【摘要】The paper presents the possibilities of the use of a high-temperature gas-cooled nuclear reactor for energy purposes in the hydrogen and electricity production process. The system provides heat for a thermochemical sulfur–iodine cycle producing hydrogen and generates electricity. Its structure and electricity generation capacity are conditioned by the demand for heat and the levels of temperature required at the sulfur–iodine cycle individual stages. In the three structures under analysis, electricity is generated in a gas turbine system and steam systems (steam, low-boiling fluids). The impact of helium parameters in a two-stage compression system with interstage cooling on power efficiency of the analyzed structures of cogeneration systems and on total power efficiency of the systems is investigated assuming that both hydrogen and electricity are produced. Thermodynamic analyses are conducted using the EBSILON Professional program. The aim of the analyses is to determine the optimum structure of the system and parameters of the mediums in terms of power efficiency.