Results of simulant effect on large corium pool behavior based on COPRA facility

This paper presents the results from COPRA eutectic molten salt tests, which were carried out to investigate the simulant effect on corium pool natural convection heat transfer characteristics. A eutectic 50%NaNO3-50%KNO3 molten salt was used to simulate the prototypical corium. Compared with the previous non-eutectic 20% NaNO3-80%KNO3 molten salt experimental data, the effects caused by simulant composition on melt pool temperature, heat flux distribution and crust behavior were studied. The comparison showed that the temperature distribution of eutectic melt pool was lower than the non-eutectic one, while the heat flux was higher than that of non-eutectic melt pool. Applying the same pool height, heating power and boundary condition, smaller modified Rayleigh number was obtained in the eutectic case. It indicated that the mush zone effect of non-eutectic melt suppressed the thermal stratification and impeded the heat transfer through the vessel wall. These results can be expected to provide further data to understand the natural convection behavior of corium pool.