Geometric Representations in the Developmental Monte Carlo Transport Code MC21

Abstract

The geometry kernel of the developmental Monte Carlo transport code MC21 is designed as a combination of the geometry capabilities of several existing Monte Carlo codes. This combination of capabilities is intended to meet efficiently the general requirements associated with in-core design products and, at the same time, be flexible enough to support highly general geometric models. This paper provides a description of the different geometry representations of MC21 and outlines how the geometric data is stored internally through the use of Fortran-90 data structures. Finally, two alternative geometric representations of a published BWR unit assembly model are discussed. Results for the two representations are contrasted, including k-effective results, relative memory footprints, and relative computational speeds. While total memory footprint is not noticeably reduced, results show significant speed advantages of one representation.

MC21 v.6.0 – A continuous-energy Monte Carlo particle transport code with integrated reactor feedback capabilities

“…MC21 includes a flexible three-dimensional (3-D) combinatorial geometry capability coupled with dedicated geometry kernels for common shapes (Donovan and Tyburski, 2006;Nease et al, 2013). This combination allows MC21 to model complex threedimensional systems and also ensures that the specialized geometries commonly encountered in reactor analysis models have a compact representation that supports efficient particle tracking.…”

CAD-based hierarchical geometry conversion method for modeling of fission reactor cores

“…The geometry of these basic parts has three common features: (1) the basic units of the geometry are easy to be represented by primitive solids; (2) the relationships of different units are rigorous; (3) the large scale geometries are repeated and nested in multiple levels. According to these features, the hierarchical geometries have been adopted in many MC codes to make the calculation model more concise and to accelerate the geometry navigation (Donovan and Tyburski, 2006;Geant4 Collaboration, 2009). For full-core MC transport simulation, modeling of whole reactor cores with millions reaction rate regions is a big challenge, such as the PWR core models proposed by Hoogenboom and William (2009) and BEAVRS benchmark released from MIT (Horelik and Herman, 2013).…”

Optimal Spatial Subdivision method for improving geometry navigation performance in Monte Carlo particle transport simulation

“…Therefore, if Monte Carlo codes are to be realistically used for whole core analysis and design, the optimization of geometry navigation should be investigated further. To the author's knowledge, several classical optimization techniques such as neighbor search method (Forrest, 2005;She et al, 2011), multi-level geometry hierarchy method (Donovan and Tyburski, 2006;Geant4 Collaboration, 2009), bounding box method Wang, 2006) and delta-tracking method (Leppanen, 2010;She et al, 2011) have been widely used in many codes to improve geometry navigation performance. And recently, another new technique named geometric template was introduced by MC21 to enhance its geometry navigation for large-scale whole core realistic models.…”