Nuclear Energy

Nuclear energy by definition is the energy
consumed or produced in modifying the
composition of the atomic nucleus. Nuclear energy
is used for things such as atomic bombs, hydrogen
bombs and other nuclear weapons. Nuclear
energy can also be used for powering
electricity-generating plants all over the world.
There are many arguments for and against nuclear
power. Nuclear power is an inexpensive clean
source of power. Others feel that because of the
hazardous radiation emitted during the producing
of the power and the radioactivity of the material
used that nuclear power is not as good as the
alternatives which are fossil fuels and solar
power.(Hansen, 1993)

If matter changes state or composition, it is
accompanied by the production of energy.
Processes such as combustion produce energy by
rearranging the atoms or molecules of that
substance.(Brain, 1998) An example of this is the
combustion of methane (natural gas)

CH(4) + 2O(2) = CO(2) + 2H(2)O + energy

In this example the amount of energy released is
eight electron volts or 8 eV. The electron volt unit
is the unit used by nuclear physicists. The electron
volt represents the gain in kinetic energy when an
electron is accelerated through a potential drop of
one volt.(Brain, 1998)

The most common nuclear reaction is nuclear
fission. Nuclear fission is the process in which a
heavy nucleus combines with a neutron and
separates the heavy nucleus into two lighter
nuclei.(Roy, 1993) The most typical fission
reaction is that of uranium-235 it is as follows:

92 U235 + 1 neutron = 38 Sr96 + 54 XE138 + 2
neutrons + energy

Another type of nuclear reaction is nuclear fusion.
Nuclear fusion occurs when two light elements
combine to form a heavier atom.(Grisham, 1993)
An example of this is:

1 H(2) + 1 H(3) = 2 He(4) +1 neutron + energy



Nuclear Fission

Nuclear fission is a complex process, but many
products are formed during this process. Not only
the two nuclei but also neutrons, beta particles,
neutrinos and gamma rays are created during the
fission process.(Roy, 1993) There are more than
fifty different ways a nucleus may undergo fission.
Some of the ways are much more common than
others. During the fission process the nucleus
breaks into to unequal parts, one lighter fragment
and a heavier fragment. These nuclei are formed
with excess energy that they do not usually have in
their ground state they must lose the extra energy.
They release this extra energy in the form of
gamma radiation or sometimes neutron emission.
The primary fragments are rich in neutrons and are
radioactive. Uranium-235 which contains 92
protons and 143 neutrons are more likely to under
go fission when bombarded by low-energy
neutrons.(Hansen, 1993)



Nuclear Fission Used in Bombs

The fission process was discovered in the late
1930s. In late 1939 two scientists Otto Frisch and
Lise Meitner discovered the fissioning of uranium
into lighter particles while they were doing an
experiment involving neutron irradiation of
uranium. The possibility of a self-sustaining chain
reaction was apparent this caused an accelerated
rate of research.(Hansen, 1993)

The United States Government researched into the
possible applications of nuclear fission at the
beginning of World War II. In order for the
weapon to be able to work properly it would
require a self-sustaining fission reaction to be
created and also that an adequate amount of
fissionable material could be produced for use in a
weapon.(Brain, 1998) On December 2, 1942 at
the University of Chicago Enrico Fermi and his
team developed the worlds first self-sustaining
reactors. The reactor was fueled with natural
uranium imbedded in graphite blocks.(Hansen,
1993) The fission occurred in the isotope of
uranium, U-235. An important factor in
developing the nuclear bomb was to separate
U-235 from U-238. Natural uranium only contains
0.7% of U-235 and the remaining 99.3% of
natural uranium is U-238. The problem with this is
that U-238 does not fission except with very high
energy neutrons which are not available from the
fission process. To separate the two materials
gaseous defusion is used. Another way of making
nuclear weapons is to use a different fissionable
nucleus. Another material that is used is a synthetic
isotope of plutonium P-239.



Nuclear Fusion

In most fusion reactions after the two atomic nuclei
merge together to form a heavier nucleus a free
nucleon is also formed. In just about all fusion
reactions between light nuclei, a portion of their
rest mass is converted into kinetic energy of the
reaction products, or into gamma rays.(Grisham,
1993) The kinetic energy and gamma rays that are
released in the process of fusion, heat the inside
keeping the temperature very high so the fusion
can continue occurring. At thermonuclear
temperatures, matter can only exist in the plasma
state. Matter at thermonuclear temperature
consists of electrons, positive ions and very few
neutral atoms. If fusion reactions occur within
plasma the reactions heat the substance even
more, because a portion