Just get the grad student lists for American and European University Science Departments for the past 30 years, and cross check them with lists of foreigners who have been naturalized or remain in the country as resident aliens. Its not like Nuke Science is a common course of study in Tehran U.
After the attack on 911 I've done a lot a analyzing and devil's advocate games and for the life of me I can't justify the training of aliens in highly technical fields that are allied to weapons development.
I don't think it's difficult to predict who might be our enemy within the producticve lifetime of a recent college graduate. Why in the hell are we training these students in advanced mathamatics, electrical and nuclear engineering, biochemistry and physics?