[ RadSafe ] [EXTERNAL] Respirable Dust as a Surrogate for Airborne Radioactivity

[Peter Collopy]

That's an excellent point but I would argue that because of the way material gets deposited in remediation sites and the subsequent way it is disturbed during excavation activity the likelihood of that phenomenon occurring is remote (but certainly not impossible). I will say though that we never do a one for one for during our work. i.e. we always set our dust action level at about 100 below the level where one would see one DAC. It turns out that the ACGIH respirable dust TLV is more controlling and in some  cases we have to abide by some coal Department of Health levels which tend to be set at 150ug/m^3 so exceeding the DAC or violating a regulatory intake level is not likely.

 In addition we correlate (daily) our airborne activity analysis with those surrogate measurements to ensure that we are not inadvertently missing a day of high activity. Plus our ALARA controls are designed to make sure regardless of soil concentrations we limit dust re-suspension through controls such as wetting and most of our operations are conducted upwind and a several meters from the actual excavation.

Without being too big of a wank I have never seen or experienced the phenomenon you describe but it sounds plausible. I do appreciate the feedback as it is an important consideration and without any other control factors (which I am sorry I omitted) one could in some circumstances have an under-estimate.  

Still in the search for papers!!!

Peter Collopy, CIH, CHP, CSP 
Director, Entropy Control 
Chaos for the Future 
3940 7th Avenue
San Diego CA 92103
518.326.6413



On Wednesday, December 4, 2013 4:33 PM, "Wasiolek, Maryla" <mwasiol at sandia.gov> wrote:
  
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.


-----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 5:05 PM
To: radsafe
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

Pete C

Peter Collopy, CIH, CHP, CSP 
Director, Entropy Control 
Chaos for the Future 
3940 7th Avenue
San Diego CA 92103
518.326.6413
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