Thermodynamics of GT-MHR-250 modular nuclear plant with helium reactor and gas turbine based on the complex Brayton cycle

Although most of the discussed Gas Turbine Modular Helium Reactor power plants are based on the Rankine cycle, the use of the complex Brayton cycle can be an advantage. However, scientific papers published in recent years do not evaluate this combination in more detail. This paper provides a thermodynamic analysis of the modular nuclear plant with thermal power of 250 MW, consisting of a helium-cooled nuclear reactor and the energy conversion unit, using the vertical gas turbine operating according to the complex Brayton cycle. Two modes of nuclear plant operation were considered, mainly electricity generation and combined electricity and heat production. The energy conversions unit parameters, such as the electrical efficiency, electrical power, and thermal power of heat regenerator and heat exchangers were obtained and analyzed. The results have confirmed that high cycle efficiency in the electricity production mode can be obtained if the best parameters of all in-plant elements currently achieved in the modern gas turbine and power engineering industries are used in the design. As found, the temperature coefficient of helium intercooling demonstrates a great impact on the nuclear plant's electrical efficiency and electrical power. The sensitive analysis was carried out to assess the reduction of GT-MHR-250 performance due to deterioration of the in-plant elements (turbine, compressor, heat exchangers) during operation. In this case decrease in the plant's electrical efficiency and electrical power is more noticeable in the combined mode rather than in the electricity generation.