CFD modeling methods applied to a lead-cooled fast reactor: A parametric study on conjugate heat transfer and thermal boundary conditions

Given the ever-increasing global demand for energy and the need to reduce greenhouse gas emissions, small modular reactors (SMRs), have emerged as potential options for increasing the contribution of nuclear energy, offering lower costs and faster deployment compared to traditional nuclear projects. In the context of this technological development, safety studies have become a priority, particularly for licensing new-generation systems such as metal-cooled fast reactors. This work models the steady-state operation of the lead-cooled SMR SEALER Arctic using Computational Fluid Dynamics. The entire primary circuit of the SEALER is modeled; the core is represented as a combination of porous media and heat sources, the pumps are represented as recirculating boundary conditions to account for momentum sources, and the steam generators are represented as porous media coupled with a temperature-dependent heat sink function. The main objective of this study is to simulate the SEALER under steady-state condition, while also accounting for the effects of heat conduction through its solid regions, and heat losses on the reactor vessel wall to the environment. For the former, the reactor is modeled with and without conductive solids and surfaces, using a conjugate heat transfer model. For the latter, natural convection and radiation heat transfer considerations are included as boundary conditions, and a parametric study is carried out with a range of external temperatures, and their effects on fuel and coolant temperatures are also discussed. Despite significant differences in local temperatures near the vessel walls, the impact on the peak fuel temperature and the average coolant temperature was less noticeable. Ultimately, the general operating parameters of the steady-state reactor design were verified, which is the first step before using the current model to evaluate fast transients and postulated events, where the thermal inertia of the solids and additional heat losses could play a crucial role on determining the system’s response to rapid temperature changes.