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My company bought (at an auction) some 14,000 lbs of "Low Background Rdiation 2x4x8 Lead bricks" from Fermilab.
I got so excited that I bought a Radiacode spectrometer.
I build a cave from the LR bricks and placed the Radiacode inside. I tried to cover up and gaps by staggering bricks (since I have a lot of them anyway).
During 15 minutes in the completely enclosed cave, starting about 9:58am, the CPS level dropped to about 0.1 CPS from normal about 3 CPS. So, these low radiation lead bricks block about 96% of ambient radiation.
