Sukhbinder Singh, Frazer-Nash Consultancy

1. Development of a Finite Element Visualisation Tool for Post-Processing Graphite Weight loss Predictions Sukhbinder Singh, Frazer-Nash Consultancy

2. Contents Background to Graphite Background to FEAT Objective of Tool Mesh Generation Creating Contour Plots Example Meshes Future Development Summary

3. Graphite in the UK Nuclear Industry • Favourable neutron scattering cross-section at fast neutron energies • High thermal and electrical Conductivity • Use in Windscale piles • Civil use in Magnox and AGR fleet, new build reactors are all PWR’s

4. Graphite Weight loss Conditions in an AGR, are favourable for radiolytic oxidation of graphite via the interaction with a free radical Weight loss results in a reduction in graphite density leading to reduced strength and less effective moderation Loss of strength can lead to brick-cracking and potentially core distortion preventing control rod insertion during reactor transients, for example Weight loss mechanism is modelled using FEAT-Graphite

5. FEAT-Graphite • FEAT – Finite Element Analysis Toolbox • FEAT-DIFFUSE6 – Weight loss and Field Variables • FEAT-COILU – Stress Analysis and Properties

6. Finite Element Method • Model Brick as elements made up of nodes, edges and faces • Set boundary conditions • Model physics equations and calculate solution • Save results at certain time steps

7. Objective of Tool • Investigate the possibility of using MATLAB to view FEAT data and plot data in a way to minimise user interaction

8. Reading FRFs • Can save whole FRFs into MATLAB structure file • Select what to save • Save space on drive • View raw numbers in MATLAB and split into sections • Statistical analysis of variable • Possible to see how variable changes over time

9. Mesh Generation - Elements The brick is split into many different elements Elements can be of different shapes, only wedges and bricks are used to model the graphite bricks Type 54 - Brick Type 53 - Wedge

10. Mesh Generation – Brick Geometry Torness Mesh Hinkley Point B Mesh

11. Creating Contour Plots • Mapping distribution of the variable onto a plane on the brick • Main use of the tool • Constant height where nodes exist • Interpolation to any height

12. Example Meshes: Axial Slice - HPB

13. Example Meshes: Axial Slice - TOR

14. Example Meshes: Polar Axial Slice - HPB

15. Non-Weight loss Plots – Cumulative Dose

16. Non-Weight loss Plots – Temperature

17. Slices through the height of the brick • Having been able to calculate how to slices at a constant height, next step was to do slices with varying heights:- • Azimuthal lines • Radial lines • User Defined lines

18. Example: Radial Slice

19. Further Development GUI Create software guidance for users Able to select nodes and follow variation of that node over time Volume and object selection Usable by any FEAT mesh – not just FEAT-Graphite Weight loss over the whole brick

20. Summary of Tool Capabilities Read in FRF and store data in a fashion which can be used to produce contour plots Recreate the mesh stored in the FRF Create contour plots of any variable across any height of the brick Create vertical slices across the brick at constant radius, angles and between user defined points

21. Thank you for listening – Any Questions? www.fnc.co.uk