Radioisotope

A radioisotope, or radioactive isotope, is a radioactive nuclide of an element that is unstable and undergoes spontaneous radioactive decay. Unlike stable isotopes, radioisotopes transform into other nuclides or energy states, emitting radiation in the process.

Radioisotopes are produced by nuclear reactors, particle accelerators, or certain natural processes. Reactor irradiation converts stable isotopes into radioactive forms via neutron capture or fission products; accelerators create radioisotopes by bombarding targets with protons or other particles. After production, isotopes are separated and purified for use.

Their nuclei decay by alpha, beta, or gamma emission, or by electron capture. Each radioisotope has a characteristic half-life, the time required for its activity to fall to half its initial value. Activity is measured in becquerels or curies.

Radioisotopes have diverse applications. In medicine, gamma emitters such as technetium-99m enable diagnostic imaging, while beta-emitters and others (eg, iodine-131, lutetium-177) are used for therapy. In science and industry, they serve as tracers, radiography sources, and calibration standards. Long-lived isotopes like carbon-14 are used in radiometric dating.

Safety and regulation are central to their use. Handling requires shielding and monitoring to limit exposure; licensing, containment, proper storage, and waste disposal are mandated to protect workers and the environment.