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U.S. Department of Health and Human Services

National Planning Scenario #11


Casualties   180 fatalities
270 injuries
20,000 detectible contaminations (at each site)
Infrastructure Damage  Near the explosion 
Evacuations/Displaced Persons
  • 10,000 evacuated to shelters in safe areas (decontamination required prior to entering shelters)
  • 25,000 in each city are given shelter-in-place instructions
  • Hundreds of thousands self-evacuate from major urban areas in anticipation of future attacks 
Contamination 36 city blocks (at each site) 
Economic Impact Up to billions of dollars 
Potential for Multiple Events  Yes 
Recovery Timeline  Months to years


Scenario Overview

General Description

In this scenario, the Universal Adversary (UA) purchases stolen cesium chloride (CsCl) to make
a radiological dispersal device (RDD), or “dirty bomb.” The explosive and the shielded cesium-137 (137Cs) sources are smuggled into the Country. Detonator cord is stolen from a mining operation, and all other materials are obtained legally in the United States. Devices are detonated in three separate, but regionally close, moderate-to-large cities.

137Cs is mostly used in the form of CsCl because it is easy to precipitate. CsCl is a fairly fine, light powder with typical particle size median at about 300 microns. Fractions below 10 microns are typically less than 1%. In an RDD, most will fall out within approximately 1,000 to 2,000 feet (although many variables exist), but a small amount may be carried great distances, even hundreds of miles.

Detailed Attack Scenario

The UA, having learned from press and scientific reports how to make an RDD, activates a U.S.-based cell to carry out attacks on U.S. cities. The UA chooses 137Cs because of its availability, high radioactivity, high dispersability, and the difficult nature of cleanup and remediation. The UA’s goal is to conduct a highly visible attack creating fatalities, fear, and social and economic disruption.

The U.S. cell spends several years slowly acquiring a large quantity of prilled ammonium nitrate (NH4NO3). UA members plan attacks on three significant cities in regional proximity. Via black-market contacts, the foreign cell purchases three stolen seed irradiators that each contains approximately 2,300 curies of CsCl and several kilograms of highly explosive Pentaerythritol Tetranitrate (PETN). The CsCl powder is removed from its containment, transferred to plastic zip-lock bags, and placed in heavy lead-shielding containers. The explosive and the shielded 137Cs sources are smuggled into the country in sea-land containers shipped separately to a U.S. port under assumed business names. Detonator cord is stolen from a mining operation without raising concern, and all other materials are obtained legally in the United States.

The sea-land containers are picked up and transferred to safe houses near the target cities, where rented vans await containing the ammonium nitrate and containers of fuel oil. The vans have been painted to appear as commercial delivery vehicles. At the safe houses, terrorists assemble the devices by carefully mixing the Ammonium Nitrate with Fuel Oil (ANFO; 95:5 by weight) inside the truck and fixing the detonator with a 0.5-kilogram highly explosive core as a booster. The total explosive yield in each device will be approximately 3,000 pounds. Because each radiation source gives off 760 rad per hour (at 1 meter), the sources are left in their lead containers until the final minutes—at that time, they are transferred to the van and inserted down into the explosive mixture. The vans arrive at the target downtown locations in the U.S. cities. Three to five individuals are involved in executing each attack.

At 11:15 a.m. during the school year, UA members detonate the 3,000-pound truck bomb containing the 2,300 curies of 137Cs in the downtown business district of City One. The explosion collapses the front of one building and causes severe damage to three others. Windows are blown out of five other buildings. The area is contaminated with 137Cs, and the contaminated detonation aerosol is lifted more than 100 feet into the air.

A similar scene plays out in two other moderate-to-large cities. The second and third explosions are timed to go off simultaneously in City Two and City Three, at approximately 12:30 p.m. on the same day. The time lag is intended to maximize press coverage and spread fear and uncertainty. Local first-response capacity, however, is depleted in City Two and City Three, because many responder assets have been dispatched to assist nearby City One with the response.

Planning Considerations:

Geographical Considerations/Description

The three cities are regionally close. They are physically similar (for the sake of this assessment), with similar building environments and geographic topography that is essentially flat. The results in each city are essentially the same. The contaminated region covers approximately 36 blocks in each city and includes the business district (high-rise street canyons), residential row houses, crowded shopping areas, and a high school. Buildings in the affected areas are principally made of concrete and brick; some are stone faced. Building heights in the entire affected area range from 2 to 20 stories, and buildings in the immediate vicinity of the blast are 8 to 16 stories. The area within a radius of five blocks of the blast is a narrow urban canyon of medium-to-tall buildings abutting sidewalks, and streets are approximately 40 feet wide.

The entire scene is contaminated with 137Cs, though not at levels causing immediate concern to first responders. Due to the size of the explosion, the radioactive contamination is blown widely such that the ground zero area is not as radioactive as might have been expected. The detonation aerosol contains 90% of the original 137Cs source with radioactive particles whose sizes range from 1 to 150 microns—the size of most of the particles is approximately 100 microns. Larger particles either penetrate building materials in the blast zone or drop quickly to the ground as fallout within about 500 feet.

Variable winds of 3 to 8 miles per hour carry the radioactively contaminated aerosol throughout an area of approximately 36 blocks (the primary deposition zone). Complex urban wind patterns carry the contamination in unpredictable directions, leaving highly variable contamination deposition with numerous hot spots created by wind eddies and vortices. Radioactivity concentrations in this zone are on the order of 5 to 50 microcuries/m2, with hot spots measuring 100 to 500 microcuries/m2; however, traces of the 137Cs plume carry more than 3.5 kilometers (~ 2.2 miles) on prevailing winds. Negative indoor building pressure draws radioactive aerosols into buildings via cracks around windows and doors. Exterior air intakes increase the contamination in the interior of larger buildings. In City One, the subway system is contaminated by radioactive aerosols entering through subway ventilation system air intakes.

In all cities, foot and vehicular traffic after deposition re-suspend and transfer contamination for hours afterward until the entire scene has been effectively controlled and cordoned, contributing to contamination spread beyond the 36-block primary deposition zone. People who were in the deposition zone also take contamination home with them in hair and clothing.

Timeline/Event Dynamics

The attacks have no advance notice or intelligence that indicates their possibility. The explosions are instantaneous, but plume dispersion continues for 20 minutes while breezes navigate the complex environments before particles have fully settled. First responders do not recognize radioactive contamination for 15 minutes in City One. The explosions in City Two and City Three are promptly identified as “dirty bombs”—this provides some advantage to first responders and government officials in managing contamination on-scene, and in communicating with the public concerning topical contamination and spread of contamination.


  • As a result of the explosions, 90% of the 2,300-curies 137Cs source is aerosolized and carried by winds, with radioactive particles ranging in size from 1 to 150 microns. The remaining fallout creates debris and contaminates surrounding structures.
  • There is no precipitation. There are light, variable winds of 3 to 8 mph. The temperature is 65º F.
  • The port of entry through which the smuggled materials enter is not equipped with radiation detection equipment that can detect the shielded 137Cs source. The target and surrounding access routes are not equipped with radiation sensors that can detect the shielded source. The acquisition of bomb-making materials does not draw the attention of law enforcement.
  • First responders from City Two and City Three assist City One.
  • A disposal facility is available for cleaning up waste.

Mission Areas Activated


Prevention efforts should include such law enforcement goals as prevention of trafficking and importation of CsCl and weapon components, reconnaissance of the site, protection, and deterrence measures taken at the site before and during the attack. Target and surrounding access routes are not equipped with radiation sensors that can detect the shielded source. DHS would be involved in detection of the shielded 137Cs radiation sources.

Emergency Assessment/Diagnosis:

The explosion in City One is not recognized as a “dirty bomb” until responding units arrive with gamma detection equipment. This leads to contamination of first responders and inadvertent contamination spread that might have otherwise been avoidable. The downwind aerosol dispersion will be a significant component of the hazard and will cause extended local and regional disruption. Actions of incident-site and EOC/Joint Field Office (JFO) personnel tested during and after the attack include providing personnel dispatch; assessing the extent of physical damage, including engineering assessments of buildings; assessing medical response needs; detecting and identifying the radiation source; establishing and preserving the site for crime scene analysis; collecting site data and information; making hazard assessments and predictions for responders and the public; and coordinating preliminary radiation monitoring, surveying, and sampling operations.

Emergency Management/Response:

Incidents result in 180 fatalities, 270 injuries, extensive environmental contamination, evacuation of thousands of individuals, and thousands of potentially exposed individuals in the downwind zone. Actions of EOC/JFO personnel required after the attack include mobilizing and operating incident command; overseeing victim triage; stabilizing the site; cordoning the site and managing and controlling the perimeter; providing notification and activation of special teams; providing traffic and access control; providing protection of at-risk and special populations; providing resource support and requests for assistance; providing public works coordination; providing direction and control of critical infrastructure mitigation; and providing public information, outreach, and communication activities.

Because first-responder assets (e.g., medical evacuation, fire, rescue, and EMS personnel) were promptly dispatched from nearby City Two and City Three to assist City One, City Two and City Three are low on response capacity, and officials find themselves unprepared when attacks strike their cities.

Hazard Mitigation:

Required actions of incident-site personnel include isolating the incident scene and defining the hazard areas, building stabilization, providing fire suppression, conducting debris management, conducting radioactive and hazardous contamination mitigation, decontaminating responders and equipment, conducting local-site contamination control, and decontaminating local citizens.


Evacuation and/or sheltering of downwind populations will be required. This must occur promptly and in an orderly fashion, but will likely not occur before the plume has passed and settled, given the lack of warning. Actions taken by Federal, State, and local EOC/JFO personnel performed after the attack include developing protective action recommendations and communicating them to the public (e.g., to evacuate the affected area and/or shelter-in-place, as appropriate, and self-decontamination); providing management of evacuation, whether ordered or spontaneous; protecting special populations, schools, and day care centers; establishing temporary sheltering alternatives and provision of food for evacuees; and offering veterinary services for pets.

Victim Care:

Injured people will require some decontamination in the course of medical treatment and, if possible, prior to hospital admission. Thousands more will likely need superficial decontamination and both short-term and long-term medical follow-ups. Actions of incident-site, local-area, hospital, and EOC/JFO personnel tested after the attack include conducting search and rescue; providing triage, emergency aid, treatment, and stabilization; decontaminating victims (ambulatory and non-ambulatory); establishing relief stations, impromptu decontamination centers, and site access portals; screening, monitoring, and decontaminating evacuees (numbers are expected to be up to 100,000 at each site); conducting victim/evacuee data and information collection and management; making radio-protective pharmaceutical decisions and efficiently providing protective and/or therapeutic drug administration; conducting patient status tracking and reporting; providing patient transport; treating ER walk-in radiation victims; providing hospital care; providing collection, decontamination, and cataloging of human remains and personal effects; and providing next-of-kin notification.


Actions of law enforcement personnel tested after the attacks include dispatching personnel, conducting site cordoning and control, collecting field data, conducting witness interviews, and performing tactical deployment and apprehension of suspects. Reconstruction of the attack will occur and will include information about the occurrence of importation of illicit materials, acquisition of materials within the United States, planning, movements, financial backing, communications, suppliers/accomplices tracking, and suspect apprehension.


Decontamination/Cleanup: The extent of contamination will be a major challenge, because 137Cs is highly water soluble and is chemically reactive with a wide variety of materials, including common building materials such as concrete and stone. Approximately 36 city blocks will be contaminated to varying degrees. Contamination will settle on streets, sidewalks, and building surfaces, and will be found in several kilometers of the subway system (City One). Building interiors will become contaminated due to ventilation systems, doors, windows (because negative building pressure can draw aerosols in through very small openings), and foot traffic. Personal property—including vehicles and items inside buildings—will also become contaminated, but many items can be adequately decontaminated for free release.

A summary of decontamination and cleanup activities is as follows:

  • Some demolition will likely be required, but most surfaces may be systematically decontaminated to low levels (a lengthy, costly process).
  • Officials may focus decontamination work first on critical infrastructure—such as major thoroughfares, the subway, and the water treatment plant—in order to restore basic functions as quickly as possible.
  • Streets with cracks are cut, refilled, and resurfaced; some must be completely removed and repaved.
  • Most sidewalks must be surface cleaned.
  • Roofing materials are mostly removed, and roofs are resurfaced.
  • Surface soil and vegetation are removed for disposal and replaced with fresh material.
  • Exterior surfaces are decontaminated with an assortment of chemical treatments (e.g., stripping, vacuum blasting, scabbling), and collected wastes are hauled off for disposal.
  • Contaminated building interiors are mostly stripped of surface coatings, carpet, drapery, furniture, etc., and are refurbished.
  • Workers try to capture decontamination wastes for disposal, but much will escape into storm drains with each spring rain. Sewers become contaminated. Some are cleaned of hot spots, but others may be left fairly contained if cleaning them is not justified.
  • Though concentrations are low, river sediment remediation will likely become a big issue with the public.

Site Restoration: Several buildings (those most damaged) will be torn down and eventually rebuilt. Decontamination activities are undertaken for building exteriors and interiors, streets, sidewalks, and other areas. Federal, State, and local officials and stakeholders hold numerous public meetings to evaluate current and future land use goals, dose/risk goals for the site, and the possible use of institutional controls if decontamination is unsatisfactory. Economic and tax incentives may need to be instituted, and Federal, State, and local governments might start a “save our city” campaign to build community support to reclaim and revitalize the area. (A heated debate is likely to ensue in public meetings and the press over the adequacy of site restoration goals and the resultant risks to the public, presenting major communication and negotiation challenges to local, State, and Federal officials.)


Secondary Hazards/Events

Small fires from ruptured gas lines occur in the vicinity of the blasts. Unstable building facades, rubble, and broken glass create physical hazards for rescue workers. Small amounts of lead, asbestos, and Polychlorinated Biphenyls (PCBs) are present in the air and on surfaces. Human remains present a biohazard, and some of these may be radioactive.


At each site, the blast results in 180 fatalities and about 270 injured requiring medical care. In addition, up to 20,000 individuals in each primary deposition zone potentially have detectable superficial radioactive contamination. Most of them also have internal contamination via inhalation and secondary ingestion. Most cases are seen in City One. In each city, tens of thousands of people located downwind have minor external and internal contamination and will require monitoring and medical surveillance.

Property Damage

In each blast, one building and 20 vehicles are destroyed (i.e., not salvageable), and eight other buildings suffer varying degrees of damage, such as minor structural damage and broken windows. Radioactive contamination is found inside buildings as well as on building exteriors, streets, sidewalks, people, and personal property over an area of approximately 36 blocks in each city. Minor contamination may be an issue further downwind as investigators perform more thorough surveys. Most of the subway system in City One is contaminated.

Over the long term, decontamination efforts are expected to be effective, but some property owners choose demolition and rebuilding. Many square blocks will be unavailable to businesses and residents for several years until remediation is completed.

Service Disruption

Transportation is severely hampered in each city. Bus, rail, and air transportation routes are altered, and officials build highway checkpoints to monitor incoming traffic for contamination. The subway system in City One, which carries 500,000 passengers a day, is completely or partially closed for an extended period. In each city, the entire contaminated zone is closed to all traffic for an extended period (though peripheral areas and some thoroughfares are opened within several weeks for limited use). Hospitals in each region, already at maximum capacity with injuries from the blasts, are inundated with up to 50,000 “worried well,” most of whom were not in the blast or plume zone but are concerned about health issues (despite special relief stations established by the incident command for contamination monitoring and public outreach).

The sewage treatment plant is quickly contaminated as a result of people showering and decontaminating personal effects. In each city, 75 businesses are closed for an extended duration while radioactive contamination is remediated. Local tax revenues plummet, and people discover that insurance claims are rejected. The schools in the contamination zones are closed, and students meet in alternate locations. Nearby towns and cities close their doors to residents of the impacted cities for fear of contamination spread. Bus, rail, and air transportation routes are altered, and officials build highway checkpoints to monitor incoming traffic for contamination.

If one of the events occurred near a border, there would be a need for intense communication and cooperation between the two border governments that would engage their respective foreign affairs organizations and the full range of other Federal, State, and local agencies. In addition, the RDD attacks may warrant limiting access to or closing U.S. borders, which would have an immediate effect on Mexico and Canada.

Economic Impact

Although technologies exist to decontaminate areas, these technologies were designed for smaller, isolated areas, and the process may take several years. Decontamination, destruction, disposal, and replacement of lost infrastructure will be costly (i.e., hundreds of millions of dollars per site). Economic losses in the area due to lost business productivity, tax revenue, and property will be significant. The entire contaminated area may be economically depressed for years.

Additionally, an overall national economic downturn may occur in the wake of the attack due to a loss of consumer confidence. Virtually all commercial insurance policies exclude radioactive contamination, so the Federal Government will be left with a massive bailout. Total economic impacts would almost certainly be in the billions of dollars. Some residents will show no signs of willingness to resettle their former domiciles. Schools may permanently relocate. Some businesses may relocate to an unaffected zone or another city altogether. However, depending on the city; its size; and its historical, economic, and political significance, the will to recover and repopulate would vary widely from long-term decline to complete revitalization.

Long-Term Health Issues

The following is a summary of human health issues likely to occur over the long term:

  • No one will suffer acute radiation syndrome.
  • Approximately 20,000 individuals are likely to become externally contaminated at each site. A high percentage of these (perhaps 40% to 60%) will have measurable internal contamination via inhalation and primary and secondary ingestions that require treatment. Low-level contamination may enter food and water supplies and may be consumed at projected doses below EPA Protective Action Recommendations. The sum of the cumulative exposures results in an increased lifetime cancer risk proportionate to the dose.
  • All exposed individuals will need to be monitored for health outcomes over their lifetimes, especially those that suffer internal contamination.
  • Many individuals, including those close to but not within the affected area, will require mental health counseling for an extended period of time. First responders make up a unique group often in need of mental health services. The total number in need of mental health services may be on the order of 5,000 to 20,000 per site.

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  • This page last reviewed: May 08, 2015