GCSE Physics revision

Nuclear fission

Nuclear fission and fusion (physics only)

AQA 4.4.4.1

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AQA student objectives

Learning pathway

ALL 🎯

Draw/interpret diagrams representing nuclear fission and how a chain reaction may occur.

MOST 🎯🎯

Interpret results or representations related to nuclear fission.

SOME 🎯🎯🎯

Analyse an unfamiliar problem involving nuclear fission and justify the method or conclusion.

Revision summary

Read on screen, then print for Cornell-style active revision.

Nuclear fission is the splitting of a large, unstable nucleus into two smaller nuclei called daughter nuclei, releasing large amounts of energy.
Fission can occur spontaneously (on its own) or by absorbing a neutron, which makes the nucleus even more unstable and causes it to split.
In practice, spontaneous fission is rare, so neutrons are used to trigger fission in nuclear reactors.

1. What is Nuclear Fission?AQA

Nuclear fission is the splitting of a large, unstable nucleus into two smaller nuclei called daughter nuclei, releasing large amounts of energy.
Fission can occur spontaneously (on its own) or by absorbing a neutron, which makes the nucleus even more unstable and causes it to split.
In practice, spontaneous fission is rare, so neutrons are used to trigger fission in nuclear reactors.

A slow-moving neutron is fired at a large unstable nucleus, such as uranium-235, causing it to become even more unstable.
The nucleus splits into two daughter nuclei and releases two or three additional neutrons along with energy in the form of gamma radiation.
The released neutrons can then go on to trigger further fission reactions in neighbouring uranium nuclei, continuing the process.

2. The Fission Process Step by StepAQA

A slow-moving neutron is fired at a large unstable nucleus, such as uranium-235, causing it to become even more unstable.
The nucleus splits into two daughter nuclei and releases two or three additional neutrons along with energy in the form of gamma radiation.
The released neutrons can then go on to trigger further fission reactions in neighbouring uranium nuclei, continuing the process.

Nuclear fission leads to a chain reaction, where each fission event releases neutrons that trigger further fission events in a self-sustaining cycle.
If the chain reaction is uncontrolled, it releases enormous amounts of energy very rapidly, which is the principle behind a nuclear bomb.
In nuclear reactors, the chain reaction must be carefully controlled to produce a steady and safe release of energy.

3. Chain ReactionsAQA

Nuclear fission leads to a chain reaction, where each fission event releases neutrons that trigger further fission events in a self-sustaining cycle.
If the chain reaction is uncontrolled, it releases enormous amounts of energy very rapidly, which is the principle behind a nuclear bomb.
In nuclear reactors, the chain reaction must be carefully controlled to produce a steady and safe release of energy.

Control rods are lowered into the reactor to absorb neutrons, slowing down the rate of fission and keeping the reaction under control.
The energy released from fission heats water, turning it into steam, which drives turbines connected to an electricity generator.
Common fuels used in nuclear reactors include uranium and plutonium.

4. How Nuclear Reactors WorkAQA

Control rods are lowered into the reactor to absorb neutrons, slowing down the rate of fission and keeping the reaction under control.
The energy released from fission heats water, turning it into steam, which drives turbines connected to an electricity generator.
Common fuels used in nuclear reactors include uranium and plutonium.

Uranium and plutonium fuel are relatively cheap and produce a large, steady amount of energy.
Nuclear power does not produce greenhouse gases, making it a cleaner energy source compared to fossil fuels.
Although not classified as a renewable energy source, nuclear power provides a reliable base-load supply of electricity.

5. Advantages of Nuclear EnergyAQA

Uranium and plutonium fuel are relatively cheap and produce a large, steady amount of energy.
Nuclear power does not produce greenhouse gases, making it a cleaner energy source compared to fossil fuels.
Although not classified as a renewable energy source, nuclear power provides a reliable base-load supply of electricity.

Nuclear power plants are very expensive to build and maintain.
Nuclear waste is hazardous and costly to dispose of safely, requiring burial in specially designed underground bunkers.
There is always a small risk of a major disaster if the plant malfunctions, which causes public concern about the safety of nuclear energy.

6. Disadvantages of Nuclear EnergyAQA

Nuclear power plants are very expensive to build and maintain.
Nuclear waste is hazardous and costly to dispose of safely, requiring burial in specially designed underground bunkers.
There is always a small risk of a major disaster if the plant malfunctions, which causes public concern about the safety of nuclear energy.