A conventional explosive or bomb containing radioactive material. The conventional bomb is used as a means to spread radioactive contamination. It is not a nuclear bomb and does not involve a nuclear explosion. Any type of radioactive material could be used in a dirty bomb, but in general, these devices would be unlikely to cause serious health effects beyond those caused by the detonation of conventional explosives. The probable effects of an RDD detonation would be:

potential for panic in the general public

contamination areas near the RDD blast site

(probably not lethal radiation dose levels

huge numbers of people think they are contaminated

small number seriously contaminated

may need regional decontamination sites to handle thousands

limited radiation detectors and trained personnel would add to the problem

A nuclear weapon used by a terrorist would produce devastating effects, including thermal (heat) impulse, blast wave, penetrating neutron and gamma radiation, and radioactive fallout with radiological contamination, and would have a tremendous psychosocial impact on the community and the entire country. There is a lower probability that terrorists will detonate a nuclear weapon than an RDD. The size of nuclear explosions is measured in kilotons (kt). The energy of one kiloton is equivalent to the explosion of one thousand tons of trinitrotoluene (TNT) high explosives.

Nuclear weapons have been made small enough to be carried by one person. A “small” nuclear detonation of less than one kiloton may be mistaken for a large truck bomb. The area of destroyed buildings may be less than a city block.