Uranophane from the Black Forest (Germany)

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Go-Figure
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Uranophane from the Black Forest (Germany)

Post by Go-Figure » 30 Aug 2020, 07:54

Hello there,
Today I had some fun with this beautiful sample of Uranophane from the Black Forest in Germany.
I had it for some time, but for one reason or another I never tested it, actually I quite forgot I had it, the other day I was checking the small safe where I keep some of my radioactive stuff and there it was, not looking spectacular inside its plastic bag, but when the sun shines on it, well, it looks pretty good. Click to enlarge, it's worth it.
01 - DSC08257_FR.jpg
Here’s the front…
02 - DSC08273_FRC.jpg
And here’s the back, or the other way around, depending on which side you start from.
03 - DSC08271_FRC.jpg

The front side is the more active one, of you place the probe where the yellow crystal is the read goes way up. Here it got up to 27K CPM on the Geiger counter.
04 - DSC08284R.jpg
Same with the PDS, placing it right on the yellow it gets as high as 2.27 μSv/h as a peak read.
05 - DSC08255R.jpg
Over a 60 minutes accumulation the average was 2.12 μSv/h, all the expected peaks from Uranium are there, so no surprise about that. Here’s the spectrum in linear and logarithmic view.
06 - Uranophane - 3600 secs - 29-08-20 - LIN.png
07 - Uranophane - 3600 secs - 29-08-20 - LOG.png
The sample was hot enough so I decided to test it with no shield in order to rule out the influence of fluorescence in the 77 keV X-rays peak from Lead 214.
As usual I calibrated with a Cesium 137 check source. I usually do a second calibration with a lantern mantle to adjust calibration at higher energies, but this time I didn't. The check source gives enough counts to dwarf any contribution from the background, but a weak peak from K40 is still visible in the spectrum, and you can spot it even better in the energy per bin view, so I used it as a third calibration point, beside the peaks at 32 keV and 661.67 keV.
And then I recorded my 12 hours background, calibration was quite good across the board, although K40 was a few keV shy.
08 - Background - Stanza Fondo - 12 Hours - 0.042 Gauss - No Shield - 28-08-20.png
08 - Background - Stanza Fondo - 12 Hours - 0.042 Gauss - No Shield - 28-08-20.png (65.98 KiB) Viewed 988 times
My background gave me the customary 256 CPS.
With the sample 3 hours were enough, I initially set the acquisition time at 4 hours, but there was no reason to go so long with 1300 CPS, enough for 14 million counts by the time I stopped the acquisition.
Lead 210 showed up as a small bump. As often happens with pretty active samples the slope buried the first Th234 peak at 63 keV, leaving the 92 keV still visible, while the 77 keV from Pb214 is the most prominent in terms of counts, as always.
The fingers and the thumb of Uranium are well visible, as well as all the Bi214 peak. The last one at 2204 keV was there as well, but I cut it off the picture.
09 - Uranophane - ID - 3 Hours - BG Subtraction - Counts x Bin - NO Shield - 0.042 Clean - 28-08-20.png
10 - Uranophane - ID - 3 Hours - BG Subtraction - Energy x Bin - NO Shield - 0.042 Clean - 28-08-20.png
And here’s the recap.
11 - Spectrum Analysis-001.jpg
After several long measurements this one was pretty quick and “painless” and although there was no surprise it was still interesting to do.
Now the sample goes back into the safe.

Have good Sunday folks, until next time.

Massimo

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GigaBecquerel
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Re: Uranophane from the Black Forest (Germany)

Post by GigaBecquerel » 30 Aug 2020, 17:27

Hi Massimo,

Very nice Report!
I like the strong separation between the lead xrf ad ²³⁴Th peak, I did not think that NaI could do it that well!

Lukas

Mike S
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Re: Uranophane from the Black Forest (Germany)

Post by Mike S » 06 Sep 2020, 09:02

As always, very nice, and very informative.

Thanks for sharing!

--Mike S.
Mike Sullivan
Central Coast of California, USA

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Svilen
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Re: Uranophane from the Black Forest (Germany)

Post by Svilen » 07 Sep 2020, 22:41

Great report as always! Thanks!
Svilen

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Go-Figure
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Re: Uranophane from the Black Forest (Germany)

Post by Go-Figure » 21 Sep 2020, 02:14

Thank you guys.
I am working on the next one, but it'll take some time.

@GigaBecquerel, I can usually tell both those peaks, and often the 63 keV as well, while this time there's only a small bump there.
Also when the sample is hot enough I don't use the lead shielding so I can rule out the 77 keV peak (which is always there anyway) comes from the shield fluorescence.

Massimo

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