Investigation on three-layer coupled molten pool heat transfer experiment with three different materials

Abstract

In the core meltdown accident, fission products are limited in the vessel bottom as indicated in the In-Vessel Retention (IVR) strategy analyses, resulting in forming a three-layer configuration that would threaten the integrity of Reactor Pressure Vessel (RPV). The three-layer test has been carried out with the Three layeR cOupled molten pool heat tranSfer Experiment (TROSE) apparatus to investigate the heat transfer in this three-layer configuration. It uses mineral oil (height = 0.2 m), water (height = 0.7 m), and Cerrobend alloy (height = 0.3 m) as the simulants for the top, middle, and bottom layers, individually. TROSE test section is a three-dimension hemispheric facility whose diameter and thickness are 2.4 m and 0.025 m, respectively. Since the sidewall temperature is smaller than the melting point of Cerrobend alloy (70 °C), the crust is formed in the bottom layer, affecting its dominant heat transfer mode. The experimental results demonstrate that upward heat transfer is found at the interface of the middle and bottom layers. Besides, the sideward heat flux decreases with the increase of the polar angle. Furthermore, heat transfer correlations of Churchill-Chu, mini-ACOPO, and COPRA could reasonably predict the experimental ratio of top cooling power to sidewall cooling power (Pup/Pdn). Finally, the previous correlations of the sideward heat flux and Nusselt number distributions, such as Mini-ACOPO correlation, can reasonably predict the experimental results of the middle layer; however, they are not suitable for the top and bottom layers.