The coolability of debris bed is a concern for reactor severe accident mitigation strategies,and the structure of debris bed has a significant impact on its coolability.In this paper,an experimental facility for the coolability of volumetrically heated debris bed was established,and the experimental study on the coolability of homogeneous,axial stratified,and radial stratified debris beds was carried out to compare and analyze the dryout phenomenon and heat flow flux for different debris bed types.The results show that under the condition of homogeneous debris bed,the larger gas-liquid flow resistance of small particles makes the permeability decrease,which leads to the smaller DHF of small particle homogeneous debris bed;under the condition of axial stratified debris bed,the DHF of axial stratified debris bed is much smaller than that of homogeneous debris bed composed of small particles at the top due to the large resistance caused by the decrease of porosity at the stratified interface;under the condition of radial stratified debris bed,due to the large gas-liquid flow resistance of small particle layer,steam will migrate and accumulate to large particle layer,resulting in DHF lower than that of the homogeneous bed composed of large particles.
Severe accidentStratified debris bedsCoolabilityDryout heat flux(DHF)
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