Influence of axial power distribution on dryout: Film-flow models and experiments

The influence of axial power distributions on dryout occurrence in nuclear fuel assemblies has been studied extensively for several decades. Even though it is well known that axial power shapes – which may significantly vary in nuclear reactors during their operation – significantly change the dryout power level, this particular influence is rather difficult to capture with current correlations. In this paper it is shown that this influence can be captured using a phenomenological liquid film model coupled to a standard sub-channel code. The model has been applied to various geometries, including a round pipe, as well as 5 × 5 and 8 × 8 fuel rod assemblies, and highly accurate predictions have been obtained.