Apocalypse proof? We need something like an IPX scale. Maybe this is like AP5: able to withstand small-arms fire, molotov cocktails and, I dunno, zombie mandibles? But not cruise missiles, direct artillery fire, or giant transforming robots.
Making something "nuclear hardened" is evidently not as high a bar as one might suppose. Setting aside that I don't know of any actual standards it appears that what's required is an ability to withstand a certain overpressure and provide some amount of radiation shielding. A windowless, reinforced concrete building would do pretty nicely without even trying for extra credit. I guess the idea being that nuclear-proof is impossible for normal, baryonic matter: a near enough blast from a big enough bomb will vaporize anything.
Making something "nuclear hardened" is evidently not as high a bar as one might suppose. Setting aside that I don't know of any actual standards it appears that what's required is an ability to withstand a certain overpressure and provide some amount of radiation shielding. A windowless, reinforced concrete building would do pretty nicely without even trying for extra credit. I guess the idea being that nuclear-proof is impossible for normal, baryonic matter: a near enough blast from a big enough bomb will vaporize anything.