Editing Polonium (section)

==Occurrence and production==
Polonium is a very rare element in nature because of the short [[half-lives]] of all its isotopes. Nine isotopes, from 210 to 218 inclusive, occur in [[trace radioisotope|traces]] as [[decay products]]: <sup>210</sup>Po, <sup>214</sup>Po, and <sup>218</sup>Po occur in the [[decay chain]] of [[uranium-238|<sup>238</sup>U]]; <sup>211</sup>Po and <sup>215</sup>Po occur in the decay chain of [[uranium-235|<sup>235</sup>U]]; <sup>212</sup>Po and <sup>216</sup>Po occur in the decay chain of [[thorium-232|<sup>232</sup>Th]]; and <sup>213</sup>Po and <sup>217</sup>Po occur in the decay chain of [[neptunium-237|<sup>237</sup>Np]]. (No primordial <sup>237</sup>Np survives, but traces of it are continuously regenerated through (n,2n) knockout reactions in natural <sup>238</sup>U.)<ref name=4n1>{{cite journal |last1=Peppard |first1=D. F. |last2=Mason |first2=G. W. |last3=Gray |first3=P. R. |last4=Mech |first4=J. F. |title=Occurrence of the (4n + 1) series in nature |journal=Journal of the American Chemical Society |date=1952 |volume=74 |issue=23 |pages=6081–6084 |doi=10.1021/ja01143a074 |bibcode=1952JAChS..74.6081P |url=https://digital.library.unt.edu/ark:/67531/metadc172698/m2/1/high_res_d/metadc172698.pdf }}</ref> Of these, <sup>210</sup>Po is the only isotope with a half-life longer than 3&nbsp;minutes.<ref name="po484">{{Cite journal| last1=Carvalho|first1=F.|last2=Fernandes|first2=S.|last3=Fesenko|first3=S. |last4=Holm|first4=E.|last5=Howard|first5=B.|last6=Martin|first6=P.|last7=Phaneuf|first7=P. |last8=Porcelli|first8=D.|last9=Pröhl|first9=G.|last10=Twining|first10=J.|title=The Environmental Behaviour of Polonium|journal=Technical Reports Series – International Atomic Energy Agency|series=Technical reports series|volume=484|publisher=International Atomic Energy Agency|location=Vienna|date=2017|page=1|isbn=978-92-0-112116-5}}</ref>

Polonium can be found in [[uranium]] ores at about 0.1&nbsp;mg per [[metric ton]] (1 part in 10<sup>10</sup>),<ref>[[#Greenwood|Greenwood]], p. 746</ref><ref>[[#Bagnall|Bagnall]], p. 198</ref> which is approximately 0.2% of the abundance of radium. The amounts in the Earth's crust are not harmful. Polonium has been found in [[tobacco smoke]] from tobacco leaves grown with [[phosphate]] fertilizers.<ref>{{cite journal| last = Kilthau | first = Gustave F. |title = Cancer risk in relation to radioactivity in tobacco |journal = Radiologic Technology |volume = 67 |pages = 217–222| pmid = 8850254| date = 1996| issue = 3}}</ref><ref>{{cite web|url=http://kidslink.bo.cnr.it/besta/fumo/epolonio.html |title=Alpha Radioactivity (210 Polonium) and Tobacco Smoke |access-date=2009-05-05 |url-status=dead |archive-url=https://web.archive.org/web/20130609055245/http://kidslink.bo.cnr.it/besta/fumo/epolonio.html |archive-date=June 9, 2013 }}</ref><ref name="Muggli08">{{cite journal |title = Waking a Sleeping Giant: The Tobacco Industry's Response to the Polonium-210 Issue |last1 = Monique | first1 = E. Muggli |journal = American Journal of Public Health |volume = 98 |issue = 9| date = 2008 |pmid = 18633078|pmc = 2509609 |doi = 10.2105/AJPH.2007.130963 |pages = 1643–50 |last2 = Ebbert |first2 = Jon O. |last3 = Robertson |first3 = Channing |last4 = Hurt |first4 = Richard D.}}</ref>

Because it is present in small concentrations, isolation of polonium from natural sources is a tedious process. The largest batch of the element ever extracted, performed in the first half of the 20th century, contained only {{convert|40|Ci|TBq|abbr=on}} (9&nbsp;mg) of [[polonium-210]] and was obtained by processing 37 tonnes of residues from radium production.<ref>{{cite journal|author=Adloff, J. P.|author2=MacCordick, H. J.|name-list-style=amp|title=The Dawn of Radiochemistry|journal=Radiochimica Acta|volume=70/71|pages=13–22|date=1995|issue=Supplement |url=http://www.nucleonica.com/wiki/Articles/Article03/Article3.htm|doi=10.1524/ract.1995.7071.special-issue.13|s2cid=99790464}}, reprinted in {{cite book|url = https://books.google.com/books?id=whGiCQywLi8C&pg=PA17|title = One hundred years after the discovery of radioactivity|isbn = 978-3-486-64252-0|last1 = Adloff|first1 = J. P.|date = 1996|page = 17|publisher = Walter de Gruyter GmbH}}{{Dead link|date=May 2024 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> Polonium is now usually obtained by irradiating bismuth with high-energy neutrons or protons.<ref name="nbb" /><ref name="g249">[[#Greenwood|Greenwood]], p. 249</ref>

In 1934, an experiment showed that when natural [[bismuth-209|<sup>209</sup>Bi]] is bombarded with [[neutron]]s, <sup>210</sup>Bi is created, which then decays to <sup>210</sup>Po via beta-minus decay. By irradiating certain bismuth salts containing light element nuclei such as beryllium, a cascading (α,n) reaction can also be induced to produce <sup>210</sup>Po in large quantities.<ref>{{cite journal |title =Neutronic Chain Reactions for Polonium-210 Production |first =Solomon |last = Lim |journal = SSRN |date = 2023 |doi = 10.2139/ssrn.4469519|s2cid =264176122 |url =https://hal.science/hal-04196973/file/Report%20210.pdf }}</ref> The final purification is done pyrochemically followed by liquid-liquid extraction techniques.<ref>{{cite journal |title =Pyrochemical Extraction of Polonium from Irradiated Bismuth Metal |first =Wallace W. |last = Schulz |author2 = Schiefelbein, Gary F. |author3 = Bruns, Lester E. |journal = Ind. Eng. Chem. Process Des. Dev. |date = 1969 |volume = 8 |issue = 4 |pages= 508–515| doi = 10.1021/i260032a013}}</ref> Polonium may now be made in milligram amounts in this procedure which uses high neutron fluxes found in [[nuclear reactor]]s.<ref name="g249" /> Only about 100&nbsp;grams are produced each year, practically all of it in Russia, making polonium exceedingly rare.<ref>{{cite web |title = Q&A: Polonium-210 |url =http://www.rsc.org/chemistryworld/News/2006/November/27110601.asp |publisher = RSC Chemistry World |date = 2006-11-27 |access-date =2009-01-12}}</ref><ref>{{cite web |date=2007-01-11 |title=Most Polonium Made Near the Volga River |url=https://www.themoscowtimes.com/archive/most-polonium-made-near-the-volga-river |publisher=The Moscow Times – News}}</ref>

This process can cause problems in [[Lead-bismuth eutectic|lead-bismuth]] based [[Liquid metal cooled reactor|liquid metal cooled nuclear reactors]] such as those used in the [[Soviet Navy]]'s [[Soviet submarine K-27|K-27]]. Measures must be taken in these reactors to deal with the unwanted possibility of <sup>210</sup>Po being released from the coolant.<ref>{{cite journal|title=Long-lived radionuclides of sodium, lead-bismuth, and lead coolants in fast-neutron reactors|journal=Atomic Energy|volume =87|issue=3 |year=1999|pages=658–662|doi=10.1007/BF02673579|last1=Usanov|first1=V. I.|last2=Pankratov|first2=D. V.|last3=Popov|first3=É. P.|last4=Markelov|first4=P. I.|last5=Ryabaya|first5=L. D.|last6=Zabrodskaya|first6=S. V.|s2cid=94738113}}</ref><ref>{{cite journal|author=Naumov, V. V. |date=November 2006|url=http://www.antiatom.ru/2006_12-11.php|script-title=ru:За какими корабельными реакторами будущее?|language=ru|journal= Атомная стратегия |volume= 26}}</ref>

The longer-lived isotopes of polonium, <sup>208</sup>Po and <sup>209</sup>Po, can be formed by [[proton]] or [[deuteron]] bombardment of bismuth using a [[cyclotron]]. Other more neutron-deficient and more unstable isotopes can be formed by the irradiation of platinum with [[carbon]] nuclei.<ref>{{cite journal| author = Atterling, H.| author2 = Forsling, W. |title = Light Polonium Isotopes from Carbon Ion Bombardments of Platinum |journal = Arkiv för Fysik |volume = 15| issue = 1 |pages = 81–88 |date = 1959 |osti =4238755}}</ref>