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Radioactive source

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A metal cylinder with a ruler next to it, 3.1cm high
A new sealed cesium-137 radiation source as it appears in its final state

A radioactive source or radiation source is a sample of a radionuclide, usually contained within a radiation-resistant container. It emits ionizing radiation (one or more of gamma rays, alpha particles, beta particles, and neutron radiation), which can be used in medicine for radiation therapy and in industry for industrial radiography, food irradiation, sterilization, disinfestation, crosslinking, and more. 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,[1] iridium-192,[2] and strontium-90.[3] The activity of a radioactive source is typically measured in Curies, despite NIST strongly advising the use of the Becquerel.[4]

Source enclosure

The various uses of radioactive sources can call for one of two broad categories of methods of enclosing a source: sealed or unsealed

A cutaway diagram of a teletherapy capsule
A cutaway diagram of a radioactive source used for teletherapy (external beam radiotherapy): A key to the lettering can be found on the file page

Sealed sources

Many radioactive sources are sealed, meaning they are permanently either completely contained in a metallic capsule or in a tightly bonded solid. The use of sealed sources removes almost all risk of dispersion of radioactive material into the environment due to mishandling,[5] but the container is not intended to be radiation proof, so further shielding is required for protection.[6] Sealed sources are used in almost all applications where the source does not need to chemically or physically react with anything, including brachytherapy.

Unsealed sources

Unsealed sources are sources that are not in a permanently sealed container, and are used extensively for medical purposes.[7] They are used when the source needs to be dissolved in a liquid for injection into a patient or ingestion by the patient.

See also

References

  1. ^ "C-188 Cobalt-60 Source". Nordion Inc. Retrieved 22 March 2016.
  2. ^ "Iridium-192". Isoflex. Retrieved 22 March 2016.
  3. ^ "Radioactive sources: isotopes and availability". Retrieved 22 March 2016.
  4. ^ "NIST Guide to the SI, Chapter 5 (paragraph 5.2)". NIST. Retrieved 22 March 2016.
  5. ^ "Implementation of the Control of High-activity Sealed Radioactive Sources and Orphan Sources (HASS) directive for nuclear licensed sites". Retrieved 22 March 2016.
  6. ^ "Disused Sealed Source Managment". International Atomic Energy Agency. Retrieved 22 March 2016.
  7. ^ "Radiation Protection Glossary". Retrieved 22 March 2016.
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