Types of NPP's

The structure of a nuclear power plant in many respects resembles to that of a conventional thermal power station, since in both cases the heat produced in the boiler (or reactor) is transported by some coolant and used to generate steam. The steam then goes to the blades of a turbine and by rotating it, the connected generator will produce electric energy. The steam goes to the condenser, where it condenses, i.e. becomes liquid again. The cooled down water afterwards gets back to the boiler or reactor, or in the case of PWRs to the steam generator.

The great difference between a conventional and a nuclear power plant is how heat is produced. In a fossile plant, oil, gas or coal is fired in the boiler, which means that the chemical energy of the fuel is converted into heat. In a nuclear power plant, however, energy that comes from fission reactions is utilized.

Several nuclear power plant (NPP) types are used for energy generation in the world. The different types are usually classified based on the main features of the reactor applied in them. The most widespread power plant reactor types are:

• Light water reactors: both the moderator and coolant are light water (H₂O). To this category belong the pressurized water reactors (PWR) and boiling water reactors (BWR).
• Heavy water reactors (CANDU) ): both the coolant and moderator are heavy water (D₂O).
• Graphite moderated reactors: in this category there are gas cooled) reactors (GCR) and light water cooled reactors (RBMK).
• Exotic reactors (fast breeder reactors and other experimental installations).
• New generation reactors: reactors of the future.

The reactors applied in the Paks NPP are PWRs, their type number is WWER-440/213.