Experimental Study on Coolability of Particulate Core-Metal Debris Bed with Oxidization, (I) Fragmentation and Enhanced Heat Transfer in Zircaloy-50 wt%Ag Debris Bed

Abstract

The oxidization and coolability characteristics of the particulate Zircaloy debris bed, which is deposited under the hard debris and through which first vapor penetrates and then water penetrates, are studied in the present paper. In the vapor penetration experiments, it is found that Zircaloy debris particles are effectively broken into small pieces after making thick oxidized layer with deep clacks by rapid oxidization under the condition that vapor with 20 cm/s penetrates for 30 to 70 min at an initial debris bed temperature of 1,030°C. It is also confirmed in the water penetration experiments that the oxidized particle debris bed has potentiality of high coolability when water penetrates through the fully oxidized particle bed because of a high capillary force originating from those particles with deep cracks on their surfaces. Based on the present study, a new scenario for the appearance and disappearance of the hot spot in the TMI-2 accident is posssible. The particulate core-metal debris bed is fir...