# Explain why nuclear fusion has not yet been developed as a large-scale commercial energy source, despite the fact that it releases more energy per kilogram of fuel than nuclear fission.

> Eduqas A-Level Physics — 3.6 Nuclear energy · Explain · 5 marks

> Scientists have been researching nuclear fusion as an energy source for many decades. Fusion powers the Sun and other stars, but producing a controlled fusion reaction on Earth that generates more energy than it consumes has proved extremely difficult.

## Mark scheme (5 marks)

1. Fusion requires extremely high temperatures (millions of degrees) to occur
2. At these temperatures, matter exists as a plasma which is very difficult to contain / no material can withstand these temperatures
3. It is difficult to produce more energy from fusion than is put in to start / sustain the reaction (break-even not yet achieved commercially)
4. The nuclei being fused must be brought close enough together / must overcome electrostatic repulsion between positively charged nuclei
5. Fusion fuel (hydrogen isotopes / deuterium / tritium) is available / the challenge is engineering not fuel supply, making continued research worthwhile

## Key terms

- [nuclear fusion](https://www.gradenine.co.uk/glossary/nuclear-fusion)

## Related

- [Revision notes for Eduqas A-Level Physics](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-nuclear-fusion-has-not-935ec716) · Published by Druglandscape Ltd.