Radioactive source

A quantity of radioactive material that emits ionizing radiation through nuclear decay. It may be used in medicine, measurement, research, or industrial testing.

Radioactive decay: The spontaneous transformation of an unstable atomic nucleus, often accompanied by emitted particles or electromagnetic radiation. Nuclear decay produces the emissions that make a radioactive source active.
Brachytherapy: A form of radiotherapy that places radioactive sources inside or near the tissue being treated. Small sources deliver radiation directly to tumors while limiting exposure to surrounding tissue.
Radionuclide: An atomic nucleus characterized by a particular number of protons and neutrons that is radioactive. A source's radioactive material consists of one or more radionuclides.
Radiation protection: The practice of protecting people and the environment from harmful effects of ionizing radiation. Protection practices govern work around radioactive sources.
Activity (radioactivity): The number of nuclear decays occurring in a radioactive sample per unit time, measured in becquerels. Activity quantifies how many decays the source produces each second.
Radiation therapy: The treatment of disease, especially cancer, using ionizing radiation. Radioactive sources provide one way to deliver therapeutic radiation.
Sealed radioactive source: Radioactive material permanently sealed in a capsule or bonded within a solid to prevent dispersal. Sealing distinguishes contained sources from material that can readily spread.
Radiation dose: A measure of energy deposited by ionizing radiation in matter, with distinct quantities for absorbed and biological effect. Dose depends on the source's emissions, distance, exposure time, and shielding.
Half-life: The time required for half the radioactive nuclei in a sample to decay. Half-life determines how a source's activity declines during use and storage.
Industrial radiography: A nondestructive testing method that uses radiation to reveal internal flaws in materials and structures. Portable sources can expose welds and components where X-ray machines are impractical.

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Dirty bombRelated: A dispersal device requires a source, often from industrial, medical, or research use.