In this work, energy and exergy studies of a water-cooled water-moderated power reactor (VVER) type nuclear power plant (NPP), which is among the pressurized water reactors have been performed. The exergy analysis has been carried out based on the second law of thermodynamics, considering the normal operation of the reactor and subsystem irreversibility. The thermal reactor with the capacity of 3900 MW heat generation is used in order to generate the nominal power of 1000 MW. The aim of the paper is to analyze the sub-system components separately and to identify and quantify the sites, which have high losses for energy and exergy. In accordance with the analyses, much energy loses have been found in reactor pressure vessel units. In addition, condenser, turbines and steam generators also contribute at the energy loss. While the thermodynamic efficiency of the NPP is found as 30%, the irreversibilities of pressure vessel and steam generator have been calculated as 49% and 13%. There exist also irreversibilities within the amount of 6% in turbines, condensers and heaters. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.