[ RadSafe ] outdoor low dose rate measurements
Ted de Castro
tdc at xrayted.com
Wed Apr 3 15:44:51 CDT 2013
It depends on the instrument of course but also on how large you expect
the elevated area to be and how fast the walk is.
I could easily discern this for narrow fields - "beams" < inch across -
with a pancake GM at the "standard" 2 inches per minute - I routinely
have to determine < 0.05 with a background of ~0.015 when surveying a
large cabinet - 4'x4'x8'.
Much faster - NO WAY.
That would be a mighty slow walk. A brisk walk is 4 mi/hr - ~70
inches/sec if I calculated correctly - so it would be an EXCEEDINGLY
SLOW walk - unless the elevated field covers a large area.
Using a larger area detector will of course increase the sensitivity -
but also the background. Still the stats would be better.
On 4/3/2013 12:39 PM, JOHN.RICH at sargentlundy.com wrote:
> I just finished a calculation that's going to require a minimally trained
> individual (not a radworker) to notice the difference between 0.03
> mrad/hr and 0.13 mrad/hr on a handheld meter while walking around an
> outdoor storage area. I'm stressing that this is a calculated result
> because it's the maximum calculated difference. The minimum calculated
> difference is between 0.02 mrad/hr to 0.04 mrad/hr. Actual dose rates
> should fall somewhere in between.
> Is this a reasonable expectation, or is it asking too much of an outdoor
> walk-around with a hand held meter? BTW, I have no idea what the radon
> conditions are.
> thx in advance - -jmr
> John Rich
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