AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
Nuclear fission: Energy is released by the fission reaction.
Every fission event transfers energy from the nuclear store of the fuel.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 4 of 9
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Every fission event transfers energy from the nuclear store of the fuel. The energy is not created; it is released because the products together are more stable than the original heavy nucleus, so the mass of the products is very slightly less than that of the nucleus and the neutron that started it. That missing mass appears as energy. Per atom this is roughly a million times more than any chemical reaction such as burning coal, which is why a small mass of fuel runs a power station for a long time. The power output depends on the number of fissions per second, so controlling how many neutrons go on to cause further fissions is exactly how the output of a reactor is controlled.
What earns the marks
- Energy being released by each fission event.
- The energy coming from the nucleus rather than from a chemical reaction.
- The energy released being carried mostly as kinetic energy of the fission products.
- Linking the number of fissions per second to the power output of the reactor.
Common mistakes and how to put them right
Writing that energy is created by fission.
Saying the energy comes from burning the uranium.
Describing the reactor as making energy rather than transferring it to the thermal store of the coolant.
Claiming the energy is supplied by the neutron that starts the fission.
Placing the energy release at the moment the neutron is absorbed rather than when the nucleus splits.
Exam tips
- Use the language of stores and transfers: energy is transferred from the nuclear store to the kinetic store of the products.
- If asked to compare with a fossil fuel, compare per kilogram or per atom, not per power station.
- Say 'released' rather than 'produced' or 'created', which examiners treat as loose.
Try the lesson
The start of the Nuclear fission: Energy is released by the fission reaction. lesson, made from checked teaching notes for this specification point.
Have a go first
What happens to energy during a fission reaction?
Listen
Every fission event transfers energy from the nuclear store of the fuel. The energy is not created; it is released because the products together are more stable than the original heavy nucleus, so the mass of the products is very slightly less than that of the nucleus and the neutron that started it. That missing mass appears as energy. Per atom this is roughly a million times more than any chemical reaction such as burning coal, which is why a small mass of fuel runs a power station for a long time. The power output depends on the number of fissions per second, so controlling how many neutrons go on to cause further fissions is exactly how the output of a reactor is controlled. A strong answer earns marks for these points. energy being released by each fission event. the energy coming from the nucleus rather than from a chemical reaction. the energy released being carried mostly as kinetic energy of the fission products. linking the number of fissions per second to the power output of the reactor. Exam tip: Use the language of stores and transfers: energy is transferred from the nuclear store to the kinetic store of the products.
Key words
Say what each word means before you turn the card.
energy released per fission
Try answering aloud or in your head before turning the card.
nuclear store
Try answering aloud or in your head before turning the card.
not a chemical reaction
Try answering aloud or in your head before turning the card.
fissions per second
Try answering aloud or in your head before turning the card.
See every definition
- energy released per fission
- Each fission event transfers energy from the nuclear store of the fuel, and per atom this is roughly a million times more than any chemical reaction such as burning coal.
- nuclear store
- The store of the fuel from which every fission event transfers energy, rather than energy being created.
- not a chemical reaction
- The energy comes from the nucleus rather than from a chemical reaction, so it is not supplied by burning the uranium.
- fissions per second
- The power output depends on the number of fissions per second, so controlling how many neutrons go on to cause further fissions is exactly how the output of a reactor is controlled.
There is more to this lesson
The full lesson goes on to check your understanding and help you earn the marks. Create a free account to carry on, with your progress saved.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge
Test your understanding of Nuclear fission: Energy is released by the fission reaction.
Active recall beats re-reading. Take an instant quiz now to test what you’ve learned and lock it into long-term memory.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge