College of Engineering
University of Wisconsin - Madison
University of Wisconsin Nuclear Reactor Tour
Nuclear Energy
Atoms are the building blocks from which matter is formed. Everything
around us is made up of atoms. Nuclear energy is contained within the center
of the atom in a place known as the nucleus.
Particles within the nucleus are held together by a strong force. If a
large nucleus is split apart (fission),
generous amounts of energy can be liberated. Small nuclei can also be combined
(fusion)
with an accompanying release of energy. Using this strong force that holds
the nucleus together to produce energy is essentially what the field of
nuclear power generation is about.
In the fission process certain heavy elements, such as some
forms of Uranium,
are split when a neutron
strikes them. When they split, they release energy in the form of kinetic
energy (heat) and radiation.
The process not only produces energy but also additional neutrons that
can be used to fission other Uranium nuclei and start a
chain
reaction. In fusion, nuclei of light elements are brought together under
conditions of high pressure and temperature, causing them to combine and
produce new elements and energy.
Fission
Fission is a nuclear reaction in which an atomic nucleus splits,
or fissions, into fragments, usually two fragments of comparable mass,
with the release of large amounts of energy in the form of heat and radiation.
In the UWNR, Uranium-235
is the fuel and it is struck by a moving neutron, which combines with the
U-235 to become U-236.
Because of the mass and energy imparted to the nucleus by the neutron,
the nucleus has enough energy to fission and breaks down into two (or more)
smaller nuclei and two or three new neutrons which together have less mass
than the original U-236 nucleus. This missing mass, sometimes known as
the mass defect, is changed into energy.
Fusion
Energy can also be produced by combining light nuclei in a process
is called nuclear fusion. As an energy source, fusion has several advantages
over fission: the light nuclei are plentiful and easy to obtain, and the
end products of fusion are usually light, stable nuclei rather than heavy
radioactive ones. There is one considerable disadvantage: before light
nuclei can be combined however, their mutual repulsion must be overcome
due to the fact that the positively charged protons
of the nuclei repulse each other. Because of this problem, fusion
reactors
are not yet producing electrical power. This is an area of great research
interest in the field of nuclear engineering and physics. We at the UWNR
do not perform fusion experiments, but if you would like some more information
on the fusion projects, click
here. (not part of tour)
