View source for Polonium-210

{{Short description|Isotope of polonium}}
{{Infobox isotope|
 | image =
 | image_caption =
 | alternate_names =radium&nbsp;F
 | mass_number = 210
 | symbol = Po
 | num_neutrons = 126
 | num_protons = 84
 | abundance = [[Trace radioisotope|Trace]]
 | halflife = {{val|138.376|0.002|u=d}}<ref name =half>Nuclear Data Center at [[KAERI]]; Table of Nuclides http://atom.kaeri.re.kr/nuchart/?zlv=1</ref> 
 | decay_product = Lead-206
 | decay_mass = 206
 | decay_symbol = Pb
 | parent = Bismuth-210
 | parent_mass = 210
 | parent_symbol = Bi
 | parent_decay =b
 | parent2 =
 | parent2_mass =
 | parent2_symbol =
 | parent2_decay =
 | mass = 209.9828736{{AME2016 II|ref}}
 | spin = 0
 | decay_mode1 =[[Alpha decay]]
 | decay_energy1 =5.40753{{AME2016 II|name}}
 | decay_mode2 =
 | decay_energy2 =
 | decay_mode3 =
 | decay_energy3 =
 | decay_mode4 =
 | decay_energy4 =
 }}
'''Polonium-210''' (<sup>210</sup>Po, Po-210, historically '''radium F''') is an [[isotope]] of [[polonium]]. It undergoes [[alpha decay]] to [[stable nuclide|stable]] [[lead-206|<sup>206</sup>Pb]] with a half-life of 138.376 days (about {{frac|4|1|2}} months), the longest half-life of all naturally occurring [[isotopes of polonium|polonium isotopes]] (<sup>210–218</sup>Po).<ref name =half/> First identified in 1898, and also marking the discovery of the [[chemical element|element]] polonium, <sup>210</sup>Po is generated in the [[decay chain]] of [[uranium-238]] and [[radium-226]]. <sup>210</sup>Po is a prominent contaminant in the environment, mostly affecting [[seafood]] and [[tobacco]]. Its extreme [[toxicity]] is attributed to intense radioactivity, mostly due to [[alpha particle]]s, which easily cause radiation damage, including [[cancer]] in surrounding tissue. The [[specific activity]] of {{chem|210|Po}} is 166&nbsp;TBq/g, i.e., {{val|1.66|e=14|u=Bq/g}}. At the same time, <sup>210</sup>Po is not readily detected by common radiation detectors, because its [[gamma rays]] have a very low energy. Therefore, {{chem|210|Po}} can be considered as a quasi-pure alpha emitter.

==History==
[[File:Decay chain(4n+2, Uranium series).svg|thumb|left|250px|The decay chain of [[uranium-238]], known as the uranium series or radium series, of which polonium-210 is a member]]
[[File:S-R-processes-atomic-mass-201-to-210.svg|thumb|left|250px|Schematic of the final steps of the [[s-process]]. The red path represents the sequence of neutron captures; blue and cyan arrows represent [[beta decay]], and the green arrow represents the alpha decay of <sup>210</sup>Po. It is the short half-lives of <sup>210</sup>Bi and <sup>210</sup>Po that prevent the formation of heavier elements, instead resulting in a cycle of four neutron captures, two beta decays, and an alpha decay.]]

In 1898, [[Marie Curie|Marie]] and [[Pierre Curie]] discovered a strongly radioactive substance in [[pitchblende]] and determined that it was a new element; it was one of the first radioactive elements discovered. Having identified it as such, they named the element polonium after Marie's home country, [[Poland]]. [[Willy Marckwald]] discovered a similar radioactive activity in 1902 and named it '''radio-tellurium''', and at roughly the same time, [[Ernest Rutherford]] identified the same activity in his analysis of the uranium decay chain and named it '''radium F''' (originally '''radium E'''). By 1905, Rutherford concluded that all these observations were due to the same substance, <sup>210</sup>Po. Further discoveries and the concept of isotopes, first proposed in 1913 by [[Frederick Soddy]], firmly placed <sup>210</sup>Po as the penultimate step in the [[decay chain#Uranium series|uranium series]].<ref name=thoennes>{{Thoennessen2016|pages=6–8}}</ref>

In 1943, <sup>210</sup>Po was studied as a possible [[neutron initiator]] in [[nuclear weapons]], as part of the [[Dayton Project]]. In subsequent decades, concerns for the safety of workers handling <sup>210</sup>Po led to extensive studies on its health effects.<ref name=why>{{cite magazine |last=Roessler |first=G. |title=Why <sup>210</sup>Po? |url=https://hps.org/documents/polonium_210_story.pdf |magazine=Health Physics News |publisher=[[Health Physics Society]] |date=2007 |volume=35 |issue=2 |access-date=2019-06-20 |archive-url=https://web.archive.org/web/20140403100938/http://hps.org/documents/polonium_210_story.pdf |archive-date=2014-04-03 |url-status=live }}</ref>

In the 1950s, scientists of the [[United States Atomic Energy Commission]] at [[Mound Laboratories]], Ohio explored the possibility of using <sup>210</sup>Po in [[radioisotope thermoelectric generator]]s (RTGs) as a heat source to power satellites. A 2.5-[[watt]] [[atomic battery]] using <sup>210</sup>Po was developed by 1958. However, the isotope [[plutonium-238]] was chosen instead, as it has a longer half-life of 87.7&nbsp;years.<ref name=AECch>{{cite book |chapter-url=https://inl.gov/wp-content/uploads/2014/10/AtomicPowerInSpaceII-AHistory_2015_chapters1-2.pdf |chapter=The Early Years: Space Nuclear Power Systems Take Flight |title=Atomic power in space II: a history of space nuclear power and propulsion in the United States. |oclc=931595589 |author=Idaho National Laboratory |date=2015 |pages=2–5|author-link=Idaho National Laboratory }}</ref>

Polonium-210 was [[Poisoning of Alexander Litvinenko|used to kill]] Russian dissident and ex-[[Federal Security Service of the Russian Federation|FSB]] officer [[Alexander Litvinenko|Alexander V. Litvinenko]] in 2006,<ref name="death">{{cite journal |last1=McFee |first1=R. B. |last2=Leikin |first2=J. B. |date=2009 |title=Death by polonium-210: lessons learned from the murder of former Soviet spy Alexander Litvinenko |url=https://www.researchgate.net/publication/24206298 |journal=Seminars in Diagnostic Pathology |volume=26 |issue=1 |pages=61–67 |doi=10.1053/j.semdp.2008.12.003 |pmid=19292030}}</ref><ref>{{cite news |first=A. |last=Cowell |date=November 24, 2006 |title=Radiation Poisoning Killed Ex-Russian Spy |url=https://www.nytimes.com/2006/11/24/world/europe/25spycnd.html |work=[[The New York Times]] |access-date=June 19, 2019 |archive-url=https://web.archive.org/web/20190619142636/https://www.nytimes.com/2006/11/24/world/europe/25spycnd.html |archive-date=June 19, 2019 |url-status=live }}</ref> and was suspected as a possible [[Cause of Yasser Arafat's death#Poisoning with polonium|cause of Yasser Arafat's death]], following exhumation and analysis of his corpse in 2012–2013.<ref>{{cite web|title=Arafat's death: what is Polonium-210?|url=http://www.aljazeera.com/video/asia-pacific/2012/07/2012746748407858.html|work=[[Al Jazeera English|Al Jazeera]]|date=July 10, 2012|access-date=June 19, 2019|archive-url=https://web.archive.org/web/20190619142649/https://www.aljazeera.com/video/asia-pacific/2012/07/2012746748407858.html|archive-date=June 19, 2019|url-status=live}}</ref> The radioisotope may also have been used to kill [[Yuri Shchekochikhin]], [[Lecha Islamov]] and [[Roman Tsepov]].<ref name="Sweeney">{{cite book | last1=Sweeney | first1=J. | title=Killer in the Kremlin | page=120 | year=2022 | isbn=9781804991206 | publisher=Penguin }}</ref>

==Decay properties==
<sup>210</sup>Po is an [[alpha decay|alpha emitter]] that has a half-life of 138.376 days;<ref name =half/> it decays directly to stable [[lead-206|<sup>206</sup>Pb]]. The majority of the time, <sup>210</sup>Po decays by emission of an [[alpha particle]] only, not by emission of an alpha particle and a [[gamma ray]]; about one in 100,000 decays results in the emission of a gamma ray.<ref>{{cite web |work=[[Korea Atomic Energy Research Institute]] |url=http://atom.kaeri.re.kr/cgi-bin/decay?Po-210%20A |title=210Po A Decay|archive-url=https://web.archive.org/web/20150224043744/http://atom.kaeri.re.kr/cgi-bin/decay?Po-210+A |archive-date=February 24, 2015 }}</ref> 

:<math> \mathrm{

^{210}_{\ 84}Po\ \xrightarrow [138.376 \ d]{}\ ^{206}_{\ 82}Pb\ + ^{\ 4}_{\ 2}He

}
</math>

This low gamma ray production rate makes it more difficult to find and identify this isotope. Rather than [[gamma ray spectroscopy]], [[Alpha-particle spectroscopy|alpha spectroscopy]] is the best method of measuring this isotope.

Owing to its much shorter half-life, a milligram of <sup>210</sup>Po emits as many alpha particles per second as 5&nbsp;grams of [[Radium-226|<sup>226</sup>Ra]].<ref>{{cite web |title=The Elements |author=C. R. Hammond |publisher=Fermi National Accelerator Laboratory |pages=4–22 |url=http://www-d0.fnal.gov/hardware/cal/lvps_info/engineering/elements.pdf |access-date=2019-06-19 |archive-url=https://web.archive.org/web/20080626181434/http://www-d0.fnal.gov/hardware/cal/lvps_info/engineering/elements.pdf |archive-date=2008-06-26 |url-status=live }}</ref> A few [[Curie (unit)|curie]]s of <sup>210</sup>Po emit a blue glow caused by [[Excited state|excitation]] of surrounding air.

<sup>210</sup>Po occurs in minute amounts in nature, where it is the penultimate isotope in the [[decay chain#Uranium series|uranium series decay chain]]. It is generated via [[beta decay]] from <sup>210</sup>[[lead|Pb]] and <sup>210</sup>[[Bismuth|Bi]].

The astrophysical [[s-process]] is terminated by the decay of <sup>210</sup>Po, as the [[neutron flux]] is insufficient to lead to further [[neutron capture]]s in the short lifetime of <sup>210</sup>Po. Instead, <sup>210</sup>Po alpha decays to <sup>206</sup>Pb, which then captures more neutrons to become <sup>210</sup>Po and repeats the cycle, thus consuming the remaining neutrons. This results in a buildup of lead and bismuth, and ensures that heavier elements such as [[thorium]] and uranium are only produced in the much faster [[r-process]].<ref name="Synthesis of the Elements in Stars">{{cite journal |last1=Burbidge |first1=E. M. |last2=Burbidge |first2=G. R. |last3=Fowler |first3=W. A. |last4=Hoyle |first4=F. |date=1957 |title=Synthesis of the Elements in Stars |journal=[[Reviews of Modern Physics]] |volume=29 |issue=4 |pages=547–650 |bibcode=1957RvMP...29..547B |doi=10.1103/RevModPhys.29.547 |doi-access=free}}</ref>

==Production==
=== Deliberate===
Although <sup>210</sup>Po occurs in trace amounts in nature, it is not abundant enough (0.1 [[parts per billion|ppb]]) for extraction from uranium ore to be feasible. Instead, most <sup>210</sup>Po is produced synthetically, through neutron bombardment of [[bismuth-209|<sup>209</sup>Bi]] in a [[nuclear reactor]]. This process converts <sup>209</sup>Bi to <sup>210</sup>Bi, which beta decays to <sup>210</sup>Po with a five-day half-life.<ref>https://doh.wa.gov/sites/default/files/legacy/Documents/Pubs//320-091_po210_fs.pdf</ref> Through this method, approximately {{Convert|8|g}} of <sup>210</sup>Po are produced in Russia and shipped to the United States every month for commercial applications.<ref name=why/> 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|url =https://hal.science/hal-04196973/file/Report%20210.pdf }}</ref>

===Byproduct===
The production of polonium-210 is a downside to reactors cooled with [[lead-bismuth eutectic]] rather than pure lead. However, given the [[eutectic]] properties of this alloy, some proposed [[Generation IV reactor]] designs still rely on lead-bismuth.

==Applications==
A single gram of <sup>210</sup>Po generates 140 watts of power.<ref>{{Cite web|url = http://www.ead.anl.gov/pub/doc/polonium.pdf|title = Polonium|publisher = Argonne National Laboratory|archive-url = https://web.archive.org/web/20120310145431/http://www.ead.anl.gov/pub/doc/polonium.pdf|archive-date = 2012-03-10}}</ref> Because it emits many [[alpha radiation|alpha particles]], which are stopped within a very short distance in dense media and release their energy, <sup>210</sup>Po has been used as a lightweight [[heat source]] to power [[Radioisotope thermoelectric generator|thermoelectric cells]] in [[artificial satellite]]s. A <sup>210</sup>Po heat source was also in each of the [[Lunokhod]] rovers deployed on the surface of the [[Moon]], to keep their internal components warm during the lunar nights.<ref>A. Wilson, ''Solar System Log'', (London: Jane's Publishing Company Ltd, 1987), p. 64.{{ISBN?}}</ref> Some anti-static brushes, used for neutralizing [[static electricity]] on materials like photographic film, contain a few [[microcuries]] of <sup>210</sup>Po as a source of charged particles.<ref>{{cite web |publisher=Company 7 |title=Staticmaster Alpha Ionizing Brush |url=http://www.company7.com/staticmaster/products/staticmaster.html |access-date=2019-06-19 |archive-url=https://web.archive.org/web/20180927235206/http://www.company7.com/staticmaster/products/staticmaster.html |archive-date=2018-09-27 |url-status=live }}</ref> <sup>210</sup>Po was also used in [[Modulated neutron initiator|initiators]] for atomic bombs through the (α,n) reaction with [[beryllium]].<ref name="HoddesonHenriksen2004">{{cite book |first1=L. |last1=Hoddeson |first2=P. W. |last2=Henriksen |first3=R. A. |last3=Meade|title=Critical Assembly: A Technical History of Los Alamos During the Oppenheimer Years, 1943–1945|url=https://books.google.com/books?id=KoTve97yYB8C|year=2004|publisher=Cambridge University Press|isbn=978-0-521-54117-6}}</ref> Small [[neutron source]]s reliant on the (α,n) reaction also usually use polonium as a convenient source of alpha particles due to its comparatively low gamma emissions (allowing easy shielding) and high [[specific activity]].

==Hazards==
{{main|Polonium#Biology and toxicity}}

<sup>210</sup>Po is extremely toxic; it and other polonium isotopes are some of the most [[Radiotoxicity|radiotoxic]] substances to humans.<ref name=death/><ref name=nukleonika>{{cite journal |last1=Skwarzec |first1=B. |last2=Strumińska |first2=D. I. |last3=Boryło |first3=A. |title=Radionuclides of iron (<sup>55</sup>Fe), nickel (<sup>63</sup>Ni), polonium (<sup>210</sup>Po), uranium (<sup>234</sup>U, <sup>235</sup>U, <sup>238</sup>U), and plutonium (<sup>238</sup>Pu, <sup>239+240</sup>Pu, <sup>241</sup>Pu) in Poland and Baltic Sea environment |journal=Nukleonika |year=2006 |volume=51 |pages=S45–S51 |url=http://www.nukleonika.pl/www/back/full/vol51_2006/v51s2p45f.pdf |access-date=2019-06-19 |archive-url=https://web.archive.org/web/20190619142638/http://www.nukleonika.pl/www/back/full/vol51_2006/v51s2p45f.pdf |archive-date=2019-06-19 |url-status=live }}</ref> With one [[microgram]] of <sup>210</sup>Po being more than enough to kill the average adult, it is 250,000 times more toxic than [[hydrogen cyanide]] by weight.<ref name=malay>{{cite journal |last1=Ahmed |first1=M. F. |last2=Alam |first2=L. |last3=Mohamed |first3=C. A. R. |last4=Mokhtar |first4=M. B. |last5=Ta |first5=G. C. |title=Health risk of polonium-210 ingestion via drinking water: An experience of Malaysia |journal=International Journal of Environmental Research and Public Health |date=2018 |volume=15 |issue=10 |pages=2056–1–2056–19 |doi=10.3390/ijerph15102056 |pmid=30241360 |pmc=6210456 |doi-access=free }}</ref> One gram of <sup>210</sup>Po would hypothetically be enough to kill 50 million people and sicken another 50 million.<ref name=death/> This is a consequence of its [[Ionizing radiation|ionizing]] [[alpha radiation]], as alpha particles are especially damaging to organic tissues inside the body. However, <sup>210</sup>Po does not pose a radiation hazard when contained outside the body.<ref>{{Cite web |date=2019-02-11 |title=Radiation Studies: CDC - Radiation: Polonium-210 {{!}} CDC RSB |url=https://www.cdc.gov/nceh/radiation/polonium-210.htm |access-date=2022-11-14 |website=www.cdc.gov |language=en-us}}</ref> The [[alpha particle]]s it produces cannot penetrate the outer layer of dead skin cells.<ref>{{Cite web |title=Penetration Abilities of Different Types of Radiation |url=https://www.cdc.gov/training/products/RN/page4976.html |access-date=2022-11-14 |website=www.cdc.gov}}</ref>

The toxicity of <sup>210</sup>Po stems entirely from its radioactivity. It is not chemically toxic in itself, but its solubility in [[aqueous solution]] as well as that of its salts poses a hazard because its spread throughout the body is facilitated in solution.<ref name=death/> Intake of <sup>210</sup>Po occurs primarily through contaminated air, food, or water, as well as through open wounds. Once inside the body, <sup>210</sup>Po concentrates in soft tissues (especially in the [[reticuloendothelial system]]) and the [[bloodstream]]. Its [[biological half-life]] is approximately 50 days.<ref name=cdcfaq>{{cite report |url=https://www.cdc.gov/nceh/radiation/fallon/Polonium_factsheet.pdf |title=Frequently asked questions about polonium-210. |publisher=[[Centers for Disease Control and Prevention]] |access-date=19 June 2019 |archive-url=https://web.archive.org/web/20170607100124/https://www.cdc.gov/nceh/radiation/fallon/polonium_factsheet.pdf |archive-date=7 June 2017 |url-status=live }}</ref>

In the environment, <sup>210</sup>Po can accumulate in seafood.<ref name=Po210>{{cite journal |last1=Richter |first1=F. |last2=Wagmann |first2=M. |last3=Zehringer |first3=M. |title=Polonium – on the Trace of a Powerful Alpha Nuclide in the Environment |journal=CHIMIA International Journal for Chemistry |date=2012 |volume=66 |issue=3 |pages=131 |doi=10.2533/chimia.2012.131 |url=https://www.researchgate.net/publication/224869922 |access-date=2019-06-19 |archive-url=https://web.archive.org/web/20190217142359/https://www.researchgate.net/publication/224869922_Polonium_-_on_the_Trace_of_a_Powerful_Alpha_Nuclide_in_the_Environment |archive-date=2019-02-17 |url-status=live |doi-access=free }}</ref> It has been detected in various organisms in the [[Baltic Sea]], where it can propagate in, and thus contaminate, the food chain.<ref name=nukleonika/> <sup>210</sup>Po is also known to contaminate vegetation, primarily originating from the decay of atmospheric [[radon-222]] and absorption from soil.<ref name=210env/>

In particular, <sup>210</sup>Po attaches to, and concentrates in, tobacco leaves.<ref name=why/><ref name=cdcfaq/> Elevated concentrations of <sup>210</sup>Po in tobacco were documented as early as 1964, and [[cigarette smoker]]s were thus found to be exposed to considerably greater doses of radiation from <sup>210</sup>Po and its parent <sup>210</sup>Pb.<ref name=210env>{{cite conference |date=2009 |last1=Persson |first1=B. R. R. |last2=Holm |first2=E. |title=Polonium-210 and Lead-210 in the Terrestrial environment: A historical review |conference=International Topical Conference on Po and Radioactive Pb Isotopes |location=Seville, Spain |url=https://www.researchgate.net/publication/256456252}}</ref> Heavy smokers may be exposed to the same amount of radiation (estimates vary from 100&nbsp;[[sievert (unit)|µSv]]<ref name=nukleonika/> to 160&nbsp;mSv<ref>{{Cite web|archive-url=https://web.archive.org/web/20130613131654/http://www.ors.od.nih.gov/sr/drs/training/GRS/Pages/sectionf.aspx|title=F. Typical Sources of Radiation Exposure |archive-date=2013-06-13 |access-date=2019-06-20 |publisher=[[National Institute of Health]] |url-status=dead |url=http://www.ors.od.nih.gov/sr/drs/training/GRS/Pages/sectionf.aspx}}</ref> per year) as individuals in Poland were from [[Chernobyl disaster|Chernobyl]] fallout traveling from Ukraine.<ref name=nukleonika/> As a result, <sup>210</sup>Po is most dangerous when inhaled from cigarette smoke.<ref name=posmoke>{{cite journal|jstor=1712451|title=Polonium-210: A Volatile Radioelement in Cigarettes|journal=Science|volume=143|issue=3603|pages=247–249|last1=Radford|first1=E. P.|last2=Hunt|first2=V. R.|year=1964|doi=10.1126/science.143.3603.247|pmid=14078362|bibcode=1964Sci...143..247R|s2cid=23455633}}</ref>

==References==
{{reflist|25em}}
{{Authority control}}

[[Category:Isotopes of polonium]]
[[Category:Carcinogens]]
[[Category:Tobacco]]
[[Category:Radioisotope fuels]]