"Bk redirects here. For other uses of the abbreviation, see
BK (disambiguation)."Berkelium (pronEng|bɚˈkiːliəm or IPA|/ˈbɝkliəm/ Fact|date=March 2008) is a synthetic elementwith the symbol Bk and atomic number97. A radioactive metallic element in the actinideseries, berkelium was first synthesized by bombarding americiumwith alpha particles ( helium ions) and was named after the University of California, Berkeley. Berkelium was the fifth transuranic elementto be synthesized.
Weighable amounts of 249Bk (half-life 314 days) make it possible to determine some of its properties using macroscopic quantities.
As of 2004it had not been isolated in its elemental form, but it is predicted to be a silvery metal that would easily oxidize in air at elevated temperatures and would be soluble in dilute mineral acidsFact|date=May 2008. X-ray diffractiontechniques have been used to identify various berkelium compounds such as berkelium dioxide (BkO2), berkelium fluoride (BkF3), berkelium oxychloride (BkOCl), and berkelium trioxide (BkO3). In 1962visible amounts of berkelium chloride(BkCl3) were isolated that weighed 3 billionths of a gram. This was the first time visible amounts of a pure berkelium compound were produced.
Like other actinides, berkelium
bio-accumulates in skeletal tissue.Fact|date=February 2007 This element has no known uses outside of basic research and plays no biological role.
Berkelium was first synthesized by
Glenn T. Seaborg, Albert Ghiorso, Stanley G. Thompson, and Kenneth Street, Jr at the University of California, Berkeleyin December 1949. The team used a cyclotronto bombard a milligram-sized target of 241Am with alpha particles to produce 243Bk ( half-life4.5 hours) and two free neutrons. One of the longest lived isotopes of the element, 249Bk (half-life 330 days), was later synthesized by subjecting a 244Cm target with an intense beam of neutrons.
radioisotopes of berkelium have been characterized, with the most stable being 247Bk with a half-lifeof 1380 years, 248Bk with a half-life of >9 years, and 249Bk with a half-life of 330 days. All of the remaining radioactiveisotopes have half-lives that are less than 5 days, and the majority of these have half-lives that are less than 5 hours. This element also has 2 meta states, with the most stable being 248mBk (t½ 23.7 hours). The isotopes of berkelium range in atomic weightfrom 235.057 u (235Bk) to 254.091 u (254Bk).
Nuclear fuel cycle
nuclear fuel cycle, berkelium is produced by beta decayof curium. The first curium isotope to undergo beta decay is Cm-249 with a halflife of just over an hour, so Bk-249 is the only isotope of berkelium produced in significant quantities in nuclear reactors. Production of Bk-249 requires 11 successive neutron captures on uranium-238without nuclear fissionor alpha decay, so it is only produced in small amounts.
249Bk has a moderately large neutron capture
cross sectionof 710 barns for thermal neutrons, 1200 barns resonance integral, but very low fission cross section for thermal neutrons. If still in a thermal reactor, much of it will therefore be converted to 250Bk which quickly decays to californium-250, but some alpha decays to curium-245.
* [http://periodic.lanl.gov/elements/97.html Los Alamos National Laboratory - Berkelium]
* [http://education.jlab.org/itselemental/ele097.html It's Elemental - Berkelium]
* [http://sciencereview.berkeley.edu/articles.php?issue=1&article=elementary Berkeley Science Review - An Elementary Problem]
* [http://www.webelements.com/webelements/elements/text/Bk/index.html WebElements.com - Berkelium]
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