of IRSs throughout the country should be upgraded promptly. This report presents the findings and recommendations of the committee of specialists assembled by the NRC in response to DOE’s request.



The challenges in preventing detonations of RDDs are immense, and they will persist for many years. Hundreds and perhaps thousands of inadequately protected IRSs that are considered dangerous by safety standards adopted by the IAEA are present in many countries. Some are in use, some are in storage, and some are awaiting permanent disposal. Also, some IRSs have simply been abandoned by their legal custodians because there were no financially affordable disposal pathways for those that had exceeded their useful lifetimes or were no longer needed. Poorly protected IRSs, particularly those that have been abandoned, can become easy prey for terrorist groups.

Detonating an RDD cannot trigger a nuclear explosion with its familiar mushroom cloud. Unlike nuclear weapons, RDDs cannot kill tens to hundreds of thousands of people and obliterate a city instantly. However, the disruption attendant to an RDD detonation could be widespread, particularly if it occurs outdoors in a densely populated urban area and the RDD is designed to maximize the dispersal of radionuclides. Although the number of victims resulting from the effects of radiation will most likely not be great, the psychological impact of a radiological attack may lead to widespread fear, serious social disruption, and potentially catastrophic economic consequences.

From the U.S. perspective, the primary concern is the prevention of detonations of RDDs within the United States or against U.S. interests abroad. A related concern is illicit spreading of radioactive material from IRSs or other sources in populated areas through water routes and other pathways. To guard against attacks in the United States, preventive measures are focused on securing inadequately controlled IRSs that are currently in the country. Unfortunately, hundreds of unwanted IRSs have not been under adequate control, but DOE, with the assistance of other federal and state agencies, has mounted an aggressive program to find, collect, and secure these orphan sources, and many have been brought under much better control.

Terrorist groups might also try to smuggle IRSs or radioactive material in other forms into the United States. A variety of homeland security programs are in place to help prevent penetration of U.S. borders. However, this is a most difficult task, and the prevention of smuggling of nuclear materials across U.S. borders must be the object of continued vigilance.



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