Thermophysical properties of molten (Fe2O3)0.95-(SiO2)0.05 measured by aerodynamic levitation

Abstract

In order to establish an evaluation method/numerical simulation for nuclear reactor safety under severe accidental conditions, it is necessary to obtain the physical properties of the relevant molten materials at very high temperatures. In particular, the reaction/interaction between the melt of stainless-steel oxide originating from the nuclear reactor component and the composition of structural concrete is an important phenomenon in terms of understanding of the progress of severe accidents in nuclear power plants and the planning/installation of equipment/devices as countermeasures. The installation of a core catcher is one possible countermeasure to safely terminate a severe accident. For this to work a sacrificial material is placed in the core catcher to increase the fluidity of the molten material. Iron oxide (Fe2O3) is considered a promising candidate. In this study, thermophysical properties such as the density and the viscosity of a (Fe2O3)0.95-(SiO2)0.05 mixture were obtained using the aerodynamic levitation method. The chosen composition is representative for the Molten-Core-Concrete-Interaction at early stages of a severe accident event. Although partial Fe2O3 changes to Fe3O4 during the experiment, this composition change would occur under the actual severe accident conditions. The physical property values of the (Fe2O3)0.95-(SiO2)0.05 mixture were almost the same as those of Fe2O3 obtained in an earlier study. Therefore, it can be concluded that the fluidity of Fe2O3 is not significantly affected in the early stages of a severe accident whereby small amounts of SiO2 (approximately 5 mol. %) are dissolved into Fe2O3.