You do understand that a modern or post-modern society will have their own tools to detect radiation? We don't need to optimize for them, we need to optimize for those people who haven't developed that far.

Yes, and do you realize that not everyone in a nuclear-capable society wanders around with a geiger counter? If an archaeologist digs up a plate with an atomic diagram of a radioactive isotope, they would at least know "hey, maybe I should get a geiger counter before digging any further."

Oh yeah? Have you seen any research demonstrating that people unfamiliar with that iconography associate it universally with death?

Dude, when humans die, they decompose, leaving behind a skull and bones. I'm not making any assumptions based on "pirate media." Pirates used the symbol because it's universally recognizably as implying "death" or "danger." It's highly arrogant and insulting for you to think any other culture wouldn't be capable of drawing that connection.

Yeah, not like millions of people have been following such rules for thousands of years.

And modern society, particularly in scientifically-minded sectors, already view that as archaic superstition. How are you going to convince enough nuclear engineers to join your cult in order to maintain an unbroken apostolic succession for millennia?

We LITERALLY have religions that survived their languages & scientific knowledge dying off, and most of our modern religious ideas are simply remixes of previous ones.

Name one religion that has survived its original language dying off. Reconstructions such as neopaganism don't count, and neither do languages that can still be translated.

Also, if the nuclear radiation cult's mythology gets "remixed" by a new religion, then it loses the intent of preserving a warning for future generations. Do you honestly believe modern christianity has maintained the same intent as the original?