Nuclear Power Plant is the electricity generating station, at which uranium is used as fuel.
The flowpath of VVER power unit with water-cooled water-moderated (VVER) reactor consists of two circuits. The primary circuit is radioactive where pressurized water performs the functions of coolant and moderator. It contains reactor pressure vessel, 4 loops with reactor coolant pumps, pressurizer, and steam generators.
Nuclear reactor is the facility where controlled chain reaction of uranium fission takes place. The main part of each reactor is the core with loaded nuclear fuel. The core is formed with hexagonal metal tubes (fuel assemblies). The fuel assemblies contain fuel elements filled with uranium pellets in zirconium alloy cladding. Energy that is released during uranium fission must be removed for further use. This is provided by continuously pumping coolant through the core by reactor coolant pumps. The coolant is heated from the interaction with hot fuel elements.
The hot coolant is pumped through a closed piping loop to steam generators where it heats a completely separate supply of water. The secondary circuit is non-radioactive. High-pressure steam is supplied to the turbine. It rotates the turbine blades causing the turbine to spin a generator and produce electricity.
Finally the steam passes through the condensers where it is cooled by water from the cooling lake. Then it passes through the steam generators again.
2 Reactor core
3 Control rod drives
4 Reactor coolant pump
5 Steam generator
10. Cooling tower or
11. Cooling lake
Reactor hall consists of the hermetic part (cylindrical containment with a spherical dome) and non-hermetic part (auxiliary building around the containment). The reactor, steam generators, reactor coolant pumps (RCPs), a pressurizer, emergency core cooling system accumulators, pipelines are located in separate rooms inside the containment. If as a result of an accident primary equipment or piping gives a leakage, all radioactive substances are localized inside the containment. The auxiliary building is divided into a restricted and non-restricted area.
The non-restricted area contains the essential power supply system for house loads, main control room, emergency control room, and ventilation systems.
The restricted area contains systems and equipment that contact radioactive primary coolant, and emergency systems providing shutdown and cooldown of the reactor.
Both the containment and the auxiliary building are placed on the same foundation with an underlying massive tectonic plate.
The configuration of the turbine hall is designed for horizontal layout of the turbine and generator. The turbine hall contains high-pressure and low-pressure heaters, boiler facility, turbo-generator support systems. In the deaerator section there is a deaerator and a unit demineralizer, which maintains quality of feed water for steam generators.
CONTROL AND SUPERVISION
The main NPP processes including reactor startup, rise to power, turbine startup, generator synchronization, unit remote control under normal operation and emergency mode, reactor and turbine planned and emergency shutdown, reactor cooldown, are controlled and supervised from the main control room. The main control room panels contain instruments for monitoring the main parameters of reactor and turbine operation. The operating data are displayed in the form of mimics, schemes, tables, and schedules.
KhNPP electric circuit is implemented according to monoblock principle (one generator is connected to one transformer). The power output is distributed through the open switchyard 750/330 kV. The open switchyard circuit provides two systems of buses and autotransformer АТ 750/330 between open switchyards of 330 kV and 750 kV. The voltage of 6 kV provides the house loads.
The essential consumers have stand-by power supply from diesel-generator and accumulator batteries.