[ RadSafe ] Gamma background radiation at ground level

Ted de Castro tdc at xrayted.com
Wed Feb 23 16:57:50 CST 2011

In the SF East Bay Area hills I always thought that the background 
measurement might be a way to to assess soil rain water saturation and 
thus the potential for slides.

On 2/23/2011 1:55 PM, McNaughton, Michael wrote:
> I agree with Ted. During the spring, we see a gradual increase in terrestrial radiation as the snow melts. We can even measure the thickness of the snow.
> (By the way, on rare occasions we also detect radiation from LANL, amounting to less than 1% of the background radiation.)
> -----Original Message-----
> From: radsafe-bounces at health.phys.iit.edu [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Ted de Castro
> Sent: Wednesday, February 23, 2011 2:36 PM
> To: The International Radiation Protection (Health Physics) Mailing List
> Subject: Re: [ RadSafe ] Gamma background radiation at ground level
> On 2/23/2011 9:21 AM, McNaughton, Michael wrote:
>> Filipe: background from terrestrial radiation is 5 to 15 microR/h, depending on the type of soil. Background from cosmic radiation is 5 to 10 microR/h depending on the altitude.  The supernova caused an increase of 0.5 microR/h at all locations so the increase was 2% to 5%. During a storm, gammas from Bi-214 and Pb-214 cause up to a factor of 2 increase, depending on the rate of the rain or snow fall.
> AND - water saturation of the ground during a rain storm/rainy season
> LOWERS the background rate measured.  Data I took at a California site
> showed a short increase at the start of rainfall (washout) but a
> continued decrease as the rain continued, leveling off at saturation
> (shielding).  There was also a clear annual pattern - generally seeming
> to reflect ground moisture.
> I was not able to detect supernova or solar x-ray bursts.
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