“…More elaborate evaluations can be performed using the MC3D-PREMIX model, slightly modified for the purpose. This 3D multiphase flow model, dedicated to evaluate the premixing stage of fuel coolant interaction (FCI) [34], is also used to evaluate the thermal-hydraulic behavior of debris beds [24,35]. Basically, for such evaluation, the debris bed is simulated with one or several numerical fields of drops (spheres) with different diameters and material properties.…”