Neutronics and thermal hydraulics multiscale simulation of a lead-cooled fast reactor

In this work, the application of an upscaling methodology to the thermal hydraulic model of an LFR is presented. The upscaling process is applied to local equations, where a rigorous mathematical process yields reactor-scale equations containing information from the pin scale, in addition to information on the properties of each phase. Two phases are considered: the fuel rods are the solid phase, and the lead coolant is the liquid phase. The upscaled thermal model is coupled with a neutron model, a simplified expression of the diffusion equation that considers reactivity feedback. The scaled thermal hydraulic model allows the entire core to be analyzed using only two heat transfer equations, which contain scaled coefficients for both phases. These were calculated at different lead velocities to understand their behavior under potential velocity changes. The core neutron parameters were calculated using the Serpent code, and the models and coupling were implemented in COMSOL Multiphysics. The results show that the neutron flux profiles, fuel and coolant temperatures behave as the reactor design values.