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Neutronics as Part of an Integrated Modelling Approach a CAD-based

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					   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   Paul Wilson (UW-FTI): Neutronics as Part of an Integrated
08.14.08                                                                   2/22
                                 Modeling Approach
         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

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

FNST Meeting     Paul Wilson (UW-FTI): Neutronics as Part of an Integrated
08.14.08                                                                     3/22
                                   Modeling Approach
         Accelerations

• Key issue: accelerate ray-tracing (fewer & faster)

• Key technology: oriented bounding box trees




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




FNST Meeting           Paul Wilson (UW-FTI): Neutronics as Part of an Integrated
08.14.08                                                                                        4/22
                                         Modeling Approach
         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    Paul Wilson (UW-FTI): Neutronics as Part of an Integrated
08.14.08                                                                    5/22
                                  Modeling Approach
         Bounding Box Accelerations

• Simple (inexpensive) bounding box test
     – Streaming
       distance to
       closest                                      dmax
       approach
     – Collision                          dstream
                                                                dmin
       distance to
       closest                                              x
       approach
                                                    dcollision

FNST Meeting   Paul Wilson (UW-FTI): Neutronics as Part of an Integrated
08.14.08                                                                   6/22
                                 Modeling Approach
         Non-manifold Geometry

• Imprinting



                             A

• Merging      F
• Each surface
                                                                               E
  in max. 2     BD
  cells                                                                    C


FNST Meeting   Paul Wilson (UW-FTI): Neutronics as Part of an Integrated
08.14.08                                                                       7/22
                                 Modeling Approach
         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   Paul Wilson (UW-FTI): Neutronics as Part of an Integrated
08.14.08                                                                   8/22
                                 Modeling Approach
         ITER First Wall & Shield

                                                         • Modules designed
                                                           at SNL
                                                           – Includes
                                                             structural, CFD,
                                          U S IT E R
                                           M o d u le
                                                             EM analyses
                                                         • Detailed
                                         A llo catio n
                                             20%


                                                           distribution of
                                                           nuclear heating
                                                         • Mapping of
                                                           radiation damage
                                                           and He production
FNST Meeting   Paul Wilson (UW-FTI): Neutronics as Part of an Integrated
08.14.08                                                                        9/22
                                 Modeling Approach
         ITER FWS
         Module Assembly
                                     Shield Module
                                     Segment
                                                     Shield Module
                                                     Segment
                                                                       Shield Module
                                                                       Segment
  First Wall                                                                           Shield Module
  Panel Assembly                                                                       Segment




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


FNST Meeting       Paul Wilson (UW-FTI): Neutronics as Part of an Integrated
08.14.08                                                                                     10/22
                                     Modeling Approach
         ITER FWS
         Module 13 Mockup
               Model generated by designers using
                common tools facilitates analysis




FNST Meeting      Paul Wilson (UW-FTI): Neutronics as Part of an Integrated
08.14.08                                                                      11/22
                                    Modeling Approach
         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   Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach
08.14.08                                                                                     12/22
         Nuclear Heating
         Module 13 CFD Mesh




FNST Meeting   Paul Wilson (UW-FTI): Neutronics as Part of an Integrated
08.14.08                                                                   13/22
                                 Modeling Approach
         Nuclear Heating
         Module 13 CFD Mesh




FNST Meeting   Paul Wilson (UW-FTI): Neutronics as Part of an Integrated
08.14.08                                                                   14/22
                                 Modeling Approach
         Nuclear Heating
         Module 13 CFD Mesh




FNST Meeting   Paul Wilson (UW-FTI): Neutronics as Part of an Integrated
08.14.08                                                                   15/22
                                 Modeling Approach
         Nuclear Heating
         Module 13 CFD Mesh




FNST Meeting   Paul Wilson (UW-FTI): Neutronics as Part of an Integrated
08.14.08                                                                   16/22
                                 Modeling Approach
         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   Paul Wilson (UW-FTI): Neutronics as Part of an Integrated
08.14.08                                                                   17/22
                                 Modeling Approach
        Multi-Physics Modeling &
        Simulation




 Neutron Source Modeling
                                                                                 CFD & Heat Transfer
          Radiation Transport                   Nuclear Heating                  (Alice Ying, UCLA)

FNST Meeting    Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach
08.14.08                                                                                         18/22
        Multi-Physics Modeling &
        Simulation
         Neutron                                                              CFD &
                                         Radiation
          source                                                               Heat
                                         Transport
         modeling                                                            Transfer


                                           Coolant
                                            MHD                            Thermo-
           Plasma                                                          structural
           Physics                                                          reponse
                                            EM
                                          Modeling

FNST Meeting   Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach
08.14.08                                                                                     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   Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach
08.14.08                                                                                     20/22
         Interoperable Technologies for Advanced
         Petascale Simulations (ITAPS)

• SciDAC-funded effort




                                                      http://www.tstt-scidac.org/research/research.html
FNST Meeting   Paul Wilson (UW-FTI): Neutronics as Part of an Integrated Modeling Approach
08.14.08                                                                                         21/22
        Questions?

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




   FNST Meeting 08.14.08

				
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