Since Molten Salt Reactors (MSRs) are designed to operate at high temperatures, thermal radiation can contribute to their thermal–hydraulic evaluation. Accordingly, this study assesses the impact of thermal radiation on the thermal–hydraulic parameters of these reactors under both steady-state and loss-of-flow transient conditions. For this purpose, a new library is developed in OpenFOAM-v2406 using C++ object-oriented programming and coupled with a multi-physics solver to model MSRs. This library uses the SP 3 method to solve the Radiative Transfer Equation (RTE) and is compatible with all OpenFOAM solvers. Additionally, an innovative boundary condition is implemented to account for the emissivity of metals, such as stainless steel and Hastelloy, commonly used in reactor vessels. This library is verified through analytical solution and validated using experimental data from Sandia Flame D. To assess the impact of thermal radiation in MSRs, a 2D axisymmetric EVOL model and a 3D Molten Salt Fast Reactor (MSFR) model are analyzed using the multi-physics solver. A grid convergence study is performed on the two models to evaluate the effect of grid resolution on solution accuracy. The results indicate that thermal radiation in these reactors is strongly influenced by geometry and flow patterns. The inclusion of thermal radiation in the steady-state analysis leads to a reduction of the temperature near the reactor vessel wall by approximately 4 K in the 2D EVOL model and 2 K in the 3D MSFR model. However, thermal radiation can have a more pronounced impact during transient modes. Thermal radiation negatively impacts natural circulation, reducing the flow rate and leading to an increase of up to 2 K in the mean reactor temperature during loss of flow transients. Moreover, due to the partial return of the cold flow from the heat exchanger to the inlet pipe under natural circulation, thermal radiation causes a temperature increase exceeding 35 K at a specific location along the pipe.
Nasr et al. (Wed,) studied this question.