Krypton-85

Presence in Earth's atmosphere

Natural production

Krypton-85 is produced in small quantities by the interaction of cosmic rays with stable krypton-84 in the atmosphere. Natural sources maintain an equilibrium inventory of about 0.09 PBq in the atmosphere.

Anthropogenic production

As of 2009, the total amount in the atmosphere is estimated at 5500 PBq due to anthropogenic sources. At the end of the year 2000, it was estimated to be 4800 PBq, The most important of these human sources is nuclear fuel reprocessing, as krypton-85 is one of the seven common medium-lived fission products. Most or all of this krypton-85 is retained in the spent nuclear fuel rods; spent fuel on discharge from a reactor contains between 0.13–1.8 PBq/Mg of krypton-85. Some of this spent fuel is reprocessed. Current nuclear reprocessing releases the gaseous 85Kr into the atmosphere when the spent fuel is dissolved. It would be possible in principle to capture and store this krypton gas as nuclear waste or for use. The cumulative global amount of krypton-85 released from reprocessing activity has been estimated as 10,600 PBq as of 2000. The global inventory noted above is smaller than this amount due to radioactive decay; a smaller fraction is dissolved into the deep oceans.

Other man-made sources are small contributors to the total. Atmospheric nuclear weapons tests released an estimated 111–185 PBq. The Chernobyl accident released about 35 PBq,

The average atmospheric concentration of krypton-85 was approximately 0.6 Bq/m3 in 1976, and has increased to approximately 1.3 Bq/m3 as of 2005. These are approximate global average values; concentrations are higher locally around nuclear reprocessing facilities, and are generally higher in the northern hemisphere than in the southern hemisphere.

For wide-area atmospheric monitoring, krypton-85 is the best indicator for clandestine plutonium separations.

Krypton-85 releases increase the electrical conductivity of atmospheric air. Meteorological effects are expected to be stronger closer to the source of the emissions.

Uses in industry

Krypton-85 is used in arc discharge lamps commonly used in the entertainment industry for large HMI film lights as well as high-intensity discharge lamps. The presence of krypton-85 in discharge tube of the lamps can make the lamps easy to ignite. and an illuminated highway sign erected in Arizona in 1969. A 60 μCi (2.22 MBq) capsule of krypton-85 was used by the random number server HotBits (an allusion to the radioactive element being a quantum mechanical source of entropy), but was replaced with a 5 μCi (185 kBq) Cs-137 source in 1998.

Krypton-85 is also used to inspect aircraft components for small defects. Krypton-85 is allowed to penetrate small cracks, and then its presence is detected by autoradiography. The method is called "krypton gas penetrant imaging". The gas penetrates smaller openings than the liquids used in dye penetrant inspection and fluorescent penetrant inspection.

Krypton-85 was used in cold-cathode voltage regulator electron tubes, such as the type 5651.

Krypton-85 is also used for Industrial Process Control mainly for thickness and density measurements as an alternative to Sr-90 or Cs-137.https://raims.co.uk/wp-content/uploads/2017/02/M85K01-v1.pdf Sealed Sources for Industrial Gauging. M85K01 Series Kr-85 Beta Sources (PDF) Retrieved on 2021-09-10

Krypton-85 is also used as a charge neutralizer in aerosol sampling systems.{{cite journal | access-date = 2023-01-04 | url-access= subscription

References

References

1. {{NUBASE2020
2. {{NNDC
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5. (1975-11-28). "Atmospheric Concentrations and Inventory of Krypton-85 in 1973". American Association for the Advancement of Science.
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8. [http://www.spectragases.com/AssetMgmt/getDocument.aspx?assetid=618 Krypton-85 (PDF)]. Spectragases.com (2004-12-30). Retrieved on 2013-07-25.
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11. NRPB and GRS. (2001). "Transport of Consumer Goods containing Small Quantities of Radioactive Materials". European Commission.
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13. (1957-02-17). "Make A-powered Rail Signal Light in D&RGW Labs". The Ogden Standard-Examiner.
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16. Walker, John. (September 2006). "HotBits Hardware".
17. Glatz, J.. (1996-12-01). "Krypton gas penetrant imaging -- A valuable tool for ensuring structural integrity in aircraft engine components". Materials Evaluation.
18. Glatz, Joseph. [https://web.archive.org/web/20080720084341/http://www.asnt.org/publications/materialseval/solution/decsolutions/decsolutions.htm Krypton Gas Penetrant Imaging – A Valuable Tool for Ensuring Structural Integrity in Aircraft Engine Components]. American Society for Nondestructive Testing
19. [http://www.oddmix.com/tubes/5651.html 5651 Sylvania Voltage Regulator Stabilizer Electron Tube]. Oddmix.com (2013-05-15). Retrieved on 2013-07-25.
20. [https://raims.co.uk/product/krypton-85-kr-85-sealed-sources-for-industrial-process-control/ Krypton-85 (Kr-85) Sealed Sources for Industrial Process Control] Retrieved on 2021-09-10