The dynamical and thermal performances of molten salt pipe during the filling process are numerically investigated using volume of fluid model. The whole filling process has three main stages, or the developing stage with the interface width quickly increasing, the fluctuating stage with the interface width fluctuating and the fully developed stage with stable interface, and then associated interface structures, flow and temperature fields are described in detail. Before the molten salt flows through a certain position, the fluid temperature will jump within a short time, while the wall temperature only linearly increases after that. The heat transport during the filling process is mainly dependent upon the pipe wall and molten salt flow, while natural convection outside can almost be ignored. The dimensionless interface temperature has similar evolution process under different surrounding temperatures, but it will apparently increase with the flow velocity rising. In addition, the pipe will be blocked when the interface temperature drops below the freezing point, so a model of penetration distance is derived by correlating the interface temperature evolution process, and it has a good agreement with available experimental results. (C) 2009 Elsevier Ltd. All rights reserved.