National Academies Press: OpenBook

Risk Analysis Methods for Nuclear War and Nuclear Terrorism (2023)

Chapter: 2 The Threat of Nuclear War and Nuclear Terrorism: Classes of Scenarios

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Suggested Citation:"2 The Threat of Nuclear War and Nuclear Terrorism: Classes of Scenarios." National Academies of Sciences, Engineering, and Medicine. 2023. Risk Analysis Methods for Nuclear War and Nuclear Terrorism. Washington, DC: The National Academies Press. doi: 10.17226/26609.
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2

The Threat of Nuclear War and Nuclear Terrorism: Classes of Scenarios

Scenarios play a critical role in scoping a risk analysis. A scenario, such as those described in this chapter, is the conjunction of events and system states that describes a situation and its possible paths of evolution so that one can then evaluate the potential risks associated with it. This chapter identifies some classes of scenarios of nuclear war and nuclear terrorism for illustrative purposes.

In developing scenarios, analysts are confronted with a fundamental question: How complex should the scenario description be? Scenarios can be made extremely complex by adding details that may not be fully relevant, to the point at which their likelihood becomes very small with the addition of each detail or component. Scenario specificity is a balancing act: analysts have to balance identifying groups of scenarios in a description that is simple enough that it can be analyzed and, at the same time, includes all the essential components that will make the results relevant.

Forecasting geopolitics is obviously difficult (Scoblic and Tetlock 2020), and the following classes of scenarios are not intended as an exhaustive set. Many other scenarios are possible, and multiple scenarios could unfold simultaneously. Rather, the committee offers these general classes of scenarios as one possible approach to organizing risk analyses related to nuclear war and nuclear terrorism.

DEVICE TYPES AND SCALES OF EVENTS

Devices used in nuclear war and nuclear terrorism can be grouped into those in which a nuclear detonation occurs and those in which it does not. Devices in which a nuclear detonation occurs can occur in both nuclear terrorism and war

Suggested Citation:"2 The Threat of Nuclear War and Nuclear Terrorism: Classes of Scenarios." National Academies of Sciences, Engineering, and Medicine. 2023. Risk Analysis Methods for Nuclear War and Nuclear Terrorism. Washington, DC: The National Academies Press. doi: 10.17226/26609.
×

scenarios. These nuclear weapons range from a terrorist-constructed improvised nuclear device or a terrorist-produced or -obtained nuclear weapon (stolen or clandestinely provided by a state) to state-developed tactical or strategic nuclear weapons. The scale of these weapons can be listed notionally from lowest to highest yield, from a fraction of a kiloton to tens of megatons.

Devices or events in which a nuclear detonation does not occur are typically related to nuclear or radiological terrorism scenarios; they include radiological dispersal devices, radiological exposure devices, and nuclear facility sabotage. The scales of destruction of these events are thought to be localized (e.g., to a city or a region) but they could have large economic, social, and psychological consequences. “Success” for a terrorist could be to create fear and may not include the release of any radioactivity.

CLASSES OF NUCLEAR WAR SCENARIOS

The risks of a conflict that involves nuclear weapons is driven by the capabilities and intentions of adversaries. Sources of tension between states with nuclear weapons, the potential for escalation from conventional warfare, cross-domain instability (e.g., crisis in space or cyber domains leading to a nuclear response), and alliance commitments can each play a role in triggering nuclear war. Many other factors are also important, such as alert status and force structure.

There are many imaginable scenarios that would involve the use of nuclear weapons between states. To help identify the risks associated with nuclear war, the following set of classes of nuclear war scenarios is presented as a possible approach to organizing classes of scenarios. If analysts intend to determine the overall risks of nuclear war, they will need to address the completeness of the set of scenario classes, the completeness of scenarios within classes, and their interdependencies and underlying assumptions.

As noted above, the classes of nuclear wars identified by the committee are not exhaustive; moreover, individual scenarios may have attributes of more than one class.

Preventive Nuclear War

The idea that a preventive nuclear war against a nonnuclear or a nascent nuclear state would prevent it from starting a nuclear war in the future has been considered, but has never been carried out. Yet future scenarios of that kind could lead to actual nuclear use.

Suggested Citation:"2 The Threat of Nuclear War and Nuclear Terrorism: Classes of Scenarios." National Academies of Sciences, Engineering, and Medicine. 2023. Risk Analysis Methods for Nuclear War and Nuclear Terrorism. Washington, DC: The National Academies Press. doi: 10.17226/26609.
×

Preemptive Nuclear War

Preemptive nuclear war refers to an instance in which an actor strikes first due to the fear that, if it does not do so, the other side will strike first or it believes it can achieve a significant advantage by striking first. Concerns about preemption were the focus of first-strike stability analyses throughout much of the Cold War.

Escalatory Nuclear War

Escalatory nuclear war refers to an instance in which ongoing conventional military conflict leads one side to initiate the use of nuclear weapons. This escalation can be either strategic, to achieve a broader goal, or tactical, to accomplish a specific mission. The threat of escalation to nuclear war is both a crisis management tool and a risk. The incentives to escalate to higher levels of violence in a conflict can arise from particular geographies, the vulnerability of military forces and command and control to enemy attack, fear of losing a conflict, evolving technologies that may create advantages (e.g., cyber and counter-space weaponry), and technologies and circumstances that reduce the time for decisions.

Catalytic Nuclear War

Catalytic nuclear war generally refers to an instance when a state initiates the use of nuclear weapons because it or one of its allies to whom it has made a firm deterrent commitment faces an existential threat from nonnuclear weapons. If the number of nuclear states increases and as nonnuclear states continue to rely on an ally’s nuclear umbrella, the possibility of catalytic nuclear war could potentially increase.

Accidental Nuclear War

Accidental nuclear war refers to instances when an unintended mishap inadvertently leads to war. Unforeseeable accidents are considered inherent characteristics of complex systems (Perrow 2011). Some complex systems and processes can be safer than simple ones if they involve effective checking processes and properly designed redundancies.

Unauthorized Nuclear War

Unauthorized nuclear war refers to an instance when the decision to use nuclear weapons is made by a subordinate without his or her leadership’s direction.

Suggested Citation:"2 The Threat of Nuclear War and Nuclear Terrorism: Classes of Scenarios." National Academies of Sciences, Engineering, and Medicine. 2023. Risk Analysis Methods for Nuclear War and Nuclear Terrorism. Washington, DC: The National Academies Press. doi: 10.17226/26609.
×

The delegation of launch authority may enhance deterrence, but it simultaneously increases the risks of an unauthorized nuclear war.

Misinformed Nuclear War

Misinformed nuclear war refers to an instance when leaders act on erroneous information or faulty analysis. A launch of nuclear-armed missiles, based on a false warning of an attack, would be an example of this category.

CLASSES OF NUCLEAR TERRORISM SCENARIOS

As with nuclear war, the many scenarios involving the use of radiological or nuclear weapons by terrorists can be classified into categories and analyzed to set priorities to deter, detect, and respond to nuclear threats. Below are three broad classes of scenarios: those involving stolen or otherwise acquired weapons or improvised nuclear devices, those involving radiological dispersal devices or radiological exposure devices, and those involving the sabotage of major nuclear facilities. Here again, the committee offers this organization of classes of scenarios to assist in identifying the risks of nuclear terrorism, but it is important to note that some questions and decisions may be better informed by organizing the classes of scenarios differently.

Acquired Weapons or Improvised Nuclear Devices

Scenarios in this class would require terrorists to gain access to special nuclear materials (plutonium and highly enriched uranium) with which to build a device or to gain access to a nuclear weapon either by stealing one or by complicity. Scenarios in this class might also include details related to the transportation and successful use of improvised nuclear devices.

Radiological Dispersal Devices and Radiological Exposure Devices

With radiological dispersal devices, radioactivity is distributed through the environment either using explosives (“dirty bombs”) or other methods. With radiological exposure devices, the radioactive source remains contained (rather than dispersed in the environment). Exposure can be significant, but would only occur when people are near the source.

Suggested Citation:"2 The Threat of Nuclear War and Nuclear Terrorism: Classes of Scenarios." National Academies of Sciences, Engineering, and Medicine. 2023. Risk Analysis Methods for Nuclear War and Nuclear Terrorism. Washington, DC: The National Academies Press. doi: 10.17226/26609.
×

Sabotage of Major Nuclear Facilities

The sabotage of a nuclear installations could lead to widespread contamination, access to nuclear material, and a general sense of panic, which was seen in the Russian seizure of Ukraine’s Chernobyl and Zaporizhzhia nuclear facilities. Sabotage can happen by intrusion or by complicity of an insider. In general, an attack on a nuclear facility cannot result in a nuclear explosion but rather in radioactive dispersal (World Nuclear Association 2021). The nuclear fissile material, if dispersed, poses direct radiological hazard due to exposure, and it can lead to contamination of the environment, including soil, atmosphere, built structures, and vegetation that can then be ingested. It can also lead to human exposure. High exposure levels can cause both short-term illness and death, as well as longer-term deaths from cancer and other diseases. The Chernobyl disaster provides an illustration of the extent of contamination and its long-term effects—some less expected, such as the reemergence of nature and the life of the few people who refused to evacuate. A nuclear power plant typically contains tons of radioactive material, in comparison with a nuclear weapon that contains on the order of tens of kilograms, and disruption of a gigawatt power plant can produce radioactive contamination of a severity comparable to that of a megaton explosion (Eisenbud and Gesell 1997).

In a National Research Council (2006) study, five possible attack scenarios were identified: (1) ground attack by a group of well-trained individuals, (2) air attack using a civilian aircraft or a smaller private aircraft carrying explosives, (3) attacks involving combined air and land attacks, (4) attack by a combination of sea and land, and (5) theft of spent fuel by terrorists to produce a dispersal device. In addition to attacks on the facility structures that contain the reactor, deliberate actions that lead to a fire in a spent fuel pool could be especially devastating due to widespread dispersal of radioactive material through a smoke plume (National Research Council 2006). The general view is that aircraft-based attacks on U.S. nuclear facilities will not cause dispersal due to the installed containment structures and missile shields.

In addition to sabotage events that could release radioactive materials, terrorists’ objectives may be focused on social or psychological effects—creating fear or panic or damaging public trust in or the reputation of the entity managing the nuclear facility—without the intention of releasing any radioactive materials (e.g., Y-12 protester break-in in 2012 [GAO 2014]).

Suggested Citation:"2 The Threat of Nuclear War and Nuclear Terrorism: Classes of Scenarios." National Academies of Sciences, Engineering, and Medicine. 2023. Risk Analysis Methods for Nuclear War and Nuclear Terrorism. Washington, DC: The National Academies Press. doi: 10.17226/26609.
×
Page 14
Suggested Citation:"2 The Threat of Nuclear War and Nuclear Terrorism: Classes of Scenarios." National Academies of Sciences, Engineering, and Medicine. 2023. Risk Analysis Methods for Nuclear War and Nuclear Terrorism. Washington, DC: The National Academies Press. doi: 10.17226/26609.
×
Page 15
Suggested Citation:"2 The Threat of Nuclear War and Nuclear Terrorism: Classes of Scenarios." National Academies of Sciences, Engineering, and Medicine. 2023. Risk Analysis Methods for Nuclear War and Nuclear Terrorism. Washington, DC: The National Academies Press. doi: 10.17226/26609.
×
Page 16
Suggested Citation:"2 The Threat of Nuclear War and Nuclear Terrorism: Classes of Scenarios." National Academies of Sciences, Engineering, and Medicine. 2023. Risk Analysis Methods for Nuclear War and Nuclear Terrorism. Washington, DC: The National Academies Press. doi: 10.17226/26609.
×
Page 17
Suggested Citation:"2 The Threat of Nuclear War and Nuclear Terrorism: Classes of Scenarios." National Academies of Sciences, Engineering, and Medicine. 2023. Risk Analysis Methods for Nuclear War and Nuclear Terrorism. Washington, DC: The National Academies Press. doi: 10.17226/26609.
×
Page 18
Next: 3 The History and Literature of Risk Assessment for Nuclear War and Nuclear Terrorism »
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The assessment of risk is complex and often controversial. It is derived from the existence of a hazard, and it is characterized by the uncertainty of possible undesirable events and their outcomes. Few outcomes are as undesirable as nuclear war and nuclear terrorism. Over the decades, much has been written about particular situations, policies, and weapons that might affect the risks of nuclear war and nuclear terrorism. The nature of the concerns and the risk analysis methods used to evaluate them have evolved considerably over time.

At the request of the Department of Defense, Risk Analysis Methods for Nuclear War and Nuclear Terrorism discusses risks, explores the risk assessment literature, highlights the strengths and weaknesses of risk assessment approaches, and discusses some publicly available assumptions that underpin U.S. security strategies, all in the context of nuclear war and nuclear terrorism.

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