"Caution: radiation, this invisible poison will destroy your DNA, this poison will destroy all who approach it. Those who do cannot solve the following puzzles ensure their own demise" followed by some d&d ass mechanical puzzle locks that test if someone understands the basics of chemistry from identifying uranium and plutonium on a periodic table to demonstrating an understanding of alpha, beta, and gamma radiation as a byproduct of nuclear fission.

But you want all that past the big scary "no honor" stuff. You need to scare away every human society from tribes focused on things like honor and taboos to curious scientific societies. To present a puzzle that very clearly states "you will definitely die in this way if you dig without understanding how to solve these puzzles and still making them dig through concrete behind those puzzle doors is a good deterrent.

Everytime this comes up the practical answer is to just not mark it and bury it as deep as you can.

If your mark it as poison, or honestly and descriptively, people will try to use it as a weapon, or a manhood test, or whatever dumb shit might happen. The patronizing warnings won't be legible to survivors and they're, quite frankly, embarassing.

My money is on descriptive warnings buried with the waste that only get exposed if it's exposed. You still run the risk of people trying to weaponize it but at least they aren't being attracted to the site by the warnings themselves.