Direct cooling of coated particles by water is a possibility for significantly increasing the power density in the core of pressurized water reactors beyond that common at present. The problems of hydrodynamics, thermodynamics, and production technology involved have been examined and found to be tractable. By means of burnout experiments using induction heating, it has been demonstrated that it is possible to safely cool packed beds of small spheres directly by water, even at the low flow rates that must be specified to limit the pressure drop to values representative of present high-power-density cores. Electron beam drilling was shown to be an adequate method for producing the perforated support structure for the particle beds. Clarification of problems with respect to neutron physics, cost-effectiveness, or specific safety engineering will require further investigation.