Computational Methodology for the Thermal-Hydraulic Behaviour of a Fuel Rod Surrounded by a Coolant Under PWR Conditions

The present study deals with the thermal-hydraulic modelization of the heating part of a test loop containing a fuel rod cooled by forced convection under PWR conditions, while the pressure tube is cooled naturally by the water from an OSIRIS reactor open pool. A renovation policy of calculation schemes leads us to carry out these studies with a 3D CEA computer F.E. code, named CAST3M, coupling 3D thermal and 1D hydraulic phenomena. In addition to the liquid single phase character of the flow cooling the fuel rod, safety concerns are taken into account, such as the possibility of nucleate boiling regime, without affecting the main safety criteria. A few numerical results show the heat balance for different values of the main inlet relevant parameters.