uranium-235

uranium-235
Name	Uranium-235
Atomic number	92
Mass number	235
Category	Actinide
Phase	Solid at STP
Density	18.95 g/cm³
Melting point	1132 °C
Boiling point	4131 °C

uranium-235 Uranium-235 is a fissile isotope of the element with mass number 235 and atomic number 92, significant for its role in nuclear fission, reactor physics, and nuclear weapons. It plays a central part in 20th and 21st century technologies and geopolitics, influencing institutions, treaties, and state programs worldwide.

Properties

Uranium-235 exhibits nuclear properties including a thermal neutron fission cross section exploited by reactors and weapons; notable related institutions include Oak Ridge National Laboratory, Los Alamos National Laboratory, and Lawrence Livermore National Laboratory, all of which contributed to characterizing neutron-induced reactions. Its decay properties and half-life were measured in programs at University of Chicago, Columbia University, and University of California, Berkeley during collaborative projects such as the efforts leading to the Manhattan Project; these measurements underpin modern reactor design at facilities like Argonne National Laboratory and standards bodies like the International Atomic Energy Agency. Material properties—density, metallurgy, and alloy behavior—were studied by laboratories associated with Babcock & Wilcox, Westinghouse Electric Company, and General Electric to support fuel fabrication for entities including Electricité de France and Tokyo Electric Power Company.

Occurrence and Production

Naturally occurring uranium contains a small fraction of the isotope; exploration and mining are organized by companies and agencies such as Rio Tinto Group, Kazatomprom, Cameco Corporation, and national programs in Canada, Australia, Kazakhstan, and Niger. Ore processing and conversion to chemical forms used for enrichment are handled at plants operated by Areva, Rosatom, Urenco, and national fuel cycle centers linked with the European Atomic Energy Community. Historic and contemporary production sites—Shinkolobwe mine, Eagle Rock, McArthur River mine, and Rossing Mine—feed supply chains managed under safeguards from the International Atomic Energy Agency and bilateral agreements like the Nuclear Non-Proliferation Treaty.

Nuclear Reactions and Fission

When a thermal neutron induces fission in the isotope, the reaction produces fission fragments, prompt neutrons, and energy—a process characterized experimentally in campaigns at CERN, Brookhaven National Laboratory, and Helmholtz Association facilities. Reaction rates, cross sections, and neutron spectra are central to codes developed by research centers such as National Nuclear Laboratory, Institut Laue–Langevin, and computational groups at Massachusetts Institute of Technology; these inform reactor kinetics in designs by corporations like Westinghouse and regulators such as the Nuclear Regulatory Commission. Detailed fission yield data and decay heat calculations were refined through collaborations with groups at Los Alamos National Laboratory and international databases coordinated with the Organisation for Economic Co-operation and Development.

Applications

The isotope is used as fuel in light-water reactors built by firms such as Areva, GE Hitachi Nuclear Energy, and Westinghouse, and in naval propulsion systems commissioned by navies including the United States Navy and the Royal Navy. Its role in weapons development was central to projects at Los Alamos National Laboratory culminating in tests at sites like Trinity Site and deployment decisions made by governments including the United States during World War II. Civilian applications also extend to research reactors at institutions such as Institut Laue–Langevin, Tsinghua University, and Kyushu University for isotope production serving hospitals and industry linked with organizations like World Health Organization and International Atomic Energy Agency programs.

Enrichment and Fuel Cycle

Natural uranium is enriched to raise the isotope fraction using technologies developed and deployed by companies and organizations such as Urenco Group, Areva (now Orano), Rosatom State Atomic Energy Corporation, and national enrichment plants in Gabon, Iran, and Pakistan. Enrichment technologies—gaseous diffusion, centrifuge cascades, and advanced laser separation—were advanced by research at Oak Ridge National Laboratory, Capenhurst, and firms like Silex Systems; the enriched product is fabricated into fuel assemblies by vendors including Framatome and Westinghouse. Spent fuel management, reprocessing, and disposition involve facilities and policies shaped by entities such as La Hague site, Sellafield, Yucca Mountain repository proposals, and agreements under the Nuclear Non-Proliferation Treaty and Comprehensive Nuclear-Test-Ban Treaty frameworks.

Safety, Health, and Environmental Impact

Handling, transport, and safety protocols for materials enriched in the isotope are governed by standards from bodies such as the International Atomic Energy Agency, World Health Organization, and national regulators including the Nuclear Regulatory Commission and Office for Nuclear Regulation (United Kingdom). Health physics research at universities like Johns Hopkins University and University of California, San Francisco informs occupational limits and emergency response coordinated with agencies such as Centers for Disease Control and Prevention and Federal Emergency Management Agency. Environmental consequences from mining and testing, including contamination events at sites like Maralinga, Semipalatinsk Test Site, and Nevada Test Site, have driven remediation managed by organizations including United Nations Environment Programme and national cleanup programs. International law, disarmament advocacy, and monitoring involve stakeholders such as the International Atomic Energy Agency, Comprehensive Nuclear-Test-Ban Treaty Organization, Treaty on the Non-Proliferation of Nuclear Weapons, and NGOs including Greenpeace.

Category:Uranium