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An orphan source is a self-contained radioactive source that is no longer under proper regulatory control.
...a sealed source of radioactive material contained in a small volume—but not radioactively contaminated soils and bulk metals—in any one or more of the following conditions
- In an uncontrolled condition that requires removal to protect public health and safety from a radiological threat
- Controlled or uncontrolled, but for which a responsible party cannot be readily identified
- Controlled, but the material's continued security cannot be assured. If held by a licensee, the licensee has few or no options for, or is incapable of providing for, the safe disposition of the material
- In the possession of a person, not licensed to possess the material, who did not seek to possess the material
- In the possession of a State radiological protection program for the sole purpose of mitigating a radiological threat because the orphan source is in one of the conditions described in one of the first four bullets and for which the State does not have a means to provide for the material's appropriate disposition
Orphan source incidents
Most known orphan sources were, generally, small radioactive sources produced legitimately under governmental regulation and put into service for radiography, generating electricity in radioisotope thermoelectric generators, medical radiotherapy or irradiation. These sources were then "abandoned, lost, misplaced or stolen" and so no longer subject to proper regulation.
For example, in different incidents, various orphan sources have been:
- 1984 - Morocco - A source was lost during radiography and taken home by other people who initially failed to recognize the source.
- 1987 - Praça Cívica, Brazil - A caesium-137 based teletherapy unit left behind at Goiânia’s Instituto Goiano de Radioterapia (IGR). This is one of the most disastrous orphan source incidents, the event is known as the Goiânia accident.
- 1996 - Gilan, Iran - A source was temporarily lost during radiography at a power plant and found by an unsuspecting worker who put the source in his chest pocket for about 90 minutes. 1 person was severely injured.
- 1997 - Tbilisi, Georgia - The Lilo Training Center had multiple sources dating back to Soviet era military activity; 11 were injured.
- 1999 - Kingisepp, Leningrad Oblast, Russia - Stolen from an RTG in a Russian lighthouse and then recovered 50 kilometres away at a bus station 
- 1999 - Istanbul, Turkey - A source was sold to a junkyard for its lead container in the city of İkitelli 
- 2000 - Thailand - A defunct cobalt therapy machine was sold to a metal junkyard in Samut Prakan, leading to three deaths.
- 2000 - Egypt - A source was taken home by an unsuspecting person near Mit Halfa, 15 km north of Cairo Qaluobiya,
- 2001 - Georgia - Three woodcutters in northern Georgia found two Soviet-era RTG elements near the Inguri River containing Strontium-90 and became sick from the high levels of radiation. As many as 300 orphan sources had been discovered in the country by 2006, when a team from the IAEA and Georgian government found two containing Caesium-137 in the Racha region. One of the sources had been kept in a home, and another in an abandoned factory used as storage by farmers.
- 2008 - Karachi, Pakistan - An orphan source was discovered within the vicinity of the OGDCL (Oil & Gas Development Company Limited). Two containers were found buried which were suspected to be left over from Soviet oil drilling operations before the OGDCL took over in late 1960s.
- 2010 - Mayapuri, India - An orphan source caused the death of one worker and irradiated seven others in a scrap yard in the Mayapuri radiological accident
- 2011 - Prague, Czech Republic - A brachytherapy source was found buried in a Prague playground, radiating 500 µSv/h from one metre away.
- 2013 - Hueypoxtla, Mexico - A defunct cobalt therapy machine en route to proper disposal was stolen, apparently inadvertently, when the heavy truck transporting it was hijacked.
- "NRC: Orphan Sources". Nrc.gov. Retrieved 2014-03-05.
-  Archived October 1, 2004, at the Wayback Machine.
- "Casablanca orphaned source, 1984". Johnstonsarchive.net. Retrieved 2014-03-05.
- "Gilan orphaned source, 1996". Johnstonsarchive.net. Retrieved 2014-03-05.
- "Lilo orphaned sources, 1996-1997". Johnstonsarchive.net. Retrieved 2014-03-05.
- "Kingisepp orphaned source, 1999". Johnstonsarchive.net. Retrieved 2014-03-05.
- "Nükleer ihmal". Milliyet.com.tr. Retrieved 2014-03-05.
- "IAEA Bulletin Volume 47, No.2 - Reducing the Risk from Radioactive Sources" (PDF). Iaea.org. Retrieved 2015-01-14.
- "Meet Halfa orphaned source, 2000". Johnstonsarchive.net. Retrieved 2014-03-05.
- "The Hunt for Hot Stuff". Smithsonianmag.com. March 2003. Retrieved 2014-12-06.
- "Radioactive Sources Recovered in Georgia". IAEA.org. 2006-07-27. Retrieved 2014-12-06.
- Baqir Sajjad Syed (2008-07-11). "Containers found with radioactive material". Dawn.Com. Retrieved 2014-03-05.
- ""Radioactive" little cylinder found underground in a park in Podolí". iDNES.cz. 29 September 2011. Retrieved 12 November 2012.
- Motl, Luboš. "Why a small cylinder buried in Prague radiates 500 μSv/h?". Retrieved 12 November 2012.
- Falvey, Christian (29 September 2011). "Passerby stumbles upon radioactive playground thanks to wristwatch". Radio Prague. Retrieved 21 November 2012.
- Will Grant (2013-12-05). "BBC News - Mexico radioactive material found, thieves' lives 'in danger'". Bbc.co.uk. Retrieved 2014-03-05.