Trinitite - Radioactive Glass from the First Nuclear Bomb Explosion

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Go-Figure
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Trinitite - Radioactive Glass from the First Nuclear Bomb Explosion

Post by Go-Figure » 17 Jun 2019, 08:26

Hi guys,
I've been wanting to test a sample of Trinitite for some time, but it wasn't easy to get one. Those who sell it (I mean the reliable ones) make clear they don't like the idea to ship outside the US, and Italy in particular is not a popular "destination" because several parcels have been lost in the past.
In the end I convinced United Nuclear to ship a "large" sized sample to me. Well, large compared to the others. It took just a couple of weeks to arrive. The package was well done with a COA inside.
The sample looks good.

Trinitite isn't a real mineral, it doesn't exist in nature. It was created during the explosion of the first nuclear bomb in Jornada del Muerto desert, New Mexico. The desert sand was blasted to the air and rained down in the form of little droplets which solidified as a sort of glass material later called "Trinitite" after the code name given to the site in which the explosion took place, Trinity.

As usual my first approach was with my Ranger, which gave me a respectable read of almost 1000 CPM, almost 20 times my background.
But as soon as I started accumulating pulses with the spectrometer it became apparent to me that I was dealing with the weakest gamma emitting sample I've ever tested. My background for this test was 257 CPS, the Trinitite addes just 3 CPS!
This is where a proper shield would be really usefull. I was worried that just a background subtraction wasn't going to be enough to see anything at all with such a low activity sample.
I initiatlly planned a 10 hours test, but given the circumstances I extended it to 24 hours. Even after such a long recording the spectrum doens't look "clean" at all. Given the extremely low activity it would probably need ten times as many hours to start to look good.
Just to put in perspective: In 24 hours I got only 263000 counts, which is the number of counts I get from my background in 15 minutes, and from my hottest sample in less than 2 minutes.

I don't know if this is the level of activity of an average sample, or if mine was particularly weak. I wouldn't mind having another one to compare them.

In the end the Cs137 usual peaks were clear more or less from the beginning. The Americium 241 ones were more mixed up in the X-ray region, but still recognisable after a few hours of accumulation.
Europium 152 was really hard to spot. In 74 years it halved almost six times. The list of its expected gamma peaks fills pages, in the end I only focused on the most likely ones. I identified three, but I am not 100% sure of any of them. I mean, I know they are there, but they look so weak it's hard to be certain. In particular I would have expected the 121 keV peak to stand up more compared to the rest.
The 1408 keV one is by far the more clear, albeit is a bit "north" than where it should be, the center of the peak is at about 1415 keV.

Before the test I calibrated with both Cs137 check source and the background, in order to have my calibration holding reasonably well at higher energy as well.

There are other potential peaks which are located where Eu152 ones are supposed to be, but they are supposed to be weaker than the ones I identified and uncertainty was too high so I left them alone, for now at least.

The quantitative analysis reflects the extreely low counts, the energy per unit time of the spectrum is negligible, it barely adds something to the background.

This is a test I plan to repeat with a proper shielding.

Below I post both the counts per bin and energy per bin versions of the spectrum.

Massimo
Attachments
DSC05482_FF_C.jpg
DSC05488_FF.jpg
DSC05509-R.jpg
Trinitite @Contact - ID - 24 Hours - BG Subtraction - Counts x Bin - No Shield - 0.036 Clean - 16-06-19.png
Trinitite @Contact - ID - 24 Hours - BG Subtraction - Energy x Bin - No Shield - 0.036 Clean - 16-06-19.png
Spectrum Analysis - 24 Hours  @ contact+1 cm-001.png

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Steven Sesselmann
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Re: Trinitite - Radioactive Glass from the First Nuclear Bomb Explosion

Post by Steven Sesselmann » 17 Jun 2019, 12:18

Massimo,

As always, a very nice report, and I think you will agree, it's time to construct some sort of shielding.

Even a small amount of lead will significantly reduce your background.

Steven
Steven Sesselmann | Sydney | Australia | gammaspectacular.com | groundpotential.org | beejewel.com.au |

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Go-Figure
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Re: Trinitite - Radioactive Glass from the First Nuclear Bomb Explosion

Post by Go-Figure » 17 Jun 2019, 22:43

Steven Sesselmann wrote:
17 Jun 2019, 12:18
Massimo,

As always, a very nice report, and I think you will agree, it's time to construct some sort of shielding.

Even a small amount of lead will significantly reduce your background.

Steven
Yes, I agree.
Testing the background is one of the main reasons I went into spectrometry and radiation detection in general, but with weak samples it can seriously get in your way, even with background subtraction.
I do my tests in two rooms of my house (depending on a a number of factors) and the background of the room where this test has been run is very stable. I saw it oscilating between 257 and 258 CPM in the space of several week, which is normally not a problem.
But when dealing with a sample giving you 3 CPS of gammas even just a 0.5 CPS fluctuation in the background could mean that 1/6 of your counts comes from there and this can really obliterate the weakest peaks.

I have some ideas on how I want to do the shielding, so let's see.

Massimo

gwgw
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Re: Trinitite - Radioactive Glass from the First Nuclear Bomb Explosion

Post by gwgw » 20 Jun 2019, 08:49

I've started building mine with thin steel plates from the hardware store, later on I got some lead from the most accessible (but definitely not the cheapest) source I could find - lead diving weights from Decathlon, a sports store nearby. At that point, the shield is incomplete and still far from what I designed initially, but it already reduced my background from about 130 CPS to about 29 - more than 4x reduction. It is currently very far from utilizing the best I can with that lead (just 6kg). So I am going to finalize it by getting 4 kg additional lead weights. I am targeting 8x background reduction, but well future will tell. The issue is I don't have a lot of space for the samples in my shield design, that really sucks and I should have thought about it more when I planned. If I would redesign it, I'd provide more space for the tested material inside the shield, that's for sure (well that also requires more lead of course). On the positive side, diving weights are "easy" - it's like building stuff from (well big and heavy) lego blocks.

4x reduction in background still helps to find some weak thorium series peaks in some (crushed) rocks though, otherwise very hard to spot without shielding. I have zero success at finding any cs137 (above MDA) in all the soil probes I've tested though. But well, I didn't really expect to find any. Looking forward to get some soil probes from the mountains.
Regards,
Milen Rangelov

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Go-Figure
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Re: Trinitite - Radioactive Glass from the First Nuclear Bomb Explosion

Post by Go-Figure » 22 Jun 2019, 08:25

My shielding is in the making, it will take some time.
I want it to be modular and simple, I don't want a 60-80 Kg block of lead which I will never be able to move from where I put it. So I will start with a hollow cilinder with a internal diameter of 8.5 cm (I want to have some room to spare, also I plan to add an internal sheet of copper and plastic to limit fluorescence). The thickness I have in mind is 3.5 cm. This first module will be 10-15 cm long, I am still deciding.
I also want to have a sort of cylindrical "cap" of lead which I can put on in case my sample fits into the "hole" to create a "chamber" and take away in case it doesn't fit. When the cap is there I want to put in place a piece of copper there too. The copper sheet will have the same shape of the cap.
This is the basic design I have in mind.
Any advice on the subject is welcome.

I also have another Trinitite sample on the way.
I read the glassy ones are more active since they were closer to the surface as they solidified, while the ones looking more "sandy" were deeper down.
I contacted United Nuclear, sent them my spectra and analisys of their sample, not that I thought that would have impressed anyone, being of the worst looking spectra I took since my infamous attempt to detect K40 in a bunch of bananas (which I will try again, as soon as the shield is ready), but apparently they liked and when I asked for a better sample they said they were going to select a high-quality-glassy-one. Let's wait and see.

Massimo

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Re: Trinitite - Radioactive Glass from the First Nuclear Bomb Explosion

Post by cicastol » 22 Jun 2019, 19:54

Hi Massimo,
for such low level samples you need a very good lead shield, at least 5cm all around the detector IMHO ,for inside chamber dimensions bigger is better for reducing backscatter.
I've made a modular lead shield made by rings that could take inside a standard 5-600cc Marinelli for 3"x3" detector, maximum ring weight is the base (27Kg) the other rings are near 16Kg, overall is well over 200Kg but easily transportable.
Ciro

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Go-Figure
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Re: Trinitite - Radioactive Glass from the First Nuclear Bomb Explosion

Post by Go-Figure » 30 Jun 2019, 18:27

cicastol wrote:
22 Jun 2019, 19:54
Hi Massimo,
for such low level samples you need a very good lead shield, at least 5cm all around the detector IMHO ,for inside chamber dimensions bigger is better for reducing backscatter.
I've made a modular lead shield made by rings that could take inside a standard 5-600cc Marinelli for 3"x3" detector, maximum ring weight is the base (27Kg) the other rings are near 16Kg, overall is well over 200Kg but easily transportable.
Yeah, I hear you.
I am considering different design options. I think I will reduce the length of the first module in order to increase the internal diameter and the thickness.

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