Editing Fermium (section)

===Production===
[[File:Elutionskurven Fm Es Cf Bk Cm Am.png|thumb|[[Elution]]: chromatographic separation of Fm(100), Es(99), Cf, Bk, Cm and Am]]
Fermium is produced by the bombardment of lighter [[actinide]]s with [[neutron]]s in a nuclear reactor. Fermium-257 is the heaviest isotope that is obtained via neutron capture, and can only be produced in picogram quantities.{{efn|All isotopes of elements Z &gt; 100 can only be produced by accelerator-based nuclear reactions with charged particles and can be obtained only in tracer quantities (e.g., 1 million atoms for Md (''Z''&nbsp;{{=}}&nbsp;101) per hour of irradiation (see Silva 2006).}}<ref>{{cite book |last1=Luig |first1=Heribert |last2=Keller |first2=Cornelius |last3=Wolf |first3=Walter |last4=Shani |first4=Jashovam |last5=Miska |first5=Horst |last6=Zyball |first6=Alfred |last7=Gervé |first7=Andreas |last8=Balaban |first8=Alexandru T. |last9=Kellerer |first9=Albrecht M. |last10=Griebel |first10=Jürgen |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2000 |doi=10.1002/14356007.a22_499 |chapter=Radionuclides |isbn=978-3527306732}}</ref> The major source is the 85&nbsp;MW [[High Flux Isotope Reactor]] (HFIR) at the [[Oak Ridge National Laboratory]] in [[Tennessee]], USA, which is dedicated to the production of transcurium (''Z''&nbsp;>&nbsp;96) elements.<ref>{{cite web|title = High Flux Isotope Reactor|url = http://neutrons.ornl.gov/facilities/HFIR/|publisher = Oak Ridge National Laboratory|access-date = 2010-09-23}}</ref> Lower mass fermium isotopes are available in greater quantities, though these isotopes (<sup>254</sup>Fm and <sup>255</sup>Fm) are comparatively short-lived. In a "typical processing campaign" at Oak Ridge, tens of grams of [[curium]] are irradiated to produce decigram quantities of [[californium]], milligram quantities of [[berkelium]] and [[einsteinium]], and picogram quantities of fermium.<ref>{{cite journal|first1 = C. E.|last1 = Porter| first2 = F. D. Jr. |last2 = Riley|first3 = R. D.|last3 = Vandergrift|first4 = L. K.|last4 = Felker|title = Fermium Purification Using Teva Resin Extraction Chromatography|journal = Sep. Sci. Technol.|volume = 32|issue = 1–4|date = 1997|pages = 83–92|doi = 10.1080/01496399708003188|url = https://zenodo.org/record/1234415}}</ref> However, nanogram<ref>{{cite journal|first1 = M.|last1 = Sewtz|first2 = H.|last2 = Backe|first3 = A.|last3 = Dretzke|first4 = G.|last4 = Kube|first5 = W.|last5 = Lauth|first6 = P.|last6 = Schwamb|first7 = K.|last7 = Eberhardt|first8 = C.|last8 = Grüning|first9 = P.|last10 = Trautmann|first10 = N.|last11 = Kunz|first11 = P.|last12 = Lassen|first12 = J.|last13 = Passler|first13 = G.|last14 = Dong|first14 = C.|last15 = Fritzsche|first15 = S.|last16 = Haire|first16 = R.|last9 = Thörle
|s2cid = 16234935|title = First Observation of Atomic Levels for the Element Fermium (''Z''=100)|journal = Phys. Rev. Lett.|volume = 90|issue = 16|page = 163002|date = 2003|doi = 10.1103/PhysRevLett.90.163002|bibcode=2003PhRvL..90p3002S|pmid=12731975}}</ref> quantities of fermium can be prepared for specific experiments. The quantities of fermium produced in 20–200&nbsp;kiloton thermonuclear explosions is believed to be of the order of milligrams, although it is mixed in with a huge quantity of debris; 4.0&nbsp;picograms of <sup>257</sup>Fm was recovered from 10&nbsp;kilograms of debris from the "[[Operation Mandrel|Hutch]]" test (16&nbsp;July 1969).<ref>{{cite journal|last1 = Hoff|first1 = R. W.|last2 = Hulet|first2 = E. K.|date = 1970|title = Engineering with Nuclear Explosives|volume = 2|pages = 1283–1294}}</ref> The Hutch experiment produced an estimated total of 250 micrograms of <sup>257</sup>Fm.

After production, the fermium must be separated from other actinides and from [[lanthanide]] fission products. This is usually achieved by [[ion-exchange chromatography]], with the standard process using a cation exchanger such as Dowex&nbsp;50 or T<small>EVA</small> eluted with a solution of ammonium α-hydroxyisobutyrate.<ref name="Silva" /><ref>{{cite journal|last1 = Choppin|first1 = G. R.|last2 = Harvey|first2 = B. G.|last3 = Thompson|first3 = S. G.|date = 1956|title = A new eluant for the separation of the actinide elements|journal = J. Inorg. Nucl. Chem.|volume = 2|issue = 1|pages = 66–68|doi = 10.1016/0022-1902(56)80105-X|url = https://escholarship.org/content/qt73d377r3/qt73d377r3.pdf?t=p0fvlf}}</ref> Smaller cations form more stable complexes with the α-hydroxyisobutyrate anion, and so are preferentially eluted from the column.<ref name="Silva" /> A rapid [[fractional crystallization (chemistry)|fractional crystallization]] method has also been described.<ref name="Silva" /><ref>{{cite journal|last1 = Mikheev|first1 = N. B.|last2 = Kamenskaya|first2 = A. N.|last3 = Konovalova|first3 = N. A.|last4 = Rumer|first4 = I. A.|last5 = Kulyukhin|first5 = S. A.|title = High-speed method for the separation of fermium from actinides and lanthanides|date =1983|journal = Radiokhimiya|volume = 25|issue = 2|pages = 158–161}}</ref>

Although the most stable isotope of fermium is <sup>257</sup>Fm, with a [[half-life]] of 100.5&nbsp;days, most studies are conducted on <sup>255</sup>Fm (''t''<sub>1/2</sub>&nbsp;= 20.07(7)&nbsp;hours), since this isotope can be easily isolated as required as the decay product of <sup>255</sup>Es (''t''<sub>1/2</sub>&nbsp;= 39.8(12)&nbsp;days).<ref name="Silva" />