Three-dimensional neutron source models for toroidal fusion energy systems

Abstract

Developments in computer architecture and neutronics code capabilities have enabled high-resolution analysis of complex 3D geometries. Thus, accurately modeling 3D source distributions has become important for nuclear analyses. In this work two methods are described which generate and sample such 3D sources based directly on the plasma parameters of a fusion device and which facilitate the ability to update the neutron source following changes to the plasma physics configuration. The cylindrical mesh method is for toroidally symmetric machines and utilizes data in a standard file format which represents the poloidal magnetic flux on an R–Z grid. The conformal hexahedral mesh method takes plasma physics data generated in an idealized toroidal coordinate system and uses a Jacobian transformation and a functional expansion to generate the source. This work describes each methodology and associated test cases. The cylindrical mesh method was applied to ARIES-RS and the conformal hexahedral mesh method was applied to a uniform torus and ARIES-CS. The results of the test cases indicate that these improved source definitions can have important effects on pertinent engineering parameters, such as neutron wall loading, and should therefore be used for high-resolution nuclear analyses of all toroidal devices.