Waste Technology Section

Low energy gamma source
(Photo credit: QSA Global)

What is a Sealed Radioactive Source?

A sealed radioactive source is a container of encapsulated radioactive material, which usually has the appearance of a small, harmless piece of metal. The capsule or material of a sealed source is strong enough to maintain leak tightness under the conditions of use for which the source was designed, and also under foreseeable mishaps. In more technical terms, it is radioactive material that is

  • permanently sealed in a capsule or
  • closely bonded and in a solid form.

The source is designed to contain the radioactive material under normal operating conditions and usually has high concentration of radioactive material in a small volume.

Teletherapy source

Where are sealed radioactive sources used?

Sealed radioactive sources are used in various applications in medicine, agriculture, industry, transportation, construction, geology, mining, research, etc. For example high activity cobalt sources are used to treat cancer. In most of these areas the use of sealed radioactive sources either cannot be replaced by other methods or provides results that are unmatched by other methods. The first sealed radioactive sources were used for medical purposes from the beginning of the twentieth century.

Well logging source

Until the 1940s sources were only using naturally occurring isotopes (radium and polonium). Today sealed radioactive sources are made of numerous artificial radioisotopes.Read more on various applications of sealed radioactive sources IAEA Nuclear Security Series No. 5, "Identification of Radioactive Sources and Devices" (PDF 4.7 MB).

What is a disused sealed radioactive source?

Sources that are no longer in use are usually called ‘disused’ or ‘spent’:

  • Disused sources are defined as sources that are no longer used and there is no intention of using them again in the practices they were authorized for.
  • Spent sources (a sub-set of disused sources) are those that are no longer suitable for their intended purposes as a result of radioactive decay.

Worldwide, the number of sources that are considered disused is very large and warrants dedicated efforts for their management in a safe and secure manner.

What are the risks with disused sealed radioactive sources?

If lost or not properly controlled, disused sealed sources can be a threat to human health and the environment. Exposure to large doses of radiation from an unshielded high activity source can be lethal or cause severe radiation injury. If the source capsule is damaged the radioactive material can be released and dispersed, resulting in contamination to the environment.

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