Uraninite from Piemonte - Sample 1

[Go-Figure]

Hello there,
I got myself two new samples to test, they’re two Uraninite specimens from Valle Antrona, Piemonte, a northwestern region of Italy.
Here I show results from the first sample, which is the better looking, although the other one is by far the hotter of the two.

Uraninite, also known as Pitchblende, is the mineral from which Marie Curie isolated Radium, you can see the black crystals in the photo below.

01-DSC01266_FC.jpg

The first test with the Geiger was a but underwhelming, around 1600 CPM on one side, and about half of it on the other one.

02-DSC01284R.jpg

I expected more, so I turned to the PDS in order to decide if the sample was hot enough for an unshielded measurement. Here you see the result of a 5 hour spectrum done actually after the test with the 2’’x2’’ NaI(Tl), but my preliminary results were quantitatively identical: roughly 80 CPS in a room with a 55 CPS background,

03-DSC01337R.jpg

The spectrum itself only reinforced expected peaks from the background.

04-Uraninite 1 - 18000 Secs - LIN - 14-02-21.png

05-Uraninite 1 - 18000 Secs - LOG - 14-02-21.png

So the sample at contact with the device gave me about 50% of the background counts, which was enough for me to go for a measurement with no shield.

06-DSC01327R.jpg

I have to say I tried something a little bit different for calibration this time. I usually do a first calibration with Cs137 and then I refine it with Thorium lantern mantle in order to have some calibration point at high energies. But it turns out you can have a high energy reference peak even just using Cs137, because some background will get in anyway and a small, almost invisible, K40 peak will form pretty much far away and unaffected by what goes on at 661.67 keV and below.
The only problem is, that peak takes a longer time to form than the Cesium ones from the check source. My calibration spectrum with Cs137 usually lasts 15-20 minutes, that’s enough to have a clean, smooth result, the same accumulation time is not enough for the K40 from the background to fully form, which I only realized later, when I was taking the background from the actual measurement. In the Cs137+background spectrum the K40 peak is so small and weak that you cannot really tell if the centroid is in the right place.
It’s something I’ll improve next time around.

I had a number of technical issues during the measurement, nothing to do with the instrument, at one point there was a brief blackout during a storm (I didn’t have the battery plugged in), at another point the computer OS crashed. Each time I was able to restart from a previous save point, since the software loads the calibration together with the spectrum file.

In the end it was a 72 hours spectrum with a 24 hour background subtraction. The result is pretty straightforward, no real surprises. It’s always good when the Pb210 at 46 keV shows up, as for the Th234 there were just hints, but we know it’s there right? So that was enough for me to label them.
I have to add I also detected clear signs of the presence of Th232, the most obvious one was the Tl208 at 2614 keV (not shown here), anyway, Th232 progeny peaks are pretty weak compared with Uranium ones, so I decided against adding them to the labels.

07-Uraninite 1 Valle Antrona - ID - 72 Hours - BG Subtraction - Counts x Bin - NO Shield - 0.042 Clean - 10_14-02-21.png

08-Uraninite 1 Valle Antrona - ID - 72 Hours - BG Subtraction - Energy x Bin - NO Shield - 0.042 Clean - 10_14-02-21.png

As for the quantitative analysis, the sample gave me 79 CPS vs 259 from the background. As usual this result is lower than that from the PDS in terms of percentage, because you can get the sample closer to where the crystal is with the PDS, being a portable, more compact device.

Spectrum Analysis-001.jpg

The test on the other Uraninite sample is in progress right now so…stay tuned.

Have a good weekend.

Massimo

[Sesselmann]

Massimo,

Nice mineral specimen and nicely documented experiment (as always).

Steven

[Go-Figure]

Massimo,

Nice mineral specimen and nicely documented experiment (as always).

Steven

Thanks Steven,
Yeah, I started with this one because it really looks good, although the other one is way hotter. More on that shortly.

Massimo