Transuranics

Transuranics are chemical elements with atomic numbers greater than 92, the element beyond uranium in the periodic table. Most transuranics are synthetic, produced in nuclear reactors or particle accelerators, though trace natural occurrences can arise in uranium ore or from cosmic processes. The category includes a broad range of elements from neptunium (93) onward to the heavier, named elements, many of which have short-lived or long-lived radioactive isotopes.

The first transuranic element discovered was neptunium in 1940, followed by plutonium and other synthetic actinides developed during or shortly after World War II. Production in reactors typically begins with neutron capture on uranium-238, followed by beta decays that build up heavier transuranics such as plutonium, americium, curium, and beyond. Reprocessing of spent nuclear fuel concentrates these elements, which can then be recycled or disposed of.

Transuranics are generally highly radioactive and chemically resemble the actinides, exhibiting multiple oxidation states and complex chemistry. Many have long half-lives, contributing to long-term radiological hazards. Their radiotoxicity is predominantly alpha radiation, which requires careful containment and shielding. Because of their chemistry and radioactivity, handling and containment require specialized facilities and procedures.

Common examples and uses include plutonium-239, a fissile material used in nuclear reactors and some weapons; americium-241, widely employed in smoke detectors and as a source of gamma radiation; and californium-252 or curium isotopes used as neutron sources in research and industry. In waste management, transuranics constitute a major portion of long-lived radioactive waste, necessitating careful isolation in deep geological repositories and strict regulatory controls.