Radiological Dispersion Device

A Radiological Dispersion Device (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.

Before a Radiological Dispersion Device Event

There is no way of knowing how much warning time there will be before an attack by terrorists using a Radiological Dispersion Device (RDD), so being prepared in advance and knowing what to do and when is important. To prepare for an RDD event, you should do the following:

  • Find out from officials if any public buildings in your community have been designated as fallout shelters. If none have been designated, make your own list of potential shelters near your home, workplace, and school, such as basements, subways, tunnels, or the windowless center area of middle floors in high-rise buildings.
  • If you live in an apartment building or high-rise, talk to the manager about the safest place in the building for sheltering and about providing for building occupants until it is safe to go out.
  • Taking shelter during an RDD event is absolutely necessary. There are two kinds of shelters - blast and fallout. 
The following describes the two kinds of shelters:
  • Blast shelters are specifically constructed to offer some protection against blast pressure, initial radiation, heat, and fire. But even a blast shelter cannot withstand a direct hit from a nuclear explosion. 
  • Fallout shelters do not need to be specially constructed for protecting against fallout. They can be any protected space, provided that the walls and roof are thick and dense enough to absorb the radiation given off by fallout particles.

During an Radiological Dispersion Device Event

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:  
Outdoors 

  • 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. 
Indoors 
  • 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.

After an Radiological Dispersion Device Event

After finding safe shelter, those who may have been exposed to radioactive material should decontaminate themselves. To do this, remove and bag your clothing (and isolate the bag away from you and others), and shower thoroughly with soap and water. Seek medical attention after officials indicate it is safe to leave shelter.

Contamination from an RDD event could affect a wide area, depending on the amount of conventional explosives used, the quantity and type of radioactive material released, and meteorological conditions.

Follow these additional guidelines after an RDD event:

  • Continue listening to your radio or watch the television for instructions from local officials, whether you have evacuated or sheltered-in-place.
  • Do not return to or visit an RDD incident location for any reason.

Description of Radiation Hazard Scale Categories

Category 5 means that radiation doses are dangerously high and potentially lethal. 

High doses of radiation can cause massive damage to organs of the body and kill the person. The exposed person loses white blood cells and the ability to fight infections. Diarrhea and vomiting are likely. Medical treatment can help, but the condition may still be fatal in spite of treatment. At extremely high doses of radiation, the person may lose consciousness and die within hours.   

Category 4 means that radiation doses are dangerously high and can make people seriously ill. Radiation doses are not high enough to cause death, but one or more symptoms of radiation sickness may appear.

Radiation sickness, also known as Acute Radiation Syndrome (ARS), is caused by a high dose of radiation. The severity of illness depends on the amount (or dose) of radiation. The earliest symptoms may include nausea, fatigue, vomiting, and diarrhea. Symptoms such as hair loss or skin burns may appear in weeks.

Category 3 means that radiation doses are becoming high enough where we may expect increased risk of cancer in the years ahead for people who are exposed. 

     Leukemia and thyroid cancers can appear in as few as 5 years after exposure. Other types of cancer can take decades to develop. Studies have shown that radiation exposure can increase the risk of people developing cancer. This increased risk of cancer is typically a fraction of one percent. The lifetime risk of cancer for the population due to natural causes is approximately 40%. The increase in risk of cancer from radiation depends on the amount (or dose) of radiation, and it becomes vanishingly small and near zero at low doses of radiation.

Category 2 means that radiation levels in the environment are higher than the natural background radiation for that geographic area. However, these radiation levels are still too low to observe any health effects.

When radiation levels are higher than what we normally have in our natural environment, it does not necessarily mean that it will cause us harm.

Category 1 means that radiation levels in the environment are within the range of natural background radiation for that geographic area.

   Low amounts of radioactive materials exist naturally in our environment, food, air, water, and consequently in our bodies. We are also exposed to radiation from space that reaches the surface of the Earth.These conditions are natural, and this radiation is called the natural background radiation.   

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