In this study current nuclear power plants situation in the world was examined. In the beginning, an overview of existing plants is given but also of plants in construction. In addition, a list of nuclear power plant types is given, divided by type of reactors. The effect nuclear power plants have on the environment and also the forms of waste they produce were described. Radioactive waste treatment, disposal and the effects of long-term depth storage are discussed. Safety of nuclear power plants and all its safety systems are explained. Alongside physical protection barriers, safeguard measures that secure their efficiency are described. A modern passive security system of nuclear power plants is illustrated on the Westinghouse AP1000 nuclear power plant. In the final part of the study the methodology of levelized cost of electricity calculation is explained. The calculation is conducted on four different electricity generation technologies: nuclear power plant, coal power plant, onshore wind farm and rooftop solar PV. The result of the calculation indicates the onshore wind farm to be the most cost effective electric power facility.