Application of spheroidal graphite cast iron in the production of spent-nuclear-fuel container contributes to improve the strength and toughness of the casting, because of the nodular shape of graphite. For a large-scale container, a forced-chilling technique is used to accelerate solidification process and raise spheroidization rate. In this paper, modeling of heat transfer in the container is performed. Influences of cooling media, inflow flux of coolant and thickness of sand layer upon the variations of cooling rate are systematically analyzed. Calculated results indicate that water as a coolant is more capable of enhancing the cooling course than air. Increasing inflow flux conducts an effective cooling job, whose influence is more apparent for air-cooling than for water-cooling. The role of decreasing the thickness of sand layer is most pronounced for raising solidification rate. The predicted cooling curves are compared with experimental measurements to validate the model.