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PAUL SCHERRER INSTITUT
PB2 TTRIP Phase 2 Coupled 3D Kinetics/Core
Thermal-Hydraulic BC Analysis with CORETRAN
H. Ferroukhi, W. Barten, P.Coddington
OECD/NRC BWR Peach Bottom-2 Turbine Trip
Benchmark 2nd Workshop, Villigen,October 2001
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CONTENTS
PAUL SCHERRER INSTITUT

• CORETRAN and RETRAN-3D at PSI
• PB2 TTRIP Phase 2 3-D Kinetics with Core T/H
  Boundary Conditions
• Steady-State Results
• Transient Results
• Summary

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PAUL SCHERRER INSTITUT
CORETRAN and RETRAN-3D at PSI

• PSI transient code environment with CORETRAN /
  RETRAN-3D

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PAUL SCHERRER INSTITUT
PB-2 Phase 2 Objectives at PSI

• ANALYSIS WITH CORETRAN Coupled 3-D
  Kinetics/Core Thermal-Hydraulic BC Model
• Steady-state at both TT2 Conditions and HZP
• Transient Analysis
• Analysis performed and submitted
• ANALYSIS WITH RETRAN-3D Coupled 3-D
  Kinetics/Core Thermal-Hydraulic BC Model
• RETRAN-3D Model needs to be set-up for Phase 3
  but can also be used for Phase 2
• Model set-up based on CORETRAN
• Lumped Model necessary in RETRAN-3D (Homogenized
  T/H Feedback Variables !)
• Steady-State analysis at HZP to verify
  consistency in Neutronic Solution
  CORETRAN-RETRAN-3D
• Steady-State and Transient Analysis at TT2
  Conditions with 33-T/H Lumped Model
• Assess differences between CORETRAN and RETRAN-3D
• Influence of T/H solution and void model
• Influence of T/H feedback homogenization
• Analysis with RETRAN 1-D Kinetics
• Additional exercise if time available
• Valuable to assess differences 1-D/3-D

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PAUL SCHERRER INSTITUT
PB2 Phase 2 CORETRAN Model of PB2

• ANM Neutronic Algorithm (ARROTTA)
• 6 Equation 2 Fluid T/H Model (VIPRE-02)
• Full Core Representation
• 1x1 Neutronic and T/H Radial Mesh
• Bypass 1 Additional T/H Channel
• No Bypass Void
• Detector Model
• X-S model modified
• X-S tables read directly
• Use of provided X-S interpolation routine
• Xenon densities read as Restart file
• No Decay Heat Model

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PAUL SCHERRER INSTITUT
PB2 Phase 2 CORETRAN Steady-State Results
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PAUL SCHERRER INSTITUT
Note on Spacer Void Model

• Spacer Void Model (SVM) available in SIMULATE-3
  to treat void accumulation at Spacer Grids
• PSI Experience with Swiss BWRs shows very good
  agreement with TIP with the SVM
• Assessment CORETRAN/SIMULATE performed at PSI for
  Swiss LWRs show that the SVM has a
• Strong impact on the axial power shape in the
  boiling zone
• Strong impact on the core reactivity (more
  negative void coefficient in boiling zone)

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PAUL SCHERRER INSTITUT
PB2 Phase 2 CORETRAN Transient Results

• Analysis 1 Boundary Condition Total Core Flow
  versus Time
• 6 Eq. NBC
• FIBWR Flow Split Model in quasi-static mode
• Pressure-Flow Convergence Problems

Power and LPRM
Core Flow
Pressure
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PAUL SCHERRER INSTITUT
PB2 Phase 2 CORETRAN Transient Results

• Analysis 2 Boundary Condition (33 T-H
  Channels) ( Bypass Channel) Flow versus Time
• No FIBWR Model

No Bypass Correction (Nominal)
With Bypass Correction (BC1)
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PAUL SCHERRER INSTITUT
PB2 Phase 2 CORETRAN Transient Results

• Sensitivity Studies Boundary Condition (33 T-H
  Channels) ( Bypass Channel) Flow versus Time
• Time Step Size
• SCRAM Signal

Time Step Size
SCRAM Signal
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PAUL SCHERRER INSTITUT
PB2 Phase 2 Summary

• CORETRAN Model for PB-2 Exercise 2 Set-Up
• Steady-State Analysis at TT2 Conditions
• Good agreement with PB1 Edit
• Axial Power Shape (Caution on spacer void)
• Core Average Void Fraction, Average Exit Quality,
  Core Pressure Drop
• Very High K-eff
• Transient Results
• Analysis with total ore flow BC FIBWR flow
  split UNAPPLICABLE
• Analysis with 33-TH Channel flow BC
• No Bypass Correction gives slight under
  prediction of power peak (Nominal Case Submitted)
• Later analysis with Bypass Correction shows
  better agreement with measurements
• Sensitivity Analysis
• Large sensitivity on time-step size
• Small Time-Step size of 1ms selected
• Choice of SCRAM on 95 power instead of defined
  t0.63 s seems more adequate
• but leads to earlier and lower power peak
  magnitude
• Next Step is to perform similar analysis with
  RETRAN-3D before Phase 3

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PAUL SCHERRER INSTITUT
PAUL SCHERRER INSTITUT
PB2 Phase 2 CORETRAN Bypass Model

• CORETRAN PB2 Bypass Model
• Defined Leakage Paths
• Core Support Plate
• Control Rod Drive Housing
• Assembly Lateral Leakage
• Path a Through Lower Tie Plate Holes (9 in
  FIBWR)
• Path b between Channel Box and Lower Tie Plate
  (8 in FIBWR)
• Path c Water Rods
• All Paths to ONE SINGLE BYPASS T/H CHANNEL
• Bypass Geometry
• Assumed Core Shroud Diameter
• D_CS 5.6 m (220.47 in)
• Based on EPRI Report NP-563
• Assumed Assembly Outer Pitch
• P_OUT 0.1365 m (5.37 in)
• Bypass Flow Area 7.5 m2 (11570 in2)

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FIBWR Model
All Leakage Paths defined by Flow-Pressure Drop
Correlations