(1) Anything that may cause radiation exposure - such as by emitting ionizing radiation or by releasing radioactive substances or materials - and can be treated as a single entity for protection and safety purposes. For example, materials emitting radon are sources in the environment, a sterilization gamma irradiation unit is a source for the practice of radiation preservation of food, an X ray unit may be a source for the practice of radiodiagnosis; a nuclear power plant is part of the practice of generating electricity by nuclear fission, and may be regarded as a source (e.g. with respect to discharges to the environment) or as a collection of sources (e.g. for occupational radiation protection purposes). A complex or multiple installation situated at one location or site may, as appropriate, be considered a single source for the purposes of application of international safety standards. Natural Source: A naturally occurring source of radiation, such as the sun and stars (sources of cosmic radiation) and rocks and soil (terrestrial sources of radiation). Examples of natural sources are the sun and stars (sources of cosmic radiation), rocks and soil (terrestrial sources of radiation), and naturally occurring radioactive material (NORM) associated with the processing of raw materials (i.e. feedstocks, intermediate products, final products, co-products and waste). Radiation Source: A radiation generator, or a radioactive source or other radioactive material outside the nuclear fuel cycles of research and power reactors. [Defined in the 2001 edition of the Code of Conduct on the Safety and Security of Radioactive Sources, but not included in the 2004 edition (IAEA, Vienna (2004); see Ref.] (2) Radioactive material used as a source of radiation. Such as those used for medical applications or in industrial instruments. These are, of course, sources as defined in (1), but this usage is less general. Dangerous Source: A source that could, if not under control, give rise to exposure sufficient to cause severe deterministic effects. This categorization is used for determining the need for emergency response arrangements and is not to be confused with categorizations of sources for other purposes. Disused Source: A radioactive source that is no longer used, and is not intended to be used, for the practice for which an authorization has been granted. The Joint Convention refers to "disused sealed sources", but does not define them. On the basis of this definition of disused source and the definition of sealed source (see below), a disused sealed source is a radioactive source comprising radioactive material that is permanently sealed in a capsule or closely bonded and in a solid form, excluding reactor fuel elements, that is no longer used, and is not intended to be used, for the practice for which an authorization has been granted. ! Note that a disused source may still represent a significant radiological hazard. It differs from a spent source in that it may still be capable of performing its function; it may be disused because it is no longer needed. Orphan Source: A radioactive source which is not under regulatory control, either because it has never been under regulatory control, or because it has been abandoned, lost, misplaced, stolen or otherwise transferred without proper authorization. Radioactive Source: Radioactive material that is permanently sealed in a capsule or closely bonded and in a solid form and which is not exempt from regulatory control. It also includes any radioactive material released if the radioactive source is leaking or broken, but does not include material encapsulated for disposal, or nuclear material within the nuclear fuel cycles of research and power reactors. This definition is particular to the Code of Conduct on the Safety and Security of Radioactive Sources