Editing Strontium (section)

===Radioactive strontium===
[[File:Soviet RTG.jpg|thumb|RTGs from Soviet-era lighthouses]]

[[strontium-89|<sup>89</sup>Sr]] is the active ingredient in [[Metastron]],<ref>{{cite web |title=FDA ANDA Generic Drug Approvals |url=https://www.fda.gov/Drugs/DevelopmentApprovalProcess/HowDrugsareDevelopedandApproved/DrugandBiologicApprovalReports/ANDAGenericDrugApprovals/UCM064272 |publisher=[[Food and Drug Administration]]}}</ref> a [[radiopharmaceutical]] used for bone pain secondary to [[metastatic]] [[bone cancer]]. The strontium is processed like calcium by the body, preferentially incorporating it into bone at sites of increased [[osteogenesis]]. This localization focuses the radiation exposure on the cancerous lesion.<ref name="BaumanCharette2005" />

[[strontium-90|<sup>90</sup>Sr]] has been used as a power source for [[radioisotope thermoelectric generator]]s (RTGs). <sup>90</sup>Sr produces approximately 0.93 watts of heat per gram (it is lower for the form of <sup>90</sup>Sr used in RTGs, which is [[strontium fluoride]]).<ref>{{cite web |url=http://www.qrg.northwestern.edu/projects/vss/docs/Power/3-what-are-the-fuels-for-rtgs.html |title=What are the fuels for radioisotope thermoelectric generators?|work=qrg.northwestern.edu}}</ref><!--Search for a better source--> However, <sup>90</sup>Sr has one third the lifetime and a lower density than [[plutonium-238|<sup>238</sup>Pu]], another RTG fuel. The main advantage of <sup>90</sup>Sr is that it is significantly cheaper than <sup>238</sup>Pu and is found in [[nuclear waste]]. The latter must be prepared by irradiating <sup>237</sup>Np with neutrons then separating the modest amounts of  <sup>238</sup>Pu. The principal disadvantage of <sup>90</sup>Sr is the high energy beta particles produce [[Bremsstrahlung]] as they encounter nuclei of other nearby heavy atoms such as adjacent strontium. This is mostly in the range of X-rays. Thus strong beta emitters also emit significant secondary X-rays in most cases. This requires significant shielding measures which complicates the design of RTGs using <sup>90</sup>Sr. The [[Soviet Union]] deployed nearly 1000 of these RTGs on its northern coast as a power source for lighthouses and meteorology stations.<ref>{{cite book |page = 459 |url = https://books.google.com/books?id=8WOza_y3IkQC&pg=PA459 |title = Nuclear safeguards, security and nonproliferation: achieving security with technology and policy |isbn = 978-0-7506-8673-0 |author1 = Doyle, James |date = 30 June 2008| publisher=Elsevier }}</ref><ref name="O'BrienAmbrosi2008">{{cite journal|last1=O'Brien|first1=R. C.|last2=Ambrosi|first2=R. M.|last3=Bannister|first3=N. P.|last4=Howe|first4=S. D.|last5=Atkinson|first5=H. V.|title=Safe radioisotope thermoelectric generators and heat sources for space applications|journal=Journal of Nuclear Materials|volume=377|issue=3|year=2008|pages=506–21|doi=10.1016/j.jnucmat.2008.04.009|bibcode=2008JNuM..377..506O}}</ref>