Sit a Geiger counter next to a jar of Brazil nuts, and time events? You would need a way of testing the Geiger counter, but that should be possible. Alternati

Sit a Geiger counter next to a jar of Brazil nuts, and time events? You would need a way of testing the Geiger counter, but that should be possible. Alternatively, buy one at surplus from a university laboratory. If they're any good, they would have already noticed it misbehaving.