Flow and heat transport in the gap between a solidified core melt and the wall of the pressure vessel

The movement of a mass of core melt into the lower plenum of the reactor pressure vessel after partial core meltdown will not necessarily lead to failure of the bottom of the pressure vessel, as gaps between the solidified melt and the bottom of the vessel would form which water could reach. This is subject to the precondition of a residual water volume being in the vessel prior to dislocation of the melt. Experiments have shown the flow conditions in these gaps and furnished information about heat transfer from the debris to the water, its protective function for the bottom of the pressure vessel, and the heat flows which can be transferred from the gap. The dependence of heat transfer on the width of the gap, its inclination, and the pressure in the vessel are explained. The dimensions required for cooling the melt and transferring its afterheat can be relatively small. (orig.)