Hledání

The Reactor unit of a power plant is usually operated for extended time periods at full power. Once a year, a shutdown of the reactor unit is scheduled for refueling, inspections and maintenance. The energy contained in nuclear fuel is spent gradually.

Nuclear safety is the basic requirement for the operation of every nuclear power plant. It is a collection of all technical and organizational measures, which have to secure that fission process of the atoms’ nuclei, which releases radioactivity, stays, under all circumstances, under human control.

The loss of control over a fission reaction results in an excessive accumulation of thermal energy. The design solution of the WWER 440 nuclear reactor guarantees that, in case of a temperature increase in the reactor's active zone, the intensity of the fission reaction is decreased and, as a consequence, the temperature in the active zone decreases also, thus it eliminates the possibility of the initiation of an uncontrollable fission chain reaction.

Steam Generator Heated steam advances from reactor through the main gate armatures to steam generators — heat exchangers. There, hot water flows through thin heat exchanging pipes, which are dipped in water of the secondary circuit.

Fission Reaction Nuclear fission reaction, which is the source of thermal energy, takes place in nuclei of isotope of uranium U 235 in the active zone of nuclear reactor. Uranium occurs in nature as a mixture of isotopes of uranium U 235 and U 238, which differ mutually by the number of neutrons in their nuclei.

Nuclear Fuel The fuel for nuclear power plants is the processed uranium. It exists in a suitable amount in nature for needs of nuclear energy industry. From two main isotopes, U 238 and U 235, only nuclei of U 235 atoms are utilizable for fission reaction.

Nuclear Reactor Fission of nuclei of isotope of uranium 235 takes place in nuclear reactor. The result of fission is origin of thermal energy and numerous radioactive isotopes. Facility of the reactor is formed by a cylindrical pressure vessel manufactured from special steel with rustless lining.

Main Circulation Pump It assures water circulation in the primary circuit. It pumps the cooled water of the primary circuit from steam generator back into reactor, where it is directed into the active zone, where it takes away the originating heat by its passing through fuel assemblies.

Turbo Generator Thermal energy of steam generated in steam generators is changed to electric energy in turbo generators. Steam flows from steam generator into turbine, which has a high-pressure part and a doubled low-pressure part.

Cooling Tower Cooling of turbines’ condensers, in which unavailable energy is taken away from the steam, is assured by the third, so called circulation cooling power plant’s circuit. Its most well-known part is formed by cooling towers, where water from condensers is cooled down.