Terrorist use of an RDD, often called a dirty nuke or dirty bomb, is considered far more likely than use of a nuclear explosive device. An RDD combines a conventional explosive device with radioactive material. It is designed to scatter dangerous and sub-lethal amounts of radioactive material over a general area.
The size of the affected area and the level of destruction caused by an RDD would depend on the sophistication and size of the conventional bomb, the type of radioactive material used, the quality and quantity of the radioactive material, and the local meteorological conditions, primarily wind and precipitation.
Use of RDDs
RDDs appeal to terrorists because they require limited technical knowledge to build and deploy compared to a nuclear device. Additionally, the radioactive materials used in RDDs are widely used in medicine, agriculture, industry, and research, and are easier to obtain than weapons-grade uranium or plutonium.
The primary purpose of terrorist use of RDDs is to cause psychological fear and economic disruption. Some devices could cause fatalities from exposure to radioactive materials.
Depending on the speed at which the area of the RDD detonation was evacuated or how successfully people sheltered-in-place, the number of deaths and injuries from an RDD might not be substantially greater than from a conventional bomb explosion.
Preparing for a RDD Attack
There is no way of knowing how much warning time there will be before an attack by terrorists using an RDD, so being prepared in advance and knowing what to do and when is important. Take the same protective measures you would for fallout resulting from a nuclear blast.