Editing Radionuclide (section)

==Origin==

===Natural===
On Earth, naturally occurring radionuclides fall into three categories: primordial radionuclides, secondary radionuclides, and [[cosmogenic]] radionuclides.
* Radionuclides are produced in [[stellar nucleosynthesis]] and [[supernova explosions]] along with stable nuclides. Most decay quickly but can still be observed astronomically and can play a part in understanding astronomic processes. Primordial radionuclides, such as [[uranium]] and [[thorium]], exist in the present time because their [[half-life|half-lives]] are so long (>100 million years) that they have not yet completely decayed.  Some radionuclides have half-lives so long (many times the age of the universe) that decay has only recently been detected, and for most practical purposes they can be considered stable, most notably [[bismuth-209]]: detection of this decay meant that [[bismuth]] was no longer considered stable. It is possible decay may be observed in other nuclides, adding to this list of primordial radionuclides.
* Secondary radionuclides are radiogenic isotopes derived from the decay of primordial radionuclides. They have shorter half-lives than primordial radionuclides. They arise in the [[decay chain]] of the primordial isotopes [[thorium-232]], [[uranium-238]], and [[uranium-235]]. Examples include the natural isotopes of [[polonium]] and [[radium]].
* [[Cosmogenic isotopes]], such as [[carbon-14]], are present because they are continually being formed in the atmosphere due to [[cosmic ray]]s.<ref>{{cite book |url = https://books.google.com/books?id=RqEhyic9VJMC&pg=PA134| pages = 134 |title = Environmental Radioactivity: From Natural, Industrial, and Military Sources |isbn = 9780122351549 |last1 = Eisenbud |first1 = Merril |last2 = Gesell |first2 = Thomas F |date = 1997-02-25| publisher = Elsevier }}</ref>

Many of these radionuclides exist only in trace amounts in nature, including all cosmogenic nuclides. Secondary radionuclides will occur in proportion to their half-lives, so short-lived ones will be very rare. For example, polonium can be found in [[uranium]] ores at about 0.1&nbsp;mg per [[metric ton]] (1 part in 10<sup>10</sup>).<ref>Bagnall, K. W. (1962). "The Chemistry of Polonium". Advances in Inorganic Chemistry and Radiochemistry 4. New York: Academic Press. pp. 197–226. doi:10.1016/S0065-2792(08)60268-X. {{ISBN|0-12-023604-4}}. Retrieved June 14, 2012., p. 746</ref><ref>Bagnall, K. W. (1962). "The Chemistry of Polonium". Advances in Inorganic Chemistry and Radiochemistry 4. New York: Academic Press., p. 198</ref> Further radionuclides may occur in nature in virtually undetectable amounts as a result of rare events such as spontaneous fission or uncommon cosmic ray interactions.

===Nuclear fission===
Radionuclides are produced as an unavoidable result of [[nuclear fission]] and [[thermonuclear device|thermonuclear explosions]]. The process of nuclear fission creates a wide range of [[fission products]], most of which are radionuclides. Further radionuclides can be created from irradiation of the nuclear fuel (creating a range of [[actinides]]) and of the surrounding structures, yielding [[activation products]]. This complex mixture of radionuclides with different chemistries and radioactivity makes handling [[nuclear waste]] and dealing with [[nuclear fallout]] particularly problematic.{{cn|date=November 2023}}

===Synthetic===
[[File:Artificial nuclide americium-241 emitting alpha particles inserted into a cloud chamber for visualisation.jpg|thumb|[[Artificial]] [[nuclide]] [[americium-241]] emitting [[alpha particle]]s inserted into a [[cloud chamber]] for visualisation]]
[[Synthetic radionuclide]]s are deliberately synthesised using [[nuclear reactor]]s, particle accelerators or radionuclide generators:<ref>{{Cite web |date=2016-07-15 |title=Radioisotopes |url=https://www.iaea.org/topics/nuclear-science/isotopes/radioisotopes |access-date=2023-06-25 |website=www.iaea.org |language=en}}</ref>
* As well as being extracted from nuclear waste, radioisotopes can be produced deliberately with nuclear reactors, exploiting the high flux of [[neutron]]s present. These neutrons activate elements placed within the reactor. A typical product from a nuclear reactor is [[iridium-192]]. The elements that have a large propensity to take up the neutrons in the reactor are said to have a high [[neutron cross-section]].
* Particle accelerators such as [[cyclotron]]s accelerate particles to bombard a target to produce radionuclides. Cyclotrons accelerate protons at a target to produce positron-emitting radionuclides, e.g. [[fluorine-18]].
* Radionuclide generators contain a parent radionuclide that decays to produce a radioactive daughter. The parent is usually produced in a nuclear reactor. A typical example is the [[technetium-99m generator]] used in [[nuclear medicine]]. The parent produced in the reactor is [[molybdenum-99]].