How Bad Would A Radiological Terror Attack Be?

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Dirty Bombs

Reports show that last week’s Brussels attackers are among many ISIS affiliates pursuing dirty bombs, renewing fears about the group’s nuclear ambitions.

Dirty bombs, also known as radiological dispersal devices (RDDs), aren’t actually nuclear weapons. Though they distribute a small amount of radioactive material upon detonation, their blast is far deadlier, and most people exposed to the radioactive blast wouldn’t receive a lethal dose.

According to a recent report from the Nuclear Threat Initiative, a dirty bomb “would not cause catastrophic levels of death and injury” but “could leave billions of dollars of damage due to the costs of evacuation, relocation, and cleanup,” contributing to the weapons’ reputation as “weapons of mass disruption.”

“Recent reports out of Iraq warn that Islamic State extremists may have already stolen enough material to build a [dirty] bomb that could contaminate major portions of a city and cost billions of dollars in damage,” the report states.

Experts agree that terrorists are more likely to use a dirty bomb than other radioactive devices because dirty bombs are less technically complicated to build and require materials that are relatively easy to obtain.

INDs

While experts believe that terrorist groups are more likely to use dirty bombs, uranium-based improvised nuclear devices (INDs) aren’t out of the question. But all INDs, which Jorgensen describes as “homemade atomic bomb[s],” are not alike.

Ground detonations and air blasts result in different casualties. Terrorists are more likely to detonate an IND from the ground, rather than dropping it from a plane. This kind of blast would cause a greater amount of fallout, which increases radiation exposure and thus, health risk.

If a terrorist group were to detonate a 15-kiloton nuclear bomb (the size of the Hiroshima bomb, considered a plausible size for a terrorist group to build or obtain), the radius for radiation sickness deaths and the radius for deaths from the blast would be about the same size.

Interestingly, the more energy that an explosion releases, the percentage of people who die from percussive blasts increases, while the percentage who die from radiation sickness decreases. That information helps us to predict deaths from the percussive blast versus deaths from radiation—and to better predict the proportion of the population who might be treatable.

If a 50-kiloton bomb were detonated over a civilian population, radiation sickness wouldn’t kill anyone – because anyone close enough for a lethal dose would already have been killed by the blast.

But energy output and altitude are far from the only variables that help us to forecast a nuclear bomb’s health impact.

Enter the Nuke Map, a project from nuclear historian Alex Wellerstein. The interactive map lets you plug in variables to see the outcome of various nuclear bomb scenarios.

For example, a 15-kiloton nuclear bomb (the size of the Hiroshima bomb, considered a plausible size for a terrorist group to obtain) dropped from a plane on downtown Washington, D.C. would leave hundreds of thousands of casualties within city limits. That same bomb set off at ground level would result in fewer immediate casualties—but fallout that extended for miles, due to the region’s northeast winds, Jorgensen explained.

And, even at non-lethal doses, radiation exposure introduces myriad concerns: How far away from the detonation site does cancer risk increase? Is it worth the risk to evacuate hospital and nursing home residents? When is it safe for displaced residents to return home?

According to Jorgensen, the best way to answer these questions later is public education now. “People… can’t even discuss the topic because they don’t know the difference between radiation and radioactivity dose. They need to have at least that much information to be engaged in the process,” he says. “We, as public health officials, should do a much better job at bringing this message to the public.”

The interactive Nukemap can be accessed below:

http://nuclearsecrecy.com/nukemap/