Fast Mix Table Construction for Material Discretization

Conference · Tue Jan 01 00:00:00 EST 2013

OSTI ID:1095710

Johnson, Seth R ^[1]

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1. ORNL

An effective hybrid Monte Carlo--deterministic implementation typically requires the approximation of a continuous geometry description with a discretized piecewise-constant material field. The inherent geometry discretization error can be reduced somewhat by using material mixing, where multiple materials inside a discrete mesh voxel are homogenized. Material mixing requires the construction of a ``mix table,'' which stores the volume fractions in every mixture so that multiple voxels with similar compositions can reference the same mixture. Mix table construction is a potentially expensive serial operation for large problems with many materials and voxels. We formulate an efficient algorithm to construct a sparse mix table in $$O(\text{number of voxels}\times \log \text{number of mixtures})$$ time. The new algorithm is implemented in ADVANTG and used to discretize continuous geometries onto a structured Cartesian grid. When applied to an end-of-life MCNP model of the High Flux Isotope Reactor with 270 distinct materials, the new method improves the material mixing time by a factor of 100 compared to a naive mix table implementation.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). High Flux Isotope Reactor (HFIR)
• Sponsoring Organization: Work for Others (WFO); USDOE National Nuclear Security Administration (NNSA)
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 1095710
• Resource Relation: Conference: International Conference on Mathematics and Computational Methods Applied to Nuclear Science \& Engineering (M\&C 2013), Sun Valley, ID, USA, 20130505, 20130509
• Country of Publication: United States
• Language: English