Editing Berkelium (section)

===Occurrence===
All berkelium isotopes have a half-life<!-- of up to 1,380 years---> far too short to be [[primordial nuclide|primordial]].<!---over ~50 My---> Therefore, any primordial berkelium − that is, berkelium present on the Earth during its formation − has decayed by now.

On Earth, berkelium is mostly concentrated in certain areas, which were used for the atmospheric [[nuclear weapons testing|nuclear weapons tests]] between 1945 and 1980, as well as at the sites of nuclear incidents, such as the [[Chernobyl disaster]], [[Three Mile Island accident]] and [[1968 Thule Air Base B-52 crash]]. Analysis of the debris at the testing site of the first [[United States]]' first [[thermonuclear weapon]], [[Ivy Mike]], (1 November 1952, [[Enewetak Atoll]]), revealed high concentrations of various actinides, including berkelium. For reasons of military secrecy, this result was not published until 1956.<ref>{{cite journal|last1=Fields|first1=P. R.|last2=Studier|first2=M. H.|last3=Diamond|first3=H.|last4=Mech|first4=J. F.|last5=Inghram|first5=M. G.|last6=Pyle|first6=G. L.|last7=Stevens|first7=C. M.|last8=Fried|first8=S.|last9=Manning|first9=W. M.|last10=Ghiorso|first10=A.|last11=Thompson|first11=S. G.|last12=Higgins|first12=G. H.|last13=Seaborg|first13=G. T.|display-authors=3|title=Transplutonium Elements in Thermonuclear Test Debris|date=1956|journal=Physical Review|volume=102|issue=1|pages=180–182|doi=10.1103/PhysRev.102.180|bibcode=1956PhRv..102..180F}}</ref>

Nuclear reactors produce mostly, among the berkelium isotopes, berkelium-249. During the storage and before the fuel disposal, most of it [[beta decay]]s to californium-249. The latter has a half-life of 351 years, which is relatively long compared to the half-lives of other isotopes produced in the reactor,<ref>{{cite web|url = http://www.nndc.bnl.gov/chart/ |editor = Alejandro A. Sonzogni (Database Manager)|title = Chart of Nuclides|publisher = National Nuclear Data Center, [[Brookhaven National Laboratory]]|access-date = 2010-03-01|year = 2008|location = Upton, New York|ref = CITEREFNNDC2008|archive-date = 10 October 2018|archive-url = https://web.archive.org/web/20181010070007/http://www.nndc.bnl.gov/chart/|url-status = dead}}</ref> and is therefore undesirable in the disposal products.

The [[transuranium element]]s from [[americium]] to [[fermium]], including berkelium, occurred naturally in the [[natural nuclear fission reactor]] at [[Oklo]], but no longer do so.<ref name="emsley">{{cite book|last=Emsley|first=John|title=Nature's Building Blocks: An A-Z Guide to the Elements|edition=New|date=2011|publisher=Oxford University Press|location=New York, NY|isbn=978-0-19-960563-7}}</ref>

Berkelium is also one of the elements that have theoretically been detected in [[Przybylski's Star]].<ref name=gopka08>{{cite journal |last1=Gopka |first1=V. F. |last2=Yushchenko |first2=A. V. |last3=Yushchenko |first3=V. A. |last4=Panov |first4=I. V. |last5=Kim |first5=Ch. |title=Identification of absorption lines of short half-life actinides in the spectrum of Przybylski's star (HD 101065) |journal=Kinematics and Physics of Celestial Bodies |date=15 May 2008 |volume=24 |issue=2 |pages=89–98 |doi=10.3103/S0884591308020049 |bibcode = 2008KPCB...24...89G |s2cid=120526363 }}</ref>