[ RadSafe ] Radon Travel in Granite

Thu Jul 31 01:31:44 CDT 2008

Hello Group:

Before we go any further in this thread, let me say that the definition of a
granite in the dimension stone business and the definition by a
geologist are not the same. Apparently pegmatites, migmatites, and
schists are likely listed as granites.  Perhaps Al can illuminate this dark
sector of the dimension stone business.  But the next time I go to Verona
for the annual world dimension stone exhibition, I'll be sure to care my
scintilation counter and perhaps my gamma spectormeter.  Perhaps the
European Federation of Geologists can send a delegation!

Al communicated with me separately that indeed he did have a "white" granite
from Namibia which was moderately radioactive.  This may likely be an
alaskitic (white, quartz-rich) granite possibly associated with the
alaskites of the Rossing U deposit.

But also, importantly, my estimate of the 0.25% total U from the apparent
pegmatite is only supported by the U-235 activity.  If this is in error,
then my estimate is also in error.  It would indeed be interesting to get a
total extractable U chemical assay from several samples (hot nitric acid
leach) to confirm the amount of U in the rock.

But I would also veer away from having an ore-grade piece of rock in the
kitchen or dressing-up the floors of my house.

Have a good day!

Dan ii

Dan W McCarn, Geologist
Albuquerque & Houston
On Wed, Jul 30, 2008 at 8:32 PM, Kai Kaletsch <eic at shaw.ca> wrote:

> 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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-- 
Dan W. McCarn
Geologist

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