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What are Radioactive Sources?

Nuclear Explained

Radioactive sources, like the one pictured, are used in various applications in medicine, agriculture, industry, and research and education. They range in size from a few millimetres to several centimetres. See more examples of radioactive sources. (Photo: IAEA)

Radioactive sources contain radioactive material of a particular radionuclide (an unstable form of an element emitting radiation), which can vary based on the application for which the source was manufactured. These sources emit ionizing radiation, typically in the form of alpha and beta particles, gamma rays or neutron radiation. Click here to learn more about radiation.

Until the 1950s, only radionuclides of natural origin, such as Radium-226 – an isotope of radium used to treat some types of cancers – were available for use. Today, radionuclides artificially produced in nuclear facilities and accelerators, including Caesium-137, Colbalt-60, and Iridium-192, are extensively used. Around the world, these radioactive sources are used for medical, industrial, agricultural, research and educational purposes.

Some examples of the application of radioactive sources include killing bacteria in food, sterilizing medical supplies and equipment, treating cancer and other diseases, mapping underground sources of water, integrity testing of mechanical structures and measuring soil density for construction projects.

Read about the use of ionizing radiation for pest control and sterilization.

Types of radioactive sources

Radioactive sources include a range of different radionuclides and amounts of radioactive material.

  • Sealed source: A radioactive source in which the radioactive material is (a) permanently sealed in a capsule or (b) closely bonded and in a solid form. The radioactive material is contained or bound within a capsule strong enough to prevent leaks, while allowing the emission of ionizing radiation under controlled use. Sealed sources typically have high concentrations of radioactive material in a small volume – ranging in size from a few millimetres to several centimetres. Teletherapy machines for cancer treatment, as well as laboratory equipment, such as gas chromatographs, liquid scintillation counters and analytical balances, may contain sealed sources.
  • Unsealed source: A radioactive source in which the radioactive material is neither (a) permanently sealed in a capsule nor (b) closely bonded and in a solid form. These types of sources, which can be in the form of a powder, liquid or gas, are used in biological research and medicine. In radiotherapy for cancer treatment, unsealed sources are injected or ingested in very small quantity into the body to target specific locations, organs or tissues. In industry, unsealed sources are used for leak detection as a radioactive tracer.
  • Disused source: A radioactive source that is no longer used, and is not intended to be used, for the practice for which an authorization had been granted.
  • Orphan source: A radioactive source that is not under regulatory control, either because it has never been under regulatory control due to a variety of historical and economic reasons or because it has been abandoned, lost, misplaced, stolen or otherwise transferred without proper authorization. These sources have led in the past to accidents because of radiation exposure.

Safety and security of radioactive sources

A team of experts from South Africa's Nuclear Energy Corporation has removed 16 highly radioactive sources from disused medical devices in the Philippines. The source removal experts used a special facility known as a "mobile hot cell" to carry out the six-week operation, which was financed by the IAEA's Nuclear Security Fund.

Concern over accidental radiation exposure, including in the metal recycling and production industries, and intentional unauthorized acts involving radioactive sources led to the IAEA Board of Governors’ approval of the Code of Conduct on the Safety and Security of Radioactive Sources (the Code of Conduct) in 2003. The Code of Conduct, and its supplementary Guidance on the Import and Export of Radioactive Sources and Guidance on the Management of Disused Radioactive Sources, is a legally non-binding instrument helping countries in the development and harmonization of policies, laws and regulations on the safety and security of radioactive sources. Each country is responsible for the regulatory control of radioactive sources, from initial production to final disposal.

The objective of the Code is to help countries reduce the likelihood of accidental exposure to radioactive sources or the malicious use of such sources to cause harm. The Code aims to prevent unauthorized access or damage to, and loss, theft or unauthorized transfer of, radioactive sources.

How can I recognize a radioactive source?

The ionizing radiation symbol indicates the presence of ionizing radiation and radioactive sources. (Photos: IAEA) 

Most radioactive sources are used and contained inside a larger piece of equipment, protected by heavy shielding. The black, magenta or yellow trefoil symbol or the words “radiation” or “radioactive” are typically used around the world to label devices or containers holding radioactive sources.

Radioactive sources can look harmless — like a small piece of metal. See examples of radioactive sources. Radiation detection instruments are used to confirm if an object is radioactive.

What should I do if I find a radioactive source?

Stay away from objects with a radiation label, and do not touch them. Contact the authorities, such as the police, immediately. If you feel unwell, see a doctor immediately and inform them that you were near a potential source of radiation. Radiation injuries can look like burns, but do not heal as a burn would. Symptoms of radiation overexposure include nausea, diarrhoea and vomiting.

What is the role of the IAEA?

Practically all countries in the world use radioactive sources. The rays they emit can be used for many beneficial purposes, in medicine, industry and agriculture. But if sources are not controlled properly, they pose a threat to human health and the environment. The IAEA is helping countries to develop effective, safe and secure control systems for their radioactive sources – from the cradle to the grave.

  • The IAEA offers reporting and information systemstraining and information exchange, review services, including Integrated Regulatory Review Service, and assistance in implementing the Code of Conduct on the Safety and Security of Radioactive Sources and its supplementary Guidance. 
  • The IAEA Incident and Trafficking Database (ITDB) provides information related to lost or stolen nuclear and other radioactive material. This ranges from the smuggling and sale of nuclear material, to the unauthorized disposal and the discovery of lost radioactive sources.  
  • The IAEA publishes standards, recommendations and guidance for the safety and security of radioactive sources in the relevant IAEA Safety Standards Series and Nuclear Security Series.
  • The IAEA supports countries to apply the standards, recommendations and guidance, as well as in coordination with other bilateral or multilateral initiatives.
  • The IAEA assists countries in the management of disused sealed radioactive sources by providing reference material and technical guidance, e-learning, hands-on trainings and review services on the safe management of disused radioactive sources.
  • The IAEA also assists countries in implementing safe and cost-effective technologies for recovering, conditioning and storing radioactive sources.


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