Transcript Fission, Fusion, and Nuclear Power

Nuclear Reactions:
AN INTRODUCTION TO
FISSION, FUSION, AND
NUCLEAR POWER
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)
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 notes

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 notes

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 notes

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 notes

The fission process is a natural one. 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 notes
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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 notes

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 notes

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
Nuclear reaction notes

Chain reaction occurs when a Uranium atom
splits

Different reactions
– Atomic Bomb in a split second
– Nuclear Power Reactor more controlled,
cannot explode like a bomb
History of nuclear power
1938– Scientists study Uranium nucleus
1941 – Manhattan Project begins
1942 – Controlled nuclear chain reaction
1945 – U.S. uses two atomic bombs on Japan
1949 – Soviets develop atomic bomb
1952 – U.S. tests hydrogen bomb
1955 – First U.S. nuclear submarine
“Atoms for Peace”
Program to justify nuclear technology
Proposals for power, canal-building, exports
First commercial power plant, England 1956
Economic advantages notes

The energy in one pound of highly
enriched Uranium is comparable to that
of one million gallons of gasoline.

One million times as much energy in
one pound of Uranium as in one pound
of coal.
Emissions Free notes
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Nuclear energy annually prevents
– 5.1 million tons of sulfur
– 2.4 million tons of nitrogen oxide
– 164 metric tons of carbon

Nuclear often pitted against fossil fuels
– Some coal contains radioactivity
– Nuclear plants have released low-level
radiation
Nuclear Power Plants
Nuclear power around the globe

17% of world’s electricity from nuclear power
– U.S. about 20% (2nd largest source)

431 nuclear plants in 31 countries
– 103 of them in the U.S.
– Built none since 1970s (Wisconsin as leader).
– U.S. firms have exported nukes.
– Push from Bush/Cheney for new nukes.
Countries Generating Nuclear Power
Country
USA
France
Japan
Germany
Russia
Canada
Ukraine
United Kingdom
Sweden
South Korea
Total MW
99,784
58,493
38,875
22,657
19,843
15,755
12,679
11,720
10,002
8,170
Technology depends on operators
Nuclear Reactor Process
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3% enriched Uranium pellets formed into rods,
which are formed into bundles

Bundles submerged in water coolant inside
pressure vessel, with control rods.

Bundles must be SUPERCRITICAL; will overheat
and melt if no control rods. Reaction converts water
to steam, which powers steam turbine
Nuclear Reactor Structure
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Reactor’s pressure vessel typically
housed in 8” of steel
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36” concrete shielding
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45” steel reinforced concrete
Back end: Radioactive waste

Low-level wastes in commercial facilities
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Spent fuel in pools or “dry casks” by plants

Nuclear lab wastes
– Hanford wastes leaked radiation into Columbia
River

High-level underground repository
– Yucca Mountain in Nevada to 2037
– Wolf River Batholith in Wisconsin after 2037?
– Risks of cracks in bedrock, water seepage
Yucca Mountain
Radioactive Waste Recycling

Disposal of radioactive waste from nuclear
power plants and weapons facilities by
recycling it into household products.

In 1996, 15,000 tons of metal were received
by the Association of Radioactive Metal
Recyclers . Much was recycled into products
without consumer knowledge.
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Depleted Uranium munitions for military.
Summary notes
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Nuclear energy has no typical pollutants
or greenhouse gasses

Nuclear waste contains high levels of
radioactive waste, which are active for
hundreds of thousands of years.

The controversy around nuclear energy
stems from all parts of the nuclear
chain.