# A nuclear power station uses uranium as a fuel. Explain how a chain reaction occurs in a nuclear fission reactor and why it is able to sustain itself.

> OCR A-Level Physics B: Advancing Physics (H557) — 6.1 Capacitors · Explain · 5 marks

> Nuclear power stations generate electricity using the energy released from nuclear fission reactions. Engineers must carefully control the chain reaction taking place inside the reactor to prevent it from becoming uncontrolled.

## Mark scheme (5 marks)

1. A large, unstable uranium nucleus absorbs a neutron / an unstable nucleus splits (undergoes nuclear fission)
2. The nucleus splits into two smaller, more stable nuclei and releases neutrons (two or three neutrons)
3. Energy is released in the form of electromagnetic radiation (gamma rays) / kinetic energy of products
4. The released neutrons are absorbed by other uranium nuclei, causing them to become unstable and undergo further fission
5. This process repeats / is self-sustaining, forming a chain reaction where each fission event triggers further fission events

## Key terms

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

## Related

- [Revision notes for OCR A-Level Physics B: Advancing Physics (H557)](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-f1d05158) · Published by Druglandscape Ltd.