Radioactive source

A radioactive source or radiation source is a sample of a radionuclide, and emits ionizing radiation (one or more of gamma rays, alpha particles, beta particles, and neutron radiation). Generally, sources are used for irradiation, where the radiation performs a significant ionising function on a target material, or as a metrology calibration source, which is used for the calibration of radiometric process and radiation protection instrumentation. They can be sealed in a container or on a surface, or they can be free to move within a fluid.

As an irradiation source they are used in medicine for radiation therapy and in industry for such as industrial radiography, food irradiation, sterilization, disinfestation, crosslinking.

Radionuclides are chosen according to the type and character of the radiation they emit, intensity of emission, and the half-life of their decay. Common source radionuclides include cobalt-60,iridium-192, and strontium-90. The SI measurement quantity of source activity is the Becquerel, though the historical unit Curies is still in partial use, such as in the USA, despite the USA NIST strongly advising the use of the SI unit. The SI unit for health purposes is mandatory in the EU.

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