UN: Nuclear Terrorism Threat Hasn't Diminished The U.N. nuclear chief says the threat of nuclear terrorism has not diminished. International Atomic Energy Agency head Yukio Amano told a high-level meeting on the sidelines of the U.N. General Assembly Friday that more than 2,200 incidents have been registered on the International Atomic Energy Agency's "Illicit Trafficking Database" since 1995. "Taken together, they show that much work is needed and that we must never become complacent," he said. Amano said a key risk is that terrorists could detonate a so-called "dirty bomb" using conventional explosives and nuclear or radioactive material to contaminate a major city. This wouldn't be a full-fledged nuclear bomb, but he said it could cause mass panic and must be prevented.