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"Dirty Bombs"

Updated: October 19, 2006
This publication is now archived.

What is a “dirty bomb”?

A “dirty bomb,” also known as a radiological weapon or a readiological dispersal device (RDD), is a conventional explosive packaged with radioactive materials. A dirty bomb kills or injures through the initial blast of the conventional explosive, and by airborne radiation and contamination (hence the term “dirty”).

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How much expertise does it take to make a dirty bomb?

Not much more than it takes to make a conventional bomb. No special assembly is required; the regular explosive simply disperses the radioactive material packed into the bomb. The hardest part is acquiring the radioactive material, not building the bomb. According to a March 2002 Washington Post report, the Bush administration’s consensus view was that al-Qaeda had radioactive contaminants, such as strontium 90 and cesium 137, which could be used to make a dirty bomb. In January 2003, British officials found documents in the Afghan city of Herat indicating that al-Qaeda had successfully built a small dirty bomb. In late December 2003, homeland security officials worried that al-Qaeda would detonate a dirty bomb during New Year’s Eve celebrations or college football bowl games, according to The Washington Post. The Department of Energy sent scores of undercover nuclear scientists with radiation detection equipment to key locations in five major U.S. cities, the Post reported.

The relative ease of constructing dirty bombs makes them particularly worrisome. Even so, expertise matters. Not all dirty bombs are equally dangerous: the cruder the weapon, the less damage it causes. It is unclear whether terrorists have access to the sophisticated technologies needed to work with high-grade radioactive material.

Is a dirty bomb a nuclear weapon?

No. Nuclear weapons involve a complex nuclear-fission reaction and are thousands of times more devastating.

Is a dirty bomb a weapon of mass destruction?

Yes, but more because of its capacity to cause terror and disruption than its ability to inflict heavy casualties. Depending on the sophistication of the bomb, wind conditions, and the speed with which the area of the attack was evacuated, the number of deaths and injuries from a dirty bomb explosion might not be substantially greater than from a conventional bomb explosion. But panic over radioactivity and evacuation measures could create chaos. Moreover, the area struck would be off-limits during cleanup efforts, effectively paralyzing a local economy and reinforcing public fears.

Has a dirty bomb ever been detonated?

No. According to a UN report, Iraq tested a one-ton radiological bomb in 1987 but gave up on the idea because the radiation levels it generated were insufficient. In 1995 Chechen rebels planted, but failed to detonate a dirty bomb consisting of dynamite and cesium 137 in Moscow's Ismailovsky Park. In 2002 the United States arrested an alleged al-Qaeda operative, Jose Padilla, for plotting to build and detonate a dirty bomb in an American city. In 2003 British intelligence agents and weapons researchers found detailed diagrams and documents in Afghanistan suggesting that al-Qaeda may have succeeded in building a dirty bomb. Al-Qaeda detainees in American custody claim such a dirty bomb exists, but none have been discovered.

Which radioactive materials could be used to make a dirty bomb?

Many types of radioactive materials with military, industrial, or medical applications could be used in a dirty bomb. Weapons-grade plutonium or freshly spent nuclear fuel would be the most deadly, but these are also the most difficult to obtain and handle. Medical supplies such as radium or certain cesium isotopes used in cancer treatments could also be used. As little as a measuring cup’s worth of radioactive material would be needed, though small amounts probably would not cause severe harm, especially if scattered over a wide area.