to prevent illicit use of fission explosive materials have a direct bearing on the control of illicit production of H-bombs. Finally, the damage that could be inflicted by fission explosions provides, we believe, sufficient justification for effective safeguards designed to prevent theft or illicit production of fission explosive materials. The possibility of pure fusion explosives is discussed briefly at the end of this chapter.

Nuclear materials do not necessarily have to explode to cause severe damage over large areas. Some radioactive materials, including many that are produced in nuclear power reactors, are among the most toxic substances known. Radiological weapons that would disperse fission products or other radioactive materials have been seriously considered for military use. We have no evidence, however, that any government has found such weapons to be sufficiently effective, compared to chemical or biological warfare agents and other weapons (including nuclear explosives), to include them in military arsenals. Nevertheless, we have considered several types of radiological devices that might be used by terrorists or other non-governmental groups—or perhaps even by individuals—to expose large numbers of people to radiation or to cause the evacuation of urban areas or major industrial facilities. We have given particular attention to possibilities for dispersing plutonium since that material is present in large quantities in nuclear power fuel cycles and is exceedingly toxic if breathed into the lungs in the form of very small particles.