[ RadSafe ] Respirable Dust as a Surrogate for AirborneRadioactivity

Brennan, Mike (DOH) Mike.Brennan at DOH.WA.GOV
Wed Dec 4 18:42:57 CST 2013

Hi, Peter.

I don't have any help in terms of the paper, but I would raise a couple of caveats about using such a conversion without validating it for the specific circumstances.

The first is that I think it is important to know the chemical and physical form of the contamination of concern.  For example, if the COC is deplete uranium particles, it is quite possible there would be enough of a density difference that the concentration in the soil and the concentration dust in the air.  The opposite is also possible if the contaminant has a lower density than the soil.

Another is that usually the contaminated area is very small compared to the area that windborne dust is picked up from.  To assume that all of soil that was source for the dust has the same concentration as the contaminated area is pretty shaky (an exception being if the contaminate is something left in tailings from a mine or mill, and the tailings cover a very large area).  

I have had my acceptance of the "conservative answers are good" position shaken by cases where truly mind-blowing amounts of resources are wasted on pointless cleanups because conservative assumptions were used in the modeling.  I have seen assumptions that actually defy the laws of physics used in modeling that drove a multi-million dollar cleanup.  The reason that this assumption (that the contaminate would spread through a volume of soil several thousand times larger without decreasing in concentration) was made was because it was conservative and easy.  Once it was put out in a document it became impossible to pull back.  

-----Original Message-----
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 4:05 PM
To: radsafe
Subject: [ RadSafe ] Respirable Dust as a Surrogate for AirborneRadioactivity

 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

Pete C

Peter Collopy, CIH, CHP, CSP 
Director, Entropy Control 
Chaos for the Future 
3940 7th Avenue
San Diego CA 92103
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