T-Rex: If you don't like using words for warning the people of 10,000 years from now about atomic waste - which is fair, language changes quickly and symbols aren't universal - there is another option!

T-Rex: GENETICALLY-ENGINEERED RADIATION DOGS.

T-Rex: You just genetically engineer all dogs to change colour when they're around dangerous radiation! Assuming future generations keep dogs - which seems likely, they're rad - then now you've got this sign when things are bad, and folklore can develop wherein dogs changing colour is a warning of danger and disease!

Utahraptor: Do we... KNOW how to make colour-changing dogs?
T-Rex: Nope!

T-Rex: Listen, I'm the IDEA person. I come up with IDEAS that are OUTSIDE MY AREA OF EXPERTISE, and then I expect those WITH the relevant knowledge to take them seriously, because I think they're good!
Utahraptor: Uh.
T-Rex: I also have theories about dark matter.

Narrator: LATER, T-REX DISCOVERS HIS RADIATION-DOG IDEA HAS ACTUALLY ALREADY BEEN PROPOSED, BUT FOR CATS INSTEAD:
T-Rex: Ah, excellent!!
T-Rex: More evidence that my hunches are both correct AND desirable