Experimental study on coolability characteristics of particulate core-metal debris bed with oxidization part 2: Zircaloy-2 debris bed

In order to understand the appearance and disappearance of hot spot in the TMI-2 accident, the coolability characteristics of Zircaloy-2 particulate debris bed into which vapor and water penetrate are studied in the present paper. In the vapor penetration experiment, it is found that Zircaloy-2 debris particles are effectively broken into small pieces by oxidization of vapor flow with 20cm/s in short time period on the condition of an initial wall temperature of 1000 degree C. It is also confirmed in the water penetration experiment that the oxidized particle debris bed has potentiality of high coolability when water penetrates into the fine oxidized particle bed because of a high capillary force originating in fine oxidized particles with cracks on their surfaces.(authors)