Fission and Fusion
Atomic Fission
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Nuclear fission occurs when a heavy
nucleus such as U-235 splits into two
smaller nuclei.
The total rest mass of the products is less
than the original rest mass.
The mass difference is converted to the
energy released using e=mc2
This process occurs naturally at a slow
rate, but can be accelerated by neutron
bombardment in the laboratory.
Neutron Bombardment of U-235

U  n U
235
92
1
0
236
92

U  X  Y  neutrons
236
92

U  Ba  Kr 3 n
236
92
141
56
92
36
1
0
U-235 absorbs a
slow moving
neutron.
U-236 is unstable
and lasts for only
10-12 s.
The U-236 nucleus
splits into two
fragments and
emits several
neutrons.
Nuclear Fusion
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Lighter nuclei undergo a process called
nuclear fusion
Fusion takes a great amount of energy to
be initiated in order to overcome the
proton-proton barrier between nuclei.
However, a greater amount of energy is
released in the process.
Stars produce their energy through the
fusion process.
Fusion Process
1
1
H  H  H  e 

H  H  He  

1
1
1
1
1
1
2
1
2
1
0
1
3
2
H  He He  e 
3
2
4
2

0
1

3
2
He  He He  H  H
3
2
4
2
1
1
1
1
Hydrogen is fused
together forming
deuterium.
He-3 is formed
from hydrogen
isotopes.
He-4 is formed
through 2 different
processes.
The energy is
produced though
the gamma,
neutrino, and
positron emission.
Nuclear Power Plants USA
Nuclear Facts
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Nuclear energy is energy that is released
either by splitting atomic nuclei or by
forcing the nuclei of atoms together.
Nuclear energy comes from mass-toenergy conversions that occur in the
splitting of atoms.
Nuclear energy is produced by a controlled
nuclear chain reaction and creates heat—
which is used to boil water, produce
steam, and drive a steam turbine.
Nuclear Facts

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Nuclear power can come from the fission
of uranium, plutonium or thorium or the
fusion of hydrogen into helium. Today it is
almost all uranium.
Nuclear power plants need less fuel than
ones which burn fossil fuels. One ton of
uranium produces more energy than is
produced by several million tons of coal or
several million barrels of oil.
Nuclear Facts
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In France, nuclear power is the most
widespread, supplying 80 percent of the
country's electricity.
As of 2004, nuclear power provided 6.5% of the
world's energy and 15.7% of the world's
electricity, with the U.S., France, and Japan
together accounting for 57% of nuclear
generated electricity.
Nuclear energy (nuclear power) accounts for
about 19 percent of the total electricity
generated in the United States.
Why Not?
Basic Components Nuclear Plant
Are You Exposed?
Yearly Dosage of Radiation
Limiting Exposure
Homework
Pg
695-696 [34-42]