CAD-based geometry type in serpent 2-application in fusion neutronics

This paper presents a practical demonstration of the CAD-based geometry type developed for the Serpent 2 Monte Carlo code. The geometry is constructed of three-dimensional solid bodies, with boundaries defined by a triangulated surface mesh. The data is read in the STL file format, which can be exported by most CAD design tools. Cell search and other geometry routines developed for handling the triangulated surfaces are introduced, and the methodology is demonstrated with a complicated full-scale model of the ITER fusion reactor. The calculations involve verification of the complex geometry and assessment of computational performance. It is concluded that Serpent is capable of modeling very large and complex geometries, which is one if the main challenges for fusion research. The work continues with the development of source sampling and variance reduction methods.