Nuclear Fusion - St Edmund's Girls' Schoolst-edmunds.eu/wp-content/uploads/Nuclear-Fusion.pdf · 4...
Transcript of Nuclear Fusion - St Edmund's Girls' Schoolst-edmunds.eu/wp-content/uploads/Nuclear-Fusion.pdf · 4...
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Nuclear Fusion
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Fission involves splitting
atomic nuclei, releasing
some of the enormous
energy they contain.
How do we get energy from atoms?
Fusion involves bringing two hydrogen atoms close
enough together to make them fuse to form helium.
Energy is produced from atoms in power stations using
the process of nuclear fission.
nucleus
electronsEnergy can also be released by
joining two small nuclei together
to form a larger one in a process
called nuclear fusion.
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Nuclear fusion is the process that powers the Sun and
other stars.
What is nuclear fusion?
A worldwide research programme is being carried out
to find ways in which nuclear fusion could be harnessed
on Earth as a clean and plentiful source of energy.
In this process, small nuclei
join together to form larger
nuclei and energy is released.
In the Sun’s core, at
temperatures of 15 million °C,
hydrogen nuclei fuse to form
helium nuclei and release
vast amounts of energy.
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What happens in nuclear fusion?
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In nuclear fusion, small nuclei fuse together to form larger
nuclei and energy is released.
What are the conditions for nuclear fusion?
Nuclear fusion happens all the time in stars at very high
pressures and temperatures. These conditions overcome
repulsive forces between the nuclei and force them together.
+ +
tritiumdeuterium helium neutronfusion + +
Scientists have found it difficult to create the extreme
conditions needed to carry out nuclear fusion on Earth.
H2
1+ H3
1 H4
2n1
0+
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Fusion – true or false?
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Why is fusion so difficult?
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Fusion in stars
In a star like our Sun, fusion
reactions happen easily.
gravity
pressure
Because the Sun is very large, its
gravity is very powerful and provides
the pressure and temperature
required for sustained fusion.
On Earth, scientists need to
recreate the pressure and
temperature required in other
ways, e.g. using magnetic fields.
Creating and safely containing such high temperature
and pressure environments is very difficult, and also
very expensive.
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The largest nuclear fusion experimental reactor is JET
(Joint European Torus) in Culham, Oxfordshire.
What does a fusion reactor look like?
Fusion on Earth
requires temperatures
about six times hotter
than the Sun’s core.
The reactor is most efficient as a doughnut shape.
This vessel uses a
magnetic field to trap
super-hot hydrogen,
which has changed
from a gas into a
high-energy plasma.
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In a fusion power station, the hydrogen plasma will be
‘squeezed’ to produce helium and high energy neutrons.
How will a fusion power station work?
The energy of the neutrons will then be transferred by a
water cooling loop to a heat exchanger to make steam.
heat exchanger
Then, like fossil fuel and fission power stations, the steam
will drive turbines to produce electricity.
It is hoped that the first fusion power station will be ready
and working by about 2045.
turbines
generatorplasma
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Successful fusion reactions on Earth
There are many technical
barriers to overcome,
however, if fusion is to be
used to as an energy
source in the future.
Fusion has been carried
out successfully on earth
since the 1950s.
Hydrogen bombs (H-bombs)
use the fission of uranium to
heat the hydrogen to the
temperatures needed for it
to undergo fusion.
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Nuclear fusion in the future
Could nuclear fusion help solve energy problems on Earth?
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There are many advantages to using fusion energy:
Why use nuclear fusion?
Abundant fuels – Deuterium can be extracted from water
and tritium is made from lithium, which is readily available.
Clean – No greenhouse or other polluting gases are made.
No weapons material produced – The products are
not suitable for making nuclear weapons.
Safe – No need to keep chain reactions under control.
Less radioactive waste – The products of nuclear fusion
are not radioactive, although the reactor walls will absorb
neutrons and become radioactive.
Small amounts of fuel – 10 grams of deuterium and
15 grams of tritium could produce enough energy for the
lifetime of an average person in an industrialized country.
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Pros and cons of using nuclear fusion
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‘Cold fusion’
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Validating scientific discoveries
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Fusion research
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Glossary
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Comparing nuclear fission and fusion
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Multiple-choice quiz