Download Fission and Fusion Power Point

Nuclear Reactions
AN INTRODUCTION TO
FISSION & FUSION
Farley Visitors Center
Matter and Energy

A basic law of science says that “matter and
energy cannot be created nor destroyed”.

We also need to understand that MATTER and
ENERGY are two forms of the same thing.
E = mc2

Matter can be changed into energy.

Einstein’s famous equation tells us E = mc2

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 fragments.

The fission fragments are generally in the form
of smaller atomic nuclei (called DAUGTHER
NUCLIDES) 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

A classic example of a fission reaction is that of U-235:
U-235 + 1 Neutron  Kr-92 + Ba-142 + 2 No + 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 and splits into two daughter nuclides.

Notice that more neutrons are released in the reaction. These neutrons
can then strike other U-235 atoms to initiate their fission.
Kr-92
No
No
Energy
U-235
No
Ba-142

Each fission can theoretically initiate TWO MORE.

1 fission  2 fissions  4 fissions  8 fissions 16 fissions…N number
of fissions. This is known as a CHAIN REACTION….the previous
occurrence initiates the next one.
Fission

Fission produces large amounts of heat energy and it is
this heat that is captured by nuclear power plants to
produce electricity.

In a nuclear power plant, the chain reaction is controlled
by inserting CADMIUM RODS into the reaction
chamber. These rods absorb some of the NEUTRONS
produced and slow the CHAIN REACTION so that it can
proceed at a CONTROLLED RATE.

In a NUCLEAR WEAPON, such as those used in WWII
in Japan, the reaction proceeds at an uncontrolled rate,
resulting in a massive release of energy.
Fusion

Fusion is a nuclear reaction whereby two light
atomic nuclei fuse or combine to form a single
larger, heavier nucleus.
H
Energy
He
H

Subatomic Particles

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 repulsive
charges of the nuclei and fuse them together.
Fusion

Unlike fission reactions, fusion reactions do not
occur naturally on our planet but are the
principal type of reaction found in stars.

The sun fuses hydrogen atoms to produce
helium, subatomic particles, and vast amounts
of energy.

The fusion reaction releases many times more
energy than an equivalent fission reaction.
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.

Nuclear Fusion
Quiz

Fission is a natural process that occurs
on the planet Earth.
A. True
B. False
Quiz

Explain this equation:
E = mc2