Uranium 238 is a beta particle emitter. The person doing the Geiger counter test erroneously thought that tinfoil would block beta emissions from the beads. The readings he got were for beta and possibly a tiny amount of alpha particles - those will be emitted from some of the other isotopes of uranium that exist in tiny amounts along side U-238. Alpha will be blocked by paper and foil.

For those of you that wear tinfoil hats, you may be interested to know that a very tiny percentage of beta particles will be stopped by the foil. The atomic collisions that stop them will emit x-rays. So by wearing your tinfoil hat you will be shooting some xrays into your brain. This isn’t bead related but I thought it was an interesting result since it may explain why people who wear tin foil hats can become crazy even if they weren’t crazy to begin with!