Highly enriched uranium (HEU) is used for two major civilian purposes: as fuel for research reactors and as targets for medical isotope production. This material can be dangerous in the wrong hands. Stolen or diverted HEU can be used-in conjunction with some knowledge of physics-to build nuclear explosive devices. Thus, the continued civilian use of HEU is of concern particularly because this material may not be uniformly well-protected. To address these concerns, the National Research Council (NRC) of the U.S. National Academies and the Russian Academy of Sciences (RAS) held a joint symposium...