Nuclear fission

Nuclear fission is a reaction in which an atomic nucleus splits into lighter nuclei, releasing energy and usually additional neutrons. It can occur spontaneously or after a nucleus absorbs a particle.

Neutron-induced fission: Nuclear fission triggered when an atomic nucleus absorbs an incoming neutron. Neutron absorption is the usual trigger in reactors and many fission weapons.
Nuclear reactor: A system that sustains and controls a nuclear chain reaction to produce useful heat or radiation. Reactors regulate fission to provide heat for electricity or other applications.
Otto Hahn: A German chemist whose experiments with uranium helped identify nuclear fission in 1938. Hahn’s chemical analysis revealed barium among the products of neutron-bombarded uranium.
Ionizing radiation: Radiation with enough energy to remove electrons from atoms or molecules. Fission products and neutron interactions produce radiation that requires shielding and careful handling.
Nuclear binding energy: The energy associated with the forces that hold protons and neutrons together in a nucleus. Fission releases energy because the products are more tightly bound per nucleon than many heavy starting nuclei.
Nuclear weapon: A weapon that releases explosive energy through nuclear reactions, including fission or fusion. Some nuclear weapons derive their explosive yield from an extremely rapid fission chain reaction.
Lise Meitner: An Austrian-Swedish physicist who provided the physical interpretation of uranium fission with Otto Frisch. Meitner explained how a uranium nucleus could split and release substantial energy.
Radioactive waste: Discarded material containing radionuclides at levels that require controlled management. Spent fuel contains fission products and other radioactive materials that remain hazardous.
Fission products: The lighter nuclei and fragments formed when a nucleus undergoes fission. Their kinetic energy and radioactive decay account for much of fission’s energy and radiation.
Nuclear fuel cycle: The processes involved in producing, using, and managing nuclear fuel and its waste. It connects fissile material supply to reactor operation and spent-fuel management.

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