The natural convection heat transfer driven by internal decay heat and the diffusive mass transfer at the crust interface are the critical problems in study of thermal behaviors in volumetrically heated reactor corium pools. In this paper, experiment and transient code were developed to analyze the heat and mass transfer characteristics in the high-Rayleigh-number corium pool. The COPRA experiment was carried out in seven tests with different heights and heating powers. The near-wall modified low-Reynolds-number k-s turbulence model was used for the natural convection simulation in the whole flow region. Both the heat transfer with phase change and the diffusive mass transfer at crust interface boundary were taken into consideration. In addition, the heat conduction in the crust and wall, as well as the heat radiation in top space were included. The validation was performed for the developed code with transient simulation of COPRA experimental tests. The calculation results agreed well with experimental data for the pool temperature, heat flux and crust distributions, proving the reliability of the transient analysis code for the corium pool simulation with heat and mass transfer. (C) 2019 Elsevier Ltd. All rights reserved.