Nuclear Reactions:
AN INTRODUCTION TO
FISSION & FUSION
Farley Visitors Center
Introduction

Nuclear reactions deal with interactions
between the nuclei of atoms

The focus of this presentation are the
processes of nuclear fission and nuclear fusion

Both fission and fusion processes deal with
matter and energy
Matter and Energy

Previous studies have taught us that “matter
and energy cannot be created nor destroyed”

We now need to understand that Matter and
Energy are two forms of the same thing
E = mc2

Matter can be changed into Energy

Einstein’s formula above tells us how the change
occurs

In the equation above:
E = Energy
m = Mass
c = Speed of Light (Universal Constant)
Energy
Mass
Light
Speed
E = mc2

The equation may be read as follows:
Energy (E) is equal to Mass (m) multiplied
by the Speed of Light (c) squared

This tells us that a small amount of mass can
be converted into a very large amount of
energy because the speed of light (c) is an
extremely large number
Fission

Fission may be defined as the process of
splitting an atomic nucleus into fission
fragments

The fission fragments are generally in the form
of smaller atomic nuclei and neutrons

Large amounts of energy are produced by the
fission process
Fission

Fissile nuclei are generally heavy atoms with
large numbers of nucleons

The nuclei of such heavy atoms are struck by
neutrons initiating the fission process

Fission occurs due to electrostatic repulsion
created by large numbers of protons within the
nuclei of heavy atoms
Fission

A classic example of a fission reaction is that of
U-235:
U-235 + 1 Neutron
2 Neutrons + Kr-92 + Ba-142 + Energy

In this example, a stray neutron strikes an atom of U-235.
It absorbs the neutron and becomes an unstable atom of
U-236. It then undergoes fission. Notice that more
neutrons are released in the reaction. These neutrons
can strike other U-235 atoms to initiate their fission.
Fission

The fission process is an a natural one as a
French researcher found a natural uranium
reactor in Gabon, West Africa; it has been
estimated to be over 2 billion years old

Fission produces large amounts of heat energy
and it is this heat that is captured by nuclear
power plants to produce electricity
Fusion

Fusion is a nuclear reaction whereby two light
atomic nuclei fuse or combine to form a single
larger, heavier nucleus

The fusion process generates tremendous
amounts of energy; refer back to Einstein’s
equation

For fusion to occur, a large amount of energy is
needed to overcome the electrical charges of
the nuclei and fuse them together
Fusion

Fusion reactions do not occur naturally on our
planet but are the principal type of reaction
found in stars

The large masses, densities, and high
temperatures of stars provide the initial
energies needed to fuel fusion reactions

The sun fuses hydrogen atoms to produce
helium, subatomic particles, and vast amounts
of energy
Review

Mass and Energy are two forms of the same
thing; neither can be created nor destroyed but
mass can be converted into energy (E = mc2)

Fission is a nuclear reaction in which a heavy
atomic nucleus is split into lighter atomic nuclei

Fusion is a nuclear reaction in which 2 light
atomic nuclei are combined into a single,
heavier atomic nucleus
Quiz

Which nuclear process produces large
amounts of energy?
A. Fission
B. Fusion
C. Both fission & fusion
D. Neither fission nor fusion
Quiz

Fission is the process that _________ atomic
nuclei.
A. Combines
B. Burns up
C. Stores
D. Splits
Quiz

Mass may be converted into energy.
A. True
B. False
Quiz

The fission process requires heavy
atomic nuclei.
A. True
B. False
Quiz

Name a nuclear reaction that occurs
within the sun:
Quiz

Fission is a natural process that occurs
on the planet Earth.
A. True
B. False
Quiz

Explain this equation:
E = mc2