July 16, 2012 Graham Allison, a Harvard University political scientist and author of a best-selling book on nuclear terrorism, said that a nuclear device is more likely to arrive in a shipping container than on a missile. But he acknowledged that preventing such an attack is expensive and that there is no guarantee prevention measures will work. "The game between hiders and seekers is dynamic, and there is no 100 percent solution," Allison said in an e-mail interview.