[ RadSafe ] Radon Travel in Granite

[Kai Kaletsch]

Hi Al and all,

Aside from any incremental increase in radon or gamma exposure (which I 
don't tend to get too excited about), 0.25% U ore would NOT be my first 
choice of food preparation surface. If those numbers are correct, then it is 
important that a sample of the same material be made available for testing 
by the other stake holders in this (by now somewhat politicized) issue.

0.25% U is quite high and, at least in Canada, there are several regulations 
dealing with radioactive materials that kick in at much lower levels. For 
example, 0.05% U (5 times lower than your rock) is considered 'source 
material' and is a 'controlled nuclear substance' (even if it is contained 
in a granite countertop) and a license is required to export the material 
from Canada. So, if your slab of granite came from Canada, and the exporter 
didn't approach our nuclear regulator to get a license ... You can see our 
Nuclear Non-proliferation Import and Export Control Regulations here: 
http://laws.justice.gc.ca/en/n-28.3/sor-2000-210/153934.html?noCookie

Before, you asked if there is a quick and dirty way of getting from cpm or 
mR/Hr to ppm. You can get in the right ballpark if you take readings on a 
bunch of  normal granite, average the readings, assume that corresponds to 
Dan's value of ~ 10 ppm and scale the result of your sample.

You can also calculate a dose rate for a given geometry as a function of 
uranium content. I have a program on my website that does this (see 
http://members.shaw.ca/eic/Tools/JavaShield/Index.html , read the 
documentation and use the rectangular source geometry). If you are using a 
pancake probe, these are not energy compensated and your reading will be off 
by a bit. More importantly, make sure you put ~ 1 mm sheet of aluminum (or 
similar) between the source and the pancake. Otherwise, your detector will 
see alpha and beta radiation and your mR/Hr reading will be meaningless (you 
want to see gamma). That is probably how you got your 10.5 mR/Hr reading, 
which is too high, even for 0.25%U.

Regards.
Kai

Kai Kaletsch
Environmental Instruments Canada Inc.

----- Original Message ----- 
From: "al gerhart" <webmaster at solidsurfacealliance.org>
To: <radsafe at radlab.nl>
Sent: Monday, July 28, 2008 9:23 PM
Subject: [ RadSafe ] Radon Travel in Granite


> Okay, let me ask some questions in carpenter terms, math challenged 
> Carpenter terms.
>
>  "1) In "ordinary" dry soils, the emanation power is 0.2-0.3, and if one 
> wants to be really conservative, one should set as much as 0.5."
>  So that would be 2% to 5% of the Radon getting out of the grain, or out 
> of the rock itself?
>
>  "In wet soil (10% water m/m) the emanation power can be doubled."
>  Radon transferred by dissolving in water? Fluid movement?
>
>  On the lab samples, I have no idea how they were prepared, sorry. There 
> is a phone number on the report and they are quite friendly and helpful, 
> would be very interested in hearing any info on this matter, good or bad. 
> Well, that doesn't sound right, how about supportive or non supportive of 
> the report.
>  I have purchased a Gamma Spectrometer, older model. Looking forward to 
> learning how to use it correctly, interesting that so much info can be 
> determined with Gamma Spectrometry. I got the shortcomings of the handheld 
> meters, especially those that we are using. Thanks though for making sure 
> we got it.
>  Now here is something I can't figure out. No doubt it will show a wide 
> gap in my understanding of decay chains. I see Radium, I see daughters 
> except for Radon. If much of the Radon produced is trapped inside, or even 
> if some of it is trapped inside, why is there no data for Radon?
>  I think I am following Dan's info, he is using the equilibrium that 
> should be present in the decay products, using the U-253 known value, one 
> can deduct a possible value for u-238. Then that value is checked against 
> what the lab report gives for Ra-226 as a method of verifying the method 
> and result?
>  And the end to all this is one quarter of one percent uranium in the 
> granite? 1 in 400? 2,000 ppm = 1 in 500? And 80 ppm could be profitably 
> mined?
>  This is Juparana Bordeaux, pretty costly.
>  This report was on a hot spot that was cored, does not represent the 
> entire slab. Sometimes only one or two hot spots, sometimes all medium 
> high like Niagara Gold, with the occasional hotter spot.
>  But, that spot was about 36 times higher than an average Rossing mine 
> granite?
>  Geezzzz, I just want to sell countertops without setting myself up for 
> being sued years later. Looks like a Physics degree, advanced math, and a 
> Geologist degree needs to be completed first :)
>  By the way, who was looking into toxic countertops?
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