Development of a three-dimensional method for thermal-hydraulics/neutronics coupling analysis and its application on CFETR helium-cooled solid breeder blanket

Blankets are of practical importance in the fusion reactor due to their main functions for engineering application. As the fusion power designed for the Chinese Fusion Engineering Test Reactor (CFETR) is increased from 200 MW to 1.5 GW during its phase II operation, more challenges are issued for blankets from the points of view of thermal-hydraulics, neutronics, mechanics, and safety. In this paper, the Coupling Analysis of Thermal-hydraulics and Neutronics Interface Code (CATNIC) was developed using the user-defined function (UDF) in the CFD software FLUENT. The explicit coupling scheme based on cell-to-cell mapping approach was adopted to transfer data between neutronics calculation and thermal-hydraulics simulation. Three-dimensional thermal-hydraulic model and neutronics model were established using Fluent and MCNP4C, respectively. The helium-cooled solid breeder (HCSB) blanket of CFETR was simplified as a slice model to reduce the computing resources. With the slice model of CFETR HCSB blanket, the coupling analysis was carried out using the developed CATNIC. The calculation results from coupling and non-coupling analyses were compared to verify the feasibility of the coupling method in this study. As the helium coolant was considered as the transparent medium for neutron, the thermal-hydraulic and neutronics analyses were both converged after two iterations. However, using the developed coupling method in this study, the detailed change of tritium production ratio (TPR) and nuclear heat deposition in different parts of the blanket was revealed, which could provide important guidance for the design of the distribution for both coolant and purge gas.