nuclear fusion - st edmund's girls'...

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Nuclear Fusion


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.


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.


What happens in nuclear fusion?


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+


Fusion – true or false?


Why is fusion so difficult?


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.


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.


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


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.


Nuclear fusion in the future

Could nuclear fusion help solve energy problems on Earth?


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.


Pros and cons of using nuclear fusion


‘Cold fusion’


Validating scientific discoveries


Fusion research


Glossary


Comparing nuclear fission and fusion


Multiple-choice quiz

nuclear fusion - st edmund's girls'...

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