Nuclear Threat

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Nuclear Threat Reduction (NTR) refers to the integrated and layered activities across the full range of U.S. government efforts to prevent and counter radiological and nuclear incidents. Reducing nuclear threats applies across a spectrum ranging from potential state adversaries to non-state actors. For state threats, NTR counters the emergence of challenges to the United States from the proliferation of nuclear weapons by emphasizing the detection of potential problems as early as possible. For non-state threats, NTR includes the capabilities to prevent, attribute, and recover from a terrorist attack that used nuclear and/or radiological materials.

DoD NTR Efforts

DoD NTR efforts are focused on three end states. The first goal of NTR is to prevent the acquisition of new nuclear weapons. For nation-states, this effort encompasses the prevention of vertical and horizontal proliferation of nuclear weapons, nuclear materials, and related technology. Vertical proliferation is the advancement or modernization of a state’s nuclear weapons capability, and horizontal proliferation is the direct or indirect transfer of nuclear weapons technologies or materials to a non-nuclear weapons state. This threat is primarily reduced through nonproliferation and arms control activities, which are supported by robust U.S. capabilities to detect proliferation. For non-state actors, the goal is to prevent terrorists and violent extremist organizations from acquiring a nuclear weapon or radiological or nuclear materials. The 2018 Nuclear Posture Review reiterated that, “Nuclear terrorism remains among the most significant threats to the security of the United States, allies, and partners. The Joint Chiefs of Staff, in 2015, emphasized, ‘Nuclear, chemical, and biological agents pose uniquely destructive threats. They can empower a small group of actors with terrible destructive potential. Thus combating weapons of mass destruction (WMD) as far from our homeland as possible is a key mission for the U.S. military.’” For non-state actors, there are numerous programs described later in this chapter to reduce the risk of radiological and nuclear materials and weapons falling out of regulatory control. Additionally, the United States seeks to deter terrorists through advanced nuclear technical forensics capabilities that can identify the source of an attempted or actual attack that included nuclear or radiological materials.

The second goal of nuclear threat reduction is to prevent the use of nuclear or radiological weapons. For state actors, this goal is accomplished primarily through strategic deterrence. For non-state actors, it is generally assumed that if a violent extremist organization obtained a nuclear or radiological weapon, it would use that weapon, making prevention paramount. There are numerous programs in place to detect and interdict nuclear and radiological materials before they could be transported to their intended target.

The third NTR goal is the minimization of the effects of a nuclear or radiological attack by state or non-state actors. DoD, primarily through its Chemical and Biological Defense Program, ensures the Joint Force can operate effectively and personnel are protected in all environments, including radiologically contaminated environments. Additionally, the United States devotes significant resources to consequence management activities to ensure the safety of the public and to support recovery efforts in the aftermath of a nuclear or radiological incident. The U.S. whole-of-government response to a nuclear or radiological incident would be led by the Department of Homeland Security (DHS) Federal Emergency Management Agency (FEMA). The policies, situations, concepts of operations, and responsibilities of the responding Federal departments and agencies are described in the Nuclear/Radiological Incident Annex of the National Response Framework (NRF).

Understanding State Threats

On December 8, 1953, at the 470th Plenary Meeting of the United Nations General Assembly, President Dwight Eisenhower delivered his famous “Atoms for Peace” address, pledging to support the peaceful use of atomic energy in exchange for a commitment to forego the development of nuclear weapons. Less than three years later, 81 countries unanimously approved the statute for the establishment of the International Atomic Energy Agency (IAEA). As defined in Article II of the IAEA statute, “The Agency shall seek to accelerate and enlarge the contribution of atomic energy to peace, health, and prosperity throughout the world. It shall ensure, so far as it is able, that assistance provided by it or at its request or under its supervision or control is not used in such a way as to further any military purpose.”

On March 5, 1970, the Treaty on the Non-Proliferation of Nuclear Weapons, commonly referred to as the Non-Proliferation Treaty or NPT, entered into force, and on May 11, 1995, it was extended indefinitely. The NPT is regarded as the cornerstone of the global nuclear nonproliferation regime, and with 191 nations participating, the NPT has the largest number of signatories of any other arms limitation or disarmament agreement.1 The NPT establishes a safeguards system, operated under the responsibility of the IAEA, to verify through safeguards agreements that countries are not diverting or misusing nuclear materials or facilities.

According to the United National Office for Disarmament Affairs, as of 2019, more than 30 countries possess nuclear power plants, and another 28 countries are interested in introducing nuclear power. Additionally, more than 50 countries possess research reactors that are used to produce medical and industrial isotopes. To reduce the possibility of nuclear proliferation at the state level, NTR focuses U.S. capabilities on detecting and countering any clandestine effort to misuse nuclear power for military use as early as possible. There are a number of activities a state must take to develop a nuclear weapon program from a peaceful nuclear energy program. These activities, which need not be done sequentially, increase the risk of proliferation such that a states’s investment in any one of them is cause for concern. There are a number of programs and strategies to address each of these proliferation activities to prevent states from developing nuclear weapons. For more information, see Chapter 15: Nuclear Fuel Cycle and Proliferation.

Motivation and Planning

Currently, there are a handful of countries with the facilities, material, and advanced technical expertise necessary for a successful nuclear weapons program. However, for a variety of reasons, these nations have decided not to pursue the development of nuclear weapons.

For decades, the United States has effectively assured the security of its allies under the U.S. nuclear “umbrella.” These allies and partners rightly place enormous value on U.S. extended nuclear deterrence which, in turn, is a key to nonproliferation. For their part, potential adversaries’ motivation not to pursue nuclear weapons may also be influenced in part by the U.S. declaratory policy regarding the potential employment of nuclear weapons:

“The United States will not use or threaten to use nuclear weapons against non-nuclear weapons states that are party to the NPT and in compliance with their nuclear non-proliferation obligations.”2

Should a state decide to pursue nuclear weapons, there are measures that can be taken to try to reverse the decision to pursue such weapons, as indicated by the numerous U.N. Security Council resolutions and sanctions applied to North Korea and Iran. It is imperative that illicit proliferation activities be detected as early as possible so the United States and the international community can act to try to prevent acquisition.

Developing Infrastructure

Nuclear weapons require a significant infrastructure. While all nations have the right to nuclear technology for peaceful uses, elements of a peaceful nuclear infrastructure are inherently dual-use and can contribute to a nuclear weapons program. Of these elements, the two fuel cycle facilities that are considered the greatest risk to potential proliferation are enrichment and reprocessing facilities. In fact, the science for these facilities was a major focus of the Manhattan Project.

There are two primary means to reduce the risk that peaceful nuclear infrastructure could be misused. The first is to alleviate the need for states to develop some of the most sensitive fuel cycle facilities. One example is the establishment of a low-enriched uranium bank to provide assurance that fuel for nuclear power will be available to all states who are party to the NPT, alleviating the need for clandestine uranium enrichment. The second is the application of NPT safeguards, which provide transparency and confidence that programs are being used for the stated purpose and not contributing to proliferation. Led by the Department of Energy (DOE) through the National Nuclear Security Administration (NNSA), the United States invests significant resources in nonproliferation research and development to improve the IAEA safeguards inspection regime.

Acquiring Expertise, Technology, and Material

Nuclear weapons technology is 75 years old, and the basic weapon design information has been spread widely since the development of the first atomic bomb. The most famous example of the illicit proliferation of nuclear technology was Abdul Qadeer Khan (A.Q. Khan) and his network, which provided nuclear weapons and missile technology to Pakistan, North Korea, Libya, and Iran.

Based on the relative availability of nuclear weapons design information, the best way to halt the spread of weapons is to prevent states from acquiring sufficient quantities of special nuclear material required for a nuclear weapons program. At the same time, it is also important to limit the further spread of information on nuclear weapons design, non-nuclear components, and delivery system technology.

As required by the Atomic Energy Act of 1954, the United States provides special protection to any information related to the design, manufacture, or use of atomic weapons; the production of special nuclear material; and the use of special nuclear material. This information is classified as Restricted Data.3 Other nations with nuclear weapons similarly provide the highest level of protection to their equivalent of Restricted Data.

Outside of Restricted Data information, there are dual-use technologies that may aid a nation in developing nuclear weapons. There are a number of regimes and agreements that provide assurance that technologies will not contribute to a weapons program. The U.S. Department of State (DOS), with support from the Departments of Commerce, Homeland Security, Treasury, Defense, and Energy, leads U.S. efforts in support of export control and nonproliferation activities. The two primary international groups are the Nuclear Suppliers Group and the Zangger Committee. The Nuclear Suppliers Group is a voluntary, multilateral export control regime with 48 participating governments that was founded in response to India’s 1974 nuclear test. The Nuclear Suppliers Group governs the transfer of civilian nuclear material and nuclear-related equipment and technology to prevent nuclear exports for peaceful purposes from being used to make nuclear weapons. The Zangger Committee was established in 1971 following the entry into force of the NPT to assist nuclear suppliers in complying with Article III.2 of the NPT which states, “Each State Party to the Treaty undertakes not to provide: (a) source or special fissionable material, or (b) equipment or material especially designed or prepared for the processing, use or production of special fissionable material, to any non-nuclear-weaponState for peaceful purposes, unless the source or special fissionable material shall be subject to the safeguards required by this Article.” The Committee currently has 39 member states, including all of the nuclear-weapons states, as defined by the NPT. The Zangger Committee developed a list of equipment that may only be exported to non-nuclear weapons states outside of the NPT when three conditions are met, and continues to maintain and update this list. These conditions are an assurance of non-explosive use, a requirement to place the items under IAEA safeguards, and an assurance that the receiving country would apply the same restrictions on any further transfer. The primary difference between the Nuclear Suppliers Group and the Zangger Committee is that the former focuses on the transfer of non-nuclear items to all non-nuclear weapons states regardless of their NPT status, while the Zangger Committee focuses on transfers to states outside of the NPT.

State for peaceful purposes, unless the source or special fissionable material shall be subject to the safeguards required by this Article.” The Committee currently has 39 member states, including all of the nuclear-weapons states, as defined by the NPT. The Zangger Committee developed a list of equipment that may only be exported to non-nuclear weapons states outside of the NPT when three conditions are met, and continues to maintain and update this list. These conditions are an assurance of non-explosive use, a requirement to place the items under IAEA safeguards, and an assurance that the receiving country would apply the same restrictions on any further transfer. The primary difference between the Nuclear Suppliers Group and the Zangger Committee is that the former focuses on the transfer of non-nuclear items to all non-nuclear weapons states regardless of their NPT status, while the Zangger Committee focuses on transfers to states outside of the NPT.

In addition to limiting nuclear materials and technology, preventing states from obtaining the capability to deliver nuclear weapons is another focus of nonproliferation. The Missile Technology Control Regime is a multilateral, informal political understanding among 35 member states that seeks to limit the proliferation of missiles and missile technology. The regime was formed in 1987 by the G7 industrialized countries and aims to limit nuclear weapons proliferation by controlling the transfer of missile equipment, complete rocket systems, unmanned air vehicles, and related technology for those systems capable of carrying a 500-kilogram payload at least 300 kilometers.

Nuclear and Non-Nuclear Testing

The first nuclear weapon, a gun-type uranium weapon, was detonated in 1945 without ever being tested. While this demonstrates that testing is not required to develop nuclear weapons, testing can support a country in developing more advanced types and designs of nuclear weapons. All countries that currently possess nuclear weapons have conducted at least one weapons-related nuclear test. There are a number of treaties that limit or ban certain types of nuclear weapons tests. The 1963 Limited Test Ban Treaty bans nuclear weapons testing in the atmosphere, in outer space, and under water. The 1974 Threshold Test Ban Treaty limits the size of underground nuclear tests to 150 kilotons, and the 1976 Peaceful Nuclear Explosion Treaty prohibits the testing of nuclear devices outside of agreed treaty sites.

The capability to detect nuclear weapons tests is paramount to ensuring compliance with these treaties and ensuring that no state can covertly test a nuclear weapon. The Air Force Technical Applications Center (AFTAC) is the sole U.S. organization with the mission to detect and report technical data from foreign nuclear explosions. AFTAC monitors signatory countries’ compliance with these treaties.

The Comprehensive Nuclear-Test-Ban Treaty (CTBT) is a legally binding global ban on nuclear explosive testing; however, it has not been ratified by the United States and is not currently in force. Since 1992, the United States has observed a unilateral moratorium on nuclear explosive testing. The United States does not intend to seek ratification of the CTBT, but it continues to support the CTBT Preparatory Committee as well as the International Monitoring System and the International Data Center. Both AFTAC and the Defense Threat Reduction Agency (DTRA) provide direct support to the CTBT. The U.S. government maintains that it will not resume nuclear explosive testing unless necessary to ensure the safety and effectiveness of the U.S. nuclear arsenal, and calls on all states possessing nuclear weapons to declare or maintain a moratorium on nuclear testing.

Understanding Non-State Threats

Terrorist groups have declared their intent to obtain fissile materials to create a nuclear threat device (NTD), which can be anything from a crude, homemade nuclear device, an improvised nuclear device (IND), a radiological dispersal device (RDD), a radiological exposure device (RED), or a weapon acquired from one of the established nuclear states that has fallen out of state control. The risk of terrorists acquiring nuclear or radiological materials that could be used in a weapon is reduced through numerous interagency programs, including those that enhance partner capabilities to interdict and prosecute nuclear smuggling, deter material support to potential terrorists, and advance nuclear forensics and attribution capabilities, which enable the United States to identify the source of fissile material.

There are a number of generic steps that must be taken to successfully carry out a radiological or nuclear attack. These “nuclear event pathway” steps are illustrated in Figure 11.1.

Figure 11.1
Figure 11.1 Nuclear Event Pathway

Terrorists do not share the same goals or need the same capabilities as states. In addition, they are not bound by international law or nuclear treaties and agreements. For a fabricated nuclear device, weight and size constraints may not be important to a terrorist; unsafe designs may be acceptable, as may hazardous materials and higher dose rates. Finally, a wide variety of delivery methods could be used, with no regard for collateral damage to civilian populations or the terrorists themselves.

A pathway to an attack begins with motivation, planning, and intent. Next, for a credible threat, the acquisition of radiological materials, nuclear materials, nuclear components, or a nuclear device is an essential step. Material acquisition of weapons-usable special nuclear material is the most critical step for a terrorist group, as the enrichment and reprocessing steps that are critical to a nationstate’s program are currently beyond the known capability of terrorist groups.

If successful in acquiring materials, a potential adversary must then design and fabricate an NTD (or be able to use a stolen or procured device), transport and store the device, get it to its intended target, and achieve successful detonation, dispersal, or exposure. There are difficulties associated with every step along this pathway, and there are specific indicators associated with each step that can facilitate the detection and interdiction of an NTD. Failing successful interdiction, rendering the device safe or unusable is the last defense in preventing a nuclear detonation.

In a post-detonation environment, the focus of the NTR mission shifts, in parallel with consequence management actions, to nuclear forensics and ultimately attribution to support prevention of subsequent attacks.

At each step along the pathway, a potential adversary must be successful; that is, failure at any point results in the overall failure of the objective. Therefore, efforts to counter the nuclear threat must only succeed in thwarting a potential adversary at any one point along the pathway to prevent a nuclear event. Additionally, even in the worst-case scenario of a nuclear detonation, there are effective steps to be taken to manage the consequences of such an event and appropriately deal with the perpetrators.

The spectrum of NTR activities against the non-state threat is illustrated in Figure 11.2. The figure highlights activities beginning well before a potential nuclear event. Materials security is the first step in preventing nuclear terrorism and nuclear proliferation. There is a continued need to scrutinize and modify the nuclear fuel cycle to ensure the production of weapons-usable materials is limited and minimize any proliferation risks inherent in the use of nuclear power for peaceful purposes.

Figure 11.2
Figure 11.2 Spectrum of NTR Activities Against the Non-State Threat

The uncertainty involved with identifying specific NTDs remains a significant challenge. When dealing with a potential NTD, it is critical to identify what the device is made of, how it is configured, how it might work, and if it will produce a nuclear yield. As a result, there is no fixed set of NTD concepts or designs, and the United States’ understanding of possibilities continues to evolve. NTDs can be developed from a variety of materials and may be configured with a high level of complexity. In general, less sophisticated devices require more nuclear material and produce lower yields. A crude device tends to be large and bulky, while sophisticated designs are smaller and lighter and achieve greater yields in relation to the mass of the fissile material.

The uncertainties associated with NTDs directly impact the ability to detect, interdict, and render a device safe. It is imperative that the United States continue its work to understand and characterize the full range of potential NTDs, including the characterization of nuclear and explosive materials as well as the range of potential configurations. Figure 11.3 illustrates the relationship between technical understanding of NTD designs and elements of a strong program for NTR.

DoD, especially through DTRA, and NNSA work with domestic and international partners to perform nuclear and explosive materials characterization, device modeling, and simulation analyses to enhance the scientific and technical understanding of NTDs. Additional efforts are spent to identify and discriminate among nuclear and explosive signatures for materials security and to perform diagnostics and threat analyses. Understanding the threat also involves the development of tools, techniques, and procedures to facilitate nuclear device vulnerability exploitation and help to perform render safe functions in a timely and effective manner.

Figure 11.3
Figure 11.3 Understanding the Threat

Actions to Reduce Non-State Nuclear Threats

U.S. strategy to combat the threat of nuclear terrorism encompasses a wide range of activities that comprise a defense-in-depth against current and emerging dangers. Under this multilayered approach, the United States strives to prevent terrorists from obtaining nuclear weapons or weapons-usable materials, technology, and expertise; counter terrorist efforts to acquire, transfer, or employ these assets; and respond to nuclear incidents, by locating and disabling a nuclear device or managing the consequences of a nuclear detonation. Key U.S. efforts under this strategy include:

  • securing nuclear weapons, materials, related technology, and knowledge to prevent their malicious use;
  • enhancing cooperation with allies, partners, and international institutions to combat nuclear terrorism;
  • deterring state support for nuclear terrorism through advanced forensics and attribution capabilities;
  • strengthening defenses against nuclear terrorism to protect the American people and U.S. interests at home and abroad; and
  • enhancing preparedness to mitigate the effects of nuclear incidents.

Numerous departments and agencies within the U.S. government and in the international arena continue their efforts to better characterize the nuclear threat. Work in these areas is divided into categories of material security, detection, nterdiction, render safe, consequence management, nuclear forensics, and attribution.

Material Security

Weapons-usable highly enriched uranium (HEU) and separated plutonium exist in hundreds of locations around the world under varying levels of security. While the large percentage of facilities are under strong, usually military, control with continual monitoring, a significant breach at one of these locations could have an impact that would profoundly change the way the world sees and addresses nuclear terrorism today. Since the early 1990s, there have been multiple instances of collaboration among countries to minimize the threat of nuclear terrorism, with a prime example being the 1991 Nunn-Lugar Cooperative Threat Reduction Act.

The Material Protection, Control, and Accounting (MPC&A) program is part of the NNSA nonproliferation program and seeks to improve the security of nuclear weapons and material accounting within former nuclear sites in Russia and other countries of the former Soviet Union (FSU) that house radiological materials. The United States has funded this program and hopes it will serve as a template for future programs with other countries. The ultimate goal of the program is to improve global nuclear security and ensure that radiological sources are not accessible to illicit markets. Since the program’s inception as part of the DoD Cooperative Threat Reduction (CTR) program, it has secured thousands of tons of weapons-grade nuclear material in the FSU.

Under the auspices of the Nunn-Lugar Act, the United States and Russia worked to build the Mayak storage facility in Russia. The facility was built to enhance security for nuclear material recovered from dismantled nuclear warheads in Russia. With space to permanently store 50,000 containers of weapons-grade plutonium from 12,500 dismantled nuclear warheads, the Mayak facility demonstrates a significant achievement in the reduction of the Russian nuclear stockpile and improved security for nuclear materials.

On July 15, 2006, President George W. Bush and Russian President Vladimir Putin launched the Global Initiative to Combat Nuclear Terrorism (GICNT). The initiative aims to broaden and enhance international partnerships to strengthen global capacity to prevent, detect, and respond to nuclear terrorism. Currently, 88 countries are involved in the initiative. Members work to integrate collective capabilities and resources to strengthen the overall global architecture to combat nuclear terrorism. They bring together experience and expertise from the nonproliferation, counterproliferation, and counterterrorism disciplines, and provide the opportunity for nations to share information and expertise in a voluntary, non-binding framework.

Domestically, DoD and NNSA are responsible for special nuclear material and nuclear weapons in their custody. Additionally, the Federal Bureau of Investigation (FBI) Nuclear Site Security Program requires each FBI field office to establish close liaison with security personnel at critical nuclear facilities, including DoD and NNSA sites as well as commercial nuclear power facilities operating under the Nuclear Regulatory Commission. This program also requires field offices to develop site-specific incident response plans and to exercise those plans with facility security personnel. Lastly, each field office has a designated, full-time special agent for all WMD-related activity, including nuclear threats.


The radiation detection mission is diverse and will not be solved by any single technology or configuration in the near term. The detection and identification of nuclear threats by current passive detection technologies is limited by three factors. First, the size and activity of the radiological sample is directly correlated with detectability. The quantities of interest for nuclear materials can be very small and some fissile materials have minimal radioactive emissions, limiting their detection by passive means. Second, shielding degrades the ability to detect radiological materials. Finally, the distance between the material and the detector limits the ability to passively detect radiological materials. Nuclear radiation, like other forms of electromagnetic radiation, decreases in intensity with the square of distance (i.e., the signal drops by a factor of four when the distance between the nuclear source and detector is doubled).

The detection mission is being addressed in interagency forums to help offset the complexity of the mission and many U.S. government components are involved in improving radiation detection. In 2005, presidential policy established the DHS Domestic Nuclear Detection Office (DNDO) to assist in management and improvement of U.S. capabilities to detect and report unauthorized attempts to import, possess, store, develop, or transport radiological and nuclear material. The Countering Weapons of Mass Destruction Act of 2018 transferred these responsibilities to the DHS Countering Weapons of Mass Destruction Office (DHS/CWMD). DHS/CWMD is responsible for enhancing and coordinating efforts to detect and prevent nuclear and radiological terrorism against the United States. In this role, it is responsible for effective sharing and use of appropriate information generated by the intelligence and counterterrorism communities, law enforcement agencies, and other government agencies as well as foreign governments. As such, DHS/CWMD conducts research, development, testing, and evaluation of detection technologies; acquires systems to implement the domestic portions of the architecture; and coordinates international detection activities. DHS/CWMD also provides support to other U.S. government agencies through the provision of standardized threat assessments, technical support, training, and response protocols. The NNSA Global Material Security Nuclear Smuggling Detection and Deterrence Program to prevent and detect nuclear smuggling also plays a significant role in countering possible terrorist activities involving nuclear weapons or devices.

Detecting Nuclear Threats

While the technical challenges to building advanced designs such as staged nuclear weapons are significant, the relative simplicity of a gun assembly (GA) design raises the possibility non-state actors with sufficient fissile material could assemble a supercritical mass and produce a nuclear detonation using an IND. The best protection from this threat is to prevent terrorists from acquiring nuclear materials for use in an IND. Maintaining close coordination between the science and the operations of countering nuclear threats is paramount.

Fission Yield and Nuclear Forensics

The fission process produces isotopes with a wide range of atomic masses and atomic numbers, though some fission fragments are more likely to be produced than others. Atomic masses follow a characteristic twin-peaked distribution and most of the isotopes produced have atomic masses near 95 and 140. The detailed shape of this fission product yield curve depends on the specific nucleus undergoing fission and on the energy of the neutrons inducing fission. Fission from Pu-239 results in relatively more heavy nuclei than from U-235 as well as higher yields.

These differences in yield can be used by nuclear forensic scientists to provide information about a nuclear device. By measuring the relative quantities of fission fragments after detonation, scientists can construct a yield curve and infer which fissile material was used in the device. This, in turn, may help with attribution efforts.

Detection of Nuclear Material

The same principles of personal protective equipment (PPE), time, distance, and shielding, which protect personnel from radiation, complicate the detection of nuclear materials. Charged particles from radioactive decay (alpha and beta particles) are easily shielded in transport. In most cases, gamma rays and neutrons emitted from shielded sources are comparable with natural background readings at distances greater than 10 meters.

The penetrating power of radiation varies greatly depending on the type of radiation in question. In general, charged particles can be shielded more easily, while neutral particles penetrate matter more deeply. Alpha particles have the least penetrating power and can be stopped by a sheet of paper or human skin. Beta particles are lighter than alpha particles and permeate more deeply, penetrating skin and traveling several feet in air, but are stopped by a fraction of an inch of metal or plastic. Gamma rays are energetic photons that can transfuse matter deeply. These require a layer of dense material, such as lead, for shielding.

Because neutrons are electrically neutral, they interact weakly with matter. Neutrons are absorbed by successively bouncing off light nuclei. As a result, shielding neutron radiation requires thick layers of materials rich in hydrogen, such as water or concrete. Figure 11.4 compares the penetration of various types of radiation.

Figure 11.4
Figure 11.4 Penetrating Power of Various Types of Radiation


Interdiction includes the seizure of materials or technologies that pose a threat to global security. Efforts in this area include research, development, testing, and evaluation of detection and interdiction technologies conducted by many federal agencies. Additional activities in this area include efforts to create exclusion zones, increase surveillance, identify transit routes, monitor choke points and known smuggling routes, sustain nuclear detection programs, and support technological enablers for these efforts. The Nuclear Trafficking Response Group (NTRG) is an interagency body responsible for coordinating the U.S. government response to nuclear and radiological smuggling incidents overseas. The NTRG supports foreign government efforts to secure smuggled material, prosecute those responsible, and develop information on smuggling-related threats.

Presidential policy articulates roles and responsibilities for U.S. government departments and agencies, both within the United States and overseas, and identifies the Attorney General as lead for coordination of law enforcement activities involving terrorist acts. The FBI response is fully coordinated with the DOS, DHS, and NNSA, while DoD provides support to each of the civil authorities, as requested. This process ensures the response is integrated and coordinated. NNSA acts as a cooperating federal agency, bringing assets and deployable technical teams to aid in the overall federal response and can assist, if requested, with the search of an asset or tactical operation. DoD has responsibility for interdicting a nuclear weapon in transit outside the United States. For this reason, DoD maintains the capabilities to interdict a weapon in the maritime, aerial, and terrestrial domains. DoD has built upon current capabilities to ensure that, should the location of a terrorist-controlled IND, RDD, or RED be known, forces can successfully and safely recover the device.

In addition to being responsible for the criminal prosecution of acts of terrorism, the Attorney General is responsible for ensuring the implementation of domestic policies directed at preventing terrorist acts. The execution of this role ensures that individuals within terrorist groups can be prosecuted under U.S. law.

Render Safe

The ability to render a nuclear device4 safe is complex. Each device (IND, RDD, and RED) is unique and requires a distinct approach to be rendered safe. The initial phase for the render safe process is the identification of the device, meaning the determination of which types of materials were used and understanding the composition of the device and how it was designed to work. In the second phase, the responders gather and analyze information as well as take appropriate render safe actions until the weapon is ready for transport. Diagnostics of a nuclear or radiological weapon will help determine render safe procedures and the weapon’s final disposition. The final phase is the disposition of the weapon, during which the radiological material and other components of the weapon are properly transported and stored. DoD and the FBI maintain specific teams trained in rendering safe these types of ordnance.

Within the United States, the FBI holds the responsibility for render safe procedures involving terrorist activity and WMD. As the primary law enforcement agency and lead federal agency for such operations, the FBI may request cooperative assistance from DoD and/or NNSA. DoD, the FBI, and NNSA execute training exercises individually and jointly to streamline the render safe process and to build relationships and share technologies across the U.S. government.

Consequence Management

Post-event consequence management activities are necessary in the event of a successful attack, but also necessary following a smaller-scale event or even a successful render safe mission. National-level guidance, such as the National Response Framework and other documents, outline interagency roles and responsibilities and guide U.S. efforts in response planning, exercises, and training. Consequence management activities include securing the incident site, assessing the dispersal of radioactive material, enhancing first responder capabilities, ensuring availability of decontamination and site remediation resources, providing radiological medical triage capabilities, and increasing population resilience and recovery capabilities. In addition to managing consequences, which minimizes the disastrous effects desired by the adversary, demonstrated preparedness can have a deterrent effect.

The FBI is the lead federal agency for crisis management response (interdiction), while FEMA is the lead federal agency for consequence management. FEMA manages and coordinates any federal consequence management response in support of state and local governments, in accordance with the NRF and the National Incident Management System (NIMS). Additionally, the Homeland Security Act of 2002 requires that specialized NNSA emergency response assets fall under DHS/FEMA operational control when they are deployed in response to a potential nuclear incident in the United States.

NNSA provides scientific and technical personnel and equipment during all aspects of a nuclear or radiological terrorist incident, including consequence management. NNSA capabilities include threat assessment, technical advice, forecasted modeling predictions, radiological medical expertise, and operational support. Deployable capabilities include radiological assessment and monitoring, identification of material, development of federal protective action recommendations, provision of information on the radiological response, hazards assessment, post-incident cleanup, radiological medical expertise, and on-site management and radiological assessment to the public, the White House, members of Congress, and coordinated through the DOS to applicable foreign governments.

Nuclear Forensics, Attribution, and Deterrence

Nuclear forensics provides information outside the scope of traditional forensics on interdicted materials or devices before detonation and on post-detonation signals and debris to support attribution. Attribution is an interagency effort requiring coordination of law enforcement, intelligence, and technical forensics information to allow the U.S. government to determine the source of the material and device as well as its pathway to its target.

The National Technical Nuclear Forensics (NTNF) program assists in identifying material type and origin, potential pathways, and design information. Technical nuclear forensics (TNF) refers to the thorough analysis and characterization of pre- and post-detonation radiological or nuclear materials, devices, and debris, as well as prompt effects from a nuclear detonation. The attribution process merges TNF results with traditional law enforcement and intelligence information to identify those responsible for the planned or actual attack.

The nuclear forensics and attribution capabilities are part of the broader NTR mission within DoD. Knowledge of the NTNF program capabilities can discourage countries from transferring nuclear or radiological materials and devices to non-nuclear states or non-state actors and can encourage countries with nuclear facilities or materials to improve their security. Aside from its necessity in detonation response, the capability also contributes to prevention by providing a viable deterrent.

The NTNF program is an interagency mission drawing on capabilities of the Department of Justice (DOJ), DoD, NNSA, DHS, DOS, and the Office of the Director of National Intelligence (ODNI). Additionally, nuclear forensics provides an important means for the global community to work together in the fight against nuclear terrorism. Because success in this effort is improved with nations acting collaboratively, the U.S. government NTNF community is engaged in a number of bilateral and multilateral activities with foreign partners.

Attribution is a confluence of intelligence, investigative, and forensics information to arrive at the nature, source, perpetrator, and pathway of an attempted or actual attack (see Figure 11.5). This includes rapid and comprehensive coordination of intelligence reporting, law enforcement information, nuclear forensics information, and other relevant data to evaluate an adversary’s capabilities, resources, supporters, and modus operandi. Forensics is the technical and scientific analysis that provides a basis for attribution or exclusion.

Figure 11.5
Figure 11.5 The Attribution Calculus

The United States has stated the importance of holding accountable any state, terrorist group, or other non-state actor that supports or enables terrorist efforts to obtain or employ nuclear devices. It is critical that the United States maintain advanced nuclear forensics capabilities to identify the source of the material used in a nuclear device and continue to improve the ability to attribute the source of a nuclear attack. A terrorist nuclear attack against the United States or its allies would qualify as an “extreme circumstance” under which the United States could consider a nuclear response.

1 “Treaty on the Non-Proliferation of Nuclear Weapons,” United National Office for Disarmament Affairs, accessed April 2019,

2 This has been a longstanding policy of the United States that was most recently reiterated in the 2018 Nuclear Posture Review.

3 “Restricted Data” is a proper noun referring to a category of classified information relating to nuclear weapons. See Chapter 18: Classification for more information.

4 Device and weapon are being used interchangeably in this chapter.