Photo representing The Threat
"It is increasingly clear that the danger of nuclear terrorism is one of the greatest threats to global security—to our collective security."
—President Barack Obama

The Threat

At the 2010 Nuclear Security Summit in Washington, President Barack Obama proclaimed that, while the threat of nuclear confrontations between nations has decreased significantly since the end of the Cold War, it is, nevertheless, "increasingly clear that the danger of nuclear terrorism is one of the greatest threats to global security-to our collective security."

Detecting and preventing acts of nuclear terrorism is one of the greatest challenges facing the international community.  The challenge is exacerbated by the nature of the terrorist threat and the increase in incidents of nuclear material theft and trafficking, particularly since the breakup of the former Soviet Union, indicating both a lapse in security at some nuclear facilities and an increased willingness by certain groups and individuals to use nuclear materials in terrorist attacks.  

 
Photo representing The Detection Challenge
“There’s the fundamental detection tradeoff: Either you set the radiation threshold on the detector high, which means you may miss some low-brightness materials, or you set it low and get a lot of false alarms.”
—Dr. Gary Gaukler

The Detection Challenge

There is concern that terrorist groups will attempt to smuggle small amounts of Highly Enriched Uranium (HEU) into the US a kilogram or two at a time and then assemble those small amounts into a nuclear weapon.  Detecting such small quantities of HEU is a much greater challenge than that of detecting a fully assembled nuclear weapon.  HEU is a dense material, so even a kilogram of material, which would be roughly the volume of a large chicken egg, could be easily concealed in a large 20 foot shipping container filled with goods.  HEU is also a low brightness material, which means that does not emit high levels of radiation.  As such, radiation detectors may miss the material if it is even lightly shielded in the container. 

Determining how to set the radiation threshold to catch smuggled nuclear detection is not a trivial matter.  Background radiation can result in nuisance alarms, or false alarms.  According to Systems and Risk Analysis Team Leader Dr. Gary Gaukler, "There's the fundamental detection tradeoff: Either you set the radiation threshold on the detector high, which means you may miss some low-brightness materials, or you set it low and get a lot of false alarms." When considering the scale of the task--scanning the approximately 12 million shipping containers entering the US each year--increasing the number of false alarms can both create significant delays and reduce the sense of urgency among port security personnel.  An ideal detection system would detect even small quantities of HEU without increasing the incidence of false alarms.

For these reasons, current detector systems alone are not sufficient to guarantee that no smuggled nuclear materials enter the US.  Current inspection practices use intelligence information to assess the risk of containers entering through the ports.  Those containers deemed "high risk" are selected for a secondary inspection.  The SHIELD team is investigating ways in which radiography imaging, coupled with software simulations, can provide a more objective measure for which containers deserve a manual inspection based on the contents of the container.

 
Photo representing Public Opinion about Nuclear Terrorism
"People are willing to accept higher costs and delays, as well as some personal intrusion, if they believe it will result in increased security.”
—SHIELD Social Science Team

Public Opinion about Nuclear Terrorism

Even the most robust and effective detection system cannot be considered successful if it is too expensive or impractical to implement or if it lacks support from the public and the government.  How concerned are US citizens about the possibility of a nuclear terrorist attack?  What costs or inconveniences are they willing to suffer for the sake of increased security? How much attention is the matter being given by members of congress?  What are the international issues and constraints to the deployment of a global detection system?

 Our Social Science Team has been working to answer these questions, and they have found that "people are willing to accept higher costs and delays, as well as some personal intrusion, if they believe it will result in increased security."  They have also found that the Department of Homeland Security and the DNDO are generally perceived as trustworthy and competent, though they have found that opinions  can differ according to demographics, political ideology, and other factors.  See more of their findings by selecting one of the topics below.