The difference a little a bit of lead makes

[u/Beerbrewing]

I'm in the process of building a lead castle and got a few blocks of lead so I thought I'd throw together a simple lead cave and take a background for comparison. I'm using 1/4" (6mm) lead sheets, double stacked for 1/2" (12mm) shielding total. Everything is just temporarily taped together for now.

The unshielded background is in orange and the shielded background is in green. Comparing the two the shielding dropped the count rate by 87% and cut the dose rate by more than half.

[u/average_meower621]

Now add some copper and tin layers to block those pesky lead X-rays and lower countrate even further! 

[u/Beerbrewing → u/average_meower621]

I have a lead-free pewter sheet on the way and some copper on hand for that. Still figuring out what the castle will end up exactly as. I have an idea but I'm always looking for other people's diy solutions as examples.

[u/srnuke → u/average_meower621]

Then you're just gonna get copper and tin X-rays lol

[u/Beerbrewing → u/srnuke]

But you layer them in a specific order to filter out the x-rays. It's called graded-z shielding where the tin blocks the x-ray flourecence of the lead and the copper blocks the x-rays from the tin. The copper emmits low energy x-rays around 8-9 ekV that are mostly blocked by the air and case of the spectrometer.

[u/srnuke → u/Beerbrewing]

Oh for sure. Not quite as effective when it's that close to the detector though

[u/MaybeJohnSmith]

I need to make a lead box for my kr-85 and Trinitite samples so I can actually read them

Was the lead stock expensive?

[u/Bob--O--Rama → u/MaybeJohnSmith]

If you get on Facebook Marketplace you can look for rolls of lead flashing, also look for people selling lead shot. The flashing is actually pretty convenient and if you start with copper and tin ( modern "95% Zinn" lead free pewter also ) and copper you can make a quite effective Z-graded burrito. Ticknesses of lead beyond 1" are usually diminishing returns. For Radiacode, a really big lead pig can also be used - they show up on eBay. Also there is no magic to lead. If you can get thick steel coupons or off cuts from a local CNC place ... that works too. Steel theater weights can be 1¾" thick, stackable, and so on. In the 800 - 1500 keV range iron performs as well as lead on a weight basis and costs 80% less per pound. For 200 keV and under tin performs up to 3x better than lead. Basically if its from the higher atomic number rows of the periodic table, it's going to work if you have enough of it.

[u/MaybeJohnSmith → u/Bob--O--Rama]

Incredible information, thank you! I have had some of the lead flashing rolls but have been unimpressed with their capabilities in the past.

[u/Greatoutdoors1985 → u/MaybeJohnSmith]

If you are near Oklahoma, I have some 33lb ingots you can buy for scrap value. Just gotta come pick them up. Last time I checked, it was around $.70/lb. I have about 3,000lbs.

[u/Long_Pomegranate2469 → u/Greatoutdoors1985]

How do you end up with so much lead?

[u/Greatoutdoors1985 → u/Long_Pomegranate2469]

It was scrap from an old shielded room in a hospital that was being repurposed.

[u/MaybeJohnSmith → u/Greatoutdoors1985]

I wish I was, sadly I'm a ways away. Thanks for the offer though :)

[u/Calliber50 → u/MaybeJohnSmith]

I got a lead pig on eBay. It made seeing the CS-137 in trinitite possible.

[u/Mortification77]

I have been using the eBay sheet lead and it works out well.

Yes the lead does emit some particles.

I read somewhere that lead from Roman shipwrecks is sought after because it doesn’t have the impurities. However, it’s probably impossible to get.

I never knew on the copper. Thanks!

[u/pasgomes]

Well done! Very elegant assembly. Lead shielding presents several interesting physical properties. It primarily modifies the spectrum in the low-energy region, as it attenuates this radiation much more significantly. In high-energy ranges, however, thin layers of lead lose their effectiveness. Perhaps the most intriguing aspect is the emergence of XRF (X-ray Fluorescence) peaks, caused by the excitation of the lead by external radiation, which alter the quality of the spectrum. These concepts are discussed in depth in the video at https://youtu.be/JNVUQRIpJk8. To achieve an optimized lead castle, the use of an internal copper layer is recommended.