[ RadSafe ] Radon Travel in Granite and concrete

Tue Jul 29 10:33:39 CDT 2008

Peter's numbers for emanation from soil are much higher than my numbers for 
U ore. I have seen some higher emanation fractions on U ore , but the 
samples were either very weathered, unrepresentative of normal ore (airborne 
dust collected on a filter, emanation determined by alpha spectrum), the 
methodology was questionable or the grade was very low. So, the question 
becomes which emanation fraction one would expect from granite.

The measured emanation fractions in both U ore and soil are much higher than 
what one would predict from a theoretical calculation, assuming the radium 
is evenly distributed in the ore grain. As Peter mentions, the range of the 
recoiling 222Rn nucleus is about 60 um in air. If we scale that by density 
to get an estimate of the range in the rock grain, we get about 0.02 um, 
which is a lot smaller than the size of the rock grain. So, it would be 
physically impossible for any significant fraction of 222Rn to escape. One 
explanation is that the host rock normally gets there first and the U (which 
is pretty mobile) gets there later and just coats the outside of the grain. 
So at low U concentrations, almost all of the U would be in range of the 
pore space. Once you get to a few percent U, the layer of Uranium (and other 
late coming materials) becomes thicker and less of the Rn has a chance of 
getting out.

In granite, do we expect the U to by inside the rock grain or on the 
outside?

While we are talking about radon movement, I have a few questions and hope 
someone on the list can help me out.

What is a reasonable diffusion length to use for Rn in concrete? Does 
concrete have air-filled pore spaces like rock? (Peter is correct that the 
convective transport is probably more important for getting radon into your 
basement than diffusion. In my application, however, I do need to know the 
diffusion transport.)

If anyone has experience with cemented tailings backfill in a U mine and is 
willing to share, please contact me off list.

Thanks,
Kai

Kai Kaletsch
Environmental Instruments Canada Inc.

 points out that
----- Original Message ----- 
From: "Peter Bossew" <peter.bossew at jrc.it>
To: "al gerhart" <webmaster at solidsurfacealliance.org>
Cc: <radsafe at radlab.nl>
Sent: Tuesday, July 29, 2008 7:31 AM
Subject: Re: [ RadSafe ] Radon Travel in Granite

> Rn transport, emanation power, etc.: I suggest consulting the standard 
> textbook,
> Nazaroff, W. W., A. V. Nero (1988): Radon and its Decay Products in Indoor 
> Air. John Wiley & Sons.
>
> 0.2 eman. power = 20% set free of a "piece" (depending on experimental 
> setup, but not too much; once out of the grain, the Rn is practically 
> free.)
> Interstitial water content: the model is, that water in the pore space (as 
> long as it is not too much) slows down the ejected recoil nuclei to an 
> extent that they are not captured by the neighbouring grain. The kinetic 
> energy of the recoil 222Rn nucleus is 86 keV, their mean range in air is 
> ca. 60 um. Experimentally, eman power in soil (!) increases up to ca. 10% 
> water, then remains approx. const. up to ca. 20-30%. After that, 
> experimentally difficult.
>
> U series assay by gamma spectrometry is not trivial.
> - 238U : Via 234Th (63.3, 93 keV), 231mPa (1001), consult literature about 
> these lines first !!
> - 226Ra: Via progenies 214Pb,Bi (295, 352, 609, 1120, 1764,...). Container 
> must be kept isolated ca. 3 weeks in order to establish sec eq of 226Ra - 
> 222Rn - progenies. For accurate measurement, sum/coinc of some lines must 
> be corrected for, if eff cal. done  with standard composed of single line 
> radionuclides (as commonly done)(otherwise up to a few % syst. error, 
> depending on geom.). Validation with certified U samples is advised. - 
> Avoid the 186 line, possible, but complicated.
> - 210Pb: 46.6 keV. Density correction is crucial.
> - 235U ff: not easy by g-spec., but possible. 144 keV line: sec. eq. 
> within 235U series required, due to contribution of 223Ra. Also 
> interference by 230Th must be accounted for.
> - 232Th series: 228Ac (338, 911), 224Ra ff (239, 583, 2615). Different 
> caveats apply.
>
> As a summary, 226Ra ff, 228Ac and 224Ra ff are relatively easy and 
> straight forward, but 238U, 235U, 210Pb require a bit of experience and 
> good QA.
>
> regards,
> Peter
>
>
> al gerhart wrote:
>> 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?
>> _______________________________________________
>> You are currently subscribed to the RadSafe mailing list
>>
>> Before posting a message to RadSafe be sure to have read and understood 
>> the RadSafe rules. These can be found at: 
>> http://radlab.nl/radsafe/radsaferules.html
>>
>> For information on how to subscribe or unsubscribe and other settings 
>> visit: http://radlab.nl/radsafe/
>>
>>
>
>
> -- 
>
>
> -----------------------------------------------------
> Peter Bossew
> European Commission (EC) Joint Research Centre (JRC) Institute for 
> Environment and Sustainability (IES)
> TP 441, Via Fermi 1 21020 Ispra (VA) ITALY Tel. +39 0332 78 9109 Fax. +39 
> 0332 78 5466 Email: peter.bossew at jrc.it
> http://rem.jrc.ec.europa.eu/
>  "The views expressed are purely those of the writer and may not in any
> circumstances be regarded as stating an official position of the European
> Commission."
>
>
> _______________________________________________
> You are currently subscribed to the RadSafe mailing list
>
> Before posting a message to RadSafe be sure to have read and understood 
> the RadSafe rules. These can be found at: 
> http://radlab.nl/radsafe/radsaferules.html
>
> For information on how to subscribe or unsubscribe and other settings 
> visit: http://radlab.nl/radsafe/
>
> No virus found in this incoming message.
> Checked by AVG - http://www.avg.com Version: 8.0.138 / Virus Database: 
> 270.5.6/1578 - Release Date: 7/28/2008 5:13 PM
>
>
> 