Objectives
Nuclear Fission
Be able to describe what nuclear
fission is and what a chain reaction is
09 April 2015
10 MINUTES!!
Copy the objectives then read the passage and answer the questions.
Nuclear fission is the process of splitting atoms, or fissioning them. Before
we talk about that, however, I would like to discuss marbles. Everyone's
played with marbles at one time or another, right? Well, imagine about 200
marbles lying on a flat surface, all jumbled together, and roughly forming a
circle. What would happen if someone took another marble and threw it at
them? They would fly all around in different directions and groups, right?
That is exactly what happens in nuclear fission. The filled circle is like an
atom's nucleus. The marble being thrown is like a "neutron bullet". The
only differences are that the marbles are protons and neutrons and the
protons and neutrons aren't in a filled circle, but in the actual atom are in
the shape of a sphere. Of course, an atom is also a bit more complicated
than a pack of marbles.
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Describe what the bold words mean.
Why does it talk about marbles?
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Outcomes
• All students should be able to describe
what a fission reaction and chain reaction
is.
• Most students should be able to describe
how a fission reactor works and how it is
kept safe.
• Some students should be able to describe
the dangers of nuclear and evaluate
models to describe chain reactions, come
up with their own and argue why we
should or should not use nuclear power.
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What is nuclear fission?
Nuclear fission occurs when a stable isotope is struck by a
neutron. The isotope absorbs the neutron, becomes unstable
and then splits apart, releasing large amounts of energy.
Unlike natural radioactive decay,
fission is not a natural event.
Isotopes that undergo fission include
uranium-235 and plutonium-239.
These isotopes can both be used
in nuclear reactors and in nuclear
weapons.
The fission of 1 kilogram of uranium-235
releases more energy than burning
2 million kilograms of coal!
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Fission
• Introduction into Nuclear Fission
• http://www.youtube.com/watch?v=N7C14
UIKuv8
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What happens in nuclear fission?
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How does nuclear power work?
http://www.youtube.com/watch?v=cnjGYHOePu0
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What’s a chain reaction?
• When one action creates a chain that makes
other actions occur without further stimulus:
• Dominoes
• FIRE:
http://www.youtube.com/watch?v=FQGtpo2IUxA&feature=fvwrel
• PING PONG?
http://www.youtube.com/watch?v=0v8i4v1mieU
• Evaluate: Which model is best to
describe a nuclear chain reaction?
Why?
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What is a chain reaction?
Nuclear fission results in a chain reaction
because each time a nucleus splits it
releases more neutrons, which can
go on and cause more fission
reactions to occur...
and so on.
+
This is why a chain reaction
releases a lot of energy so rapidly.
If a chain reaction is uncontrolled, heat
builds up very quickly. A chain reaction must
be controlled to maintain a steady output of heat.
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What happens in a chain reaction?
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How are neutrons controlled?
For nuclear fission to start in a reactor, a uranium-235 atom
must absorb a low speed neutron. High speed neutrons
are not as readily absorbed by uranium nuclei.
water
However, high speed neutrons
carrying
are released during fission.
away
heat
The reactor’s graphite core
slows down the released
neutrons so the chain
reaction can keep going.
Control rods made of boron
absorb excess neutrons to
prevent chain reactions
getting out of control.
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control
rod
fuel
rod
graphite
core
© Boardworks Ltd 2007
Nuclear Fission
• Task:
• Summarise the 5 most
important points from the
information given to you.
• You MUST describe
what a fission reaction
and draw what a chain
reaction is.
• You SHOULD describe
how a fission reactor
works and how it is kept
safe.
• You COULD describe
the dangers of nuclear.
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concrete
water
carrying
away
heat
control
rod
fuel
rod
graphite
core
© Boardworks Ltd 2007
Review and Revise
• Self Assess
• You MUST describe what a fission
reaction and chain reaction is.
• You SHOULD describe how a fission
reactor works and how it is kept safe.
• You COULD describe the dangers of
nuclear.
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Pros and cons of using nuclear fission
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Review
Independent
Enquirer
Creative Thinker
• All students should be able to describe
what a fission reaction and chain
reaction is.
• Most students should be able to
describe how a fission reactor works
and how it is kept safe.
• Some students should be able to
describe the dangers of nuclear and
evaluate models to describe chain
reactions, come up with their own and
argue why we should or should not
Reflective Learner
use nuclear power.
Team Worker
• Describe which
Effective Participator outcomes you have met
today and what skills
you have used to
achieve them.
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Self Manager
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Wordsplat/Bingo
Fission
Neutron
Turbine
Control Rod
Uranium
Nucleus
Chain
Reaction
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Fusion
Plutonium
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Wordsplat/Bingo
Fission
Uranium
Chain
Reaction
Plutonium
Neutron
Nucleus
Turbine
Fusion
Control Rod
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Wordsplat/Bingo
Fusion
Uranium
Nucleus
Fission
Neutron
Chain
Reaction
Plutonium
Turbine
Control Rod
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