Study on Heat Transfer and Interlayer Crust Characteristics of Two-layer Corium Pool Based on Visualization Experiments

To study the formation characteristics of the interlayer crust between the oxide layer and the metal layer in the two-layer corium pool, and analyze the effect of the interlayer crust on the flow and heat transfer of the corium pool, a two-layer corium pool visualization experimental device was designed and built in this study. 50 mol%NaNO₃-50 mol%KNO₃ molten salt and high-temperature heat transfer oil were used as simulants of oxide layer and metal layer respectively, and the modified Rayleigh number of corium pool is 10⁹~10¹². The study includes six experiments to observe the dynamic formation characteristics of the interlayer crust. The corium pool temperature, sidewall heat flux, crust thickness and heat transfer correlations were obtained, and the impact of the interlayer crust on the heat transfer characteristics in a two-layer corium pool was analyzed. The results indicate that the interlayer crust grows from the side wall and its formation weakens the upward heat transfer in the two-layer corium pool, resulting in the highest temperature in the melt pool below the interlayer crust. This study addresses the challenge of observing the growth process of the interlayer crust in a two-layer corium pool and summarizes the variations in the state of the interlayer crust, providing data support for safety analysis of severe accidents.