Editing Actinide (section)

== Applications ==
[[File:InsideSmokeDetector.jpg|thumb|Interior of a [[smoke detector]] containing [[americium-241]].]]
While actinides have some established daily-life applications, such as in smoke detectors (americium)<ref>[https://web.archive.org/web/19960101/http://www.uic.com.au/nip35.htm Smoke Detectors and Americium], Nuclear Issues Briefing Paper 35, May 2002</ref><ref name=g1262>Greenwood, p. 1262</ref> and [[gas mantle]]s (thorium),<ref name=g1255>Greenwood, p. 1255</ref> they are mostly used in [[nuclear weapon]]s and as [[nuclear fuel|fuel]] in nuclear reactors.<ref name=g1255 /> The last two areas exploit the property of actinides to release enormous energy in nuclear reactions, which under certain conditions may become self-sustaining [[Nuclear chain reaction|chain reactions]].

[[File:Cerenkov Effect.jpg|thumb|left|upright|Self-illumination of a nuclear reactor by [[Cherenkov radiation]].]]
The most important isotope for [[nuclear power]] applications is [[uranium-235]]. It is used in the [[thermal reactor]], and its concentration in natural uranium does not exceed 0.72%. This isotope strongly absorbs [[thermal neutron]]s releasing much energy. One fission act of 1&nbsp;gram of <sup>235</sup>U converts into about 1 MW·day. Of importance, is that {{nuclide|U|235}} emits more neutrons than it absorbs;<ref name=g220>Golub, pp. 220–221</ref> upon reaching the [[critical mass]], {{nuclide|U|235}} enters into a self-sustaining chain reaction.<ref name="Yu. D. Tretyakov">{{cite book|editor=Yu.D. Tretyakov|title=Non-organic chemistry in three volumes|place=Moscow|publisher=Academy|year=2007|volume=3|series=Chemistry of transition elements|isbn=978-5-7695-2533-9}}</ref> Typically, uranium nucleus is divided into two fragments with the release of 2–3 neutrons, for example:
: {{nuclide|U|235|link=yes}} + {{nuclide|neutronium|1|link=yes}} ⟶ {{nuclide|Rh|115}} + {{Nuclide|Ag|118}} + 3{{nuclide|neutronium|1}}

Other promising actinide isotopes for nuclear power are [[thorium-232]] and its product from the [[thorium fuel cycle]], [[uranium-233]].
{| class="wikitable"  style="float:right; width:40%;"
|-  style="background:lightblue; text-align:center;"
| [[Nuclear reactor]]<ref name="Yu. D. Tretyakov" /><ref>{{cite book|author1=G. G. Bartolomei|author2=V. D. Baybakov|author3=M. S. Alkhutov|author4=G. A. Bach|title=Basic theories and methods of calculation of nuclear reactors|location=Moscow|publisher=Energoatomizdat|year=1982}}</ref><ref>Greenwood, pp. 1256–1261</ref>
|-
| <small> The core of most [[Generation II reactor|Generation II nuclear reactors]] contains a set of hollow metal rods, usually made of [[zirconium]] alloys, filled with solid [[nuclear fuel]] pellets – mostly oxide, carbide, nitride or monosulfide of uranium, plutonium or thorium, or their mixture (the so-called [[MOX fuel]]). The most common fuel is oxide of uranium-235.</small>
[[File:Heterogeneous reactor scheme.png|border|150px|left|Nuclear reactor scheme]]
<small>[[Neutron temperature|Fast neutrons]] are slowed by [[Moderator (Nuclear Reactor)|moderators]], which contain water, [[carbon]], [[deuterium]], or [[beryllium]], as [[thermal neutrons]] to increase the efficiency of their interaction with uranium-235. The rate of nuclear reaction is controlled by introducing additional rods made of [[boron]] or [[cadmium]] or a liquid absorbent, usually [[boric acid]]. Reactors for plutonium production are called [[breeder reactor]] or breeders; they have a different design and use fast neutrons.</small>
|}
Emission of neutrons during the fission of uranium is important not only for maintaining the nuclear chain reaction, but also for the synthesis of the heavier actinides. [[Uranium-239]] converts via [[Beta decay|β-decay]] into plutonium-239, which, like uranium-235, is capable of spontaneous fission. The world's first nuclear reactors were built not for energy, but for producing plutonium-239 for nuclear weapons.

About half of produced thorium is used as the light-emitting material of gas mantles.<ref name=g1255 /> Thorium is also added into multicomponent [[alloy]]s of [[magnesium]] and [[zinc]]. Mg-Th alloys are light and strong, but also have high melting point and ductility and thus are widely used in the aviation industry and in the production of [[missile]]s. Thorium also has good [[electron emission]] properties, with long lifetime and low potential barrier for the emission.<ref name=g220 /> The relative content of thorium and uranium isotopes is widely used to estimate the age of various objects, including stars (see [[:Category:Radiometric dating|radiometric dating]]).<ref>{{cite journal|author1=Sergey Popov|author2=Alexander Sergeev|title=Universal Alchemy|url=http://www.vokrugsveta.ru/vs/article/6214/|language=ru|journal=Vokrug Sveta|year=2008|volume=2811|issue=4}}</ref>

The major application of plutonium has been in [[nuclear weapon]]s, where the isotope plutonium-239 was a key component due to its ease of fission and availability. Plutonium-based designs allow reducing the [[critical mass (nuclear)|critical mass]] to about a third of that for uranium-235.<ref>{{cite book|author=David L. Heiserman|title=Exploring Chemical Elements and their Compounds|location=New York|year=1992|publisher=TAB Books|isbn=978-0-8306-3018-9|chapter=Element 94: Plutonium|page=338|chapter-url=https://archive.org/details/exploringchemica01heis/page/338}}</ref> The "[[Fat Man]]"-type plutonium bombs produced during the [[Manhattan Project]] used explosive compression of plutonium to obtain significantly higher densities than normal, combined with a central neutron source to begin the reaction and increase efficiency. Thus only 6.2&nbsp;kg of plutonium was needed for an [[Nuclear weapon yield|explosive yield]] equivalent to 20 kilotons of [[Trinitrotoluene|TNT]].<ref>{{cite book|author=John Malik|url=https://fas.org/sgp/othergov/doe/lanl/docs1/00313791.pdf|title=The Yields of the Hiroshima and Nagasaki Explosions|publisher=Los Alamos|id=LA-8819|date=September 1985|page=Table VI|access-date=15 February 2009|archive-url=https://web.archive.org/web/20090224204106/https://fas.org/sgp/othergov/doe/lanl/docs1/00313791.pdf|archive-date=24 February 2009|url-status=live}}</ref> (See also [[Nuclear weapon design]].) Hypothetically, as little as 4&nbsp;kg of plutonium—and maybe even less—could be used to make a single atomic bomb using very sophisticated assembly designs.<ref>{{cite web|url=https://fas.org/nuke/intro/nuke/design.htm|title=Nuclear Weapon Design|publisher=Federation of American Scientists|year=1998|access-date=7 December 2008|archive-url=https://web.archive.org/web/20081226091803/https://fas.org/nuke/intro/nuke/design.htm|archive-date=26 December 2008|url-status=dead}}</ref>

[[Plutonium-238]] is potentially more efficient isotope for nuclear reactors, since it has smaller critical mass than uranium-235, but it continues to release much thermal energy (0.56 W/g)<ref name=g1262 /><ref>John Holdren and Matthew Bunn [https://web.archive.org/web/20101105035505/http://www.nti.org/e_research/cnwm/overview/technical2.asp Nuclear Weapons Design & Materials]. Project on Managing the Atom (MTA) for NTI. 25 November 2002</ref> by decay even when the fission chain reaction is stopped by control rods. Its application is limited by its high price (about US$1000/g). This isotope has been used in [[thermopile]]s and water [[distillation]] systems of some space satellites and stations. The [[Galileo (spacecraft)|Galileo]] and [[Apollo program|Apollo]] spacecraft (e.g. [[Apollo 14]]<ref>[http://www.hq.nasa.gov/alsj/a14/A14_PressKit.pdf Apollo 14 Press Kit – 01/11/71] {{Webarchive|url=https://web.archive.org/web/20190721143247/http://www.hq.nasa.gov/alsj/a14/A14_PressKit.pdf |date=21 July 2019 }}, NASA, pp. 38–39</ref>) had heaters powered by kilogram quantities of plutonium-238 oxide; this heat is also transformed into electricity with thermopiles. The decay of plutonium-238 produces relatively harmless alpha particles and is not accompanied by [[gamma ray]]s. Therefore, this isotope (~160&nbsp;mg) is used as the energy source in heart pacemakers where it lasts about 5 times longer than conventional batteries.<ref name=g1262 />

[[Actinium-227]] is used as a neutron source. Its high specific energy (14.5 W/g) and the possibility of obtaining significant quantities of thermally stable compounds are attractive for use in long-lasting thermoelectric generators for remote use. <sup>228</sup>Ac is used as an indicator of [[radioactivity]] in chemical research, as it emits high-energy electrons (2.18 MeV) that can be easily detected. [[Actinium-228|<sup>228</sup>Ac]]-[[Radium-228|<sup>228</sup>Ra]] mixtures are widely used as an intense gamma-source in industry and medicine.<ref name="Himiya aktiniya" />

Development of self-glowing actinide-doped materials with durable crystalline matrices is a new area of actinide utilization as the addition of alpha-emitting radionuclides to some glasses and crystals may confer luminescence.<ref name=burakov>{{cite book|author1=B.E. Burakov|author2=M.I Ojovan|author3=W.E. Lee|title=Crystalline Materials for Actinide Immobilisation|publisher=World Scientific|year=2010|url=https://books.google.com/books?id=BWriuXxa7CYC|isbn=978-1-84816-418-5}}</ref>