Depleted Uranium 238

[Marco75]

Hello Forum,
I am writing this post because I have been an enthusiast for 30 years but I am recently entering the world of gamma spectrometry so I would like to share some doubts with you to take advantage of the greater experience of some of you.
Because measuring the radioactive minerals in my collection is still complex given the overlapping of many radioisotopes, I preferred to start analyzing single elements and after CS137, Co60, K40 and TH232 (which I also use for calibration), I switched to a piece of depleted uranium.
Below you will find a spectrum obtained with a 2" CsI probe and Spectacular Spectacular spectrometer, PRA software and a measurement time of about one day (22 million counts) to obtain a nice "smooth" spectrum
What I expect is Uranium U238 with only first children and a small percentage of U235 and first children (U235 in % lower than which would be found with natural uranium, being depleted).
I have doubts about a couple of peaks so I would like to share the results with you. I also used Interspec to help identify.
U238 inserted in self-made shielded case with Pb (6cm), Cu (8mm), Al (2mm), Plastic (1mm)

Peaks:
A = here I have a doubt as the peak falls halfway between two possible main emissions, one of U238 and one of U235 as can be seen from the Interspec low energy image. Both are "probable", the first, for U238, Pa234m>U234 at 43.5 KeV while the second, for U235, Th231>Pa231 at 25.65KeV. It is obvious that here I should have better calibrated the probe using maybe the 32kev line of the Cs137 and perhaps the peak would have fallen more precisely. But anyhow… What do you think?? The peak is at 32.33 KeV but probably miscalibrated

B = Th234>Pa234m at 63.29 KeV (U238 series)

C = U238>Th234 at 92.38 and 92.8 KeV (U238 series)

D = here I don't know ! Interspec tells me that in this position there should be U235>Th231 and Th234>Pa234m but they are really insignificant as probabilities while here the peak is high. The peak is at 107-108 KeV. Even with uranium ore or various sources, I always get this peak but can't identify it.

E = peaks at 143 and 163 KeV of U235 (in uranium glass having more U235 they are seen distinct and evident, therefore they are "weak")

F = U235>Th231 at 185.71 KeV (U235 series)

G = a slight “hump” is seen around 255 KeV. Is it Pa234m>U234 at 258.26 KeV( U238 series) ??

H = correct to say that it is Pa234m>U234 at 766.37 KeV (U238 series)?

I = correct to say that it is Pa234m>U234 at 1000.99 KeV (U238 series)?

Thanks in advance
Marco

U238.jpg (46.76 KiB) Viewed 2337 times

[Sparky]

Marc,

In reference to your "D" peak, my RaDecay V3 program lists U235 photon emissions at both 105 and 109 keV. The probabilities are not very high, but maybe combined it might be responsible for that peak.

Sparky

[MartinM]

"D" might also be the U X-Ray
For reference:

u235_d.gif (10.12 KiB) Viewed 2323 times

[Marco75]

thanks a lot for the answers!! so it seems a combination of different things. Interesting also the RaDecay software, I did not know that. I will surely check it ;-)
So now only the A peak is left and to check if the assumptions for peaks H and I are correct

thanks!!

[MartinM]

Here my spectrum made using the CapeSym SrI2(Eu) with temperature compensation.
I calibrated this with Cs137 for its 32 keV peak too, it's quite sensitive at lower energies, so it should be accurate. It's showing a similar peak @ 34 keV.
The reference picture above says it's escape peaks.

U.png (23.3 KiB) Viewed 2313 times

[Marco75]

Hi Martin,
very interesting your spectrum and compliments for the probe, impressive! Seeing the result of your better probe (it is evident that the resolution is higher in your spectrum!!), I can say that I am very satisfied by the good work done by Steven with my 2" CsI :-)

So seeing your reference spectrum for U and your spectrum above it is confirmed this peak at 33-34KeV and it is escape peaks. Honestly I did not imagine to have a so "high" peak from the escape peaks.

2) what are in your opinion peaks at 773 and 1005 in your spectrum? In my opinion it is confirmed Pa234m>U234 (766 and 1000 KeV referring to Interspec)

Many thanks

[MartinM]

Hi Marco,

on the contrary, I'm rather impressed by your device as it delivers very good results given it's a larger crystal and CsI.. Also your peaks are pretty well calibrated, not far off.
Yes, I believe the "H" and "I" peaks are coming from Pa234m: http://nucleardata.nuclear.lu.se/toi/nu ... =I&sortA=E
1001.03 0.837 %
766.38 0.294 %

Cheers,
Martin

[Marco75]

Thanks Martin also for the nice comment! I am new in this hobby and so it is very well appreciated.
For the calibration I am using a "home made" mix of some Thorium mantles plus two Cs137 sparks. This gives a combination of 8-12 known peaks from 32 to 2614 keV . Yes, not very professional but it seems it works. Below 32keV I still need to find something usable, which is not easy I guess.