Re: temporal? variations in background

[Kai Kaletsch <info@eic.nu>]

Ted,



I was talking about radon, not gamma. Radon gets displaced from the pore

spaces in the soil by the water and gets into the air and into your house.



The displacement of radon gas is probably part of the reason gamma goes

down. Remember, 95% of the gamma radiation from the U decay series comes

from the short lived radon progeny, Bi-214 and Pb-214. Water would also add

a bit to the shielding. Radon would take a few days to grow back in after

the soil has dried. Do you notice a lag like that in your gamma readings?



We do operational checks on our Ventilator radon sniffers before we sell

them or before I take them on a consulting job. The first few times after a

rain, I thought we had managed to contaminate the detector, because it was

counting so high.



One of these days I'll get organized and run a radon sniffer 24/7 in the

crawlspace under my house and put the data on the web.



Regards,

Kai

http://www.eic.nu



----- Original Message -----

From: "Ted de Castro" <tdc@xrayted.com>

To: "Kai Kaletsch" <info@eic.nu>

Cc: "radsafe" <radsafe@list.vanderbilt.edu>

Sent: Saturday, September 07, 2002 6:05 PM

Subject: Re: temporal? variations in background





> actually no!  wrt gamma background and rain - SOMETIMES you can see a

> "washout" from the atmosphere for the first 1/2 hour when the rain

> starts - but in general the more it rains the lower the background -

> when it stops going down - the ground is saturated.  This also clearly

> shows in the annual variation - highest JUST before the fall rains and

> lowest just after the spring storms.

>

> I have years of environmental data taken with a very sensitive GM tube

> (1 x 12 inch active area) that shows this.  Sensitivity 650k counts per

> mREM - so it certainly has the sensitivity to show this.

>

>

> Kai Kaletsch wrote:

> >

> > While the discussion on variation in BG is going on: Does anyone have an

> > idea of the variations in BG radiation over time? There are short term

> > spikes in radon after a rain and there are changes in cosmic ray fluxes

etc.

> > How do these phenomena affect the long term average exposure?

> >

> > For example, if my radiation exposure last year was 3.0 mSv and I live

in

> > the same place and do the same things this year, how close to 3.0 mSv

can I

> > expect my exposure to be this year?

> >

> > How do these temporal variations in natural BG compare with events such

as

> > atmospheric weapons testing, Chernobyl etc...?

> >

> > Thanks,

> > Kai

> > http://www.eic.nu

> >

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