HeaderTable of Contents

  1. What is nuclear energy?
  2. What is nuclear energy used for?
  3. Where does uranium come from?
  4. What countries use nuclear energy?
  5. How harmful is nuclear energy to the environment?
  6. What is the outlook for nuclear energy?
  7. Data
    • Generation
    • Capacity



1.  What is nuclear energy?

Energy is released when the bonds that hold together the nucleus of an atom are broken. That energy can be used to generate electricity.  There are two ways that the bonds of an atom’s nucleus can be broken:  nuclear fusion and nuclear fission.

Nuclear fusion:  In nuclear fusion, energy is released when atoms are combined or fused together to form a larger atom. This is how the sun produces energy. Fusion is the subject of ongoing research, but it is not yet clear that it will ever be a commercially viable technology for electricity generation.Fission

Nuclear fission:  In nuclear fission, atoms are split apart to form smaller atoms, releasing energy. Nuclear power plants use this energy to produce electricity.


The fuel most widely used by nuclear plants for nuclear fission is uranium. Uranium is a common metal found in rocks all over the world. Nuclear plants use a certain kind of uranium, referred to as U-235. This kind of uranium is used as fuel because its atoms are easily split apart. Though uranium is quite common, about 100 times more common than silver, U-235 is relatively rare.

Most U.S. uranium is mined in the Western United States. Once uranium is mined, the U-235 must be extracted and processed before it can be used as a fuel.

During nuclear fission, a small particle called a neutron hits the uranium atom and splits it, releasing a great amount of energy as heat and radiation. More neutrons are also released. These neutrons go on to bombard other uranium atoms, and the process repeats itself over and over again. This is called a chain reaction.



Learn more


2.  What is nuclear energy used for?

Nuclear power is only used to generate electricity, unlike oil, natural gas, and coal that can be used for other purposes, e.g. transportation fuel, production input.  Nuclear power plants generate electricity by harnessing the energy released during nuclear fission to boil water and create steam that spins large turbines that generate electricity.  Just like other power plants burn coal or natural gas to boil water and create steam, nuclear power plants unlock the energy in Uranium atoms to do the same thing.

At the center of a nuclear reactor, where nuclear fission takes place, is the core that contains the uranium fuel. The uranium fuel is formed into ceramic pellets. The pellets are about the size of your fingertip, but each one produces roughly the same amount of energy as 150 gallons of oil. These energy-rich pellets are stacked end-to-end in 12-foot metal fuel rods. A bundle of fuel rods, sometimes hundreds, is called a fuel assembly. A reactor core contains many fuel assemblies.

The United States has 65 nuclear power plants with 104 nuclear reactors. Thirty-six of the plants have two or more reactors. Nuclear power plants are located in 31 different states but most are located east of the Mississippi. Nuclear power has generated about one-fifth of U.S. electricity each year since 1990.

In February 2012, the U.S. Nuclear Regulatory Commission voted to approve Southern Company’s application to build and operate two new nuclear reactors – Units 3 and 4 at its Vogtle plant. The Vogtle units are the first reactors to receive construction approval in over 30 years, and are expected to be operational in 2016 and 2017. The last new reactor to enter commercial service was the Tennessee Valley Authority’s (TVA) Watts Bar 1 in Tennessee in 1996.


3.  Where does uranium come from?

Owners and operators of U.S. civilian nuclear power reactors purchased the equivalent of 58 million pounds of uranium during 2011. Uranium delivered to U.S. reactors in 2011 came from six continents:

  • 9% of delivered uranium came from the United States
  • 91% of delivered uranium was of foreign-origin:
    • 40% originated in Kazakhstan, Russia and Uzbekistan
    • 31% was from Australia and Canada
    • 20% came from Namibia, Niger, and other countries


4.  What countries use nuclear energy?

The United States has more nuclear capacity and generates more electricity from nuclear power than any other nation. However, the United States is not as reliant on nuclear power as a share of total electricity generation as some other countries. France, the country with the second most nuclear capacity, relies on nuclear power for nearly 80% of its electricity. Other countries that get a significant share of their electricity from nuclear power include Russia, Japan, South Korea, and Germany.


5.  How harmful is nuclear energy to the environment?

The main environmental concerns for nuclear power are radioactive wastes such as uranium mill tailings, spent (used) reactor fuel, and other radioactive wastes. These materials can remain radioactive and dangerous to human health for thousands of years. They are subject to special regulations that govern their handling, transportation, storage, and disposal to protect human health and the environment. The U.S. Nuclear Regulatory Commission regulates the operation of nuclear power plants.

The radioactivity of nuclear waste decreases with the passage of time through a process called radioactive decay. The amount of time necessary to decrease the radioactivity of radioactive material to one-half the original level is called the radioactive half-life of the material.

Radioactive wastes are classified as low-level and high-level.  By volume, most of the waste related to the nuclear power industry has a relatively low-level of radioactivity. Low-level radioactive wastes includes uranium mill tailings, tools, protective clothing, wiping cloths, and other disposable items that get contaminated with small amounts of radioactive dust or particles at nuclear fuel processing facilities and power plants. High-level radioactive waste consists of “irradiated” or used nuclear reactor fuel (i.e., fuel that has been used in a reactor to produce electricity). The used reactor fuel is in a solid form consisting of small fuel pellets in long metal tubes.

Spent reactor fuel assemblies are highly radioactive and must initially be stored in specially designed pools resembling large swimming pools, where water cools the fuel and acts as a radiation shield, or in specially designed dry storage containers. An increasing number of reactor operators now store their older spent fuel in dry storage facilities using special outdoor concrete or steel containers with air cooling. There is currently no permanent disposal facility in the United States for high-level nuclear waste. High-level waste is being stored at nuclear plants.

When a nuclear power plant stops operating, the facility must be decommissioned. This involves safely removing the plant from service and reducing radioactivity to a level that permits other uses of the property. The Nuclear Regulatory Commission has strict rules governing nuclear power plant decommissioning that involve cleanup of radioactively contaminated plant systems and structures, and removal of the radioactive fuel.

An uncontrolled nuclear reaction in a nuclear reactor can potentially result in widespread contamination of air and water with radioactivity for hundreds of miles around a reactor. The risk of this happening at nuclear power plants in the United States is considered to be very small due to the diverse and redundant barriers and numerous safety systems at nuclear power plants, the training and skills of the reactor operators, testing and maintenance activities, and the regulatory requirements and oversight of the Nuclear Regulatory Commission. A large area surrounding nuclear power plants is restricted and guarded by armed security teams. U.S. reactors have containment vessels that are designed to withstand extreme weather events and earthquakes.


Learn more


6.  What is the outlook for nuclear energy?

While there is an enthusiasm for nuclear energy because it does not produce greenhouse gases that cause climate change, the threat of nuclear disasters diminishes its popularity.  Especially with the recent Fukushima nuclear disaster in Japan, few countries are interested in pursuing new nuclear energy projects.  Nonetheless in 2012 the U.S. Nuclear Regulatory Commission did approve the Vogtle plant.


 7.  Data

  • Generation

Generation - World - Graph

Generation - Country - Graph

Generation - Table


  • Capacity

Capacity - World - Graph

Capacity - Country - Graph

Capacity - Table


**The information on this website was obtained from various pages of the U.S. Department of Energy website ( and the U.S. Environmental Protection Agency website (  The data on this website was obtained from various pages of the U.S. Energy Information Administration website (  Please consult those websites for further information.