Numerical estimation of reactor core melt cooling (original) (raw)

During a hypothetical severe accident, a melt pool may form in the lower plenum of the reactor vessel as a consequence of reactor core overheating and melting. High temperatures and further heat generation due to fission products decay may jeopardize the integrity of the reactor vessel. To prevent this the plenum walls would have to be externally cooled. At present, external vessel flooding is one of the possible emergency procedures. To determine the cooling characteristics of the melt pool, the heat transfer through the lower plenum wall must be known. The natural convection behaviour of the melt pool was studied for this purpose. Although some experimental studies have been carried out in the paste it is not feasible to perform large-scale experiments at realistic reactor conditions. Extensive numerical studies were also carried out regarding the lower plenum cooling problem using one of k-epsilon models to model turbulent motion. Because of extensive computational requirements of the k-epsilon models, we propose a modified Smagorinsky Large-Eddy Simulation model which is mainly used in forced convection turbulence calculations.