radionuklid

A radionuclide, or radioactive nuclide, is a nucleus that is unstable and undergoes radioactive decay, emitting ionizing radiation in the form of alpha particles, beta particles, or gamma rays. Decay is a random process described by the half-life, the time required for half the nuclei in a sample to decay. The activity of a sample is the decay rate, measured in becquerels (disintegrations per second).

Radionuclides occur naturally or can be produced in laboratories. Natural radionuclides include primordial nuclides with long half-lives such as uranium-238, thorium-232, and potassium-40, as well as cosmogenic nuclides like carbon-14 formed by cosmic rays. Artificial radionuclides are generated in reactors or accelerators and include technetium-99m, iodine-131, and lutetium-177, among others. Each nuclide has characteristic decay modes, energies, and half-lives, spanning from microseconds to billions of years.

They have a wide range of applications. In medicine, radiopharmaceuticals enable diagnostic imaging and targeted radiotherapy; for example, technetium-99m and fluorine-18 are used in imaging, iodine-131 for thyroid treatment, and lutetium-177 for certain cancers. In industry and research, radionuclides serve as tracers in hydrology and process studies, as well as tools for radiometric dating and environmental monitoring.

Safety and regulation are essential due to radiation exposure risks. Doses depend on activity, emission energy, and biological uptake. Measurements use becquerels for activity and dosimetric units such as grays and sieverts. Handling requires appropriate shielding, containment, and waste management in accordance with national and international guidelines.