"Congress has long sought, through legislation and oversight, to protect the United States against terrorist threats, especially from chemical, biological, radiological, and nuclear (CBRN) weapons. Radiological dispersal devices (RDDs) are one type of CBRN weapon. Explosive-driven 'dirty bombs' are an often-discussed type of RDD, though radioactive material can also be dispersed in other ways. This report provides background for understanding the RDD threat and responses, and presents issues for Congress. Radioactive material is the necessary ingredient for an RDD. This material is composed of atoms that decay, emitting radiation. Some types and amounts of radiation are harmful to human health. Terrorists have shown some interest in RDDs. They could use these weapons in an attempt to cause panic, area denial, and economic dislocation. While RDDs would be far less harmful than nuclear weapons, they are much simpler to build and the needed materials are used worldwide. […] Governments and organizations have taken steps to prevent an RDD attack. Domestically, the Nuclear Regulatory Commission has issued regulations to secure radioactive sources. The Department of Homeland Security develops and operates equipment to detect radioactive material. The National Nuclear Security Administration has recovered thousands of disused or abandoned sources. Some state and local governments have taken steps to prepare for an RDD attack. Internationally, the International Atomic Energy Agency has led efforts to secure radioactive sources. Its Code of Conduct on the Safety and Security of Radioactive Sources offers guidance for protecting sources. The G8 Global Partnership has secured sources in Russia and elsewhere."
CRS Report for Congress, R41891
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html