Electricity Education - Nuclear
How Important is Nuclear Power?
According to the Nuclear Energy Institute (www.nei.org), about 20% of the United States' electricity comes from nuclear power plants. There are 103 commercial nuclear reactors with operating licenses at 64 sites in 31 states. Most of these are found in the eastern half of the US. The newest plant is Watts Bar 1, built in Tennessee in 1996. The oldest operating plant is Nine Mile 1, built in New York in 1969.
In 2002, 20.2% of the electricity generated in the US came from nuclear reactors. This amounted to 780.2 billion kilowatt-hours (KWh). Only a tiny part of this, 27,346,163 megawatt hours (MWh) was generated in Virginia. Virginia has four commercial nuclear reactors: North Anna 1, North Anna 2, Surry 1 and Surry 2.
Generation from nuclear power has generally increased since the 1950s, and this trend continues. Since 1984, nuclear plants have provided the second largest share of total U.S. electric utility generation of electricity, after coal-fired plants.
How a Nuclear Power Plant Works
Nothing is burned or exploded in a nuclear power plant. Rather, the uranium fuel generates heat through a process called fission. In this process, the nucleus of a heavy element, such as uranium, splits when bombarded by a free neutron in a nuclear reactor. With uranium atoms, this yields two smaller atoms, one to three free neutrons, plus energy. Because more free neutrons are released during uranium fission than are required to initiate it, the reaction can become self-sustaining-a chain reaction.
Rods inserted among the tubes holding the fuel control the nuclear reaction. These control rods are made of a material that absorbs neutrons and prevents them from hitting atoms that can fission. That way, the nuclear reaction can be sped up or slowed down by varying the number of control rods withdrawn and the extent that they are withdrawn. When atoms split, heat energy is produced.
The heat boils water, creating steam. The steam or water turns a turbine, which spins the shaft of a generator. Inside the generator, coils of wire spin in a magnetic field and electricity is produced. The steam condenses and changes back to water, and then is returned to the generator to be heated again, producing more steam. The white cloud you can see coming out of the top of a nuclear power plant isn't radioactive-it's just steam rising from the cooling tower.
See a Macromedia Flash Animation of how a Nuclear Power Plant Works
Nuclear power has unique advantages thanks to its fuel source-uranium. Uranium has huge energy potential compared with fossil fuels like coal and oil. When uranium is used in a Magnox reactor, a 10-kilogram fuel element produces enough energy to generate electricity equal to burning 150 tons of coal.
The uranium is formed into ceramic pellets about the size of the end of your finger. These pellets are inserted into long, vertical tubes within the reactor.
Nuclear fuel is a solid material containing two kinds, or isotopes, of uranium atoms. One isotope - U-235 - makes up less than one percent of natural uranium but fissions readily. The other isotope - U-238 - makes up most of natural uranium but is practically non-fissionable.
Through a process known as "enrichment," the concentration of U-235 in the uranium is increased to three or four percent. Enrichment allows the reactor to be smaller than it would be if fueled with natural uranium. The concentration of U-235 is so low that a bomb-like nuclear explosion is impossible.
Nuclear power plants produce two types of radioactive waste: high-level and low-level. Nearly all high-level waste is used fuel. Low-level waste includes such things as protective clothing, tools and equipment that may contain small amounts of radioactive material. Used fuel is handled by remote control and safely stored inside the plant in steel-lined, concrete pools filled with water or on the plant property in huge steel-lined, concrete containers. Low-level waste can be shipped to a disposal facility or stored at the plant.
Used nuclear fuel is safely stored at the nation's nuclear power plants. But the plant storage facilities are only temporary. They're not designed to be permanent. The ideal permanent disposal for used nuclear fuel is deep underground in a network of tunnels that safely isolates the used fuel from people and the environment. Special containers are used to ship the used fuel from the plant to a repository. Before the Nuclear Regulatory Commission approved their designs, containers must be subjected to crash and fire tests. Used nuclear fuel has been transported without harm to people or the environment for over 30 years.
Nuclear generating plants are normally very clean. They do not produce CO2 and only produce tiny amounts of other air pollutants.