Nuclear fusion is the process used to generate electricity in nuclear power plants. is the process in which a large nucleus spontaneously splits into two or more smaller nuclei. is the process in which two smaller nuclei combine to form a larger nucleus. is the process in which a large nucleus is bombarded with a neutron and then splits into two or more smaller nucleir.

Nuclear fusion can be defined asva reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles ( neutrons or protons). The difference in mass between the reactants and products is manifested as either the release or absorption of energy . This difference in mass arises due to the difference in atomic " binding energy " between the atomic nuclei before and after the reaction. Fusion is the process that powers active or " main sequence " stars , or other high magnitude stars.

A fusion process that produces nuclei lighter than iron-56 or nickel-62 will generally release energy. These elements have relatively small mass per nucleon and large binding energy per

nucleon . Fusion nuclei lighter than these releases energy (an exothermic process), while fusion of heavier nuclei results in energy retained by the product nucleons, and the resulting reaction is endothermic .

Nuclear fusion generates electricity (as a proposed form of power) by using heat from nuclear fusion reactions. In a fusion process, two lighter atomic nuclei combine to form a heavier nucleus, while releasing energy. The devices designed to harness this energy are known as fusion reactors.