On the basis of reasonable core meltdown conditions that can be postulated for GenIV sodium fast reactors, during a severe accident, good safety margins can be achieved for corium confinement and cooling inside the reactor vessel, by the use, in the lower plenum, of a core catcher. Such a device has to be designed to withstand to extreme thermal-mechanical conditions that rise as consequence of the large mechanical energy release and high temperature of molten corium. In the frame of the activities carried out within the CP-ESFR Project of the 7th Framework Programme Euratom, and considering the postulated accident conditions assumed for a reference 1500 MWe pool-type sodium fast reactor, the present work provides a preliminary analysis of the thermal response of a possible core catcher placed within the vessel. The dynamic thermal behaviour of the corium-structure-coolant system is analyzed with the computer code CORIUM-2D, an original simulation tool developed by RSE with the aim to assess the thermal interaction among corium, structures and coolant under severe accident conditions in both LWRs and LMFBRs. Temperatures reached by the core catcher, vessel and safety vessel, at the end of thermal transients, have been compared with safety criteria assumed for the demonstration of the corium coolability and long term integrity of these components. The results show that the steady-state coolable configuration of core debris and the structural integrity of main containment structures can be reached in a limited number of partial core meltdown situations.