Radiological Dispersion


A radiation threat, commonly referred to as a dirty bomb or radiological dispersion device (RDD), is the use of common explosives to spread radioactive materials over a targeted area.

An RDD combines a conventional explosive device — such as a bomb — with radioactive material. It is designed to scatter dangerous and sub-lethal amounts of radioactive material over a general area.

Such RDDs appeal to terrorists because they require limited technical knowledge to build and deploy compared to a nuclear device. 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 and other factors. The area affected could be placed off-limits to the public for several months during cleanup efforts.

While the explosive blast will be immediately obvious, the presence of radiation will not be known until trained personnel with specialized equipment are on the scene.


If the explosion or radiological release occurs inside, get out immediately and seek safe shelter. Otherwise, if you are:


  • Seek shelter indoors immediately in the nearest undamaged building.

  • If appropriate shelter is not available, cover your nose and mouth and move as rapidly as is safe upwind, away from the location of the explosive blast. Then, seek appropriate shelter as soon as possible.

  • Listen for official instructions and follow directions.


  • If you have time, turn off ventilation and heating systems, close windows, vents, fireplace dampers, exhaust fans, and clothes dryer vents.

  • Retrieve your disaster supplies kit and a battery-powered radio and take them to your shelter room.

  • Seek shelter immediately, preferably underground or in an interior room of a building, placing as much distance and dense shielding as possible between you and the outdoors where the radioactive material may be.

  • Seal windows and external doors that do not fit snugly with duct tape to reduce infiltration of radioactive particles. Plastic sheeting will not provide shielding from radioactivity nor from blast effects of a nearby explosion.

  • Listen for official instructions and follow directions.


Intentional acts include:

  • Contaminating food/water with radioactive material

  • Spreading radioactive material into the environment

    • Using conventional explosives (e.g., dynamite) – this is called a dirty bomb

    • Using wind currents or natural traffic patterns

  • Bombing or destroying a nuclear reactor

  • Causing a truck/train carrying nuclear material to spill its load

Unplanned acts include:

  • Dirty Bombs

  • Nuclear Blast

  • Nuclear Reactor Accidents

  • Transportation Accidents (unintentional spill of radioactive material from a truck or train)

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