Uranium Glass – Different Glassware, Still Natural Uranium

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Go-Figure
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Uranium Glass – Different Glassware, Still Natural Uranium

Post by Go-Figure » 02 Aug 2020, 21:43

Hello there,
This past week my spectrometer has been busy with another piece of uranium glassware: a small cup that I bought more than a year ago, but for some reason I never tested it properly.
As usual the best way to look at a piece of uranium glassware is under UV light in the dark.
01 - DSC08112_FR.jpg
Under ordinary visible light the cup displays the typical pale yellow-green colour.
02 - DSC08170_FRC.jpg
The cup is not very hot, the best I could get with the Geiger counter was less than 450 CPM (the background is around 50 CPM), so I expected to get very little gammas from it.
03 - DSC08123R.jpg
That was confirmed when I first tested it with the PDS: 54.80 CPS at contact with the body of the device, roughly 50 of which coming from the background, so that was in the region of 10% of the background in terms of counts, and roughly half of it in terms of exposure from gamma radiation since the kind of uranium used for these kind of objects is refined, it does not contain all the products of the decay chain like Radium, Lead and Bismuth which are responsible of the high energy part of natural uranium spectrum, so you are left with only the low energy part of it.
04 - DSC08147R.JPG
The PDS spectrum was of very little significance. The device doesn’t allow you to subtract the background therefore the signal from the sample is buried in the background curve. There’s maybe a hint of a counts excess in the 92 keV (Th234), but it’s too weak and messy to tell for sure. Linear first, then logarithmic.
05 - Uranium Glass Cup - 25-07-20 - LIN - 6 Hours.png
06 - Uranium Glass Cup - 25-07-20 - LOG - 6 Hours.png
Now the problem was that the sample was too big to be put into my shield’s chamber. I could make the chamber bigger taking away the copper and plastic layers and wrapping the lead and the pewter with a radius big enough to contain the cup inside, but in the end I decided against it. I wanted to see what I could do with such a weak sample with no shield at all so I went for a “no-shield” measurement.
I first recorded a 24 hour unshielded background, then I had a 96 hours with the sample and then an additional 48 hour background.

This is the resulting 72 background. It’s worth noting that in the middle of the week Italy got in the middle of a heat wave, probably the hottest days of the summer, and that inevitably affected the calibration. I saw the K40 peak moving south by more than 30 keV over the week. Luckily the interesting part of the spectrum of this sample is at lower energies which are less affected in absolute terms, simply because 2% of 185 is a lot less visible than 2% of 1460.
07 - Background - Stanza Fondo - 72 Hours - 0.03 Gauss - No Shield - 26-07 + 30-07_01-08-20.png
07 - Background - Stanza Fondo - 72 Hours - 0.03 Gauss - No Shield - 26-07 + 30-07_01-08-20.png (67.95 KiB) Viewed 1038 times


Here’s how the measurement was taken. I tried to optimize the geometry. As mentioned before, there was no shield.
08 - DSC08173_FC.jpg
And here’s the result, both in counts and energy per bin. The whole measurement lasted a week.
Once again it turned out to be Natural Uranium, you can tell by the fact that the U235 peaks are too strong to be depleted uranium, so this must be a pre-WW2 piece. You can see the thermal drift in the two Pa234m peaks which are considerably lower than they were supposed to be in terms of energy.
Again, there’s a 30-35 keV peak which I still cannot identify.
Also, since activity was so low and no shield was involved, the result is a bit noisy, which is particularly visible in the energy per bin view.
09 - Uranium Glass Cup - ID - Natural U - 96 Hours - BG Subtraction - Counts x Bin - No Shield - 0.030 Clean - 26_30-07-20.png
10 - Uranium Glass Cup - ID - Natural U - 96 Hours - BG Subtraction - Energy x Bin - No Shield - 0.030 Clean - 26_30-07-20.png
In the end the cup gave me 17.47 CPS, less than 7% of my background, so not an easy sample to test with no shield in place. The good thing with refined uranium is that counts are spread over a comparatively low number of peaks so you have a better chance to see something even with such a low activity.

Until next time.

Massimo
11 - Spectrum Analysis-001.jpg

Sparky
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Re: Uranium Glass – Different Glassware, Still Natural Uranium

Post by Sparky » 10 Aug 2020, 21:40

"Again, there’s a 30-35 keV peak which I still cannot identify."

In a previous thread (Shielding - Modular Shield for 2” Detectors), Ciro (Cicastol) suggested that this peak is an Iodine Ka1 Escape peak from the NaI detector. The Ka1 characteristic x-ray for Iodine is 28.6 keV, so if an incident Th234 gammas at 63.3 interacts with the detector crystal such that the Iodine x-ray escapes, such a peak could be created at 34.7 keV.

A friend loaned me an Amptek SiPin system from GEOelectronics. I am still learning how to use it. I am a bit like a monkey with a slide rule with it… I can manipulate it, but don’t understand the principals very well. I think its peak efficiency is below 35 keV, but I would expect to see this peak and I don’t. I believe this lends support to Ciro’s Iodine escape peak idea.

BTW, I think you did very well with this such a weak source as this new U-glass specimen.
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Bauer SiPin 08092020.png
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Peter-1
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Re: Uranium Glass – Different Glassware, Still Natural Uranium

Post by Peter-1 » 11 Aug 2020, 02:17

Hello,
it can come from iodine. The K-beta line is at 32.3 keV. The line can also be seen well in an experiment with an old colored glass from Schott VG3.
2020_08_10-Schott-VG3.png
2020_08_10-Schott-VG3.png (97.3 KiB) Viewed 988 times
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Go-Figure
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Re: Uranium Glass – Different Glassware, Still Natural Uranium

Post by Go-Figure » 11 Aug 2020, 06:27

Yeah, I think Iodine could be the right answer.
Lately I've been in touch with a couple of authors of the Trinitire paper I linked in my last Trinitite thread and after finding that peak in yet another spectrum I asked them for their interpretation, because I really couldn't figure it out.
Here's what one of the two told me after talking about it with the other:

"He says FitzPeaks identifies a prominent peak in that region as a Ba x-ray and it definitely shows up when there is barium present in the glass or ore. If you aren’t using shielding and there’s no barium near the detector, then it might be iodine. Ka1 and Ka2 levels emit x-rays near 28.5 KeV and Kb1 and Kb3 x-rays near 32.2 KeV. I found the graph below online plus a paper titled “Iodine escape peak to photopeak intensity ratios in NaI(Tl) crystals.” I don’t have free access to the paper so I can’t be sure it supports this idea."
image001.jpg
image001.jpg (44.56 KiB) Viewed 978 times
I find the Iodine's escape peak option particularly convincing considering this peak doesn't show up clearly in all spectra, but only in those where the Th234 peak at 63 keV is present and strong.
So I would say the issue is probably settled, thank you all for playing :)

http://nucleardata.nuclear.lu.se/toi/xr ... =list&el=I

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Peter-1
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Re: Uranium Glass – Different Glassware, Still Natural Uranium

Post by Peter-1 » 11 Aug 2020, 23:30

I did a little test to see if I can see the Ka or Kb line of iodine. To do this, I used Am241 to irradiate a container with potassium iodide. I shielded the direct radiation from Am241 with lead. As you can see, my calibration is quite good.
X-ray-KI.jpg
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Re: Uranium Glass – Different Glassware, Still Natural Uranium

Post by Sparky » 12 Aug 2020, 08:46

Peter,

I did a somewhat similar test to see if I could create an Iodine escape peak with a shielded Am241 source. First I calibrated with the Am241 source directly and then with a silver coin (Ka1=22.16 keV). I then used the backscatter radiation of the shielded Am241 source (water generates a huge backscatter peak!) at 48.25 to create an escape peak at about 20 keV.

http://www.sciencecalculators.org/nucle ... cattering/
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Am241+Ag+H2O.png
Am241+Ag+H2O.png (95.66 KiB) Viewed 950 times
Michael Loughlin

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