{{short description|Radioactive isotope of strontium}} {{About|the chemical isotope|the band|Strontium 90 (band)|fictional references to strontium-90|Materials science in science fiction}} {{use dmy dates |date=May 2023}} {{Infobox isotope | alternate_names = | symbol =Sr | image = Strontium 90 (test source) in tin.jpg | image_caption = Strontium-90 test source in tin | mass_number =90 | mass = 89.907728{{AME2020 II |ref}} | num_neutrons =52 | num_protons =38 | abundance = syn | halflife = {{val|28.91|u=years}}<ref>{{NUBASE2020}}</ref> | decay_product =yttrium-90 | decay_symbol =Y | decay_mass =90 | decay_mode1 =Beta decay | decay_energy1 =0.546<ref name="auto">{{NNDC}}</ref> | decay_mode2 = | decay_energy2 = | decay_mode3 = | decay_energy3 = | decay_mode4 = | decay_energy4 = | parent = | parent_symbol = | parent_mass = | parent_decay = | parent2 = | parent2_symbol = | parent2_mass = | parent2_decay = | spin = | excess_energy = | binding_energy = }}

'''Strontium-90''' ({{SimpleNuclide|strontium|90}}) is a radioactive isotope of strontium produced by nuclear fission, with a half-life of 28.91&nbsp;years. It undergoes β{{sup|−}} decay into {{simpleNuclide|yttrium|90|link=y}} with a decay energy of 0.546&nbsp;MeV. {{simpleNuclide|Sr|90}} has applications in medicine and industry and is an isotope of concern in fallout from nuclear weapons, nuclear weapons testing, and nuclear accidents.<ref name="EPA">{{cite web |url=http://www.epa.gov/rpdweb00/radionuclides/strontium.html#environment |title=Strontium &#124; Radiation Protection &#124; US EPA |publisher=EPA |date=24 April 2012 |access-date=18 June 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120511030249/http://www.epa.gov/rpdweb00/radionuclides/strontium.html |archive-date=11 May 2012}}</ref>

==Radioactivity== Naturally occurring strontium ({{simpleNuclide|strontium|link=y}}) is nonradioactive and nontoxic at levels normally found in the environment, but {{simpleNuclide|strontium|90}} is a radiation hazard.<ref name="ATSDR">{{citation |url=http://www.atsdr.cdc.gov/toxprofiles/tp159.pdf |title=TOXICOLOGICAL PROFILE FOR STRONTIUM |publisher=Agency for Toxic Substances and Disease Registry |date=April 2004 |access-date=2014-10-13 |archive-date=7 May 2021 |archive-url=https://web.archive.org/web/20210507010823/https://www.atsdr.cdc.gov/ToxProfiles/tp159.pdf |url-status=live }}</ref> {{simpleNuclide|Sr|90}} undergoes β{{sup|−}} decay with a half-life of 28.91&nbsp;years and a decay energy of 0.546&nbsp;MeV distributed to an electron, an antineutrino, and the yttrium isotope {{simpleNuclide|yttrium|90|link=y}}, which in turn undergoes β{{sup|−}} decay with a half-life of 64.05&nbsp;hours and a decay energy of 2.28&nbsp;MeV distributed to an electron, an antineutrino, and occasionally a gamma ray, leaving stable {{simpleNuclide|zirconium|link=y}}.<ref name="auto"/> The gamma-emitting branches are so weak that for most purposes {{simpleNuclide|strontium|90}} and {{simpleNuclide|yttrium|90}} can be considered pure beta particle emitters.

{{Medium-lived fission products}}

==Fission product== <sup>90</sup>Sr is a product of nuclear fission. It is present in significant amount in spent nuclear fuel, in radioactive waste from nuclear reactors and in nuclear fallout from nuclear tests. For thermal neutron fission as in today's nuclear power plants, the fission product yield from uranium-235 is 5.7% and 6.6% from uranium-233, but only 2.0% from plutonium-239<ref name="IAEALiveChart">{{cite web |url=https://www-nds.iaea.org/relnsd/vcharthtml/VChartHTML.html |title=Livechart - Table of Nuclides - Nuclear structure and decay data |publisher=IAEA |access-date=2014-10-13 |archive-date=23 March 2019 |archive-url=https://web.archive.org/web/20190323230752/https://www-nds.iaea.org/relnsd/vcharthtml/VChartHTML.html |url-status=live }}</ref> {{citation needed span|date=January 2026|(commercial reactors derive energy both from uranium-235 and plutonium-239 in comparable amounts).}}

===Nuclear waste=== {{simpleNuclide|Sr|90}} is classified as high-level waste. Its 29-year half-life means that it can take hundreds of years to decay to negligible levels. Exposure from contaminated water and food may increase the risk of leukemia and bone cancer.<ref name=Potera>{{cite journal |last=Potera |first=Carol |title=HAZARDOUS WASTE: Pond Algae Sequester Strontium-90 |journal=Environ Health Perspect |date=2011 |volume=119 |issue=6 |pages=A244 |pmid=21628117 |doi=10.1289/ehp.119-a244|pmc=3114833 |doi-access=free }}</ref> Reportedly, thousands of capsules of radioactive strontium containing millions of curies are stored at Hanford Site's Waste Encapsulation and Storage Facility.<ref>https://www.energy.gov/sites/prod/files/2014/04/f14/OAS-L-14-04.pdf {{Webarchive|url=https://web.archive.org/web/20231010054948/http://www.energy.gov/sites/prod/files/2014/04/f14/OAS-L-14-04.pdf |date=10 October 2023 }} "Long-Term Storage of Cesium and Strontium at the Hanford Site" Inspector General Report No. OAS-L-14-04 . March 2014.</ref>

=== Remediation === Algae has shown selectivity for strontium in studies, where most plants used in bioremediation have not shown selectivity between calcium and strontium, often becoming saturated with calcium, which is greater in quantity and also present in nuclear waste.<ref name=Potera/>

Researchers have looked at the bioaccumulation of strontium by ''Scenedesmus spinosus'' (algae) in simulated wastewater. The study claims a highly selective biosorption capacity for strontium of ''S.&nbsp;spinosus'', suggesting that it may be appropriate for use of nuclear wastewater.<ref>{{cite journal |title=Biosorption of Strontium from Simulated Nuclear Wastewater by Scenedesmus spinosus under Culture Conditions: Adsorption and Bioaccumulation Processes and Models |journal=Int J Environ Res Public Health |date=2014 |doi=10.3390/ijerph110606099|doi-access=free |last1=Liu |first1=Mingxue |last2=Dong |first2=Faqin |last3=Kang |first3=Wu |last4=Sun |first4=Shiyong |last5=Wei |first5=Hongfu |last6=Zhang |first6=Wei |last7=Nie |first7=Xiaoqin |last8=Guo |first8=Yuting |last9=Huang |first9=Ting |last10=Liu |first10=Yuanyuan |volume=11 |issue=6 |pages=6099–6118 |pmid=24919131 |pmc=4078568 }}</ref>

A study of the pond alga ''Closterium moniliferum'' using stable strontium found that varying the ratio of barium to strontium in water improved strontium selectivity.<ref name=Potera/>

==Biological effects==

===Biological activity=== {{simpleNuclide|Sr|90}} is a "bone seeker" that exhibits biochemical behavior similar to calcium, the next lighter group 2 element.<ref name="ATSDR" /><ref name="NRCglossary">{{cite web |url=https://www.nrc.gov/reading-rm/basic-ref/glossary/bone-seeker.html |title=NRC: Glossary -- Bone seeker |publisher=US Nuclear Regulatory Commission |date=7 May 2014 |access-date=2014-10-13 |archive-date=1 April 2019 |archive-url=https://web.archive.org/web/20190401045831/https://www.nrc.gov/reading-rm/basic-ref/glossary/bone-seeker.html |url-status=live }}</ref> After entering the organism, most often by ingestion with contaminated food or water, about 70–80% of the dose gets excreted.<ref name="EPA" /> Virtually all remaining {{simpleNuclide|Sr|90}} is deposited in bones and bone marrow, with the remaining 1% remaining in blood and soft tissues.<ref name="EPA" /> Its presence in bones can cause bone cancer, cancer of nearby tissues, and leukemia.<ref>{{cite web |title=STRONTIUM-90 |url=https://dhss.delaware.gov/dhss/dph/files/strontiumfaq.pdf |access-date=14 December 2020 |archive-date=22 May 2023 |archive-url=https://web.archive.org/web/20230522231511/https://dhss.delaware.gov/dhss/dph/files/strontiumfaq.pdf |url-status=dead }}</ref> Exposure to <sup>90</sup>Sr can be tested by a bioassay, most commonly by urinalysis.<ref name="ATSDR" />

The biological half-life of {{simpleNuclide|Sr|90}} in humans has variously been reported as 14&nbsp;to 600&nbsp;days,<ref>{{citation |chapter-url=http://hanford-site.pnnl.gov/envreport/2001/env01_45.pdf |title=Hanford Site 2001 Environmental Report |chapter=4.5 Fish and Wildlife Surveillance |last1=Tiller |first1=B. L. |publisher=DOE |year=2001 |access-date=2014-01-14 |archive-date=11 May 2013 |archive-url=https://web.archive.org/web/20130511040509/http://hanford-site.pnnl.gov/envreport/2001/env01_45.pdf |url-status=dead }}</ref><ref>{{citation |url=http://www.osti.gov/bridge/servlets/purl/10136486-6sLptZ/native/10136486.pdf |title=Ecotoxicity Literature Review of Selected Hanford Site Contaminants |doi=10.2172/10136486 |osti=10136486 |publisher=DOE |last1=Driver |first1=C.J. |year=1994 |access-date=2014-01-14 |archive-date=22 October 2021 |archive-url=https://web.archive.org/web/20211022143220/https://www.osti.gov/biblio/10136486 |url-status=live }}</ref> 1,000&nbsp;days,<ref>{{cite web |url=http://www.areaivenvirothon.org/freshwaterecology.htm |title=Freshwater Ecology and Human Influence |publisher=Area IV Envirothon |access-date=2014-01-14 |archive-date=1 January 2014 |archive-url=https://web.archive.org/web/20140101063834/http://www.areaivenvirothon.org/freshwaterecology.htm |url-status=dead }}</ref> 18&nbsp;years,<ref>{{cite web |url=https://www.epi.alaska.gov/eh/radiation/RadioisotopesInFood.pdf |title=Radioisotopes That May Impact Food Resources |access-date=2014-01-14 |publisher=Epidemiology, Health and Social Services, State of Alaska |archive-date=21 August 2014 |archive-url=https://web.archive.org/web/20140821162026/http://epi.alaska.gov/eh/radiation/RadioisotopesInFood.pdf |url-status=live }}</ref> 30&nbsp;years<ref>{{cite web |url=http://www.gsseser.com/FactSheet/Strontium.pdf |title=Human Health Fact Sheet: Strontium |publisher=Argonne National Laboratory |date=October 2001 |access-date=2014-01-14 |archive-date=24 January 2014 |archive-url=https://web.archive.org/web/20140124000858/http://www.gsseser.com/FactSheet/Strontium.pdf |url-status=live }}</ref> and, at the upper limit, 49&nbsp;years.<ref>{{cite web |url=http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/biohalf.html |title=Biological Half-life |publisher=HyperPhysics |access-date=2014-01-14 |archive-date=14 December 2021 |archive-url=https://web.archive.org/web/20211214105931/http://hyperphysics.phy-astr.gsu.edu/hbase/Nuclear/biohalf.html |url-status=live }}</ref> The wide-ranging published biological half-life figures are explained by strontium's complex metabolism within the body. However, by averaging all excretion paths, the overall biological half-life is estimated to be about 18&nbsp;years.<ref>{{cite book |chapter-url=http://www.fourmilab.ch/etexts/www/effects/eonw_12.pdf |title=The effects of Nuclear Weapons |last1=Glasstone |first1=Samuel |last2=Dolan |first2=Philip J. |year=1977 |access-date=2014-01-14 |chapter=XII: Biological Effects |page=605 |archive-date=10 March 2023 |archive-url=https://web.archive.org/web/20230310111251/https://www.fourmilab.ch/etexts/www/effects/eonw_12.pdf |url-status=live }}</ref>

The elimination rate of {{simpleNuclide|Sr|90}} is strongly affected by age and sex, due to differences in bone metabolism.<ref name="ShaginaBougrov2006">{{cite journal |last1=Shagina |first1=N B |last2=Bougrov |first2=N G |last3=Degteva |first3=M O |last4=Kozheurov |first4=V P |last5=Tolstykh |first5=E I |title=An application of in vivo whole body counting technique for studying strontium metabolism and internal dose reconstruction for the Techa River population |journal=Journal of Physics: Conference Series |volume=41 |year=2006 |issue=1 |pages=433–440 |issn=1742-6588 |doi=10.1088/1742-6596/41/1/048|doi-access=free |bibcode=2006JPhCS..41..433S }}</ref>

Together with the caesium isotopes {{simpleNuclide|Cs|134}} and {{simpleNuclide|link=y|Cs|137}} and the iodine isotope {{simpleNuclide|link=y|I|131}}, {{simpleNuclide|Sr|90}} was among the most important isotopes regarding health impacts after the Chernobyl disaster. As strontium has an affinity to the calcium-sensing receptor of parathyroid cells that is similar to that of calcium, the increased risk of liquidators of the Chernobyl power plant to suffer from primary hyperparathyroidism could be explained by binding of {{simpleNuclide|Sr|90}}.<ref name=BoehmNEJM>{{cite journal|vauthors=Boehm BO, Rosinger S, Belyi D, Dietrich JW |title=The Parathyroid as a Target for Radiation Damage|journal=New England Journal of Medicine|date=August 2011|volume=365|issue=7|pages=676–678|doi=10.1056/NEJMc1104982|pmid=21848480|doi-access=free}}</ref>

==Uses==

===Radioisotope thermoelectric generators (RTGs)=== The radioactive decay of {{simpleNuclide|Sr|90}} generates a significant amount of heat, 0.920&nbsp;W/g in the form of pure strontium metal or 0.445&nbsp;W/g as strontium titanate<ref>Calculated from NNDC decay energies, mean life (half-life / log 2), and other constants.</ref> and is cheaper than the alternative {{simpleNuclide|link=y|Pu|238}}. It is used as a heat source in many Russian/Soviet radioisotope thermoelectric generators, usually in the form of strontium titanate.<ref name="NRPA2005">{{citation |title=Assessment of environmental, health and safety consequences of decommissioning radioisotope thermal generators (RTGs) in Northwest Russia |url=http://www.nrpa.no/dav/c600d1d288.pdf |number=StrålevernRapport 2005:4 |year=2005 |publisher=Norwegian Radiation Protection Authority |location=Østerås |last1=Standring |first1=WJF |last2=Selnæs |first2=ØG |last3=Sneve |first3=M |last4=Finne |first4=IE |last5=Hosseini |first5=A |last6=Amundsen |first6=I |last7=Strand |first7=P |access-date=14 January 2014 |archive-date=3 March 2016 |archive-url=https://web.archive.org/web/20160303210325/http://www.nrpa.no/dav/c600d1d288.pdf |url-status=dead }}</ref> It was also used in the US "Sentinel" series of RTGs.<ref name=OTA94>{{cite web |title=Power Sources for Remote Arctic Applications |date=June 1994 |location=Washington, DC |publisher=U.S. Congress, Office of Technology Assessment |url=http://govinfo.library.unt.edu/ota/Ota_1/DATA/1994/9423.PDF |id=OTA-BP-ETI-129 |access-date=19 October 2012 |archive-date=9 October 2022 |archive-url=https://ghostarchive.org/archive/20221009/http://govinfo.library.unt.edu/ota/Ota_1/DATA/1994/9423.PDF |url-status=live }}</ref> Startup company Zeno Power is developing RTGs that use strontium-90 from the DOD, and is aiming to ship product by 2026.<ref>{{Cite web|url=https://www.zenopower.com/|title=Zeno Power|website=Zeno Power|access-date=2 March 2024|archive-date=2 March 2024|archive-url=https://web.archive.org/web/20240302211412/https://www.zenopower.com/|url-status=live}}</ref>

===Industrial applications=== {{simpleNuclide|Sr|90}} finds use in industry as a radioactive source for thickness gauges.<ref name="EPA" />

===Medical applications=== {{simpleNuclide|Sr|90}} finds extensive use in medicine as a radioactive source for superficial radiotherapy of some cancers. Controlled amounts of {{simpleNuclide|Sr|90}} or of {{simpleNuclide|link=y|Sr|89}} can be used in treatment of bone cancer, and to treat coronary restenosis via vascular brachytherapy. It is also used as a radioactive tracer in medicine and agriculture.<ref name="EPA" />

===Aerospace applications=== {{simpleNuclide|Sr|90}} is used as a blade inspection method in some helicopters with hollow blade spars to indicate if a crack has formed.<ref name="helo">{{Cite web|url=https://patents.google.com/patent/US7176812B1/en|title=Wireless blade monitoring system and process|access-date=31 May 2018|archive-date=17 April 2021|archive-url=https://web.archive.org/web/20210417163452/https://patents.google.com/patent/US7176812B1/en|url-status=live}}</ref>

===Radiological warfare=== {{Further|radiological warfare}} In April 1943, Enrico Fermi suggested to Robert Oppenheimer the possibility of using the radioactive byproducts from enrichment to contaminate the German food supply. The background was fear that the German atomic bomb project was already at an advanced stage, and Fermi was also skeptical at the time that an atomic bomb could be developed quickly enough. Oppenheimer discussed the proposal with Edward Teller, who suggested the use of {{simpleNuclide|Sr|90}}. James Bryant Conant and Leslie R. Groves were also briefed, but Oppenheimer wanted to proceed with the plan only if enough food could be contaminated with the weapon to kill half a million people.<ref>{{Cite book|last1=Rhodes|first=Richard|url=http://worldcat.org/oclc/1096260191|title=The making of the atomic bomb|date=2012|publisher=Simon & Schuster|isbn=978-1-4711-1123-5|pages=510ff|oclc=1096260191|author-link1=Richard Rhodes}}</ref>

==<sup>90</sup>Sr contamination in the environment== {{simpleNuclide|Sr|90}} is not quite as likely as {{simpleNuclide|link=y|Cs|137}} to be released as a part of a nuclear reactor accident because it is much less volatile, but is probably the most dangerous component of the radioactive fallout from a nuclear weapon.<ref name="hyperphysics">{{cite web |url=http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/fisfrag.html#c5 |title=Nuclear Fission Fragments |publisher=HyperPhysics |access-date=18 June 2012 |archive-date=15 June 2012 |archive-url=https://web.archive.org/web/20120615094946/http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/fisfrag.html#c5 |url-status=live }}</ref>

A study of hundreds of thousands of deciduous teeth, collected by Dr.{{px2}}Louise Reiss and her colleagues as part of the Baby Tooth Survey, found a large increase in {{simpleNuclide|Sr|90}} levels through the 1950s and early 1960s. The study's final results showed that children born in St. Louis, Missouri, in 1963 had levels of {{simpleNuclide|Sr|90}} in their deciduous teeth that was 50&nbsp;times higher than that found in children born in 1950, before the advent of large-scale atomic testing. Reviewers of the study predicted that the fallout would cause increased incidence of disease in those who absorbed {{simpleNuclide|Sr|90}} into their bones.<ref>{{cite journal|last=Schneir|first=Walter|author-link=Walter Schneir|title=Strontium-90 in U.S. Children|journal=The Nation|date=April 25, 1959|volume=188|issue=17|pages=355–357}}</ref> However, no follow up studies of the subjects have been performed, so the claim is untested.

An article with the study's initial findings was circulated to U.S. President John F. Kennedy in 1961, and helped convince him to sign the Partial Nuclear Test Ban Treaty with the United Kingdom and Soviet Union, ending the above-ground nuclear weapons testing that placed the greatest amounts of nuclear fallout into the atmosphere.<ref name=Reiss>Hevesi, Dennis. [https://www.nytimes.com/2011/01/10/science/10reiss.html "Dr. Louise Reiss, Who Helped Ban Atomic Testing, Dies at 90"] {{Webarchive|url=https://web.archive.org/web/20190419195654/https://www.nytimes.com/2011/01/10/science/10reiss.html |date=19 April 2019 }}, ''The New York Times'', January 10, 2011. Accessed January 10, 2011.</ref>

The Chernobyl disaster released roughly 10&nbsp;PBq, or about 5% of the core inventory, of {{simpleNuclide|Sr|90}} into the environment.<ref>{{citation |url=https://www.oecd-nea.org/rp/reports/2003/nea3508-chernobyl.pdf |chapter-url=https://www.oecd-nea.org/rp/chernobyl/c02.html |title=Chernobyl: Assessment of Radiological and Health Impacts |chapter=II: The release, dispersion and deposition of radionuclides |publisher=NEA |year=2002 |access-date=13 October 2014 |archive-date=22 June 2015 |archive-url=https://web.archive.org/web/20150622010856/https://www.oecd-nea.org/rp/reports/2003/nea3508-chernobyl.pdf |url-status=live }}</ref> The Kyshtym disaster released {{simpleNuclide|Sr|90}} and other radioactive material into the environment. It is estimated to have released 20&nbsp;MCi (800&nbsp;PBq) of radioactivity. The Fukushima Daiichi disaster had from the accident until 2013 released 0.1{{tsp}}to 1{{tsp}}PBq of {{simpleNuclide|Sr|90}} in the form of contaminated cooling water into the Pacific Ocean.<ref name="PovinecAoyama2013">{{cite journal |last1=Povinec |first1=P. P. |last2=Aoyama |first2=M. |last3=Biddulph |first3=D. |last4=Breier |first4=R. |last5=Buesseler |first5=K. |last6=Chang |first6=C. C. |last7=Golser |first7=R. |last8=Hou |first8=X. L. |last9=Ješkovský |first9=M. |last10=Jull |first10=A. J. T. |last11=Kaizer |first11=J. |last12=Nakano |first12=M. |last13=Nies |first13=H. |last14=Palcsu |first14=L. |last15=Papp |first15=L. |last16=Pham |first16=M. K. |last17=Steier |first17=P. |last18=Zhang |first18=L. Y. |title=Cesium, iodine and tritium in NW Pacific waters &ndash; a comparison of the Fukushima impact with global fallout |journal=Biogeosciences |volume=10 |issue=8 |year=2013 |pages=5481–5496 |issn=1726-4189 |doi=10.5194/bg-10-5481-2013 |display-authors=3|bibcode=2013BGeo...10.5481P |doi-access=free |hdl=1912/6245 |hdl-access=free }}</ref>

==See also== * Gray and Sievert * Lia radiological accident * Radiation poisoning

==References== {{reflist|30em}}

==External links== *{{cite web |url=https://pubchem.ncbi.nlm.nih.gov/source/hsdb/7403 |work=Hazardous Substances Data Bank (HSDB) |title=Strontium, Radioactive |publisher=pubchem.ncbi.nlm.nih.gov |access-date=15 May 2023 }}

Category:Fission products Strontium-090 Category:Radioisotope fuels Category:Radioactive contamination