Nuclear Fusion

Nuclear fusion is the process in which two light nuclei combine to form a heavier nucleus, releasing energy in the process. It is the power source of every star in the universe, including our Sun, and it has the potential to provide virtually unlimited clean energy here on Earth — if we can solve the enormous engineering challenges involved.

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Why Fusion Releases Energy

Looking at the binding energy per nucleon curve, light nuclei (low A) have low binding energy per nucleon. When two light nuclei fuse, the product has a higher binding energy per nucleon, meaning the nucleons are more tightly bound in the product. The increase in total binding energy corresponds to a decrease in mass (via E = mc²), and this mass difference is released as energy.

For example, deuterium (²₁H) has a binding energy per nucleon of about 1.11 MeV, while helium-4 has about 7.08 MeV per nucleon. Fusion reactions involving hydrogen isotopes therefore release enormous amounts of energy per nucleon.

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Conditions for Fusion