"The use of a nuclear weapon would be the ultimate al Qaeda terrorist outrage. Over the past decade, however, the prevailing assessment of the likelihood of terrorist acquisition and use of nuclear (specifically), biological, chemical, or radiological (NBC/R) weapons has been reversed. In the 1990s, most policymakers and analysts were highly skeptical of warnings of terrorist use of these weapons. Today, the widespread assumption is that al Qaeda's acquisition of NBC/R weapons would be rapidly followed by their use"that is, employment via the release of an agent, the dispersal of radiological materials, or the detonation of a nuclear explosive. This paper explores that proposition. In so doing, it seeks to illuminate the conditions and calculations that could shape al Qaeda's posture regarding employment of NBC/R weapons, as well as to highlight possible contributions to the overall U.S. war on terror at the margin of deterrence."
National Defense University, Center for the Study of Weapons of Mass Destruction: http://www.ndu.edu/WMDCenter/