What does a moderator do in a nuclear reactor GCSE?

The moderator material is generally graphite or water. These materials do not absorb or react with the neutrons, they simply act to slow down fast moving neutrons. If neutrons are moving too quickly they are not captured by Uranium nuclei and the chain reaction stops. Once they are moving at the correct speed they will be captured by Uranium nuclei and the chain reaction can continue.It is important to note that the moderator in a nuclear fission reactor is not the same as the control rods. Both the moderator and the control rods can be used to change and maintain the rate of the chain reaction within the reactor. But the control rods are used to absorb neutrons, reducing the number of neutrons available for further chain reactions. Whilst the moderator is installed to slow down neutrons, making them more likely to be captured by Uranian nuclei, increasing the rate of chain reactions.

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What do moderators do in a nuclear reactor?
What does a moderator do BBC Bitesize?
What does a moderator do in a nuclear reactor BBC?
How does a nuclear reactor work GCSE?

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Radioactivity

Nuclear Power. The Moderator and Control Rods.

Fission causes a chain reaction in the core of a nuclear reactor.

The speed of the chain reaction must be controlled
because the ever increasing numbers of splitting nuclei
will very quickly release a large amount of heat energy
and this would cause the nuclear reactor to explode.

The moderator and control rods together
control the rate of reaction in the core of the nuclear reactor.

What is the Moderator in a Nuclear Reactor?

The moderator is a material which slows down the speed
of the neutrons. The moderator is
usually made from water but some reactors use graphite.

Neutrons released from the chain reaction must be moving
at the right speed for other atoms of uranium to capture them.
If the neutrons are moving too fast then they do not get
captured by the nucleus of another uranium atom and the chain
reaction stops. The moderator slows the neutrons down
so that they can be captured and keep the chain reaction going.

What are the Control Rods in a Nuclear Reactor?

The control rods prevent the chain reaction happening too quickly.
Some control rods are made from an alloy of silver and cadmium.
Some are made from boron mixed with iron or carbon. The control
rods are very good at absorbing neutrons. They reduce
the number of neutrons available to continue the chain reaction.

The control rods can be moved up and down inside the reactor core.
As they are lifted up and out of the reactor, the less neutrons they absorb,
the fasterthe chain reaction happens and the reactor gets hotter.
The heat is then used to generate electricity. The further down
the control rods go, the more neutrons they absorb,
the slower the chain reaction happens and the reactor gets colder.
The control rods can used to shut the reactor down completely.

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What do moderators do in a nuclear reactor?

A material, such as ordinary water, heavy water, or graphite, that is used in a reactor to slow down high-velocity neutrons, thus increasing the likelihood of fission.

What does a moderator do BBC Bitesize?

A graphite core moderator - slows the neutrons down so that they are more likely to be absorbed by the U-235 nuclei in the fuel rods. Control rods - these can absorb neutrons so that for every 2 or 3 neutrons that are released from a fission reaction, only 1 goes on to produce further fission.

What does a moderator do in a nuclear reactor BBC?

The moderator and control rods together control the rate of reaction in the core of the nuclear reactor. Most nuclear reactors use water as a moderator, which can also act as a coolant, although some do use graphite rods.

How does a nuclear reactor work GCSE?

In a nuclear reactor , a neutron is absorbed into a nucleus (typically uranium-235). This causes the nucleus to become uranium-236, which is violently unstable. The entire nucleus splits into two large fragments called 'daughter nuclei '.