Defining the Threats
Seizing an Intact Nuclear Weapon
Experts typically classify nuclear and radiological terrorism into four threat categories. First, a non-state actor such as a terrorist or criminal or a group of terrorists or criminals could acquire a nuclear weapon from an arsenal of a nuclear-armed state. The acquisition could occur through theft because the weapon was unsecured or through a gift because a custodian wants the non-state actor to have the weapon, or one or more officials of that state wants to transfer one or more weapons to the non-state actor. Conceivably, the non-state actor could blackmail nuclear custodians by making credible threats to the custodians themselves or their loved ones.
Making an Improvised Nuclear Device
The second nuclear threat is that a non-state actor could acquire sufficient fissile material such as highly enriched uranium (HEU) or plutonium to build an improvised nuclear device (IND). An IND could have as much explosive yield as the bombs that destroyed the cores of the cities of Hiroshima and Nagasaki. Nuclear security experts agree that HEU poses the greatest danger because of the relative ease of using it to make a “gun-type” IND, similar to the bomb dropped on Hiroshima. In contrast, plutonium could only be used in the more technically challenging “implosion-type” bomb that was dropped on Nagasaki.
These two nuclear terrorism threats are low probability events in that they are unlikely to occur due to the relatively high security for nuclear weapons and most fissile material, but they are very high consequence because of the massive destruction that would occur if a non-state actor could detonate one or more nuclear weapons or INDs on one or more cities.
Dispersing Radioactive Materials and Attacking Nuclear Facilities
The first radiological threat is the so-called dirty bomb in which radioactive material is dispersed by use of conventional explosives or perhaps other means. Experts often use the term radiological dispersal device (RDD) to refer to the “dirty bomb.” The second radiological threat is possible attack or sabotage of a nuclear facility such as a nuclear power plant or nuclear waste storage.
The radiological terrorism threats are more likely to occur due to the relatively larger number of commercially used radioactive materials and hundreds of nuclear facilities worldwide, but the consequences are much lower than nuclear terrorism because there would not be nuclear explosions but instead dispersal of radioactive materials that emit ionizing radiation.
Thus, nuclear terrorism would involve weapons of mass destruction while radiological terrorism would involve weapons of mass disruption.
Detecting and Stopping Nuclear and Radiological Terrorism
Soon after the founding of FAS in 1945, there were concerns that a non-state actor could acquire nuclear or other radioactive materials to use in a crime or an act of terrorism. It is difficult to protect against these threats because of the relative ease in shielding fissile material useful for making nuclear weapons and the widespread availability of radioactive substances for commercial purposes. In the late 1940s, for instance, J. Robert Oppenheimer, the Scientific Director of the Manhattan Project, testified to a congressional committee that the only way to reliably detect nuclear material or nuclear weapons being smuggled into the country would be to open every container with a screwdriver. This remark became the basis of the famous classified “screwdriver report” commissioned by the Atomic Energy Commission. Because of the thousands of miles of borders and the millions of people and containers annually crossing these borders, the United States cannot rely on detection methods to stop non-state actors or even states from smuggling in nuclear weapons or the fissile material to make these weapons.
Highly radioactive commercial sources have a better chance of being detected because their radiation signature would be harder to shield. But detection alone is not an effective prevention technique.
Defense-in-Depth Nuclear Security and Risk Reduction
Nuclear and radiological security experts at FAS and other organizations agree that an effective defensive strategy relies on “defense-in-depth,” or multiple layers of protection and response.
Each layer of defense is imperfect but as more layers are added, the overall defense system becomes more effective. Complementing defense-in-depth is a risk reduction concept that emphasizes both reduction of the probability and consequences of nuclear and radiological terrorism. Risk is a function of the probability of something happening such as a terrorist group acquiring nuclear material and the consequences if an event occurs such as a terrorist group detonating a nuclear explosive.
Reducing Probability of the Events from Occurring
Methods to reduce probability include securing nuclear and other highly radioactive materials, eliminating as much as possible these materials by developing and deploying alternative technologies, leveraging intelligence and law enforcement information to interdict non-state actors before they can use nuclear or radiological weapons, improving security at and around nuclear power plants and other potentially vulnerable nuclear facilities, and deploying radiation detection equipment at ports and border crossings as well as around high profile targets such as New York City. Another method is to reduce the motivations of terrorists to engage in nuclear or radiological acts. This latter method is arguably harder to perform that the others because as terrorism expert Dr. Jerrold Post has said, “We know more of the interior of the atom than we do of the interior of the mind of the terrorist.”
Mitigating the Consequences if the Events Occur
Methods to reduce consequences include equipping and training first responders such as police, fire, and hazardous material response forces, developing and deploying more effective methods to clean up radioactive materials and decontaminate buildings, creating better crisis management strategies for all levels of government (local, state, and federal), developing better means for crisis management leaders to coordinate with first responders, decontamination crews, and medical personnel, and communicating with the public about measures that they need to take in the event of an act of nuclear or radiological terrorism.