[ RadSafe ] Radon Travel in Granite

Thu Jul 31 19:08:22 CDT 2008

Dan W. McCarn, Geologist; 3118 Pebble Lake Drive; Sugar Land, TX 77479; USA 
HotGreenChile at gmail.com   UConcentrate at gmail.com

Dear Group, Kai & Al:

Back to basics, and a little simplified, but what the heck!

Primary mineralized uranium is usually the reduced species uraninite, UO2,
also known as pitchblende.  When uraninite comes in contact with oxidizing
groundwater, the redox state changes rapidly from +4 to +6.  Normally,
oxidized uranyl species UO2 +2 reacts with groundwater to form the highly
soluble solid species UO2(OH)2 H2O (Schoepite) and then to form carbonate
anionic aqueous species e.g. UO2(CO3)2 -2 or UO2(CO3)3 -4 because of the
high abundance of bicarbonate (HCO3-) in oxidizing natural groundwater
conditions.  This includes the range of pH from about 6.2 – >10.  Below a pH
of 6.2 the neutral aqueous species, UO2(CO3)2 0 forms.  So, at a pH of 7,
the dominate form of aqueous uranyl species is UO2(CO3)2 -2.  When solution
mining, this species is concentrated in anion exchange resins (bumps Cl -1
off) and the pH is maintained close to 7 to optimize the bicarbonate
complexation of uranyl.

How much concentration? Up to several hundred mg/L U concentration depending
on the bicarbonate ion concentration.  Sometimes NaHCO3 is added to enhance
the groundwater's ability to complex uranium.  Because the kinetics are
quite good, the reaction goes pretty fast.

Note: rain water, equilibrated to atmospheric CO2 and O2 is easily able to
rapidly mobilize uraninite (UO2) forming quite a nice, mildly acid leaching
solution of pH = about 5.6.  As a geologist, this is quite exciting, and I
can only add, "Yippee".

Dan ii

From: Kai Kaletsch [mailto:eic at shaw.ca] 
Sent: Thursday, July 31, 2008 6:31 AM
To: al gerhart
Cc: Dan W McCarn
Subject: Re: [ RadSafe ] Radon Travel in Granite

Uranium is usually pretty mobile and either acids of bases will leach it.
Even if you just dig up the ore and leave it sitting outside, the oxygen and
water are enough to leach it and you will find a yellow crust on the bottom
of the rocks or a yellow stain leading to the floor drain after a few years.

I meant that you could back calculate U content from dose rate (not for risk
assessment). 3.5 mR/hr still sounds a bit too high (but more realistic than
10.5). On a large thick slab, that would correspond to ~ 0.5 %U. If I
remember correctly, pancake detectors tend to read high on U ore (even if
you shield out the alphas and betas). So, your pancake reading could be
reasonably consistent with the 0.25% from Dan's calculation. On a smaller
piece of ore, you need a higher U concentration to get the same dose rate.
How thick was the slab and how big was the hot area?

Regards,
Kai
----- Original Message ----- 
From: al gerhart 
To: Kai Kaletsch 
Sent: Wednesday, July 30, 2008 10:12 PM
Subject: Re: [ RadSafe ] Radon Travel in Granite

Hi Kai,

I've heard that Uranium can leach out with water or slightly acidic
liquids,  Professor Nussebaum brought it to our attention.  Good to hear
another voice on the issue.  We will look into it.  I understand that a lead
test swab will react to the Uranium as if it is lead, but are there Uranium
swabs that don't react to lead content?

Or do we have to use acid and precipitate it out?   Then have it measured. 
I talked to a local chemist we have done work for and he recommended lab if
need be.

This is indeed getting very political and commercial on some levels, no one
is spending this much time and effort without something rewarding their
risk.  Let's face it, nothing gets done without an interested party on some
level.  But, if the concerns are valid, then it matters little the
motivation, just be glad someone stepped up and took a shot at it.

As to the other stakeholders, they were shown reports just like this long
ago along with a request that it be looked into.  Once was a huge stone
company, the other time it was a PhD level Professor.  Nothing got done. 
Too much money at stake.

Regulation, yes, we would love to have the protection you guys were smart
enough to pass.  As it is, not many countries will allow this stuff to be
imported, so America becomes the dumping ground for too hot material.

What a great idea on using the low level granite to provide a baseline!  Why
didn't I think of that?  We will do just that.

I will use your calculator for the risk assessment.  I need to take the time
to learn more about the Geometry aspect of radiation measurements, soaking
up a little on Geiger Counter Enthusiasts and the other Rad groups of George
Dowel.

The high reading is total radiation, 12.5 or so before we chopped up the
slab into samples for the five scientists that are studying it.  I used a
piece of  paper for an Alpha shield, got 10.5 mR if I remember right.  I
didn't have any aluminum, but I used 1/8" of plastic for a Beta shield and
got around 3.5 mR/hr.

All measurements were taken with a LENi Geiger counter (George Dowel sells
them) with a pancake probe, with about 8 or 9 mm standoff.   I've got the
measurements in cpm too, or multiply  the results by 600 to get a close
idea.

Thanks for the info, it has been invaluable.  I'll post this tomorrow on
Radsafe, wanted to thank you personally for the time and effort.

Thanks,
AL

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" 
To: 
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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