A nuclear power plant is a thermal power station in which the heat source is a nuclear reactor. As is typical in all conventional thermal power stations the heat is used to generate steam which drives a steam turbine connected to an electric generator which produces electricity.
Layout of nuclear power plant – Picture
The heat is produced by fission in a nuclear reactor and passes into the primary cooling water. This heat, deposited in the cooling water, is conducted to the steam generators situated in the containment building. Steam generators produce high pressurized steam. The pressurized steam is then usually fed to a multi-stage steam turbine. Steam turbines in western nuclear power plants are among the largest steam turbines ever.
Components of a nuclear power plant
The key components common to most nuclear power plants are:
- Nuclear Reactor. A nuclear reactor is a key device of nuclear power plants. Main purpose of the nuclear reactor is to initiate and control a sustained nuclear chain reaction.
- Steam Generators. Steam generators are heat exchangers used to convert feedwater into steam from heat produced in a nuclear reactor core. They are used in pressurized water reactors (PWR) between the primary and secondary coolant loops.
- Pressurizer. Pressure in the primary circuit is maintained by a pressurizer, a separate vessel that is connected to the primary circuit (hot leg) and partially filled with water which is heated to the saturation temperature (boiling point) for the desired pressure by submerged electrical heaters. Temperature in the pressurizer can be maintained at 345 °C (653 °F), which gives a subcooling margin (the difference between the pressurizer temperature and the highest temperature in the reactor core) of 30 °C.
- Reactor Coolant Pumps. Reactor coolant pumps are used to pump primary coolant around the primary circuit. These pumps are powerful, they can consume up to 6 MW each and they can be used for heating the primary coolant before a reactor start-up.
- Safety Systems. According to the U.S. Nuclear Regulatory Commission primary objectives of nuclear reactor safety systems are to shut down the reactor, maintain it in a shutdown condition and prevent the release of radioactive material. Reactor safety systems consist of:
- Reactor Protection Systems
- Essential service water system
- Emergency core cooling systems
- Emergency power systems
- Containment systems
- Steam Turbine. A steam turbine is a device that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft.
- Generator. A generator is a device that converts mechanical energy of the steam turbine to electrical energy.
- Condenser. A condenser is a heat exchanger used to condense steam from last stage of turbine.
- Condensate-Feedwater System. Condensate-Feedwater Systems have two major functions. To supply adequate high quality water (condensate) to the steam generator and to heat the water (condensate) to a temperature close to saturation.