nuclear fission

nuclear fission
Name	Nuclear fission
Type	Physical process
Discovered	1938–1939
Discoverers	Otto Hahn; Lise Meitner; Fritz Strassmann
Applications	Power generation; weapons; isotope production

nuclear fission

Nuclear fission is a nuclear reaction in which a heavy atomic nucleus splits into two or more lighter nuclei, accompanied by the release of neutrons and a large amount of energy. This process underpins commercial energy production in civilian power plants and the explosive yield of nuclear weapons, and it has shaped twentieth- and twenty-first-century politics, diplomacy, and science policy. Studies of fission link to experimental work at institutions such as the Cavendish Laboratory, the Kaiser Wilhelm Institute, and the Los Alamos National Laboratory.

Overview

Fission releases energy primarily via conversion of nuclear binding energy into kinetic energy of fragments, producing prompt neutrons, delayed neutrons, and gamma radiation in processes studied at facilities like the CERN, the Brookhaven National Laboratory, and the Lawrence Berkeley National Laboratory. Chain reactions were engineered during the Manhattan Project era and later regulated by bodies including the International Atomic Energy Agency and national agencies such as the Nuclear Regulatory Commission. Public and political responses to fission technology have intersected with events like the Three Mile Island accident, the Chernobyl disaster, and the Fukushima Daiichi nuclear disaster.

Physics and mechanisms

Fission of heavy nuclides occurs when a nucleus absorbs a neutron or undergoes excitation via photon or particle interaction as studied in experiments at the Los Alamos National Laboratory and the Oak Ridge National Laboratory. The process involves overcoming the nuclear binding energy and traversing a potential-energy surface characterized by saddle points and fission barriers modeled using theories from the Liquid Drop Model era and advanced computational approaches developed at the Max Planck Institute for Nuclear Physics and the Lawrence Livermore National Laboratory. Fragment mass and kinetic energy distributions, shell effects, and scission dynamics are topics investigated in collaborations between the Institut Laue–Langevin, the CERN, and university groups at the University of Cambridge and the Massachusetts Institute of Technology. Neutron moderation and multiplicity influence criticality experiments historically performed at the Metallurgical Laboratory and more recently at the Joint European Torus and national research reactors.

Types and fissile/fertile materials

Fission can be induced in fissile isotopes such as Uranium-235, Plutonium-239, and Uranium-233, while fertile isotopes like Uranium-238 and Thorium-232 can transmute to fissile nuclides via neutron capture and beta decay chains studied at the Idaho National Laboratory and the Paul Scherrer Institute. Fast fission, thermal fission, spontaneous fission, and neutron-induced fission are categories distinguished in reactor design and weapons engineering within programs at the Atomic Energy Commission and successor agencies in countries like United States, United Kingdom, France, Russia, China, and India. Isotope separation and fuel cycle technologies were developed at facilities such as Oak Ridge National Laboratory, Cadarache, and Tarapur Atomic Power Station.

Applications and reactors

Civilian applications include electricity generation in light-water reactors, heavy-water reactors, fast breeder reactors, and advanced concepts like molten salt reactors advanced by research centers including the Argonne National Laboratory, the Électricité de France, and university consortia at the Imperial College London. Naval propulsion uses fission reactors in vessels commissioned by navies such as the United States Navy and the Russian Navy. Medical isotope production, district heating demonstrations, and desalination pilot projects have been pursued by institutions like the International Atomic Energy Agency and national research centers in France, Japan, and Germany.

Weapons and proliferation

Fission weapons were developed in the Manhattan Project and deployed in the Atomic bombings of Hiroshima and Nagasaki. The technology and materials control regimes responding to proliferation risks include the Non-Proliferation Treaty, IAEA safeguards, and multilateral export control arrangements such as the Nuclear Suppliers Group. State nuclear weapons programs and policies have involved actors like Los Alamos National Laboratory, national ministries in Russia, United Kingdom, Pakistan, North Korea, and diplomatic frameworks including the Treaty on the Non-Proliferation of Nuclear Weapons.

Safety, environmental and health impacts

Operational safety and accident response draw on lessons from incidents at Three Mile Island, Chernobyl, and Fukushima Daiichi nuclear disaster and are overseen by regulators such as the Nuclear Regulatory Commission and the International Atomic Energy Agency. Radiological health effects research connects to studies by the World Health Organization, the International Commission on Radiological Protection, and national public health agencies. Waste management strategies—geologic disposal, reprocessing, and interim storage—have been pursued in programs at Yucca Mountain, La Hague, Sellafield, and repositories in Finland and Sweden.

History and discovery

The discovery period involved experimental and theoretical contributions from scientists at the Kaiser Wilhelm Institute and the Cavendish Laboratory and key figures affiliated with institutions such as the University of Berlin and the University of Copenhagen. Crucial developments occurred amid geopolitical events like the Second World War and collaborations such as the Manhattan Project, with postwar civilian programs influenced by policies from the Atomic Energy Commission and international organizations including the United Nations.

Category:Nuclear physics Category:Energy technology