Validation of CFD models for jets and plums in fission reactors. The cooling system of nuclear reactor is very important, as the safety of the whole system significantly depends on it. Nowadays, it’s design and the design of the fission and fusion power plants depends on the models that can simulate a fluid flow in a given geometry taking into account all the environmental and other conditions. There are variety of models available that are results of different approaches, thus the computational time will also vary depending on the approach. Nevertheless, most of these approaches are based on the Navier-Stokes equations.