What distinguishes nuclear fusion from nuclear fission?

Nuclear fusion is distinguished from nuclear fission primarily by the conditions under which it occurs, particularly temperature. Fusion involves the process of combining light atomic nuclei, such as hydrogen isotopes, into heavier nuclei, which releases energy. This process typically requires extremely high temperatures, often in the millions of degrees Celsius, to overcome the repulsive electrostatic forces between the positively charged nuclei.

In contrast, fission involves the breaking apart of heavy atomic nuclei, such as uranium or plutonium, into lighter nuclei, which releases energy as well but under different physical conditions. The energy generated in fission can be achieved at much lower temperatures compared to fusion and operates through a chain reaction of neutron-induced reactions.

Understanding the temperature requirements highlights why fusion is not only fundamentally different from fission but also contributes to the challenges of harnessing fusion as an energy source. For practical energy production through fusion, the reactor would need to sustain extremely high temperatures to maintain the necessary conditions for the fusion reactions to occur efficiently.