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

R&D UK Centre Modelling local effects of cracked bricks in ageing AGR graphite cores Philippe Martinuzzi Journée des Utilisateurs de SalomeMeca: 20 th March 2018 1

Table of contents - Context and Background - Presentation of the CBNAs 1 - Results - Conclusion and future work 1 CBNA: Cracked Brick Neighbourhood Arrays R&D UK Centre - Nuclear 2

R&D UK Centre Nuclear Context and background

Context and background The AGR fleet: 14 reactors across the UK Torness Hunterston B Three challenging objectives: 0/65/10 Heysham 1&2 0 Harm Hartlepool 65 TWh 10 Years of extension Hinckley Point B Dungeness B R&D UK Centre - Nuclear 4

Context and background Functions of the graphite bricks -Moderator -Structural -Channel for fuel and control rods R&D UK Centre - Nuclear 5

Context and background Vocabulary R&D UK Centre - Nuclear 6

Context and background Dimensional change causing brick cracking Graphite is evolving and likely to crack What consequence for the whole reactor? R&D UK Centre - Nuclear 7

Context and background Scale 1: One graphite brick Crack propagation is Ageing of graphite is performed in MoFEM performed in code_aster Ultimate goal: facilitate interaction between code_aster and MoFEM R&D UK Centre - Nuclear 8

Context and background Today’s Scale 2: From Multi-Layer-Model (MLM) to CBNA presentation Development of CBNA models in Crack propagation on MLM model code_aster at the UK Centre at Wood (With XFEM) R&D UK Centre - Nuclear 9

Context and background Scale 3: Whole core models Attention: Not representative of behaviour in actual reactor R&D UK Centre - Nuclear 10

R&D UK Centre Nuclear Presentation of the CBNA models

Presentation of the CBNAs Description: CBNA XxYxZ R&D UK Centre - Nuclear 12

Presentation of the CBNAs Description: Field variable evolution Field 1: Temperature Field 2: Irradiation dose Field 3: Weight loss R&D UK Centre - Nuclear 13

Presentation of the CBNAs 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 R&D UK Centre - Nuclear 14

Presentation of the CBNAs Description: Boundary conditions and loading z (layer) y (row) DX=0 x (column) DY=0 y (row) x (column) Symmetric boundary conditions R&D UK Centre - Nuclear 15

Presentation of the CBNAs Description: Boundary conditions and loading Bottom nodes blocked in Z + springs with small R&D UK Centre - Nuclear stiffness to remove rigid body motion 16

Presentation of the CBNAs Description: Boundary conditions and loading Gravity and weight of top bricks R&D UK Centre - Nuclear 17

Presentation of the CBNAs Description: Contact For each component, contact surfaces have been defined R&D UK Centre - Nuclear 18

Presentation of the CBNAs 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 19

Presentation of the CBNAs 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 20

Presentation of the CBNAs Description: Automatic definition and post-processing 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). R&D UK Centre - Nuclear 21

R&D UK Centre Nuclear Results

Nodes Elements Results 63 000 76 000 Results Benchmark with ABAQUS – 1x1x1 5,00E+00 0,00E+00 0 10 20 30 40 Displacement (mm) -5,00E+00 DX_Code_Aster DY_Code_Aster -1,00E+01 DZ_Code_Aster -1,50E+01 DX_ABAQUS DY_ABAQUS -2,00E+01 DZ_ABAQUS -2,50E+01 -3,00E+01 Time (fpy) code_aster ABAQUS Good Agreement Displacement R&D UK Centre - Nuclear 23

Results Results Benchmark with ABAQUS – 1x1x1 ABAQUS code_aster Identical Spatial evolution of Young’s Modulus at 40 fpy R&D UK Centre - Nuclear 24

Results Results Benchmark with ABAQUS – 1x1x1 Bore 30 Opening in the Y direction (mm) 25 KW 20 Bore_Code_Aster 15 KW_Code_Aster Bore_Abaqus 10 KW_Abaqus 5 0 0 10 20 30 40 Time (fpy) Similar trends Crack opening R&D UK Centre - Nuclear 25

Results Results Benchmark with ABAQUS – 1x1x1 4,00E+01 3,00E+01 2,00E+01 Stress (MPa) SYY_Code_Aster 1,00E+01 SYY_Abaqus 0,00E+00 0 10 20 30 40 -1,00E+01 -2,00E+01 Time (fpy) Good agreement Hoop stress at keyway root R&D UK Centre - Nuclear 26

Nodes Elements Results 63 000 76 000 Results Benchmark with ABAQUS – 1x1x1 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 . R&D UK Centre - Nuclear 27

Nodes Elements Results 374 000 453 000 Results Benchmark with ABAQUS – 3x3x1 ABAQUS code_aster ABAQUS (1cpu) code_aster (1cpu) Similar observations for 3x3x1 8 days 8 days R&D UK Centre - Nuclear 28

R&D UK Centre Nuclear Crack insertion with ZCracks

Results Crack insertion with Zcracks - Group conservation - Additional groups for crack + = R&D UK Centre - Nuclear 30

Results Crack insertion with ZCracks New crack : Old/Default crack : Displacement Magnitude Displacement Magnitude R&D UK Centre - Nuclear 31

Results Crack insertion with ZCracks Cracks could come from: Inspection - - Crack propagation tools - Extreme test scenarios Ageing analysis with on-the-fly crack insertion R&D UK Centre - Nuclear 32

Results Libraries of crack can now be inserted in CBNA models New crack Default crack No-crack (from Zcracks) R&D UK Centre - Nuclear 33

R&D UK Centre Nuclear Conclusion and future steps

Conclusion and future steps 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 35

Acknowledgments 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 36

code_aster user day in the UK code_aster User Day 11 th September 2018 The University of Manchester, Sackville street Building Manchester, United Kingdom R&D UK Centre - Nuclear 37