What makes fusion energy different to fission?

Fusion can be thought of as the opposite of fission – combining lighter atoms rather than splitting heavier ones. Fission splits a large nucleus into smaller nuclei, normally through a chain reaction. Fusion combines smaller nuclei together to create a larger nucleus. These nuclei naturally repel each other, so a great amount of effort has to go into pushing them together.

With fusion, there is no chain reaction, so there’s no risk of a ‘runaway’ where the reaction could get out of control.  Another difference is the product of the reaction. Where fission produces unstable nuclei, fusion only produces helium (an unreactive gas found in nature) and a neutron. Fusion promises to be a safe, low carbon and sustainable part of the world’s future energy supply.

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