An orphan source is a self-contained radioactive source that is no longer under regulatory control.
The United States Nuclear Regulatory Commission definition is:[1] ...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: 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.
[citation needed] These sources were then "abandoned, lost, misplaced or stolen" and so no longer subject to proper regulation.
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