The threat of radiological terrorism has recently come to the attention of the international community, as it became clear that terrorist organizations are seeking nuclear and radiological material to manufacture and use improvised nuclear devices (IND) and “dirty bombs,” and/or commit acts of sabotage against nuclear power infrastructure. But while nuclear weapons and INDs, much deadliermore destructivestill remain relatively secure from terrorist access, radiological material is more readily available in large quantities throughout the world. Also, radiological explosives or other dispersal devices are easier to manufacture and use. There is, therefore, a much higher probability that an act of terrorism with the use of radiological material rather than nuclear explosion may occur in the future. According to a survey of more than 100 top foreign policy experts released in June 2006, the probability of attack using dirty bombs was rated at 20 percent followed by attack on chemical or nuclear plant (11 percent), chemical weapon attack (10 percent), biological weapon attack (9 percent), and nuclear weapon attack (6 percent).

Radiological dispersal devices (RDDs) come in many shapes and sizes. A dirty bomb uses a conventional explosion to scatter radioactive material over an area whose actual size is determined by a multitude of variables and hard to predict in real time. Terrorists could launch an attack by placing a container of radioactive material in a public place and allowing the airflow from the ventilation system to distribute it. An airplane can easily disperse radioactive material as a powder or an aerosol. On a grand scale, a nuclear facility could become an RDD. Intentional damage done to a nuclear power plant or other site could release radiation, contaminating the immediate surroundings or even beyond. RDDs of any kind present a potent and effective terrorist weapon because they threaten to expose civilian populaces to radiation – engendering panic out of proportion to the modest number of casualties likely to result from limited doses of radiation. Coming to terms with the psychological and social dimensions of radiological attacks – areas that are inadequately studied and assessed – is thus a matter of considerable importance for those entrusted with national, and ultimately international, security.