What could possibly make a 1960s-era nuclear war worse than you'd already assumed it would be? How about being packed like sardines into a fallout shelter with 13 of your soon-to-be-closest friends?
Frank Munger is a senior reporter with the Knoxville News Sentinel, where he covers Oak Ridge National Laboratory—a nearby energy research facility that previously did a lot of civil defense research. Munger turned up this, and several other photos, of mockup nuclear shelter arrangements tested out in the basement at ORNL when the facility was trying to establish best practice scenarios for surviving the Apocalypse.
They look ... less than pleasant.
That said, though, they may not have been meant as long-term arrangements. Munger linked to an Atlantic article that makes an interesting case related to these photos: If what you're talking about is one relatively small nuclear bomb (as opposed to massive, hydrogen bomb, mutually assured destruction scenarios), the idea of "Duck and Cover" isn't as ridiculous as it sounds. If you could get these 14 people out of the way of the fallout for a couple weeks, their chances of survival would rise exponentially. Fallout shelters were not meant to be "the place you and your people live for the next 50 years."
The radiation from fallout can be severe -- the bigger the bomb, and the closer it is the the ground, the worse the fallout, generally -- but it decays according to a straightforward rule, called the 7/10 rule: Seven hours after the explosion, the radiation is 1/10 the original level; seven times that interval (49 hours, or two days) it is 1/10 of that, or 1/100 the original, and seven times that interval (roughly two weeks) it is 1/1000 the original intensity.