By the time I was growing up, the imminent threat of nuclear annihilation was either passed or mutually assured destruction was guaranteed, so protecting one's self would have been futile. We didn't practice the air raid drill and we weren't told to "duck and cover" except for a tornado. I can't help but think that if you were anywhere close to an atomic explosion you would be instantly vaporized. I could be wrong, though.
Here it is for your enjoyment, Duck and Cover...with a catchy jingle, too.