Experimental study on the pressure drop of a packed bed with reactor material particles

Abstract

When a severe accident with reactor vessel failure occurs, molten core material can be released from the reactor vessel to the reactor cavity. According to a pre-flooding strategy, molten core material are released into the pre-flooded cavity and fragmentized into fine particles. Then, a particulate debris bed can be formed at the bottom of the cavity. Penetration of the coolant into the debris bed is important to ensure long term coolability of the debris bed, which is closely related to the two-phase flow pressure drop characteristics of the porous debris bed. This study analyzed the basic characteristics of non-explosive TROI (Test for Real cOrium Interaction with water) particles collected from steam explosion tests with reactor materials and then conducted single- and two-phase pressure drop experiments in the non-explosive TROI particle bed. Based on an analysis of the experimental data with existing pressure drop models, we found that the Ergun model with an effective diameter of 1 mm predicted single-phase pressure drop results most precisely and the Schmidt model with an effective diameter of 3 mm and the Schulenberg & Muller model with an effective diameter of 2 mm predicted the two-phase pressure drop results well. In addition, this paper discusses in detail the effects of the TROI particulate bed characteristics, irregularity, polydispersity and high porosity on pressure drop characteristics. Accordingly, the paper suggests a modified two-phase pressure drop model reflecting the measured porosity in the TROI bed particle.