Thermophysical properties of austenitic stainless steel containing boron carbide in a solid state

In a core disruptive accident scenario, boron carbide, which is used as a control rod material, may melt below the melting temperature of stainless steel owing to the eutectic reaction with them. The eutectic mixture produced is assumed to extensively relocate in the degraded core, and this behavior plays an important role in significantly reducing the neutronic reactivity. However, these behaviors have never been simulated in previous severe accident analysis. To contribute to the improvement of the core disruptive accident analysis code to simulate these eutectic melting and relocation behavior, the thermophysical property database of the eutectic mixture implemented into the analysis code should be developed. As part of this database development, this study measured the thermophysical properties of the eutectic mixture in the solid state. In this study, pre-alloyed austenitic stainless steel containing boron carbide, which has the prescribed concentration of boron carbide and is homogeneous, is used as eutectic samples to reduce the uncertainty of samples and achieve accurate measurement. Based on these evaluation results, the effect of adding boron carbide on the thermophysical properties of austenitic stainless steel are discussed. Furthermore, regression equations that show the temperature (and boron carbide concentration) dependence are created for each thermophysical property. (author)