u/NorthComparison4356

Just wanted to share my little Trinitite investigation. I have a 1‑gram sample (visually very glassy, green‑golden tones, some tiny red‑metallic bits, plus bubbles and cavities). I got this sample from eBay UK; the seller claims it's the real thing…

It comes with lots of papers and so called "certificates" - but that is just paper right, does not mean anything.

On the bench I tried to measure the contact activity with my BC412: I see an incremental 300CPM on contact. Nice.

Equipment:

• GS‑CsI(Tl)‑1515 detector
• GSMAX8000 spectrometer

I ran a long background‑subtracted spectrum inside a lead castle with copper shielding (2 hours). The sample is small, but I clearly see parts of the classic Trinity fingerprint:

• Ba X‑rays (~32 keV) – from Cs‑137 decay
• Am‑241 (sharp peak at ~59 keV) – trace activation product
• Cs‑137 (main photopeak at 662 keV)
• Eu‑152 – very weak peak at ~124 keV and a weak shoulder on the low‑energy side of the K‑40 peak (~1406 keV) – or am I just overinterpreting?

Given the visual features (glass fusion, metallic spherules) and this gamma suite – Cs, Am, Ba, and especially Eu‑152 – is this the real thing?

Not a perfect spectrum, but for 1 g and an amateur CsI detector it's at least way better than my son's RC102 result…

The last image is the spectrum taken in 2001 from the bulk (the lower one), its the one supplied from the ebay seller; it's quite similar, and also quite weak in those peaks…

Please share your thoughts on whether that's legit or not…. I guess faking those materials would be too much of an effort?

Why did I buy this? I am not a collector - I am just curious on low radioactive materials I can throw at my gamma spectrometer, to see nuclides I have not seen before. So I thought I can see Eu152.....but now I am a bit disappointed. Of course I know that Eu152 has a HL of only 13.5 years, so about 6 HL have passed so far, quite a lot.

So I recently picked up a BC412 3"x2.25" detector for my Ludlum Model 3. I was super excited to take it to a flea market, thinking it would be my ultimate uranium/radium hunting companion.

Long story short: I came home disappointed. I walked past so much uranium glass (UV light confirmed) and got barely any increase above background. I found a few radium watches, sure, but zero Fiestaware, zero uranium glaze ceramics. I started grumbling to myself that the BC412 was maybe too insensitive (although of its massive size).

Then my wife reminded me she has a small Fiestaware plate in the kitchen.

I figured I'd do a quick sanity test. Held the BC412 up to it.

26,000 CPM. The Ludlum was screaming like mad. My RC110 next to it? Barely a whimper.

Wait, what?

So I did what I should have done before the flea market: I actually looked up the BC412 specs. "Charged particles." Oh. Right. Betas.

That sent me down a rabbit hole of a very janky, low-fi experiment. I made a "beta shield" out of 50 layers of aluminum foil (yes, kitchen foil — I know, I know). Here's the rough qualitative takeaway:

• RC110 on Fiestaware: no difference with/without shield (Image 1)
• RC110 on Uranium Glass: no difference with/without shield (Image 2)
• BC412 on uranium glass: no difference with/without shield (Image 3)
• BC412 on thorium glass (AliExpress BS): no difference (Image 4)
• BC412 on Fiestaware: 26k CPM (unshielded) → 10k CPM (shielded) (Image 5)

Holy cow. The BC412 is absolutely picking up betas, and way better than the CsI in my RC110. That 16k CPM drop is almost certainly beta. No wonder it screams on Fiestaware — that orange glaze is putting out a lot more than just gamma.

So what did I learn?

1. I didn't find Fiestaware at the flea market because there wasn't any — not because my detector couldn't see it. The BC412 would have found it instantly.
2. The BC412 is actually a quite nice all-rounder for flea markets as it sees betas way better than the RC110 - but the massive size of that thing - but it gives the advantage that you come in contact with the flea market folks quite easy, as they are quite curious on what that "Ghost Busters Device" does...
3. Read the dang specs before you go shopping. (But the specs sheet has no check for betas, but charged particles? Should be the same right?)

Major caveats:

• My "beta shield" is 50 sheets of grocery store aluminum foil. That's not a proper beta shield. Attenuation is questionable. Distance wasn't perfectly controlled. This is a backyard experiment, not a lab measurement.
• I'm aware that counting rates change with geometry. I tried to keep things consistent, but take these numbers as hints, not data.

But still with Uranium glass, I am disappointed, it is quite close to what the RC110 can do, but the RC110 is much smaller and more convenient to carry around. And stick to the UV light method....

But the RC110 doesnt pick up the beta from the fiesta-ware like the BC412 does, for sure.

I recently measured 1 kg of Brazil nuts on my gamma spectrometer. I was looking for Ra‑226, but found none…

Instead, the spectrum was dominated by the characteristic Th‑232 chain:

• 2614 keV peak of Tl‑208 (the highest‑energy gamma in nature), but very weak.
• 583 keV (Tl‑208) and 239 keV (Pb‑212) lines
• No 609 keV Bi‑214 peak, confirming no measurable U‑238 / Ra‑226 (although the Tl208 peak at 583keV could be mistaken as the Bi214 peak)
• and I can also sense 911 & 969keV from Ac228, which is a strong indication for Th232 chain.

How does Th‑232 get into Brazil nuts when the tree’s roots can’t take it up?
This goes back to Otto Frindik (1989) in „Zeitschrift für Lebensmittel‑Untersuchung und -Forschung, 189:236‑240“. 

The explanation is soil resuspension: fine Th‑bearing soil particles become airborne and stick to the large, rough surface of Brazil nuts. The Th isn’t taken up by the plant – it’s a physical dust deposit on the shell. Frindik calculated that Thorium activity is enriched 740‑fold in Brazil nuts relative to the soil, far beyond what any root uptake could achieve.

So what I measured isn’t a failure to find Ra‑226 – it’s a demonstration of a completely different (and often overlooked) contamination pathway: atmospheric dust deposition, not root uptake.

So those Brazil nuts cannot only contain Ra226, they can also be contaminated with Thorium via a completely different mechanism….

To be honest: I did not like those nuts from the very start, but rather the taste of those nuts and the circumstances under which they are harvested. I don't want to open that "pandora-box" here, if that finding is of any "biological"-significance. The discussion would not make any sense either, as I can't calculate any activity concentration due to the lack of a proper efficiency calibration.

But I sent a sample to the German BfR ("Bundesinstitut für Risikobewertung"), it's a governmental institute to have a watch on food-safety. They can then decide if that is of any significance or not. I hope I get a feedback from them :-)

*Equipment: GS1515‑CsI(Tl) scintillator, GS‑MAX‑8000 digital MCA, custom lead/copper shield (>90 % background reduction)*

Just picked up a small piece of lutetium metal and thought I’d give it a whirl in my gamma spectrometer. The Luⁱ natural abundance is about 2.7% for the radioactive isotope Lu-176, so I was curious to see what would show up. Turns out it has a really nice, clean spectrum!

The most prominent peaks are from the beta decay of ⁱ⁷⁶Lu to ⁱ⁷⁶Hf, specifically the prompt gamma rays at 307 keV and 202 keV, and a smaller one at 88 keV. It's pretty cool to see such clear lines from something sitting right on the lab bench.

But there is a shoulder at 500-525keV, I don't know where that might come from, any hints from you guys?

Getting into the history of the element itself, it’s quite a story. Lutetium was the last of the rare earth lanthanides to be discovered in 1907. It was found independently by three different scientists all working on the same mineral, ytterbia: Georges Urbain in France, Carl Auer von Welsbach in Austria, and Charles James in the United States.

This sparked one of the longest and most heated priority disputes in chemistry. Each claimed to have isolated it first. Urbain's paper was published earlier, but he delayed his results, while von Welsbach claimed his methods were the most accurate. Charles James wisely stayed out of the fight entirely! The conflict got so fierce that for decades, the element was known as "Lutetium" (from "Lutetia," the Latin name for Paris) in most of the world, but German-speaking chemists stubbornly continued to call it "Cassiopeium" (Cp) after the constellation Cassiopeia, which von Welsbach had proposed.

The matter wasn't finally settled until 1949 when IUPAC officially adopted the name Lutetium (changing the spelling from the original "Lutecium" to align better with Latin) and closed the book on "Cassiopeium" for good.

That Lu176 half-life of about 38 billion years means that each decay is a rare event, yet it still produces a usable signal. It’s also a "cosmochronometer" used to date the age of the universe.

Anyway, happy to share the spectral result and the history behind element 71! Has anyone else here taken a spectrum of Lu or any other "weakly" radioactive elements that turned out better than expected?

I recently measured 1 kg of Brazil nuts on my gamma spectrometer. I was looking for Ra‑226, but found none…

Instead, the spectrum was dominated by the characteristic Th‑232 chain:

• 2614 keV peak of Tl‑208 (the highest‑energy gamma in nature), but very weak.
• 583 keV (Tl‑208) and 239 keV (Pb‑212) lines
• No 609 keV Bi‑214 peak, confirming no measurable U‑238 / Ra‑226 (although the Tl208 peak at 583keV could be mistaken as the Bi214 peak)
• and I can also sense 911 & 969keV from Ac228, which is a strong indication for Th232 chain.

How does Th‑232 get into Brazil nuts when the tree’s roots can’t take it up?
This goes back to Otto Frindik (1989) in „Zeitschrift für Lebensmittel‑Untersuchung und -Forschung, 189:236‑240“. 

The explanation is soil resuspension: fine Th‑bearing soil particles become airborne and stick to the large, rough surface of Brazil nuts. The Th isn’t taken up by the plant – it’s a physical dust deposit on the shell. Frindik calculated that Thorium activity is enriched 740‑fold in Brazil nuts relative to the soil, far beyond what any root uptake could achieve.

So what I measured isn’t a failure to find Ra‑226 – it’s a demonstration of a completely different (and often overlooked) contamination pathway: atmospheric dust deposition, not root uptake.

So those Brazil nuts can not only contain Ra226, they can also be quite contaminated with Thorium via a completely different mechanism….

To be honest: I did not like those nuts from the very start, LOL, not my taste….

*Equipment: GS1515‑CsI(Tl) scintillator, GS‑MAX‑8000 digital MCA, custom lead/copper shield (>90 % background reduction)*

Just wanted to share my new setup and get some thoughts from the group.

I recently picked up a custom gamma scintillator probe for my Ludlum Model 3. It’s a Bicron BC412 polyvinyl toluene plastic scintillator with organic fluors, specifically for gamma detection. The crystal measures 3” diameter x 2.25” thick, polished on all sides with a reflective coating before coupling to the PMT.

The tube is a quality 3” photomultiplier, and the dynode chain is spec’d at >100 MΩ, so it plays nicely with battery-powered meters like the Ludlum Model 3 (no HV droop issues).

First numbers:

• Background: ~2400 CPM (40 CPS) on the Ludlum
• Radiacode 110 background: ~13 CPS

So the BC412 is seeing about 3x the gross count rate in background compared to the RC110. Makes sense given the massive volume difference, but it’s fun to see it quantified. Of course, the plastic scintillator has a different energy response than the CsI(Tl) in the Radiacode, so not a direct 1:1 sensitivity comparison, but still impressive.

The downside? Stealth mode is fully disabled. This thing is chunky and very obviously not a phone or a pager.

Testing on real sources:
The ebay-seller of the Ludlum was so kind to include a uranium glaze vase with the meter. The BC412 rushed up to 3k CPM almost instantly – very responsive. The Radiacode struggled to pick it up reliably by comparison.

Where I’m a bit disappointed: uranium glass. On weak pieces (thin or low-U content), the BC412 wasn’t dramatically better than the Radiacode. Maybe I expected too much given how hot the glaze source looked.

Overall, it’s a fun new toy. Looking forward to taking it to flea markets and watching people’s faces when the needle starts climbing. Absolute terror device. 😂

Anyone else running a large plastic scintillator on a Ludlum? Curious about your background counts and how it performs on low-activity stuff.

Just wanted to share my new setup and get some thoughts from the group.

I recently picked up a custom gamma scintillator probe for my Ludlum Model 3. It’s a Bicron BC412 polyvinyl toluene plastic scintillator with organic fluors, specifically for gamma detection. The crystal measures 3” diameter x 2.25” thick, polished on all sides with a reflective coating before coupling to the PMT.

The tube is a quality 3” photomultiplier, and the dynode chain is spec’d at >100 MΩ, so it plays nicely with battery-powered meters like the Ludlum Model 3 (no HV droop issues).

First numbers:

• Background: ~2400 CPM (40 CPS) on the Ludlum
• Radiacode 110 background: ~13 CPS

So the BC412 is seeing about 3x the gross count rate in background compared to the RC110. Makes sense given the massive volume difference, but it’s fun to see it quantified. Of course, the plastic scintillator has a different energy response than the CsI(Tl) in the Radiacode, so not a direct 1:1 sensitivity comparison, but still impressive.

The downside? Stealth mode is fully disabled. This thing is chunky and very obviously not a phone or a pager.

Testing on real sources:
The ebay-seller of the Ludlum was so kind to include a uranium glaze vase with the meter. The BC412 rushed up to 3k CPM almost instantly – very responsive. The Radiacode struggled to pick it up reliably by comparison.

Where I’m a bit disappointed: uranium glass. On weak pieces (thin or low-U content), the BC412 wasn’t dramatically better than the Radiacode. Maybe I expected too much given how hot the glaze source looked.

Overall, it’s a fun new toy. Looking forward to taking it to flea markets and watching people’s faces when the needle starts climbing. Absolute terror device. 😂

Anyone else running a large plastic scintillator on a Ludlum? Curious about your background counts and how it performs on low-activity stuff.

On this night 40 years ago, the Chernobyl disaster happened. Today I visited my mother at her house on the outskirts of Munich. She is 81 now and unfortunately has dementia – she can't remember that time anymore. But I remember it quite well. I was 8 years old back then.

Now I live near the Austrian border, very close to the Alps. In the forest soils nearby I can find up to 1028 Bq/kg of Cs-137 (top 10 cm layer). So today I got curious: how much fallout actually hit us back then in Munich, where I was born and grew up?

I collected some soil from my mother's garden and measured it with my amateur gamma spec setup. The result: up to 145 Bq/kg Cs-137 – still remarkably high, even after 40 years. When I put the sample in the Marinelli beaker and started the acquisition, the Cs-137 peak came up very fast. After just 40 seconds I could clearly see it.

For me this was a surprise – certainly not alarming levels, but the average values in northern Germany today are around 10–20 Bq/kg.

Just thought I'd share this small time capsule from my mother's garden, exactly 40 years later.

This is a follow-up to my [first post] where I shared results from my garden soil. Now I've taken several more samples from the undisturbed woods around our village – and here's the full picture.

Disclaimer: this experiment is only amateur level. It has several shortcomings and limitations (some mentioned below). The results are considered as semi-quantitative and I am aware that there is plenty of room for improvement. But I am happy to hear any suggestions from you guys.

Background

This is the Bavarian Woods near our home. At sunset, it’s beautiful and quiet. But this landscape holds a darker secret dating back to April 26, 1986 - now 40 years ago - the fallout from the NPP accident in Chernobyl.

Of course, Ukraine and Belarus suffered the most – the scale of agony and displacement, and long-term health consequences there is almost unimaginable. We in Western Europe received only a fraction of that fallout, but still enough to be quite concerning back then. Today it remains measurable in our soil, which is what made this project possible.

I was 8 years old when Chernobyl melted down. I remember seeing my parents truly afraid for the first time. As kids, we were terrified of an invisible threat – no smell, no taste, no sound. Just an omnipresent danger. But on the other hand it remained absolutely fascinating to this day, this topic of radioactivity.

Today, that fear has largely faded from public memory – though the HBO series reminded many of the human toll. But I recently asked myself: Can we still detect the Cs137 in the soil right in front of our house?

The half-life is 30 years. The "ten half-life rule" says it takes 300 years to become „undetectable“. We are only 40 years in – 260 years to go.

The setup:

To answer this question – and more importantly, to spark my son’s (12y) interest in science – we built our own gamma spectrometer setup (lead castle and marinelli beaker). We used a 3D printer (he’s the expert) to print the casing.

Sampling:

We took soil samples from several spots around our village, roughly 1 to 1.5 km apart from each other, to see how the contamination varied across a small area.

The results

Cs137 is still very much here.

Forest soil (undisturbed): Most Cs137 remains in the top 10cm. Activity up to ~1.1 kBq/kg. I think it is very interesting that the top layer in the forrest soil is still the most contaminated - the migration speed of Cs is very, very slow. This is a match to scientific publications around this topic. (Journal of Environmental Radioactivity, Volume 100, Issue 4, April 2009, 315-321; Environ. Sci. Technol. 2023, 57, 13601−13611)

Garden soil (disturbed, from Part 1): It has migrated to 30-40cm depth. Activity slightly lower due to mixing and gardening activities in the last 40 years.

Source attribution: According to official assessments by German authorities (e.g., BfS), about 90% of the Cs137 found in Bavarian soils today comes from Chernobyl, while the remaining 10% originates from global nuclear weapons tests in the 1950s and 1960s.

Risks: Not a direct health risk, but I wouldn’t recommend eating wild mushrooms or boar from our region (without confirmation by gamma spectrometry, ICP-MS). And its not only Cs137, which came from Chernobyl: it is also Sr90, which has a similar half-life and which is invisible in a gamma spectrometer, being a pure beta emitter.

Specifications & Limitations

Detector & spectrometer:

Detector: GS1515-CsI(Tl)

Spectrometer: GSMAX-8000

Shielding & Aquisition time:

Custom-built lead castle with 50kg lead + 2kg copper (achieving ~90% background reduction)

Akquisition time: 3600 sec.

Sample geometry:

Marinelli beaker, 1.2L volume; for all samples strictly same geometry.

Sample preparation:

Removal of stones only – no sieving, no drying (not an accurate practice!). Filling all samples in a 1.2L Marinelli, and a weighing step.

Calibration & uncertainty:

Only one efficiency calibration point, based on one sample sent to a professional lab.

A ±25% uncertainty was applied to all following samples (with the advice from the professional lab technician, looking at my shortcomings and setup flaws)

Additional testing:

As recently posted I tried to see if the nearby milk-production shows any hints of Cs137. A 1L sample of fresh raw milk showed no Cs137 above the detection limit (which I do not know btw).

Final thoughts:

There is the debate on nuclear weapons testing (50s&60s)/ vs Chernobyl (80s) C137 contribution - on how much is coming from what incident. And that is also a topic for scientific investigations. In fact you can distinguish between those two. This is possible due to the ratio of Cs135/Cs137: That ratio for nuclear weapons testing is about Cs135/Cs137=2. For the Chernobyl accident it is 0.5.

Why is the ratio different? Cs135 is formed much less in NPP as the thermal neutron flux is much higher in a NPP setting and the precursor of Cs135 is Xe135, which absorbs thermal neutrons quite readily to form stable Xe136. So that is the reason why in a NPP much less Cs135 is formed, and that’s why Chernobyl Cesium has much less of the isotope 135.

And that can be seen as well in the Cs135/Cs137 distribution in soil samples: the Chernobyl Cesium is to be found in the top layers, whereas the weapons testing Cesium is to be found in the lower depths. You can read on this much more in detail in this very nice publication: Environ. Sci. Technol. 2023, 57, 13601−13611.

Personal thoughts:

This two-month project – designing, printing, fixing with epoxy, and measuring – was more than just amateur science. It was fresh air, curiosity, and showing my son that the past leaves traces we can actually measure - and of course a deep respect for the history of that disaster. And also coming back to my personal childhood - refreshing the memories of 1986….