An orphan source is a self-contained radioactive source that is no longer under regulatory control.
It is defined by the United States Nuclear Regulatory Commission as:
<blockquote>...a sealed source of radioactive material contained in a small volumeâÂÂbut not radioactively contaminated soils and bulk metalsâÂÂin any one or more of the following conditions:
Most known orphan sources were, generally, small radioactive sources produced legitimately under governmental regulation. They were used for a variety of purposes including gauges, static eliminators, and various devices used in nuclear medicine. These sources were then "abandoned, lost, misplaced or stolen" and so no longer subject to proper regulation. Sources that were never under regulatory control can still be considered orphan sources.
They can be accidentally incorporated into scrap metal, contaminating the resulting recycled metal. This necessitates expensive cleanup measures, and can expose manufacturing workers or the users of the metal products to harmful doses of ionizing radiation.