There's a book called "The Bomb in My Garden", about the man responsible for Iraq's nuclear weapons program in the 90's, which get pretty in depth to the length he had to go to in order to get "not very close".

It gets into a lot more detail than this article, so if you're interested I'd recommend checking it out: http://www.amazon.com/Bomb-My-Garden-Secrets-Mastermind/dp/0...