FreeCAD based modeling study on MCNPX for accelerator driven system

MCNPX is a general purpose Monte Carlo radiation transport code designed to track many particle types over broad ranges of energies and it has the potential to deal with Accelerator Driven System (ADS) problems. The neutronics design and analysis of ADS using MCNPX code is significantly complex mainly on constructing the three dimensional geometry model, especially when there is an additional spallation target coupled with the subcritical reactor constructed by abundant nested repeated structures in several levels. This modeling process has long been recognized as a time consuming, tedious and error-prone task, which is hard to master for novice users. Therefore, it is imperative to build a code system that can translate CAD models of ADS to the native language of MCNPX code. In this context of demand, a code system named CAD-PSMC (FreeCAD based parsing script for MCNPX code) has been developed to solve the ADS modeling conversion problems. In the framework of this code, hierarchical tree-based basic geometry classes and Boolean&Affine operations have been established with a mapping relationship to MCNPX code. Additionally, ray-casting technology and Markov chain based iteration method have been proposed to solve the problem of spline surfaces in complex geometries. Finally, the applicability and accuracy of CAD-PSMC code have been demonstrated by comparing with various reference models and numerical calculation results.