THREE-DIMENSIONAL ANALYSIS ON THE COOLABILITY OF INHOMOGENEOUS DEBRIS BED WITH THE CODE MEWA 3D

摘要

Particulate debris bed may be formed during different phases in the course of a severe accident in a light water reactor. The coolability of such particulate debris beds is a major issue for the progression and possible terminations of the accident. During the TMI-2 accident a debris bed has been formed in the lower plenum of the reactor pressure vessel which was eventually cooled. Post-accident examinations showed that this debris bed was neither homogeneous nor one (or two)-dimensional To give a more realistic ID-description of debris bed cooling a three dimensional code for MElt and WAter interaction, MEWA 3D, is being developed at developed at IKE, University of Stuttgart. In order to investigate the dryout behaviour of inhomogeneous debris bed, MEWA 3D is validated against DEBRIS experiments carried out by IKE. These experiments were carried out at different absolute pressures (1, 3 and 5 bar), bed inventory (particle size) and stratification (axial, radial and azimuthal). The simulation results are presented and compared to the experimental data which showed good agreement. As an application for debris bed quenching on reactor scale, three cases with different inhomogeneous debris bed configurations were analysed. The results, obtained with MEWA 3D obtained the minimum pressure down to which quenching of the debris bed is successful.