High-fidelity 3D neutronics and thermal-hydraulics coupling analysis of a liquid metal-cooled fast reactor

To investigate the coupling characteristics between neutronics and thermal-hydraulics in liquid metal-cooled fast reactors, the study developed a three-dimensional high-fidelity pin-by-pin neutronics and thermal-hydraulics coupling code based on OpenFOAM. The neutron transport equation solved by Simplified SPherical harmonics approximation (SPN) is used to describe neutron behavior, while CFD equations solved by Semi-Implicit Method for Pressure Linked Equations (SIMPLE) are used to describe thermal hydraulic phenomena, and the Picard iteration is employed for coupling. Focusing on a liquid metal-cooled fast reactor, MicroURANUS, the study found that after coupling, the core power was flattened, with the central power peak decreasing by 11.0%-12.1%, while the power in high-enrichment fuel region significantly increasing by 29.5%-31.1%, and an asymmetric phenomenon of increased axial power at the top of the reactor appeared. An analysis using first principles of the impact of thermal-hydraulic parameters on neutron behavior indicated that the coupling characteristics of liquid metal-cooled fast reactors are related to fuel enrichment, energy spectrum and core materials.