Utilization of nuclear energy is an effective way of solving the global warming resulting from CO2 emissions. Thermal energy accounts for more than two thirds of total energy utilization at present and therefore it is significant to extend the utilization of nuclear heat for the effective reduction of CO2 emissions in the world. This paper describes a coal gasification system using HTGR nuclear heat in an ammonia production plant in terms of industrial utilization of the nuclear heat. The system uses the nuclear heat directly in addition to generating electricity. A steam reforming method using a two-stage coal gasifier is employed: it improves the heat utilization efficiency of the secondary helium gas from the: HTGR. Finally, the paper clarifies that the nuclear gasification system can reduce CO2 emissions by about five hundred thousand tons per year from that of a conventional system using fossil fuel.