Re: Environmental Research Corporation; Fluid Atomization Generators

["Otto G. Raabe" <ograabe@ucdavis.edu>]

May 23, 2000
Davis, CA

You are describing a standard Kr-85 discharger used to reduce the charge on
aerosol particles. The Kr-85 gas is placed in a thin-walled stainless-steel
tube (about 1/8 inch diameter, 1 mil wall thickness) at ambient pressure
which allows the beta radiation to penetrate the wall and ionize the
surrounding air which contains the aerosol. There is a beta radiation
hazard associated with the tube since it is releasing betas in all
directions and the range in air is substantial. Hence the tubes are placed
in a container (usually a cylinder) through which the aerosol to be treated
is passed, and the ends usually have beta shields to prevent irradiation of
the eye of a curious researcher who looks into the end. 

I have constructed many of these devices, and they usually start with about
a millicurie of Kr-85. If the Kr-85 leaks out it it occurs slowly since the
tubes are not pressurized and the Kr-85 is quickly dispersed in and diluted
by the aerosol flow and exits the lab via the exhaust system. You can check
the level of Kr-85 in the tube with a gamma survey instrument and determine
if it has leaked out. Clearly, there is no particular risk to releasing
0.15 mCi of Kr-85 in a hood where it is mixed with exhaust air and exits
into the outside air, but you should compare the release concentration to
the appropriate regulations and discuss it with your radiation safety
officer. Since Kr is inert, it is not absorbed into or concentrated in the
body. Since it is easy to get and you are dealing with a small amount, you
probably do not need to try to recycle it.

Otto
	*****************************************************
	Prof. Otto G. Raabe, Ph.D., CHP
	Institute of Toxicology & Environmental Health (ITEH)
	(Street Address: Bldg. 3792, Old Davis Road)
	University of California, Davis, CA 95616
	E-Mail: ograabe@ucdavis.edu
	Phone:(530) 752-7754, FAX:(530) 758-6140
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