Re: Kr-85

[Michael Kay <mikekay@teleport.com>]

The radiation information on Kr-85 posted here is correct, but the
production and use of Kr-85 is not. Kr-85 is a very important
radionuclide in commerce. It is captured and condensed from any type of
fission product reprocessing--even such processes as production of
fission product Mo-99 for medical use. 

Kr-85 is condensed and then used to make low pressure beta sources for
thickness gauges. Web gauges for plastics and other low-density (low in
grams per square centimeter) materials. Amersham makes many source
models for Kr-85 sources.

The main advantage of Kr-85 sources is that they are exempt from
financial responsibility regulations as specifically stated in the
general provisions. They are also very easy to plan accidental release
scenarios for. There is no cleanup after the source has diluted to
unrestricted levels. This is only a few minutes in most industrial
buildings for a 200 milliCurie source. This is in stark contrast to
Sr-90 or other beta emitters that are not gases.

The release of Kr-85 from atmospheric testing, venting of underground
nuclear explosions, normal reactor operations, and reprocessing has
raised the background level around the world, and is the reason Kr
cannot be used as a counting gas.

Michael Kay, ScD, CHMM
mikekay@teleport.com