Executive Summary

For nearly eight decades, America and the world have been navigating the dangers of the nuclear age. Despite cold war tensions and the rise of global terrorism, nuclear weapons have not been used in conflict since Hiroshima and Nagasaki in 1945.

It is no accident that the world has been spared the catastrophic consequences of a nuclear attack. Strategic deterrence, arms control, and nonproliferation agreements, U.S.-led global counterproliferation and counterterrorism efforts, and multi-year defense outlays together have helped to keep nuclear incidents at bay. A key contributor has also been decades of shared bipartisan commitment and investment in nuclear safety and security. But there is no guarantee of continued success. Indeed, there is a growing array of worrisome developments that may make nuclear terrorism more, not less, likely in the future.

The 2021 National Defense Authorization Act directed the National Academies to undertake a new study on the risks of nuclear terrorism. To respond to the broad congressional mandate, the committee conducted meetings, received briefings, and collected data from senior government officials, international partners, and experts. Drawing on the depth of expertise and experience of its dozen members, the result is the comprehensive and sobering assessment outlined in this report.

The committee does not foresee an imminent nuclear terrorist attack, but its review found that long-standing measures need fresh attention and enhancement. The committee also found gaps in programs and capabilities for interdicting nuclear weapons and materials and the nation’s ability to deal with a nuclear terrorist attack.

There are several overarching findings that should guide ongoing efforts to combat nuclear terrorism and inform future budget allocations:

• Federal agencies across the U.S. government, staffed by seasoned experts, provide domestic and international programs and capabilities that have built a

• strong foundation for managing and reducing nuclear terrorism risks. There is, however, no agency assigned a lead role. It falls to the White House to provide active and sustained oversight to assure close interagency coordination and focus.
• Maintaining an all-of-government focus on nuclear terrorism is being challenged by the pressures on the defense and intelligence communities to shift their focus from terrorism to the risks associated with great power competition. Agencies such as the Department of Homeland Security (DHS), the Department of Energy (DOE), the Department of Defense(DOD), the Federal Bureau of Investigation (FBI), the Federal Emergency Management Agency (FEMA), the Centers for Disease Control and Prevention (CDC), the U.S. Coast Guard, and Customs and Border Protection are facing difficult choices arising from constraints on discretionary spending and the demands of their other missions. At the state and local levels, governors and mayors are confronted with competing priorities, making it difficult to devote the attention required to prepare for a low-probability/high-consequence threat. Overall, attention to the nuclear terrorism risk is waning even as important guardrails that have kept the risk in check are becoming less effective.
• Trends are pointing to a potential reversal of the post–Cold War progress in reducing the supply side of the nuclear threat. U.S.–Russian arms control agreements are lapsing with little prospect of renewal while China continues to expand its nuclear arsenal. Russia was once a major partner in advancing global nonproliferation and counterproliferation efforts, but that is no longer the case. The civil nuclear sector is expanding into countries with little experience in operating nuclear facilities and safeguarding materials.
• Terrorism is a transnational threat. U.S. domestic terrorists are developing overseas ties, and foreign terrorist organizations are recruiting Americans. This presents challenges for federal agencies that must operate under differing authorities for international versus domestic counterterrorism activities.
• Nuclear weapons, materials, and expertise are almost entirely controlled by state actors. For a terrorist organization to carry out a nuclear attack with either a nuclear weapon or an improvised nuclear device, they need either the complicity of a state or the failure of a state and its controls. In other words, the nature of nuclear terrorism is that it involves both state and non-state actors. This creates the potential for blind spots in detecting this threat if a shift in focus to state actors comes at the expense of efforts to monitor and thwart terrorist organizations.
• The radiological materials in commercial and industrial applications could be used to produce a dirty bomb or exposure device. Such a device would be less destructive than a nuclear bomb or an improvised nuclear device (IND), but the materials are easier to obtain. This makes a dirty bomb more likely to be used by terrorists than a nuclear weapon or improvised nuclear device, although the risk to lives is dramatically lower than for a nuclear weapon. But successfully exploding such a device would have significant economic consequences and

• cause public fear and uncertainty. Deterring the movement of radioactive materials or the targeting of the global supply system with a dirty bomb could be strengthened by comprehensive use of advanced scanning technologies and artificial intelligence (AI).
• Under the U.S. system of government, the responsibility for disaster response and recovery lies primarily at the state and local levels where there is limited capacity for dealing with a nuclear incident. Misinformation, disinformation, and mal-information (MDM), enhanced by AI, will significantly complicate the public communications challenge for local officials in the aftermath of a nuclear attack.

The committee’s 38 findings and 16 recommendations are organized around nine chapters. Chapter 1 provides an overview of the federal entities that play the most significant role in addressing the nuclear terrorism risk. Chapter 2 describes and assesses nuclear threats, and then chapter 3 looks at the evolving nature of the nuclear terrorism risk. Chapters 4 and 5 examine recent trends in the geopolitical environment and civil nuclear energy sector that are affecting this risk. Chapters 6 and 7 focus on the dangers associated with highly enriched uranium (HEU), plutonium, and radioactive source materials and the challenges of keeping them out of the hands of terrorists. Chapter 8 assesses how non-state actors might exploit well-established smuggling pathways to move nuclear weapons, materials, and equipment even in the face of current measures for detecting and interdicting such movements. Chapter 9 addresses the need for comprehensive, multi-agency emergency response and recover strategies should efforts to prevent a nuclear incident fall short. A classified annex is available as a resource with supplemental information.