The 'Dirty' Details About Explosive Devices

One year ago today, 15 April 2013, I was among the many who were stopped by race marshals at mile 25.5 of the Boston Marathon course. The frustration, confusion, and even anger of the growing crowd of runners, halted just moments from Boylston Street, was evident. Having only run a few miles of the race in support of a friend, I was not exhausted nor fueled by adrenaline and, thus, quickly realized the potential gravity of the situation unfolding at the finish line. My hobby of running had suddenly collided with my profession of chemical, biological, radiological, nuclear, and high-yield explosive (CBRNE) preparedness and response.

As dozens of emergency responders sped through neighborhoods lined with spectators, it was clear that this was not an ordinary medical emergency or traffic incident. Mutterings of “an explosion” began as that worst-case scenario unfolded. Text messages with friends waiting near the finish line confirmed that the explosions were not fireworks, nor planned events gone awry. In the absence of any information or instructions from race officials, these “facts” heightened suspicion that an improvised explosive device (IED) had been detonated near the finish line and there was a potential for additional targets and explosions. Despite the danger, many runners waited less than half a mile from the deadly blasts until law enforcement officials confirmed that the race was over and requested that all runners clear the streets.

Rumors and misinformed reports soon surfaced – including news broadcasts of additional bombs and explosions throughout the city – that continued for days after the event. Of particular concern were reports that erroneously referenced the IEDs as “dirty bombs,” which most commonly describe certain radiological dispersal devices (RDD) and denote a radioactive property that technically and theoretically is more damaging than IEDs. An article published in May 2013, by Bulletin of the Atomic Scientists examined how the scenario in Boston would have been significantly different if the IEDs had been dirty bombs.

Basic Concepts of Complex Devices 

For appropriate emergency response efforts, it is imperative that the media distinguish an IED from a dirty bomb attack and accurately convey that information. Promoting awareness of this topic to media outlets and the public, though, requires that law enforcement officers, emergency response officials, and public health personnel also be familiar with both the common and unique technical characteristics of each type of threat.

In simple terms, RDDs include radioactive material and IEDs employ myriad conventional explosives with no radioactive material; various forms of IEDs are defined in the National Improvised Explosive Device Prevention and Preparedness Act of 2008. Each is notorious in its most popular form – the “explosive-driven dirty bomb” (an RDD) and the “roadside bomb” (an IED, described in detail by The Washington Post) – although equally dangerous versions of each device exist. The dispersion of shrapnel – including ball bearings and nails – from the pressure-cooker bombs used in the Boston attacks may have been the reason the IEDs were erroneously labeled as dirty bombs. However, the word “dirty” in this context exclusively, identifies radioactive material.

Although all dirty bombs are RDDs, not every RDD is a dirty bomb. In fact, RDDs need not be explosive devices at all, but rather can be any device that disperses radioactive material. In addition to explosion, methods of dispersion include: (a) contamination of large areas using a crop duster; (b) introduction into a food or water supply; or, more rudimentarily, (c) placement of a device in a high-traffic area. Even without the use of a device, according to the Department of Homeland Security’s Protective Action Guides for RDD and IND Incidents, response efforts should treat any dissemination of radioactive material as an RDD.

Radiological & Nuclear Factors to Consider 

Experts often suggest that, depending on the size and type of device, the greatest harm likely will occur from the blast of an explosive RDD, rather than by exposure to radiation. This comment, however, fails to factor in additional casualties when first responders are unable to immediately triage and treat exposed and contaminated victims.

In Boston, for example, video and photo evidence showed dozens of law enforcement, emergency responders, and even unharmed bystanders rushing to the aid of victims – three people killed and 260 injured by the explosions. Several accounts credit on-scene tourniquets and other immediate – formal and informal – medical attention for saving lives. Had radiation been present and detected, many of these immediate efforts would have been considerably complicated or ceased because of the threat to responders’ health and safety. Although it is likely that the explosion of an RDD poses the greatest risk of immediate injury and death, the presence of radiological material directly increases that risk by limiting lifesaving efforts.

An improvised nuclear device (INDs) is another type of device that is commonly associated and confused with RDDs because they both contain a radioactive element. Radioactivity, though, is perhaps the only technical commonality of the two weapons; the radioactive materials, properties, processes, and impacts differ dramatically. In its “Code of Conduct on the Safety and Security of Radioactive Sources,” the International Atomic Energy Agency (IAEA) identifies 16 radionuclides commonly used in medical, industrial, and research capacities that could pose a threat for radiological dispersal.

According to a report by the National Research Council, four of these – cobalt-60, cesium-137, iridium-192, and americium-241 – pose a significant risk in the United States, where they are widely used in civilian applications. On the other hand, by definition, an IND contains special nuclear, or “fissile,” material – plutonium, uranium-233, or uranium enriched in the isotopes U-233 or U-235 – that do not occur naturally in the environment and are subject to extensive safeguards, making them difficult to acquire and traffic illicitly. For this reason, the threat of an IND attack by a nonstate actor may not be as plausible as the threat of an RDD.

If an adversary state or terrorist group were able to create and detonate an IND, it would likely be far more destructive than an RDD scenario. Unlike an RDD, an IND produces a nuclear explosion, which is characterized by an intense flash of light, extreme heat, a blast wave, and prompt radiation. Such radiation would be acutely lethal for an extended distance, whereas that produced by an RDD would cause concern for chronic risks rather than immediate harm. If, due to poor design, construction, or lack of expertise, the IND fizzles – meaning the weapon does not achieve nuclear yield because fission does not occur – the results then would resemble those of an RDD explosion.

Emergency Response in a Radiological Event 

Many resources exist to inform emergency planners and responders about radiological and nuclear incidents. In the United States, primary government-issued resources include:

Although by no means inclusive of all available resources pertaining to emergency response to a radiological event, these resources provide valuable information to aid response efforts for an RDD or IND attack. A coordinated response, with all stakeholders being aware of the differences between IEDs, RDDs, and INDs, would help reduce the risks and consequences to life and property following any radiological, nuclear, and/or explosive incident.

Courtney Gavitt
Courtney Gavitt

Courtney Gavitt, MS, is an analyst at Gryphon Scientific where she focuses on chemical, biological, radiological, nuclear, and high-yield explosive (CBRNE) consequence management in support of the Federal Emergency Management Agency. As a Nonproliferation Graduate Fellow at the Department of Energy (DOE), National Nuclear Security Administration (NNSA), she contributed to U.S. interagency export control and interdiction efforts designed to curb proliferation of CBRNE weapons and dual-use materials. She served as part of the U.S. delegation to the Proliferation Security Initiative and supported DOE’s Australia Group representative. Before working at NNSA, she was a contractor at the U.S. Department of Homeland Security Customs & Border Protection. She holds an MS in biodefense from George Mason University.



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