Neutronics as Part of an Integrated Modeling Approach a CAD-based Domain Representation

1. Neutronics as Part of an Integrated Modeling Approacha CAD-based Domain Representation Paul P.H. Wilson UW-Madison Fusion Technology Institute

2. Overview • DAGMC • Ray-tracing acceleration technologies • ITER First Wall & Shield Analysis • Mesh-interpolation for multi-physics analysis • Future Developments • Multi-physics Modeling & Simulation • Common Domain Representation • ITAPS SciDAC Tools Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach

3. MCNP(X) MCNPX Native Geometry MOAB & CGM CAD Voxels (Other) DAGMCDirect Accelerated Geometry Monte Carlo • Use MOAB and Common Geometry Module (CGM) tointerface MC code directly to CAD (& other) geometry data • Previous efforts found CAD-based raytracing to be too slow (20-50x) • What’s new? • Implement ray-tracing approximations to reduce calls to exact CAD function • Can be implemented once & reused for all representations Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach

4. Accelerations • Key issue: accelerate ray-tracing (fewer & faster) • Key technology: oriented bounding box trees s Hierarchical Subdivision Oriented Bounding Box Inside Bounding Box (w/ path length limit) Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach

5. Hierarchical Oriented Bounding Box • Axis-aligned bounding box oftenlarger than necessary • Oriented bounding box makessmaller boxes • OBB on facets allows finer-granularity boxes • Tree of OBBs reduces # teststo log(n) Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach

6. Bounding Box Accelerations • Simple (inexpensive) bounding box test • Streaming distance to closest approach • Collisiondistance toclosestapproach dmax dstream dmin x dcollision Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach

7. Non-manifold Geometry • Imprinting • Merging • Each surface in max. 2 cells A F E B D C Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach

8. Implicit Complement • Defining void space is common source of difficulty • CUBIT performs imprinting & merging • All surfaces have only two volumes/cells • Often fails with explicit complement • Defines implicit complement = all surfaces with only one cell • New OBB tree collects all surfaces of each volume into single tree • Efficient search of implicit complement • Standard capability – in production • Implicit complement can have material Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach

9. ITER First Wall & Shield • Modules designed at SNL • Includes structural, CFD, EM analyses • Detailed distribution of nuclear heating • Mapping of radiation damage and He production Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach

10. ITER FWSModule Assembly Shield Module Segment Shield Module Segment Shield Module Segment First Wall Panel Assembly Shield Module Segment Inter-Module Coaxial Flow Dividers First Wall Panel Assembly (Shown Mounted) Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach

11. ITER FWSModule 13 Mockup Model generated by designers using common tools facilitates analysis Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach

12. High-fidelity mesh tallies in MCNP Large orthogonal regular grids (e.g. 26M voxels) Interpolate to CFD & heat transfer analysis mesh Large unstructured tet-mesh (e.g. 15M elements) Based on MOAB scalable open-source infrastructure KD-tree for MCNP mesh elements Centroid or vertex interpolation on piecewise uniform mesh Store Volumetric heating on vertices, and/or Integral heating on elements Mesh Interpolation for Multi-Physics Analysis Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach

13. Nuclear HeatingModule 13 CFD Mesh Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach

14. Nuclear HeatingModule 13 CFD Mesh Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach

15. Nuclear HeatingModule 13 CFD Mesh Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach

16. Nuclear HeatingModule 13 CFD Mesh Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach

17. Future Methods Development • Conformal mesh tallies • Efficient ray-tracing through mesh • Functional expansion on mesh • hp-refinement questions • Robustness to geometric flaws • Transport approximations to small overlaps • Hi-fidelity activation/isotopics • Detailed photon dose Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach

18. Multi-Physics Modeling & Simulation Neutron Source Modeling CFD & Heat Transfer(Alice Ying, UCLA) Radiation Transport Nuclear Heating Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach

19. Multi-Physics Modeling & Simulation Neutron source modeling Radiation Transport CFD & Heat Transfer Coolant MHD Thermo-structural reponse Plasma Physics EM Modeling Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach

20. Develop a common framework for representing the geometric (phase space) domain Benefits Facilitate transfer of data among physics modules Take advantage of ongoing development in tools and services Optimization for performance of analysis Optimization for performance of system Common Domain Representation Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach

21. SciDAC-funded effort Interoperable Technologies for Advanced Petascale Simulations (ITAPS) http://www.tstt-scidac.org/research/research.html Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach

22. Questions? wilsonp@engr.wisc.edu http://fti.neep.wisc.edu/ncoe