Re: Floor monitor - background increasing

[AndrewsJP@AOL.COM]

In a message dated 8/21/2001 1:37:48 PM Eastern Daylight Time, Cehn@AOL.COM 

writes:



> I have a Ludlum 43-37 floor monitor surveying a large concrete pad - 
>
> outdoors.  On very hot days (>105), the instrument background goes up.  We 
>
> take it into a cool trailer, cool it down, and background stays up.  Any 
>
> ideas? 
>
>
> My favorite theory so far is radon coming off the concrete in the heat, and 
>
> the daughters sticking to the detector.  That would also account for the 
>
> backgrounds returning to normal the next morning. 
>
>
> Joel I. Cehn, CHP 
>
> cehn@aol.com 
>
> Oakland, CA 


Makes sense to me.  I have seen similar phenomena with monitoring soil, but 

without the heat and with a different detector.  We routinely monitored the 

background during the measurement runs and used a moving background count 

rate to analyze the data.  If you are using digital logging equipment you 

could monitor the decay of the background at the end of the day and see if it 

followed the "about 30" minutes half-life you would expect from the decaying 

radon daughters.  That would prove your theory.


John Andrews

Knoxville, Tennessee