Editing Xenon (section)

=== From fission ===
Some radioactive isotopes of xenon (for example, <sup>133</sup>Xe and <sup>135</sup>Xe) are produced by [[neutron]] irradiation of fissionable material within [[nuclear reactor]]s.<ref name="lanl" /> [[Xenon-135|<sup>135</sup>Xe]] is of considerable significance in the operation of [[nuclear reactor|nuclear fission reactors]]. <sup>135</sup>Xe has a huge [[Neutron cross-section|cross section]] for [[thermal neutron]]s, 2.6×10<sup>6</sup>&nbsp;[[Barn (unit)|barns]],<ref name="stacey">{{cite book
| first     = Weston M.
| last      = Stacey
| date      = 2007
| title     = Nuclear Reactor Physics
| page      = 213
| url       = https://books.google.com/books?id=y1UgcgVSXSkC&pg=PA213
| publisher = Wiley-VCH
| isbn      = 978-3-527-40679-1
}}</ref> and operates as a [[neutron absorber]] or "[[nuclear poison|poison]]" that can slow or stop the chain reaction after a period of operation. This was discovered in the earliest nuclear reactors built by the American [[Manhattan Project]] for [[plutonium]] production. However, the designers had made provisions in the design to increase the reactor's reactivity (the number of neutrons per fission that go on to fission other atoms of [[nuclear fuel]]).<ref>{{cite web
| author       = Staff
| url          = http://www.cfo.doe.gov/me70/manhattan/hanford_operational.htm
| archive-url  = https://web.archive.org/web/20091210094859/http://www.cfo.doe.gov/me70/manhattan/hanford_operational.htm
| archive-date = December 10, 2009
| title        = Hanford Becomes Operational
| work         = The Manhattan Project: An Interactive History
| publisher    = U.S. Department of Energy
| access-date  = October 10, 2007
}}</ref>

<sup>135</sup>Xe reactor poisoning was a major factor in the [[Chernobyl disaster]].<ref>{{cite book
| title     = Modern Physics: An Introductory Text
| date      = 2000
| first     = Jeremy I.
| last      = Pfeffer
| author2   = Nir, Shlomo
| pages     = 421 ff
| publisher = [[Imperial College Press]]
| isbn      = 1-86094-250-4
| url       = https://books.google.com/books?id=KmMYWP56t98C&pg=PA421
}}</ref> A shutdown or decrease of power of a reactor can result in buildup of <sup>135</sup>Xe, with reactor operation going into a condition known as the [[iodine pit]]. Under adverse conditions, relatively high concentrations of radioactive xenon isotopes may emanate from cracked [[fuel rod]]s,<ref>{{cite book
| first     = Edwards A.
| last      = Laws
| date      = 2000
| title     = Aquatic Pollution: An Introductory Text
| page      = 505
| publisher = John Wiley and Sons
| isbn      = 0-471-34875-9
| url       = https://books.google.com/books?id=11LI7XyEIsAC&pg=PA505
}}</ref> or fissioning of uranium in [[Water cooling|cooling water]].<ref>{{cite news
| author       = Staff
| date         = April 9, 1979
| title        = A Nuclear Nightmare
| magazine     = [[Time (magazine)|Time]]
| url          = http://www.time.com/time/magazine/article/0,9171,920196-4,00.html
| archive-url  = https://web.archive.org/web/20071012190713/http://www.time.com/time/magazine/article/0,9171,920196-4,00.html
| url-status   = dead
| archive-date = October 12, 2007
| access-date  = October 9, 2007
}}</ref>

Isotope ratios of xenon produced in [[natural nuclear fission reactor]]s at [[Oklo]] in Gabon reveal the reactor properties during chain reaction that took place about 2 billion years ago.<ref name="Meshik PRL 2004">{{cite journal
| last1   = Meshik
| first1  = A. P.
| last2   = Hohenberg
| first2  = C. M.
| last3   = Pravdivtseva
| first3  = O. V.
| title   = Record of Cycling Operation of the Natural Nuclear Reactor in the Oklo/Okelobondo Area in Gabon
| journal = Phys. Rev. Lett.
| volume  = 93
| date    = 2004
| issue   = 18
| page    = 182302
| issn    = 0031-9007
| doi     = 10.1103/physrevlett.93.182302
| pmid    = 15525157
| bibcode = 2004PhRvL..93r2302M
}}</ref>