[ RadSafe ] FW: ...detection (BUSBY)
C.Busby at ulster.ac.uk
Tue Aug 9 12:30:06 CDT 2011
I already answered this one .
The activity on the filter is the activity on the filter, as you say. But we dont know how much of the particles in the air are trapped. So we can only use the activity in the filter as a indication of the activity in the air. I assumed 50% mass wiould stick in the filter. This was based on my reasearches on DU particles and filters. Actually now I have gone to the manufacturers and I do know. The manufacturers tell me that they trap 96% of all particles above 5-6 microns AMAd and let the rest through. The particle size spectrum of atmospheric partciles over the land has been measured (Christian Junge, Atmospheric Radioactivity 1963 Table 28). Using this we can see that actually only 11% are above 3.2 microns. So that means we can calculate that there is more radioactivity in the air than I thought, by a factor of 4 to 5.
Is that helpful?
From: radsafe-bounces at agni.phys.iit.edu on behalf of radbloom at comcast.net
Sent: Mon 08/08/2011 20:47
To: The International Radiation Protection (Health Physics) Mailing List
Subject: Re: [ RadSafe ] FW: ...detection (BUSBY)
I'm confused. How could the activity on the filter be larger if your assumptions change? Isn't the activity on the filter simply what you measure, i.e., the activity on the filter? The calculations (and assumptions) are all related to determining activity concentrations. Granted the you could say that the there would have been more or less activity on the filter if collection efficiency, air flow, etc. changed, but all that is getting you back to concentration.
I would also imagine the uncertainty in the guestimated air flow is pretty large and the other contributors' comments regarding particle size distributions, collection efficiency, etc., and driving scenarios (fast, slow, stop and go, idle time) add to the confounding of such calculations.
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