With a half-life between 700 million years (for U-235) and 4 billion years (for U-238). And it's dense stuff that will immediately settle on the ground. You'r

With a half-life between 700 million years (for U-235) and 4 billion years (for U-238). And it's dense stuff that will immediately settle on the ground. You're not going to detect it from afar.