Two different down comer configurations (cylindrical and perforated cylindrical tubes with inner diameters of 10 mm each) are used to investigate the multidimensional cooling effects. The down comer is concentrically installed inside the debris bed which is contained in a cylindrical crucible with an inner diameter of 125 mm. Different bed configurations, e.g. polydispersed particle bed with spherical particles 2, 3 and 6 mm in diameters and irregular particles of equivalent diameters 2-10 mm, have been used with a bed height of 640 mm. A layer of ceramic balls of diameter 4 mm with 40%porosity is used to make up a water pool at the bottom of the bed. The bottom inflow via the down comer tube as well as the lateral inflow of water through the perforated down comer tube into the bed improves the coolability of the debris bed, and therefore an increase of the dryout heat flux can be observed. Experimental results also show that the system pressure has no significant effect on the characteristics of pressure gradients inside the bed, whereas with increasing system pressure the coolability limits are increased.