Krypton-86
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There are 31 known isotopes of krypton (Kr).^[1] Naturally occurring krypton is made of five stable and one slightly radioactive isotope. Its spectral signature can be produced with some very sharp lines. ⁸¹Kr, the product of atmospheric reactions is produced with the other naturally occurring isotopes of krypton. Being radioactive it has a half-life of 250,000 years. Krypton is highly volatile when it is near surface waters and ⁸¹Kr has been used for dating old (50,000 - 800,000 year) groundwater.^[2]

⁸⁵Kr is an inert radioactive noble gas with a half-life of 10.76 years. It is produced by fission of uranium and plutonium. It is produced by nuclear bomb testing and nuclear reactors. ⁸⁵Kr is released during the reprocessing of fuel rods from nuclear reactors. Concentrations at the North Pole are 30% higher than at the South Pole as most nuclear reactors are in the northern hemisphere.^[3]
Standard atomic mass: 83.798(2) u

Table

Notes

• The isotopic composition refers to that in air.
• Geologically exceptional samples are known in which the isotopic composition lies outside the reported range. The uncertainty in the atomic mass may exceed the stated value for such specimens.
• Commercially available materials may have been subjected to an undisclosed or inadvertent isotopic fractionation. Substantial deviations from the given mass and composition can occur.
• Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
• Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC which use expanded uncertainties.

References

• Isotope masses from Ame2003 Atomic Mass Evaluation by G. Audi, A.H. Wapstra, C. Thibault, J. Blachot and O. Bersillon in Nuclear Physics A729 (2003).
• Isotopic compositions and standard atomic masses from Atomic weights of the elements. Review 2000 (IUPAC Technical Report). Pure Appl. Chem. Vol. 75, No. 6, pp. 683-800, (2003) and Atomic Weights Revised (2005).
• Half-life, spin, and isomer data selected from these sources. Editing notes on this article's talk page.
  • Audi, Bersillon, Blachot, Wapstra. The Nubase2003 evaluation of nuclear and decay properties, Nuc. Phys. A 729, pp. 3-128 (2003).
  • National Nuclear Data Center, Brookhaven National Laboratory. Information extracted from the NuDat 2.1 database (retrieved Sept. 2005).
  • David R. Lide (ed.), Norman E. Holden in CRC Handbook of Chemistry and Physics, 85th Edition, online version. CRC Press. Boca Raton, Florida (2005). Section 11, Table of the Isotopes.