How a nuclear power plant works

In a nutshell, the heat produced when uranium atoms split—or fission—is used to boil water, creating steam. The steam turns the blades of a turbine, which spins the shaft of a generator. Inside the generator, coils of wire and magnetic fields interact—and electricity is produced.

A nuclear power plant consists of a reactor and what is called the "balance of plant." The reactor includes:

• a pressure vessel containing the uranium fuel
• devices for removing the heat produced by the fissioning fuel
• measuring and controlling instruments
• protective devices.

The balance of plant includes:

• the turbine
• the generator.

The water flowing through the reactor carries the heat away. It also slows down the speed of the neutrons, increasing the probability of fission. Any loss of water would slow down the chain reaction—the continued repetition of fission that is necessary to produce enough heat to turn the water into steam. The chain reaction can also be slowed down or stopped by inserting "control rods" into the reactor to absorb some of the neutrons.

Two types of nuclear power plants are used in the United States: the pressurized water reactor (PWR) and the boiling water reactor (BWR). In a PWR, the water is kept under pressure so it does not boil. The pressurized water flows through a steam generator, where it is turned into steam. In a BWR, the water in the reactor actually boils into steam.

In both types of nuclear power plants, after the high-pressure steam is used to turn the turbine, it is condensed back into water and used again in the reactor.

For an illustration of how nuclear power plants work, you may want to visit Nuclear Reactors in the Students' Corner of the Nuclear Regulatory Commission’s Web site.

Another site that may be helpful is The Virtual Nuclear Tourist.   Scroll down through the table of contents until you get to the heading Power Plant Designs Around the World. Click on Pressurized Water Reactor and Boiling Water Reactor. The section also includes information on other nuclear plant designs. If you scroll down further through the table of contents, you’ll get to the heading Running a Nuclear Power Plant. You may find the information and photographs in that section helpful.

Also see the section Key Areas of a Nuclear Power Plant for diagrams and photos.  To see the layout of a PWR plant and a BWR plant, click on The Virtual Nuclear Tourist and scroll down to Plant Designs, then click on Pressurized Water Reactor (PWR) and Boiling Water Reactor (BWR). For a "tour" of a nuclear power plant, scroll down to Featured Links and click on SONGS On-line Tour.  

Nuclear Energy Institute—Washington, DC
August 2000