The Energy Story

  Energy Is Born
  Energy Types
  Energy Changes
  Energy Generation

The Energy Problem

  Conservation of Energy
  Aging of Energy
  Finite Resources
  The Oil "Crisis"
  Energy Pollution
  Discussion Topics

The Energy Solution

  Conserving Electricity
  Appliance Efficiency
  Heating Conservation
  Renewable Energy

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Teacher Guide

About the Author

Scret Lives Title - The Energy Story

agif - sun
The Ten Types
Nuclear Energy

There are two types of nuclear energy, fission and fusion. Both forms of energy are stored as mass in the atoms of certain elements. This mass can be changed into energy under the proper conditions according to Albert Einstein's famous equation:

E=mc Squared
where E = energy, m=mass, and c=speed of light

As you will see below, both types of nuclear energy can be stored, either in the atoms of hydrogen or the atoms of radioactive elements like uranium. Therefore, nuclear is a potential form of energy.


This leads us back to the beginning of the universe at the time of the big bang. Right after the big bang, the universe was so hot that it consisted entirely of energy. As the universe cooled, matter formed, mostly into hydrogen atoms and some helium atoms. Gravity pulled these atoms of hydrogen together forming the objects we find in the universe today, like galaxies and stars. Stars formed when enough hydrogen atoms got together so that gravity was able to compress them and heat them to extremely high temperatures. Under these conditions what are called nuclear reactions occur. One of the most common nuclear reactions is two hydrogen atoms combining to form one helium atom. During these nuclear reactions not only are new elements formed, but a tiny amount of mass (nuclear energy) is turned into energy. This energy, however, is substantial as you can see from Einstein's equation above. The energy is proportional to the speed of light SQUARED, and the speed of light is already a BIG number, 186,000 miles per second. The diagram below illustrates the most common nuclear reaction that turns hydrogen into helium and releases large amounts of energy.

fusion reaction graphic
(c) 2002 AJ Software & Multimedia
All Rights Reserved, used with permission

Nuclear reactions occur because the new elements are more stable than the original elements. Nuclear reactions can continue changing lighter elements into heavier elements up to the element oxygen. Elements heavier than oxygen are more stable and cannot be changed into heavier elements via nuclear reactions. This is one reason that elements heavier than helium are present in the universe today, these elements being manufactured in the middle of stars like our sun. So all of the carbon atoms that we are made of and all of the oxygen atoms we breathe were made in the nuclear reactions of stars a long time ago.

There are not a lot of different examples of fusion. Fusion occurs in the middle of stars, is used in the hydrogen bomb, and in some experimental laboratories trying to construct a fusion energy producing plant. The fuel for these experimental plants is hydrogen, which can easily be obtained from water.


Fission, the 2nd form of nuclear energy, is in a way the exact opposite of fusion. While in fusion atoms are "fused" together, in fission atoms are broken apart. While in fusion lighter elements form heavier elements, in fission heavier elements form lighter elements.

You might ask, if the universe started as almost totally hydrogen, and no elements heavier than oxygen can be produced by fusion reactions, where did all of the heavier elements come from? It turns out that when very large stars get done burning all of their hydrogen, helium, and elements up to oxygen, they tend to collapse. The huge gravitational forces pulling the star's matter inward is no longer held back by the burning of these nuclear fuels. The following explosion, called a supernova, causes a large part of the star to be blown into space and the high temperatures and pressure of the explosion cause the heavier elements to be produced.

Some of these heavier elements are radioactive, or not stable, and tend to break apart losing a small amount of mass and giving off energy in the form of light or radiation and heat. If these elements are purified and the fission reactor controlled properly, this nuclear energy can be extracted in a nuclear reactor. The most common nuclear fuel element is, of course, uranium. The diagram and animation below illustrate the fissioning of a uranium atom.

fission reaction graphic
(c) 2002 AJ Software & Multimedia
All Rights Reserved, used with permission

The animation below requires the Macromedia flash player. If you don't see the animation, you can download and install the flash player from the following site: Download Flash Player

Fission nuclear energy is much more common than fusion nuclear energy on the earth. Many of these radioactive elements can be found and mined. Fission nuclear reactors have become a major part of our civilization's energy supply.

For more information, check out the web sites listed below:

The Nuclear Age A movie gallery, including quick time movies of nuclear reactions.
The Reaction Fission and fusion animations.
Energy Story Chapter 7: Nuclear Energy - Fission and Fusion