Is a process in nuclear physics in which the nucleus of an atom splits into two or more smaller nuclei as fission products, and usually some by-product particles. Hence, fission is a form of elemental transmutation. The by-products include free neutrons, photons usually in the form gamma rays, and other nuclear fragments such as beta particles and alpha particles. Fission of heavy elements is an exothermic reaction and can release substantial amounts of useful energy both as gamma rays and as kinetic energy of the fragments (heating the bulk material where fission takes place). Nuclear fission produces energy for nuclear power and to drive explosion of nuclear weapons.