[en] Analyses of hypothetical severe core damage accidents in nuclear reactors require knowledge of post-accident heat removal capability from degraded core fragments. Such fragments may settle on available horizontal surfaces in the core (such as spacer grids or lower core support structures), or perhaps on the bottom of the reactor vessel and form debris beds. If the debris beds, which could be several meters high, are submerged the liquid coolant surrounding the UO² fuel particles will provide some cooling. However, if the overlaying liquid coolant cannot penetrate swiftly enough into the beds to offset vaporization, portions of the bed will dryout and may eventually melt. Much modeling and experimental research has been performed to determine the conditions that may cause dryout in debris beds. This paper reports experimentally measured porosites and capillary heads for beds of single-sized steel spheres (shot), steel grit and actual vapor-explosion fragments (solid density approx. 3.7 g/cm₃) from the FITS-9B experiment (sieved into single-sized groups). The effects on bed porosity of the method of forming the bed (i.e., in air and in water) and the settling intensity of the solids were also investigated