Not an atomic apocalypse, but I found Soylent Green (1973) powerful - especially the parts where the old man (Edward G. Robinson, I believe, in what may have been his last role) is remembering the world as it had been.  Little things, like strawberries or celery, move him to tears.  

And when he's being euthanized while watching a movie of nature long gone, Charlton Heston's character bursts into the room.  The old man turns to the young one, momentarily slack-jawed at the beauty we take for granted, and they have the following exchange (courtesy of Google):

Can you see it?
Yes.
Isn't it beautiful?
Oh, Yes.
I told you.
How could I know? How could I... How could I ever imagine?

Fear of leaving a world like that to my children keeps me going, day after day, doing my bit to oppose the current regime in DC...

What is the use of a house if you haven't got a tolerable planet to put it on? - Thoreau