Experimental study on influence of crust formation on heat transfer characteristic in corium pool

Large scale COPRA experiments were performed to study the natural convection heat transfer in corium pools. Both water and a non-eutectic binary mixture of 20%NaNO₃-80%KNO₃ (in mole fraction) compositions were employed as the simulant material. The Rayleigh number within the pool could reach up to 10¹⁶, matching those in the prototypical situation for PWR. The comparisons of the pool temperature and heat flux distributions from water and molten salt experiments show that the crust formation along the inside curved wall is of significant impact to the heat transfer phenomenon in the melt pool. Heat transfer correlations were obtained from COPRA experiment and the heat flux distribution compared well with other experiments. The downward heat transfer towards the curved wall is lower than those from other experiments within the same range of Rayleigh number.