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: 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 ...