content: Most radiation isn't very dangerous if it isn't ingested. You even ingest amounts of K-40 when you eat bananas and they do nothing because it is rapidly removed from your system, Brazil nuts are the most radioactive food. The other thing to worry about is high energy gamma rays, which, you can avoid by not using sources that create these. Gamma ray capture cross sections for atoms are typically proportional to nucleic size, and so are caught most often by calcium in bones, since its the largest typical nucleus in your body. Again, this isn't a problem if the radiological substance in question doesn't create these. Neutrons are the most worrisome thing in terms of harm generally, but almost nothing produces free neutrons with any reliability. If that wasn't true the entire world would be a nuclear reactor. Alphas and betas are effectively blocked by tinfoil or skin at almost any quantities or energies, and the ones in this battery are being blocked by diamonds. Probably everything you learned about nuclear physics came from an activist with a degree in history or pre-med. I mean this literally. Go to an anti nuclear activist page, and see what their expertise is. I found one once that studied physics in undergrad for 5 semesters and never graduated. He had the 2nd most expertise I ever found, second to a liar with a phd who received lots of money to lie.