[ RadSafe ] [EXTERNAL] Respirable Dust as a Surrogate for Airborne Radioactivity
mwasiol at sandia.gov
Wed Dec 4 18:32:56 CST 2013
It is not correct to assume that that the number resulting from using the method you are describing is always conservative. It depends on how the activity is distributed in or on the soil particles. If the activity is primarily on the surface of the soil particles, then small (e.g., respirable) particles, having a larger surface area to mass ratio, will have a greater activity concentration per unit mass than the larger particles or the average for the soil. In other words the activity concentration (Bq/kg) of suspended soil particles will be greater than the activity concentration in the soil. In the inhalation exposure models this effect is accounted for by using the, so called, enhancement factor.
From: radsafe-bounces at health.phys.iit.edu [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Peter Collopy
Sent: Wednesday, December 04, 2013 5:05 PM
Subject: [EXTERNAL] [ RadSafe ] Respirable Dust as a Surrogate for Airborne Radioactivity
Looking for help in identifying papers/presentations where the paper addresses the use of respirable dust measurements as a real time surrogate for airborne radioactivity. I did a bunch of on line searching but couldn't come up with any papers or presentations even though I know they are out there. For example abut 20 years ago at the HPS Midyear in Coeur d'Alene I first heard about using this technique from someone at the DOE discussing soil remediation and radiation protection controls. Unfortunately I had to move numerous times (its a long and sordid story why) so I don't carry any of my old materials from those conferences.
The HP Journal search turns up an excessive amount of papers on respirable fraction which is not what I am looking for.
For those who have never used the technique its simply using the soil concentrations and by assuming the ratio of activity per gram of soil must be the same as that in air one converts the respirable dust measurement to pCi/g. In math terms that is ug/m^3 (respirable dust measurement) * pCi/g (soil concentration) = uCi/cc with the proper units conversion. The number is always conservative because not all the activity in the soil is of a respirable size even when re-suspended in air. Obviously it can't be used for volatile or semi-volatile substances.
Any leads are appreciated
Peter Collopy, CIH, CHP, CSP
Director, Entropy Control
Chaos for the Future
3940 7th Avenue
San Diego CA 92103
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