This paper deals with the thermo-hydraulic properties of Generation IV Gas Cooled Fast Reactors. The paper is focused on the comparison of direct and indirect thermodynamic cycles of helium cooled reactors from a thermodynamic point of view. The calculation includes pressure losses at all major parts of the equipment — reactor, heat exchangers, pipe lines, etc. The compressor and the gas turbine efficiencies are included in calculation as well. The working fluid used in the primary circuit is helium. In the secondary circuit a mixture of helium and nitrogen is used. The cycle characteristic point and efficiency calculation reflects mixture properties of the real gas — especially for N2.
Calculations point out the influence of the mixture composition on the basic structural parameters of the turbines, compressors and heat exchangers. Thermodynamic cycle efficiency, specific heat input/output, heat flux and cycle work will be presented as characteristic parameters.