If you call it a "prime lens" because it's a fixed-focal length (i.e. not a zoom lens), then as Inigo Montoya said so eloquently, "You keep using that word. I do not think it means what you think it means."
Put things in perspective: how much radiation will you get when you have an x-ray? Or an MRI? Or a CT scan? In all probability, the average house has much, much more radiation in it from appliances. All of those are infinitely more powerful than occasional exposure to a thorium-tainted lens. No big deal. Old Pentax Takumars had it. Whatever it was purported to do has long since faded into history, but such lenses are sought out by collectors for their curio value, if not actually used for photography. Speaking of which, it's probably time to get more lens work done than worrying about radioactivity.
Re Wikipedia's rules, as I understand 'em Wikipedia allows nothing that hasn't been posted on the 'web. "I measured it" isn't allowed, neither is citing anything published on paper and not available on the 'web.
Wrong, wrong, wrong. The vast majority of Wikipedia sources cited are paper originals--books, newspapers, and professional/technical/trade journals. Wikipedia does not allow ORIGINAL research as a source, ie, that which has not been submitted to peer review.