Analysis of the Particulate Debris Bed Quenching During Top and Bottom Flood

The quenching characteristics of particulate debris bed during bottom and top flood is analyzed in this paper. The top flood model is formulated by dividing the quenching process into downward frontal period and upward frontal period, which are controlled by the counter-current flow limitation (CCFL) condition and effects of the incoming coolant subcooling and steam cooling in dry channels during quenching process. The bottom flood model is based on porous media theory under the assumption that the height of the two phase region is negligible and the particulate debris bed is divided into single phase liquid and single phase vapor region. The results calculated by these models were compared with the experimental data. The influences of porosity, initial debris temperature and other parameters on both the top and bottom quenching process were studied in this paper. During the top flood, the quenching velocity increased with the increase of the porosity and the decrease of the initial debris temperature. The porosity and initial debris temperature had a larger influence on quenching velocity compared with other parameters, such as initial coolant temperature and coolant flow rate. During the bottom flood, the quenching velocity also increased with the increase of the porosity and the decrease of the initial debris temperature. However, the coolant flow rate had a large influence on the quenching velocity unlike that during the top flood. Quenching from bottom may be superior to the quenching from top. The results can be expected to be useful to evaluate the quenching process of the particulate debris bed.