[ RadSafe ] Radon Travel in Granite
eic at shaw.ca
Wed Jul 30 20:32:37 CDT 2008
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:
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.
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
> 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
> 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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