subcooling is not directly available, it can be estimated from: \(h_{core\ inlet} = [h_{FW} \cdot \dot{m}_{FW} + h_{sat} \cdot (\dot{m}_{core} - \dot{m}_{FW})] / \dot{m}_{core}\)

Friction Inputs

Edge NFF KFAC KFACR ICFLG
1 1 Manufacturer suction loss, or 7.0 (tune to match ΔP) Manufacturer reverse loss, or 0.0 0
2–4 1 0.0 0.0 0
5 1 Manufacturer discharge loss, or 1.0 (sudden expansion) Manufacturer reverse, or 0.5 (sudden contraction) 0
6 1 0.0 0.0 1 (choked flow)
7–8 1 0.0 0.0 0
9 1 50 fT (close-pattern return bend) 50 fT 0

Jet Pump Internal Losses

Losses associated with the jet pump nozzle/diffuser geometry are accounted for internally by TRACE. Do not add KFAC values at edges 2–4 and 6–8 to avoid double-counting. KFAC at edge 1 is used to tune the overall jet pump pressure drop.

General Inputs

Parameter Value
JCELL 1 (driving nozzle connects to top of cell 1)
COST 1.0 (vertical side tube connection)
NJETP 10 (typical for BWR/3-6)
EPSDFF 5.5 (forward diffuser form loss coefficient — use default)
EPSDFR 0.38 (reverse diffuser form loss coefficient — use default)
EPSNZF 5.5 (forward nozzle form loss coefficient — use default)
EPSNZR 0.38 (reverse nozzle form loss coefficient — use default)
FINLET 0.04 (suction form loss — use default)
FOUTLET 0.45 (discharge form loss — use default)
ICONC 0 (no boron in BWR)
IPOW 0 (no fluid power)
EPSW Plant-specific or 4.572 × 10⁻⁵ m
Use Pipewall False (attach HTSTR manually to cells 1–3 for throat/diffuser walls and cells 4–5 for ram's head metal mass)

EPSDFF, EPSDFR, EPSNZF, EPSNZR

These are not the same as KFAC. They are coefficients used with the diffuser/nozzle angle and area change to compute internal form losses within the JETP component. The default values are recommended.

Steady-State Checklist

Steady-State Verification

  • Jet pump M-ratio (suction/driving flow) matches plant data (adjust FAedge1 if needed)
  • Jet pump ΔP matches plant data (adjust KFACedge1 if needed)
  • Core flow rate is correct
  • Driving nozzle velocity is physically reasonable
  • 10:1 adjacent cell volume ratio is satisfied

Cross-References

This page faithfully extracts jet pump modeling guidance from BWR Modeling Guidance §9. The JETP component uses TRACE's specialized jet pump model with internal nozzle/diffuser physics — the analyst primarily needs to specify geometry, NJETP count, and tune edge-1 suction losses for the correct M-ratio.