What is a Universal Obvious Sign for Danger-Danger Nuclear Waste That Someone could read 10,000 Years from Now? Picture Writing like they used on the Pyramids in Egypt and Mexico...

We Could Use A Nuclear Waste Priesthood.
Monks that tell the next generation of the Danger.

Headline: FYI: IT'S NUCLEAR OVER HERE —
How do you leave a warning that lasts as long as nuclear waste?
Burying radioactive waste is seen as the safe way—how do we tell future generations?
https://arstechnica.com/science/2019/09/how-do-you-leave-a-warning-that-lasts-as-long-as-nuclear-waste/ 

Danger Danger Faces
 Graphic Warning Sign of Atomic Waste

Nuclear Semioticians (sign experts): how to warn future generations of the wastes danger.
https://antinuclear.net/2016/02/20/nuclear-semioticians-sign-experts-how-to-warn-future-generations-of-the-wastes-danger/