Radioactive sources vary greatly in terms of entity size and nature, amount of radioactivity, and availability.

Medical sources In medicine, radiation sources are used for diagnostic and therapeutic purposes. Radiological clinical diagnostic examination can be divided into two parts: in vivo examination (functional measurement and imaging technology) and in vitro examination (competitive radiological analysis, etc.). Clinical diagnosis of nuclear medicine is to use radionuclide as a tracer, and measure its distribution and intensity in the organs through nuclear instruments, which can diagnose diseases, including thyroid iodine-131 analysis and iodine-125 radioimmunoassay. Extracorporeal beam (often called teleradiotherapy) treatment, such as cobalt therapy equipment. Or make the radiation source directly contact the tissue (usually called brachytherapy, which includes the application of the source in the interstitial cavity, intraluminal application and superficial application) for radiation therapy, such as radium needle implantation.

Industrial sources There are many radioactive sources used in industry for product irradiation, radiography and metrology. There are a large number of industrial irradiation installations all over the world. They are giant devices that contain a lot of radioactivity and are usually used for disinfection of medical products (such as syringes) and food preservation. The radioactive element used in industrial irradiation devices is mainly metal cobalt-60. Thousands of cobalt-60 pellets that constitute the radioactive source are packed in a large number of "rods", but some devices are still equipped with cesium-137 sources.

A large number of radioactive sources are used for industrial radiography purposes, the number of which is estimated to be tens of thousands. Approximately 80% of this source contains the radioactive element iridium-192; the rest are cobalt-60, selenium-75 and ytterbium-169 sources. The typical activity of each source is about 50-100 Curie. Their physical form is usually the metal contained in the source box, which makes them very strong and difficult to disperse. Although these sources are therefore unlikely to cause serious pollution hazards, they can cause significant harm to individuals exposed to the source. It is easier to steal an industrial radiographic source, but it is more difficult to accumulate in large quantities because they are usually stored in different industrial locations.

Finally, millions of sources with lower radioactive content are used for industrial metrology and other purposes. They usually contain cobalt-60, cesium-137 or americium-241, and they have a variety of physical forms, and many countries do not strictly control them. Although they are only a minor hazard, they can cause small-scale and easily measurable pollution. To

Unprimed sources Government regulatory authorities around the world exercise control over most radioactive sources. The competent authority usually implements methods of registration, licensing, authorization and periodic inspection of sources. However, as sources reach their expected working life, they are no longer needed, and sometimes even sources that may never be under regulatory control or begin to be regulated due to the removal of control are eventually abandoned, lost or misplaced, stolen, or moved without authorization. It is not clear how many unhosted sources are in the hundreds each year in the world, and their locations are basically unknown.