Speaker
Description
The stellarator has re-emerged as a promising fusion concept, supported by the success of Wendelstein 7-X. Within EUROfusion, the HELIAS stellarator concept has previously been continuously developed. In addition, stellarator-based reactor concepts are increasingly emerging as a mainstream reactor concepts among private fusion companies worldwide, due to their grid-friendly operation and inherent plasma stability. However, the complex geometry of stellarators poses significant challenges for modeling and neutronics simulations. Existing approaches based on constructive solid geometry (CSG) and facet modelling still do not fully address those limitations in a streamlined analysis including fast in geometry modeling and integration, computational efficiency, and the application of variance reduction techniques.
At Karlsruhe Institute of Technology, a mesh-based modeling approach has been developed to enable rapid conversion from CAD models to unstructured meshes for neutronics simulations using MCNP6. The workflow starts with a CAD model of the stellarator, which is exported as a faceted STL geometry and subsequently tetrahedralized using the TetGen tool. This approach preserves boundary detail while reducing internal mesh complexity, allowing complete mesh generation of complex stellarator geometries within minutes. The method is integrated with tools such as SpaceClaim and the McCad–SALOME platform to provide a streamlined pipeline for facet export, mesh generation, and MCNP6 input preparation. The approach has been validated using an open stellarator model available on GitHub. Benchmarking models against established CSG-based models built with the SHANE and HeliasGeom tool for the new-generation optimized quasi-isodynamic configuration CIEMAT-QI4X has been performed. Comparisons of mesh tallies, cell tallies, and nuclear responses demonstrate the accuracy and efficiency of the proposed method.
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