Deterministic method for calculating fusion neutron emission probability distribution in tokamak through mesh mapping

The high-fidelity 3D neutronics analysis of fusion systems has been enabled by advanced computer-aided design (CAD)-based simulation tools, and is being driven by an increasing desire to couple the analysis results with other physical field analyses. With increase in the level of output detail, the effects of the fusion neutron source spatial distribution have become increasingly important. The current fine-resolution neutron source model was established based on the Monte Carlo (MC) method, which is a time-consuming approach to reduce the deviations at low-intensity positions. This work presents a deterministic method to calculate the fusion neutron emission probability (FNEP) distribution in a tokamak machine with high resolution. In this deterministic method, the mesh-mapping technique is utilized to transfer neutron intensity data from an irregular (a, φ) mesh to a structured or unstructured (R, Z) mesh. The intensity data on (R, Z) mesh can be used directly by a deterministic neutronics code, or further be integrated and normalized in every grid to obtain the FNEP for an MC neutronics code. This deterministic scheme was implemented in the code EDITON, and the neutron source map can be generated subsequently by this code. EDITON exhibited high efficiency, and its accuracy was verified by comparing the obtained FNEP distribution and neutron wall loading (NWL) with the corresponding data from the TRANSGEN code, which is a tokamak fusion neutron spatial distribution calculation code based on the MC method.