How does nuclear fusion produce less radioactive waste than fission?

Nuclear fusion produces less radioactive waste than fission because it primarily uses lighter elements and generates fewer long-lived isotopes.

In nuclear fusion, light atomic nuclei, such as hydrogen isotopes (deuterium and tritium), combine to form a heavier nucleus, typically helium. This process releases a tremendous amount of energy. The primary by-products of fusion are helium, a non-radioactive gas, and a small amount of neutron radiation. These neutrons can activate surrounding materials, making them slightly radioactive, but the level and longevity of this radioactivity are significantly lower compared to fission.

On the other hand, nuclear fission involves splitting heavy atomic nuclei, such as uranium or plutonium, into smaller fragments. This process also releases a large amount of energy but produces a variety of radioactive isotopes as by-products. These fission products include elements like iodine-131, caesium-137, and strontium-90, which have long half-lives and can remain hazardous for thousands of years. Managing and storing this high-level radioactive waste is a significant challenge.

Fusion's waste products are less problematic because the primary fuel, deuterium, is abundant and non-radioactive, and tritium, while radioactive, has a relatively short half-life of about 12 years. The materials activated by neutron radiation in a fusion reactor can be chosen to minimise long-term radioactivity, and their radioactivity typically decays to safe levels within a few decades.

In summary, the key difference lies in the nature of the reactions and the materials involved. Fusion uses lighter elements and produces fewer and less hazardous radioactive by-products, making it a cleaner alternative to fission in terms of radioactive waste.