[ RadSafe ] Radon Travel in Granite
peter.bossew at jrc.it
Tue Jul 29 08:31:19 CDT 2008
Rn transport, emanation power, etc.: I suggest consulting the standard
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
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
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?
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