Thermal energy recovery from a Brayton cycle nuclear power plant for efficiency improvement via compressor inlet cooling: Thermoeconomic optimization

Due to the well-known limitations of renewable energy resources, nuclear power is considered as another alternative for carbon-free electricity generation. A great deal of interest has been paid to developing gas-cooled reactors due to their efficient and cost effective electricity generation ability. Among these systems, the GT-MHR is a promising one which employs the Brayton closed cycle for power generation with an energy efficiency of around 47% and a waste heat of around 300 MWth. The present work aims at utilizing this waste heat to produce additional power (via an ORC) and inlet gas cooling of compressor via employing absorption chiller. In this respect a combined GT-MHR/ORC/ARC structure is designed and assessed thermodynamically and economically and is compared with the standalone GT-MHR performance. A sensitivity analysis is implemented to inspect the influences of design variables, and then optimizations are conducted based on cost and exergy. Results revealed better performance for combined system in comparison to the GT-MHR. Under the optimal working conditions obtained for cost optimal design case, the combined cycle yields 12.4% higher efficiency and 9.7% lower LCOE compered to GT-MHR power plant. Another interesting outcome is obtained, as under the optimal operation, the total levelized investment cost for the novel combined cycle (9065 $/h) is less than the GT-MHR system (9285 $/h). This is due to the larger optimal pressure ratio for compressor in combined cycle which causes less helium flow rate, as a result of which the components sizes and costs are decreased.