Difference between fusion and fission

Nuclear Fission

Fission is the splitting of a large atom into two or more smaller ones. 

Fission reaction does not normally occur in nature. 

Fission produces many highly radioactive particles. 

Takes little energy to split two atoms in a fission reaction.

The energy released by fission is a million times greater than that released in chemical reactions.

Fission is used in nuclear 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.

Few radioactive particles are produced by fusion reaction

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. Uranium is the primary fuel used in power plants. Hydrogen isotopes (Deuterium and Tritium) are the primary fuel used in experimental fusion power plants.