How do nuclear fusion and fission differ?
Nuclear Fission: Fission is the splitting of a large atom into two or more smaller ones. Fission reaction does not normally occur in nature. Critical mass of the substance and high-speed neutrons are required. It takes little energy to split an atom in a fission reaction. The energy released by fission is a million times greater than that released in chemical reactions, but lower than the energy released by nuclear fusion. Fission is used in nuclear power plants. Uranium is the primary fuel used in power plants.
Nuclear Fusion: Fusion is the fusing of two or more lighter atoms into a larger one. Fusion occurs in stars, such as the sun. High density, high temperature environment is required. Extremely high energy is required to bring two or more protons close enough that nuclear forces overcome their electrostatic repulsion. The energy released by fusion is three to four times greater than the energy released by fission. Fusion is an experimental technology for producing power. Hydrogen isotopes (Deuterium and Tritium) are the primary fuel used in experimental fusion power plants.