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:
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.
Fusion
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 hour. The diagram below illustrates
the most common nuclear reaction that turns hydrogen into
helium and releases large amounts of energy.
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
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.
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
Created by Tom Chandler, OME Educator
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 site listed below:
