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An orphan source is a self-contained radioactive source that is no longer under proper regulatory control. The United States Nuclear Regulatory Commission defines an orphan source more exactly as: ...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 ==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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Orphan source」の詳細全文を読む スポンサード リンク
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