To paraphase one of the scientists on the Manhattan Project in regards to nuclear weapons:
"The first time it is done, it is the work of a Nobel Prize laurelate. The second time, its the work of a machinist."
I feel no less safe now than before I read this. If I took the right classes here at my university, I could design a nuclear bomb within 4 years. However, I admit I go to a big school, with a nuclear science program, so you couldnt do this at just any school. Hell, we even have a university run nuclear power plant. The point being, designing a bomb is not so difficult that a person who got a master's degree couldnt do it. They cant just lay ahold of weapons grade plutonium or HEU.