They probably thought the dial paint would fluoresce brightly when exposed to radiation, like some florescent substances glow when exposed to UV. Would it work for alpha or gamma radiation? ¯\_(ツ)_/¯
Whatever the case, sure, it's certainly not a reliable safety test. But it was wise to keep this thing away from people. RTG's do have highly dangerous materials like polonium or strontium and there have been accidents.
Comments
They probably thought the dial paint would fluoresce brightly when exposed to radiation, like some florescent substances glow when exposed to UV. Would it work for alpha or gamma radiation? ¯\_(ツ)_/¯
Whatever the case, sure, it's certainly not a reliable safety test. But it was wise to keep this thing away from people. RTG's do have highly dangerous materials like polonium or strontium and there have been accidents.