This paper deals with the application of an evolutionary algorithm to multi-objective thermoeconomic optimization of coupling a multi stage flash desalination (MSF) plant with a pressurized water reactor (PWR) nuclear power plant. The thermodynamic simulation of this initial PWR plant has been performed in a Thermoflex simulator. An Excel add-in called Thermoflex Link has been developed to calculate the exergy of each stream from Thermoflex simulation results. Meanwhile, a computer code has been developed for thermoeconomic and improved combined pinch-exergy analysis in Matlab environmen. Both the design configuration (feed water heater structure) and the process variables are optimized simultaneously. The optimization algorithm can choose among several design options included in a superstructure of the feed water heater in dual purpose plant. For the assumptions and simplifications made in this study, a 3000MW (thermal) PWR power plant such as the Bushehr power plant has been considered. A detailed exergy and exergoeconomic analysis of selected final optimal design identifies the magnitude, location and causes of the thermodynamic inefficiencies. Improved combined pinch and exergy analysis has been applied to display the system information graphically for one to visualize the performance of the system in the initial and final case.