Modelling local effects of cracked bricks in ageing AGR graphite - - PowerPoint PPT Presentation

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Modelling local effects of cracked bricks in ageing AGR graphite - - PowerPoint PPT Presentation

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R&D UK Centre Modelling local effects of cracked bricks in ageing AGR graphite cores Philippe Martinuzzi Journe des Utilisateurs de SalomeMeca: 20 th March 2018 1 Table of contents - Context and Background - Presentation of the CBNAs 1

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R&D UK Centre

Modelling local effects of cracked bricks in ageing AGR graphite cores

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Philippe Martinuzzi Journée des Utilisateurs de SalomeMeca: 20th March 2018

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Table of contents

  • Context and Background
  • Presentation of the CBNAs1
  • Results
  • Conclusion and future work

1CBNA: Cracked Brick Neighbourhood Arrays

R&D UK Centre - Nuclear

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R&D UK Centre Nuclear

Context and background

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Context and background

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R&D UK Centre - Nuclear

The AGR fleet: 14 reactors across the UK

Heysham 1&2 Hunterston B Torness Hartlepool Dungeness B Hinckley Point B

Three challenging

  • bjectives:

0/65/10

0 Harm 65 TWh 10 Years of extension

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Context and background

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R&D UK Centre - Nuclear

Functions of the graphite bricks

  • Moderator
  • Structural
  • Channel for fuel and control rods
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Context and background

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R&D UK Centre - Nuclear

Vocabulary

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Context and background

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Dimensional change causing brick cracking Graphite is evolving and likely to crack What consequence for the whole reactor?

R&D UK Centre - Nuclear

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Context and background

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Scale 1: One graphite brick

R&D UK Centre - Nuclear

Ageing of graphite is performed in code_aster Crack propagation is performed in MoFEM Ultimate goal: facilitate interaction between code_aster and MoFEM

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Context and background

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Scale 2: From Multi-Layer-Model (MLM) to CBNA

R&D UK Centre - Nuclear

Development of CBNA models in code_aster at the UK Centre Crack propagation on MLM model at Wood (With XFEM) Today’s presentation

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Context and background

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Scale 3: Whole core models

R&D UK Centre - Nuclear

Attention: Not representative of behaviour in actual reactor

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R&D UK Centre Nuclear

Presentation of the CBNA models

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Presentation of the CBNAs

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Description: CBNA XxYxZ

R&D UK Centre - Nuclear

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Presentation of the CBNAs

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Description: Field variable evolution

R&D UK Centre - Nuclear

Field 1: Temperature Field 2: Irradiation dose Field 3: Weight loss

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Presentation of the CBNAs

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R&D UK Centre - Nuclear

Description: Material Properties Irradiated graphite material behaviour as a function of fast neutron dose, radiolytic weight loss, temperature and creep strain 121+ Material properties, among which

  • E, NU
  • ALPHA
  • Creep
  • Lots of ‘Switches’ to account for evolution since the 1990s

106+ Internal variables Use of User MATerial (UMAT) routine, readable in code_aster thanks to UMAT interface

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Presentation of the CBNAs

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Description: Boundary conditions and loading

R&D UK Centre - Nuclear

Symmetric boundary conditions

x (column) y (row) z (layer) x (column) y (row)

DX=0 DY=0

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Presentation of the CBNAs

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Description: Boundary conditions and loading

R&D UK Centre - Nuclear

Bottom nodes blocked in Z + springs with small stiffness to remove rigid body motion

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Presentation of the CBNAs

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Description: Boundary conditions and loading

R&D UK Centre - Nuclear

Gravity and weight of top bricks

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Presentation of the CBNAs

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Description: Contact

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For each component, contact surfaces have been defined

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Presentation of the CBNAs

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Description: Cracked brick

  • No fracture mechanics involved
  • From t=0 to t=t_crack: tied surfaces
  • From t=t_crack to t=40: contact

R&D UK Centre - Nuclear

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Presentation of the CBNAs

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Description: Solver STAT_NON_LINE

  • Initial phase 1:

 BC, Weight and Contact

  • Initial phase 2:

 Load

  • Initial phase 3:

 Start Up

  • Ageing phase 1:

 Closed crack

  • Ageing phase 2

 Open crack  In total about 200 time step (+ sub steps if no convergence)

R&D UK Centre - Nuclear

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Presentation of the CBNAs

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Description: Automatic definition and post-processing

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  • CBNA extremely easy to set up.
  • Size, position of crack and post-processing are selected using

a CBNA python script.

  • All files are created automatically (including the .astk).
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Results

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Results

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Results Benchmark with ABAQUS – 1x1x1

R&D UK Centre - Nuclear

  • 3,00E+01
  • 2,50E+01
  • 2,00E+01
  • 1,50E+01
  • 1,00E+01
  • 5,00E+00

0,00E+00 5,00E+00 10 20 30 40 Displacement (mm) Time (fpy) DX_Code_Aster DY_Code_Aster DZ_Code_Aster DX_ABAQUS DY_ABAQUS DZ_ABAQUS

Displacement

ABAQUS code_aster

Good Agreement Nodes Elements 63 000 76 000

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Results

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Results Benchmark with ABAQUS – 1x1x1

R&D UK Centre - Nuclear

Spatial evolution of Young’s Modulus at 40 fpy ABAQUS code_aster Identical

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Results

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Results Benchmark with ABAQUS – 1x1x1

R&D UK Centre - Nuclear

Crack opening

5 10 15 20 25 30 10 20 30 40 Opening in the Y direction (mm) Time (fpy) Bore_Code_Aster KW_Code_Aster Bore_Abaqus KW_Abaqus

Bore KW

Similar trends

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Results

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Results Benchmark with ABAQUS – 1x1x1

R&D UK Centre - Nuclear

  • 2,00E+01
  • 1,00E+01

0,00E+00 1,00E+01 2,00E+01 3,00E+01 4,00E+01 10 20 30 40 Stress (MPa) Time (fpy) SYY_Code_Aster SYY_Abaqus

Hoop stress at keyway root Good agreement

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Results

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Results Benchmark with ABAQUS – 1x1x1

R&D UK Centre - Nuclear

ABAQUS (1cpu) code_aster (1cpu) Reduced integration 10h 14h Full integration 24h 21h Attention: models are run on different machines and are not rigorously identical in terms of model, contact algorithm, and convergence criteria. Nodes Elements 63 000 76 000

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Results

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Results Benchmark with ABAQUS – 3x3x1

R&D UK Centre - Nuclear

Similar observations for 3x3x1

ABAQUS code_aster

ABAQUS (1cpu) code_aster (1cpu) 8 days 8 days Nodes Elements 374 000 453 000

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Crack insertion with ZCracks

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Results

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Crack insertion with Zcracks

  • Group conservation
  • Additional groups for crack

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+ =

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Results

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Crack insertion with ZCracks

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New crack :

Displacement Magnitude

Old/Default crack :

Displacement Magnitude

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Results

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Crack insertion with ZCracks Cracks could come from:

  • Inspection
  • Crack propagation tools
  • Extreme test scenarios

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Ageing analysis with

  • n-the-fly crack insertion
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Results

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Libraries of crack can now be inserted in CBNA models

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New crack (from Zcracks) Default crack No-crack

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Conclusion and future steps

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Conclusion and future steps

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Conclusion:

  • Capabilities of solving large contact problems in code_aster demonstrated
  • Fully functional and automatic CBNA model
  • Good agreement with ABAQUS in terms of performance and accuracy

Future steps

  • Improve performances (e.g.: Aster massively parallel, convergence)
  • Use new contact algorithm (LAC)
  • Perform parametric studies (cracked shape, material properties)
  • Enhance the interaction with MoFEM software

R&D UK Centre - Nuclear

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Acknowledgments

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The technical support from EDF R&D is kindly acknowledged. Thanks for ERMES and PERICLES departments for their advice and support that have been paramount in the development of activities in the UK Centre. Special thanks to Dr. Dzifa Kudawoo whose technical expertise and advice have been crucial in this particular project.

R&D UK Centre - Nuclear

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code_aster user day in the UK

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R&D UK Centre - Nuclear

code_aster User Day 11th September 2018 The University of Manchester, Sackville street Building Manchester, United Kingdom