All steam-electric power plants—nuclear, coal, gas and oil—run according to the same principles. Water is boiled to make steam. The steam is used to drive a turbine. The blades of the turbine spin the shaft of a generator. Inside the generator, coils of wire and magnetic fields interact—and electricity is created.
Nuclear power plants produce electricity for one of every five homes and businesses and are America’s largest source of clean air energy. In a nuclear plant, uranium—in the form of pellets about the size of a finger tip—is the fuel that heats water, or a gas with some plant designs, to create the steam.
Uranium is mined from the earth through surface, underground, or solution mining. In the United States, nearly all uranium is solution mined. A solution is injected into the uranium ore deposit then pumped out. The uranium then is separated from the solution. Uranium also is obtained as a by-product in the production of phosphate, sulfur, vanadium, copper and gold. After the uranium is mined, it must be refined through further processing.
Drums of uranium ore concentrate are shipped to a conversion plant, where they will be cleansed of impurities and converted to uranium hexafluoride, shown here in cylinders. The uranium hexafluroide is heated to become a gas, then cooled and condensed to a solid.
These are uranium centrifuges—one method of enriching uranium. Uranium contains two kinds—or isotopes—of uranium. The enrichment process concentrates the isotope that is most useful in energy production. Enriched uranium will operate a nuclear power plant, but is not concentrated sufficiently to make a nuclear bomb.
Finally, the uranium hexafluoride is shipped to a fuel fabricator, where it is manufactured into solid ceramic pellets, about the size of the end of a finger.
The pellets are inserted into long metal tubes called fuel rods. The fuel rods are made of zirconium—which resists heat, radiation and corrosion. The rods are bundled together into fuel assemblies, which are placed in the reactor.
When a nuclear power plant starts up, neutrons are released. When they strike the uranium atoms in the fuel pellets, the atoms split—or fission.
The splitting or fissioning of the atoms then releases neutrons, along with energy in the form of heat.
This process continues in a chain reaction, producing a great deal of heat. It is this process—creating heat through the splitting of atoms—that turns water to steam. The steam is moved from the reactor to turn the turbine-generator, which makes electricity. All radioactive water stays within the reactor system and is not released into the environment.
Plant operators can control the chain reaction. Long rods are inserted among the fuel assemblies. These &quot;control rods&quot; are made to absorb neutrons, so the neutrons can no longer hit atoms and make them split. To speed up the chain reaction, plant operators withdraw the control rods, either partially or fully. To slow it, they insert the control rods.
There are two kinds of nuclear power plants in the United States—boiling water reactors and pressurized water reactors. Inside a boiling water reactor, heat from the chain reaction boils the water and turns it to steam. The steam is piped from the reactor vessel directly to the turbine. The steam turns the turbine's propeller-like blades, which spins the shaft of a huge generator. Inside the generator, coils of wire and magnetic fields interact—and electricity is created.
In the pressurized water reactor, water is heated by the nuclear fuel, but is kept under pressure in the pressure vessel, so it will not boil. The water inside the pressure vessel is piped through separate tubing to a steam generator. The steam generator acts like a heat exchanger. There is a second supply of water inside the steam generator. Heated by the water from the pressure vessel, it boils to make steam for the turbine. Other reactor designs, which use helium gas rather than water to produce steam, are also under development and may eventually be built in the United States.
Nuclear power plants use a series of physical barriers to make sure radioactive material cannot escape. In today’s water-cooled reactors, the first barrier is the fuel itself: the solid ceramic uranium pellets. Most of the radioactive by-products of the fission process remain inside the pellets. The pellets are sealed in zirconium rods, 12 feet long and half an inch in diameter. The fuel rods are placed inside a large steel reactor vessel, with walls 8 inches thick. The vessel is surrounded by 3 feet of concrete shielding. At most plants, a leak-tight steel liner covers the inside walls of the containment building. The containment building is a massive, reinforced concrete structure with walls 4 feet thick.
nuclear power plant
Nuclear Power Plants
Nuclear Power Plant Turbine and Generator Spinning turbine blades and generator Boiling water Steam
Nuclear Energy Powers 1 in 5 U.S. Homes and Businesses