Trinitite with Graded Shield

[Go-Figure]

Hello there,
This weekend I tested my third Trinitite sample and it was also an opportunity to test version 1 of my shield.
The graded shield is made of an cylinder of plastic inside a cylinder of copper with lead sheets wrapped around it. The lead is Radmax sheets from United Nuclear. The sheets are 15 cm wide and 3.60 meters long (divided in four sheets) for an equivalent thickness of lead between 1.2 cm and 1.5 cm. A single sheet of lead is placed in front of the shield, creating a sort of room for the sample. This needs to be improved as well.
This is not the final version, so I won’t report about it in the shielding section yet.
Anyway, the goal is to have something that can be easily assembled, disassembled, with the chance to add or take away parts of it independently from the rest. In one word: flexibility.

The shield needs to be improved, I need more lead and also (thanks to Steven tip) also some pewter to attenuate fluorescence from lead.
Anyway, version 1 of the shield still worked not too bad. CPS from the background decreased from 256 to 64, that’s 75% less. In terms of energy the decrease was 55%, which is an indication the shield is more effective in blocking low energy rather than high energy gammas. That’s no surprise of course.
The fluorescence from the shield is clearly visible in the background spectrum.

Background - CPS - 12 Hours - Counts x Bin - Shield V1 - 0.045 Gauss - 21-09-19.png (7.99 KiB) Viewed 10074 times

There’s nothing new to say about Trinitite and about the expected peaks. This sample was made of three pieces, two medium sized ones and a small one.

The three of them together gave me 2100 CPS on my Geiger counter. As usual never judge a sample by its size, the most active one was by far the little one, 1200 CPS versus less than 500 each from the bigger ones.

After recording a 12 hours background I went for a 24 hours measurement of the samples.
This time I had roughly 9 CPS from the sample versus 64 CPS from the background therefore, once the background was removed, the noise is clearly reduced compared to my pervious attempts and the spectrum looks better. Here they are both in counts per bin and energy per bin.

Cs137 and Am241 are always “easy” to spot, the challenge is “catching” Eu152. The 121 keV peak is more visible (there’s a clear Gaussian correlation right there, see image below), but there’s also another peak around 100 keV which I cannot identify.
Another clear correlation emerged at 344 keV (again Europium), while the peak between 400 and 500 keV is probably Cs137 compton edge. There’s an Eu152 peak in that region, but it has ten times less probability than the one at 344 keV, so probably it’s not the main thing we see there.
There’s nothing “north” of Cs137. The absence of Eu152 peak at 1408 keV was surprising to me.

Trinitite @Contact - 24 Hours - BG Subtraction - Counts x Bin - Shield V1 - 0.035 Gauss - 21-22 - 09-19.png (50.52 KiB) Viewed 10074 times

Quantitative analysis shows what’s been said above.

In the end it was a good first test for version 1 of the shield. The noise is much less than before which is good.
Anyway, I am not entirely satisfied with the sample so, be prepared, there will be a fourth attempt with another one.

Today I also recorded another spectrum with the hottest sample I had the chance to test so far…more on this in the coming days.

Massimo

[Sesselmann]

Massimo,

Pardon me for asking, but how does Radmax lead sheet from United Nuclear differ from ordinary lead flashing bought in a hardware store?

According to Radmax web site "A proprietary manufacturing process that involves manipulating the grain structure of the material makes it far superior to other types of metallic shielding."

What could they possibly do to a lead sheet other than rolling it flat?

That said, their advertised price is about the same as the local hardware store, but shipping is surely more.

This is my local hardware store in Australia: [broken link removed - Steven]

Keep in mind that 1 AUD = 0.7 USD so it's about $4 kg.

Steven

[Go-Figure]

Massimo,

Pardon me for asking, but how does Radmax lead sheet from United Nuclear differ from ordinary lead flashing bought in a hardware store?

According to Radmax web site "A proprietary manufacturing process that involves manipulating the grain structure of the material makes it far superior to other types of metallic shielding."

What could they possibly doing to a lead sheet other than rolling the lead flat?

I guess the accurate answer is "pretty little", if anything. As far as I can see it's lead, plain and simple, but of course I didn't have any chance to compare it with "ordinary lead". Since I am a client I might ask for more details.
Anyway, I had other "items" on the way from United Nuclear so I decided to combine shipping. In the end it was not that much all considered and in case it's really superior for whatever reason, that's a bonus!
A big problem I have is time, during the week it's very unlikely that work leaves me enough time to go to a hardware store or any store and explain what I need, I only have some time at night and on sunday and stores tend to be close in both cases, so I buy online a lot.
Even the shoes I am currently wearing are bought online, luckily the size was right :)

Massimo

[Sparky]

Massimo,

I have a little (6g) piece of Trinitite and a shield set-up similar (89%) to yours. There is a peak around 40 keV that is particularly interesting to me. Based on a HP-Ge survey from D. Pettauerova's paper (see links below), I believe it is a composite peak of various xrf and Pu239 emissions. Pu239 is unburnt fuel from the "gadget". I have tried to resolve an actual Pu Photopeak here by increasing the voltage on my NaI probe, but I am not sure if I have, or if it is even possible. The Pu239 emissions are very weak, and I am not 100% sure of my linearization. I have had problems with thermal drift, but I think I have that solved now, see photo below.

Both the attached spectrums were taken over about 9 hours. My shielded background is about 7.5 cps, unshielded background is about 70cps, the Trinitite gives about 23 cps in the shield.

My next step will be a longer survey of the lower energy end, and to try and better confirm linearization by checking with various sources in this region. More lead would help also. Maybe Santa will bring me another wrap.

https://www.semanticscholar.org/paper/R ... ad5a870932

https://pdfs.semanticscholar.org/ea58/a ... 1577197316

Mike Loughlin

[Go-Figure]

Hi Mike,
I have a Trinitite measure in progress right now. I got two samples from Mineresco (Mineralogical Research Company) and they are definitely the best pieces of Trinitite I got so far.
Surprisingly the less active (7 CPS versus 16 CPS of the other one) is the most interesting, Eu152 peaks are so strong (compared to the other) I couldn't believe my eyes. I mean, it's expected to find Eu152 in Trinitite samples, but in my previous attempts with five samples from two different seller the best I could manage was just a hint of it.

I have the 40 keV peak you mentioned, as well as another one around 85 keV and I a trying to figure out both. Pu239 could have something to do with the first one, while for the second one candidates could be Ba133 and Eu155.
Eu155 looks a long shot to me, it's half-life is less than 5 years, so I didn't expect to detect any of it. Ba133 is more likely (10.51 years), but it should be 81 keV rather than 85. I have Am241 and Eu152 peaks all around so I know how by much my calibration is off and I will have to figure out if that difference fits.

Anyway, since what I am getting is by far my best Trinitite spectrum so far I am extending the measurement to make it look smoother. I am at 7 days now and I plan to go on to at least 10, possibly 14, as long as it keeps on improving. The peaks of course won't change, I just want it to look better.

Massimo

[Cosmic]

Hi Massimo,

Surprisingly the less active (7 CPS versus 16 CPS of the other one) is the most interesting, Eu152 peaks are so strong (compared to the other) I couldn't believe my eyes. I mean, it's expected to find Eu152 in Trinitite samples, but in my previous attempts with five samples from two different seller the best I could manage was just a hint of it.

Maybe you've got a "Type 5" sample

http://www.minresco.com/trinitite/trin5.htm

[Sparky]

Massimo,

I am really looking forward to your results from such long surveys.

In my last attempt, I was concentrating on trying to resolve that peak at around 40. I hoped to ID a Pu249 peak at 38.7 keV.
The LANL paper linked below mentions that they were unable to confirm Pu239 in some of their spectrums, and they have larger samples and much better equipment than I do.
It is difficult to work below 100keV, because of linearity problems and interference from x-rays. In the attached spectrum, I got a peak at the right place with a 12 hour survey, but when I checked my linearity afterwards, with Cs-137 (32.2), Am241 backscatter (48.2) and Am241 (59.5), my peak at 32.2 didn't line up correctly. The brown line is the Trinitite. I repeated the survey and didn't get the little bump at 38.7, just broad peak in the region. This was frustrating, so I gave up for now. I post this inconclusive spectrum now just for reference.

Regarding the broad peak at 83keV, the Pittaeurova paper's (reference the link in my last post) HPGe spectrum shows 3 peaks in that region, but no dominate peak, so it might be hard to resolve that one with a NaI(Tl) probe.


https://permalink.lanl.gov/object/tr?wh ... R-11-03597

Mike

[Go-Figure]

Hi Massimo,

Surprisingly the less active (7 CPS versus 16 CPS of the other one) is the most interesting, Eu152 peaks are so strong (compared to the other) I couldn't believe my eyes. I mean, it's expected to find Eu152 in Trinitite samples, but in my previous attempts with five samples from two different seller the best I could manage was just a hint of it.

Maybe you've got a "Type 5" sample

Yeah, exactly. I've got a Type 1 and a Type 5.
I asked them to test the samples with a Geiger before buying them and since there was a type 1 so much more active than the Type 5 I selected I decided to take both of them.
Geiger counters can be very misleading, because most of what they get from these samples are betas and alphas, very little gammas, but in the end even the gamma spectrometer confirmed that the Type 1 is the more active, but the Type 5 is giving me a far better spectrum. Pity I couldn't test it in 2001 like the guy they reference in the website, the activity of Eu152 would have been more than twice as much as it's today.

Anyway I am going to send them the results of both when it's done.

Regarding the broad peak at 83keV, the Pittaeurova paper's (reference the link in my last post) HPGe spectrum shows 3 peaks in that region, but no dominate peak, so it might be hard to resolve that one with a NaI(Tl) probe.

I know. When I can't resolve it i put more than one label on the same peak, provided that I am reasonably sure it's accurate.

I saw the spectrum you mentioned the other day before, here https://qsl.net/k0ff/Nuclear_Physics_10 ... eDRAFT.pdf
But the document you linked is the original so it's much easier to read, thank you!

Massimo

[Sparky]

I have a friend that recently acquired a Si-Pin detector system. His scan of Trinitite is attached (with his permission). I don’t know much about his hardware, except it has great resolution but is limited to a range of about 2-50keV, with the best sensitivity below 30. I think I understand most of his spectrum, but it does require some interpretation. The red spectrum represents the natural gamma and x-ray emissions from the Trinitite. The orange lines represent the combined spectrum of the natural emissions and xrf created by an Am241 (smoke detector button) exciter, which also includes many spurious xrf from his shielding and components of the exciter. He has identified these spurious lines in small red letters above the spectrum.

His Spectrum (without the Am241 exciter) identified Uranium L shell x-ray lines (as did the Pittauerova HP-Ge detector, paper referenced in posts above), and a peak at around 20 that he has tentatively identified as Rhodium x-rays. ?? I am not so sure about that one. With the exciter, a Fe Ka1 x-ray line is visible and the U x-ray lines are much more prominent.
The iron could be coming from the soil itself, or perhaps the steel tower, etc. that they vaporized during the test. I am thinking the Uranium is from the tamper of the device, reference link below.

http://blog.nuclearsecrecy.com/2014/11/ ... s-uranium/