HPS masthead
Contact: President Brooke Buddemeier

Radiological Dispersive Devices Working Group

Terrorist or other radical organizations may attempt to use radioactive materials to further their social, economic or political goals. The Radiological Dispersive Devices Work Group's goal is to provide information about these dispersive devices to help education the public and support emergency response organizations.

Charter of the Radiological Dispersive Devices Working Group

The Members of the Radiological Dispersive Devices Working Group are:

Abraham Chupp, Chair (achupp@llu.edu)
Shraddha Rane

Definition from NCRP 138

3.1.0 Radiological Dispersal Events

For convenience and clarity, radiological dispersal incidents are divided into two broad categories: those involving small and generally highly localized sources and those involving the dispersal of large amount of radioactive materials over large areas.

3.1.1 Localized Sources

A single or a few, small low-level (containing small amounts of radioactive material) sources may be used with the principal objective of causing fear within a population and ultimately of disrupting the social order. The radioactive material could be packaged in a small container such as an ampule, shoe box, or even a suitcase-sized container. If in liquid form, the material could be dumped into a water reservoir or spilled over some small area; or, to create mayhem over a larger area, it could be released in small amounts from a bicycle, motor vehicle, or even an aircraft. Because the amount of radioactivity is mall, the exposure to individuals would also be expected to be low. Thus, the harm from this kind of source is primarily psychosocial, and whatever low external or internal dose is received should produce no immediate adverse health effects and only a small probability of long-term health effects. Health effects consequences from exposures to low levels of ionizing radiation are discussed in Section 4 and psychosocial effects in Section 5.

While the principal rout of exposure is external, some internal contamination could occur if the radioactivity is inhaled or enters the food chain. For a well-localized event this would be treated like the spill of any hazardous material. Protective clothing will prevent or at lease help to minimize the contamination of emergency responders. However, it will not be possible to shield against penetrating radiation and care should be taken to minimize the time spent in close proximity to high concentrations of the material. Generally these sources are easily located with the use of radiation detection instrumentation and effective protective measures designed to control the source and limit exposures to the public may be taken very quickly. Detailed guidance is provided for medical personnel in Section 4 and for other emergency response personnel in Section 9.

3.1.2 Widely Dispersed Sources

Of greater concern are events that result in the dispersal of radioactive materials over large areas through the use of explosives coupled with large amounts of radioactive material. If the target area is populated, individuals injured by the explosion are likely to be contaminated with radioactivity. Greater amounts of radioactive materials would likely be used in such devices and radiation casualties my include individuals who could have received life-threatening levels of exposure. The objective of such a device is similar to that of a smaller source, but is intended to affect an extended area or population.

The most likely scenarios involve the use of a solid radioactive material that would be of low enough activity that the construction and delivery of the RDD will not seriously inhibit the terrorist from carrying out the attack. Large sources of penetrating radiation are difficult to handle safely and without detection by authorities. Shielding materials that are adequate to protect both the individuals who construct these devices and those who are to deploy them complicate the design and fabrication of effective weapons. Although not insurmountable, these challenges can only be overcome with considerable technical expertise and sophisticated resources.

Although the most likely devices involve a high explosive coupled with a solid, usually pellets or powder, the radioactive material could also be in some kind of solution, or even be a radioactive gas.

The area over which these materials will be dispersed depends on the amount of explosive, atmospheric conditions, and the extent to which the radioactive material adheres to dust or other material dispersed by the explosion. Any gases will escape, but finely dispersed radioactive particulates, or just chunks of metal, will contaminate the ground and the surfaces of structures. In this scenario, it is most likely that only a small area of a few city blocks would be involved, but like a chemical spill, care is needed to avoid the spread of the material into other areas. As before, it is expected that most exposures would be low and the principal health and psychosocial effects in the aftermath of such an event would be similar to those discussed in Section 3.1.1, but for a larger population.

Nuclear reactors, adjacent spent fuel storage depots, nuclear fuel reprocessing facilities, transport vehicles, or any high-level waste site are potential targets for the use of high explosives to disperse into the atmosphere the very high levels of radioactivity associated with materials at these facilities. A successful incursion into a nuclear power reactor would require a very heavily armed force, since commercial reactors would require a very heavily armed force, since commercial reactors are very well protected. Only when a reactor is being refueled and the containment structure is open would atmospheric dispersion of the reactor’s nuclear fuel be likely as a result of the use of high explosives. However, after reactor shutdown, less radioactive material is contained in the fuel than during normal operations because short-lived fission products quickly decay to low or negligible levels. Also, because there is less decay heat in the fuel, there is less energy to drive fission products out of partially damaged fuel.

Spent nuclear fuel elements could also be targeted, but they contain much less radioactive material than an operating reactor plant because of the rapid decay of fission products.

Concerning the affect area, health hazards expected from dispersal of highly radioactive nuclear fuel would be similar to that which occurred at Chernobyl, but on a significantly smaller scale. Radioactive gases, liquids and particulates would serve as sources of both external and internal exposure. Within the containment structure, exposure rates could be high enough to result in lethal doses within a matter of hours. With increasing distance, both exposures and other hazards would be lower. The areas at risk from high-level radioactive waste dispersed by a large explosive device can be many miles from the source. With a smaller amount of source material and explosive, the area of concern is more in the range of several city blocks or a few miles from the target area.

The inventory of radioactive material at research reactors in universities or other facilities is very small in comparison to that in power reactors. Therefore, the anticipated impact from such an attack would also be significantly less.

Articles and Publications of Interest:

http://blogs.scientificamerican.com/guest-blog/we-need-to-educate-the-public-about-dirty-bombs/ By David Ropeik on February 23, 2016

Case study: A radioactive IED Terrorist groups realize that merely having the capability to put together a radioactive IED can tap into public fear By Lina Kolesnikova

CRCPD's Handbook for Responding to a Radiological Dispersal Device First Responder's Guide

Article by Dr. Robin McFee Homeland Security:Is this 2008 or 2001? Seven Years and Still Playing Catch Up!

Dispersive devices are commonly referred to as RDDs which stands for Radiological Dispersal Devices. How many types of RDDs can be made? The answer lies in the creativity of the deranged mind. Three common types of RDDs are presented below:

1. A high energy radioactive source that's strapped to the bottom of a park bench, or left in a busy public location.
Availability: Significant radioactive sources are not readily available.
Health Impact: Can deliver a significant radiation dose to a relatively small number of people.
Psychosocial Effects: The device is insidious, but the effect on society would probably be low to moderate because: (1) it's likely to expose a small number of individuals and (2) persistent contamination is unlikely.
Discovery and Remediation: High energy sources are generally easy to detect and remediate.

2. A radioactive liquid dispersed from a moving vehicle or into a body of water.
Availability: Significant concentrations of radioactive liquids are not easily attained.
Health Impact: Generally low to moderate. Large numbers of individuals may be exposed if dispersed into a drinking water source but dilution would lower each individual's personal exposure.
Psychosocial Effects: Can be significant. Large numbers of individuals may be exposed and they may overreact to an unfamiliar hazard. Unexposed individuals, concerned about their exposure potential may overwhelm available resources.
Discovery and Remediation: May be difficult to detect. Remediation may involve significant resources.

3. A conventional explosive used to disperse radioactive material across a target area also known as a Dirty Bomb.
Availability: Small sources can be obtained from many commercial sources including consumer products like smoke detectors or exit signs. Significant sources are not as easily attained.
Health Impact: In most instances, the conventional explosive itself would have more immediate lethality than the radioactive material. At the levels created by most probable sources, not enough radiation would be present in a dirty bomb to kill people or cause severe illness.
Psychosocial Effects: Significant. Large numbers of individuals may be exposed and they may overreact to an unfamiliar hazard. Psychosomatic symptoms may be present in the unexposed and their quest for evaluation and treatment may overwhelm existing resources.
Discovery and Remediation: Prompt response and discovery is likely. Remediation, to pre-event background radiation levels (if possible) is likely to involve significant efforts and resources.

Size Does Matter! Small radioactive sources are likely to affect a localized area and cause relatively low doses to members of the pubic, while large sources are more likely to cause widespread contamination and significant radiation doses.

Most injuries from a dirty bomb would probably occur from the heat, debris, radiological dust, and force of the conventional explosion used to disperse the radioactive material, affecting only individuals close to the site of the explosion. At the low radiation levels expected from an RDD, the immediate health effects from radiation exposure would likely be minimal.

Dirty Bombs are not nuclear weapons. A nuclear bomb creates an explosion that is thousands to millions of times more powerful than a conventional explosive that might be used in a dirty bomb. It's been said that nuclear warheads are weapons of mass destruction while dirty bombs are weapons of mass disruption.

So what helps protect us from RDDs?

  1. Effective Radioactive Material Security. Federal and State agencies insist that radioactive source owners keep the materials locked up securely - when not in use or under direct surveillance. This level of security helps ensure that sources do not fall into the wrong hands.

  2. Routine Use of Radiation Monitoring Equipment will help detect clandestine high energy radioactive sources especially during high profile events and large citizen gatherings.

  3. Reporting Suspicious Activities to the appropriate authorities.

  4. Good Hygiene. Simple soap and water cleaning and good housekeeping practices can be very effective in reducing and removing radioactive contamination and will significantly reduce radiation exposure from dispersed radioactive materials.

Additional information about RDDs and related emergency response information is available from:

1. The National Academies and the Department of Homeland Security information about radiological terrorism, RDDs and emergency response.

2. The New York State Department of Health Dirty bomb information.

3. The Radiation Emergency Assistance Center/Training Site. Radiological emergency response and training.

Individual members of the Society have suggested these websites as useful references for additional information on the subject of RDDs and emergency response to radioactive material incidents.

The Center for Strategic and International Studies (CSIS), a non-partisan group specializing in research on issues affecting domestic and international security, have published two reports on radiological and nuclear terrorism. Wild Atom; Nuclear Terrorism is a report a 1996 war game concerning the detonation of a terrorist nuclear weapon. The Nuclear Black Market reports on the history of the international black market in nuclear and radiological materials.

What is the potential contamination levels and radiation exposures resulting from the dispersal of an explosive RDD. The Lawrence Livermore National Laboratory developed a computer code to model this dispersion. Hotspot is available on the LLNL website. The program RESRAD (developed at the Argonne National Laboratory) can be used to estimate exposures to people who may live in areas contaminated by radioactive materials following an RDD attack.


National Council on Radiation Protection and Measurements. Management of Terrorist Events Involving Radioactive Material. Bethesda, MD: National Council on Radiation Protection and Measurement; NCRP Report No 138; 2001.

Website for ICRP 175

http://www.icrp.org/docs/Anne%20Nisbet%20Decision%20 Making%20for%20Late%20Phase%20Recovery%20from%20Nuclear%20or%20Radiological %20Incidents%20New%20Guidance%20from%20NCRP.pdf