# A nuclear power station uses uranium as a fuel. Explain how a chain reaction occurs inside the reactor core, and why the process releases large amounts of energy.

> OCR A-Level Physics A (H556) — 6.3 Nuclear and particle physics · Explain · 5 marks

> Nuclear power stations generate electricity by harnessing the energy released during nuclear fission. Inside the reactor core, uranium nuclei undergo fission, triggering a self-sustaining chain reaction.

## Mark scheme (5 marks)

1. A neutron is absorbed by a large, unstable uranium nucleus
2. The unstable nucleus splits (undergoes fission) into two smaller nuclei
3. Two or three neutrons are released during the fission event (along with energy / gamma rays)
4. The released neutrons are absorbed by other uranium nuclei, causing further fission events — this is the chain reaction
5. Mass is converted into energy (mass-energy equivalence), so a small loss of mass produces a very large release of energy

## Key terms

- [chain reaction](https://www.gradenine.co.uk/glossary/chain-reaction)

## Related

- [Revision notes for OCR A-Level Physics A (H556)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-nuclear-power-station-uses-uranium-d645a7e1) · Published by Druglandscape Ltd.