Neutronics as Part of an Integrated Modeling Approach

a CAD-based Domain Representation

Paul P.H. Wilson UW-Madison Fusion Technology Institute FNST Meeting 08.14.08

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 FNST Meeting 08.14.08

Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach 2/22

DAGMC Direct Accelerated Geometry Monte Carlo • Use MOAB and Common Geometry Module (CGM) to interface MC code

directly

to CAD (& other) geometry data – Previous efforts found CAD-based ray tracing 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 FNST Meeting 08.14.08

MCNP(X) MCNPX Native Geometry CAD MOAB & CGM Voxels (Other)

Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach 3/22

Accelerations

• Key issue: accelerate ray-tracing (fewer & faster) • Key technology: oriented bounding box trees

Hierarchical Subdivision

FNST Meeting 08.14.08

Oriented Bounding Box Inside Bounding Box (w/ path length limit)

Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach 4/22

Hierarchical Oriented Bounding Box

• Axis-aligned bounding box often larger than necessary • Oriented bounding box makes smaller boxes • OBB on facets allows finer-granularity boxes • Tree of OBBs reduces # tests to log(n) FNST Meeting 08.14.08

Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach 5/22

Bounding Box Accelerations

• Simple (inexpensive) bounding box test – Streaming distance to closest approach – Collision distance to closest approach d max d stream x d collision d min FNST Meeting 08.14.08

Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach 6/22

Non-manifold Geometry

• Imprinting • Merging • Each surface in max. 2 cells F A FNST Meeting 08.14.08

Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach C E 7/22

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 FNST Meeting 08.14.08

Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach 8/22

ITER First Wall & Shield

FNST Meeting 08.14.08

• Modules designed at SNL

U S IT E R

– Includes structural, CFD, EM analyses

M o d u le A llo c a tio n 2 0 %

• Detailed distribution of nuclear heating • Mapping of radiation damage and He production Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach 9/22

ITER FWS

Module Assembly

First Wall Panel Assembly Shield Module Segment Shield Module Segment Shield Module Segment Shield Module Segment

FNST Meeting 08.14.08

Inter-Module Coaxial Flow Dividers First Wall Panel Assembly (Shown Mounted)

Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach 10/22

ITER FWS

Module 13 Mockup

Model generated by designers using common tools facilitates analysis FNST Meeting 08.14.08

Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach 11/22

Mesh Interpolation for Multi-Physics Analysis • 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 FNST Meeting 08.14.08

Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach 12/22

Nuclear Heating Module 13 CFD Mesh FNST Meeting 08.14.08

Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach 13/22

Nuclear Heating Module 13 CFD Mesh FNST Meeting 08.14.08

Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach 14/22

Nuclear Heating Module 13 CFD Mesh FNST Meeting 08.14.08

Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach 15/22

Nuclear Heating Module 13 CFD Mesh FNST Meeting 08.14.08

Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach 16/22

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 FNST Meeting 08.14.08

Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach 17/22

Multi-Physics Modeling & Simulation

Neutron Source Modeling Radiation Transport FNST Meeting 08.14.08

Nuclear Heating CFD & Heat Transfer (Alice Ying, UCLA) Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach 18/22

Multi-Physics Modeling & Simulation

Neutron source modeling Radiation Transport CFD & Heat Transfer Plasma Physics Coolant MHD Thermo structural reponse EM Modeling FNST Meeting 08.14.08

Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach 19/22

Common Domain Representation

• 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 FNST Meeting 08.14.08

Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach 20/22

Interoperable Technologies for Advanced Petascale Simulations (ITAPS) • SciDAC-funded effort FNST Meeting 08.14.08

http://www.tstt-scidac.org/research/research.html

Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach 21/22

Questions?

[email protected]

http://fti.neep.wisc.edu/ncoe FNST Meeting 08.14.08