A preliminary study on concrete ablation during ex-vessel cooling in pre-flooded Westinghouse 3-loop NPP reactor cavity

Abstract

We develop an analytical model about concrete ablation during ex-vessel cooling in a pre-flooded cavity. The model considers the melting of dry debris bed, the formation of crust, the growth of crust and the thermal ablation of concrete. This model can obtain concrete ablation depth during ex-vessel cooling. It is evaluated the adequacy of ex-vessel cooling in the pre-flooded reactor cavity of Westinghouse 3-loop nuclear power plants. If the debris bed is formed only in the zone directly below the reactor vessel narrowly and thickly, the characteristic of the debris bed should be like POMECO BED-5 and the pressure should be 2 bar or above to keep the integrity of the containment. However, if the debris bed is evenly distributed on the reactor cavity, it is assessed the pressure should be equal to or greater than 1 bar, 2 bar and 3 bar for POMECO BED-5, STYX BED and COOLOCED-8 BED, respectively.