Radionuklide

Radionuklide are radioactive nuclides—atoms with unstable nuclei that decay spontaneously into lighter nuclei, emitting ionizing radiation in the process. Each radionuklide is defined by its half-life, decay mode (alpha, beta, gamma), and the energy of the emitted radiation. The biological and environmental impact of a radionuklide depends on its chemical behavior, radiotoxicity, and how it concentrates in tissues or ecosystems.

Natural radionuklide occur in the earth and environment, such as uranium-238, uranium-235, thorium-232, potassium-40, and carbon-14. Artificial or man-made radionuklide are produced in reactors or particle accelerators and include technetium-99m, iodine-131, cobalt-60, cesium-137, and many others.

Decay is described by half-life; activity is measured in becquerels (decays per second) or curies. The type of radiation—alpha, beta, or gamma—affects penetration and biological dose. Shorter half-lives deliver dose over a brief period; long-lived nuclides persist in the environment for extended times.

Applications span medicine (diagnostic imaging with technetium-99m, PET isotopes such as fluorine-18, and radiotherapy with iodine-131 or lutetium-177), industry (radiography and tracers), and research. Safety considerations include shielding, containment, dosimetry, and regulatory controls to minimize exposure to workers and the public.

Environmental management of radionuklide addresses natural background radiation, waste disposal, decommissioning of facilities, and monitoring of contamination. Ethical and regulatory frameworks aim to balance the benefits of radioactive applications with protection of health and the environment.