John Aristotle Phillips ... designed a nuclear bomb as a junior paper.

No.
http://www.phyast.pitt.edu/~blc/book/chapter13.html#4

The effort by the Princeton student, John Phillips, was much more widely publicized. He made extravagant claims that his bomb would explode with a force of more than 10,000 tons of TNT. He took on a publicity agent, wrote a book, appeared on many TV and radio shows, received very wide newspaper coverage, and even ran for Congress.

What he claimed to have produced was a design for a bomb in a term paper prepared for a physics course. I spoke to his professor in that course, who said that there was nothing in his paper that would ordinarily be called a design. There were only crude sketches without dimensions. There were no calculations to support his claim that his bomb would work. He had collected a lot of information that would be useful in designing a bomb, for which the professor gave him an A grade.

Phillips was being called by media people so frequently that he had to have a separate telephone installed in his dormitory for that purpose. His professor told me that he himself had been contacted by many newsmen, but they never printed what he told them — they only trumpeted that Phillips had designed a workable bomb.

Several people have told me that professional government bomb designers have said that a design for a bomb by some student would work. I know that this could not be true because it would be a very serious breach of security regulations for a person who was ever involved with the government program to comment on a design that is available to the public. Note that the MIT student's design was judged by a "Swedish expert." With regard to such claims about Phillips' design, no professional could possibly consider a sketch without dimensions to be a design capable of being evaluated for performance. Science and technology are highly quantitative disciplines, but apparently Phillips does not understand that fact.

There have been numerous statements in newspapers, including our university paper, that any college student could design a nuclear bomb. In reply, I published an offer in our university paper of an unqualified A grade in both of the two courses on nuclear energy that I was teaching for any student who can show me a sketch of a workable plutonium bomb together with a quantitative calculation showing that it would work. My offer has been repeated about 10 times over the last 15 years. Three students turned in papers, but none of them had as much as 5% of what could be called a design.

All of this discussion has been about designs on paper, but as is clear from the above quoted statements by experts, that is only a small part of the task faced by terrorists. The fabrication requires a wide degree of expertise and experience in technical areas. It requires people capable of carrying out complex physics and engineering computations, handling hazardous materials, arranging electronically for a hundred or so triggers to fire simultaneously within much less than a millionth of a second, accurately shaping explosive charges, attaching them precisely and connecting the triggers to them, and so on. Where would terrorists find this expertise?