Re: I-125 standards for cartridges

["William A. Fendt" <35346@strauss.udel.edu>]

Mark  this would make a great operational topic paper/note in the HP Journal.

On Fri, 28 Jul 1995 MARKT@HARV-EHS.mhs.harvard.edu wrote:

> I was forwarded your message about developing I-125 standards for carbon 
> cartridges. I have done research in this area and may have useful 
> information. I started by sealing 7-8 spiked filter papers in laminated 
> plastic; the filters were spiked with NIST-traceable I-125 solution. Next 
> I opened several cartridges, and placed the sealed-moist filters at a 
> different depth for each of them. This provided me with a series of 
> cartridges containing known I-125 activities at known depths. The 
> cartridges were then resealed and analyzed using a front/back counting 
> technique (Montgomery; in Radioactivity & Radiochemistry, Vol.1, pages 
> 4-9, 1990). The front/back technique is quite useful and allowed me to 
> establish relationships between the front/back count ratio, depth of 
> burial, and counting efficiency, i.e., calibration curves.
> 
> These curves can be used in operational sample analysis to determine the 
> cartridge counting efficiency based on the observed front/back count 
> ratio. If you have many samples, you may wish to determine an average 
> efficiency for all samples based on a determination of average depth of 
> burial. 
> 
> Good Luck Wes,
> 
> Mark A. Tries 
> Harvard University, Radiation Protection Office
> 46 Oxford Street
> Cambridge, MA  02138-1995
>