Related Terms. Ratio of the density of a substance at 20Â°C or 68Â°F to the density of water at 4Â°C or 39.2Â°F.
Nuclear fission. NUCLEAR FISSION. Nuclear fission is a reaction in which an atom's nucleus is broken apart, releasing a tremendous amount of energy. Nuclear fission is used in many power plants on Earth (and is used in atomic weapons). nuclear fission: Reaction that splits nuclei into less massive fragments.nuclear fusion: Reaction that joins the nuclei of atoms to form more massive nuclei. - (n.). The splitting of an atomic nucleus into two large fragments. nuclear fusion - (n.) ... ~ reactors naturally produce free neutron s; their role is to sustain the energy-producing chain reaction.
Nuclear fission is a process in which the nucleus of a heavy atom is broken apart into two or more smaller nuclei. The reaction was first discovered in the late 1930s when a target of uranium metal was bombarded with neutrons.Uranium nuclei broke into two smaller nuclei of roughly equal size with the emission of very large amounts of energy.he control of nuclear fission energy was actually achieved before the production of the first atomic bomb. In 1942, a Manhattan Project research team under the direction of Italian physicist Enrico Fermi (1901â1954) designed and built the first nuclear reactor.