A nuclear power plant has a complex structure and is composed of several facilities, which are technologically connected. The main element of an NPP is the power-generating unit. Production of electricity at an NPP can be described as follows: the reactor vessel installed in the power-generating unit heats water to make steam, which activates a turbine. The turbine in its turn rotates a rotor magnet. Electric current is produced due to the induction of electromotive force in the closed conducting circuit due to the change of magnetic flux that goes through the circuit. By rotating inside the stator stationary coil the rotor produces an electric current. All that is left is to “scoop” voltage from the generator winding and to transfer electricity to external consumers. Behind the simplicity of this description is hidden a great number of producing, controlling and operating facilities, instruments and devices that are rigidly thoughtfully and efficiently united in a single technological chain. Running such a number of instruments and devices requires some power as well, so some electricity produced at the power plant is consumed for this purpose. When all power units of the NPP are taken out of operation, all devices and machinery of the NPP get electricity from outside sources through three independent electricity transmission lines. There are reserve diesel-generator units (three for each power unit) and in addition battery units for emergency power supply for the control and safety systems to ensure uninterrupted power supply of the NPP equipment under any circumstances, primarily that of the safety system equipment. Pumping houses, the water purification plant, spray cooling ponds and cooling towers provide effective cooling of the NPP machinery and devices that are required to operate the NPP. Special facilities are allocated to process new fuel and purify the coolant from radioactive residuals, as well as for a waste treatment plant. An NPP requires systems of electric power output and distribution along with many other devices, machinery and instruments finely tuned to one another to produce electricity whilst ensuring the safety of people and environment.