radionucléides

Radionuclides, called radionucléides in French, are nuclides that are radioactive. A nuclide is a distinct form of an element defined by its proton and neutron count. Some elements have both stable and unstable forms; those unstable forms are radionuclides. Their nuclei are energetically unstable and decay over time, emitting radiation in the form of alpha, beta, or gamma rays and gradually transforming into different nuclides.

Key properties include half-life, decay mode, emitted radiation energy, and the chemical form. Half-lives span fractions of a second to many billions of years, affecting how long a radionuclide remains hazardous or useful. Activity, the rate of decay, is measured in becquerels (disintegrations per second). The type of radiation and its energy determine potential medical, industrial, or environmental applications and safety precautions.

Radionuclides arise naturally or be manufactured. Naturally occurring radionuclides include uranium-238, uranium-235, thorium-232, and potassium-40. Synthetic radionuclides are produced in reactors or accelerators, such as technetium-99m, iodine-131, cobalt-60, cesium-137, and iridium-192. Their uses are varied: medical imaging and therapy, sterilization of equipment, industrial radiography, and tracer studies in biology and environmental science.

Safety and regulation are central to radionuclide use. Handling requires radiological protection, monitoring, containment, and appropriate storage. Production and disposal are governed by national authorities and international guidelines to limit exposure and environmental release. Doses are described with gray for absorbed energy and sievert for biological effect; contamination risk is mitigated by containment and shielding.

Examples of research and dating methods rely on radionuclides: radiotracers track processes in living systems; radiocarbon dating uses carbon-14 to estimate age; other nuclides power diagnostic imaging and targeted therapies in nuclear medicine.