In the weeks after September 11, while the nation was still grappling with the trauma of the attacks, U.S. leaders confronted the possibility that an even more unimaginable horror was unfolding before them. In October 2001, the CIA director informed the president and other senior officials that a source, code-named “Dragonfire,” had confided that al-Qaeda, which had been entertaining thoughts of nuclear terrorism since the mid-1990s, had smuggled a 10-kiloton nuclear device into the United States and planned to detonate it New York City. At the president’s direction, scientists from the Department of Energy’s Nuclear Emergency Support Team (NEST) quietly scoured the city for the device as part of operation “Radiant Angel” until the CIA learned its initial report was erroneous. Yet in the years that followed, the fear that the world’s most potent weapons would fall into the hands of fanatics would remain a central preoccupation at the highest levels of the U.S. government.
In the first presidential campaign after 9/11, both major party candidates agreed during a debate that nuclear terrorism was “the single most serious threat to the national security of the United States.” Moreover, the prevailing wisdom in the national security community was that the likelihood of such an attack was high. In 2005, Sen. Richard Lugar (R-Ind.) conducted a survey of experts to elicit their best estimate of the probability of a nuclear attack in the next 10 years, and the average response was 29.2 percent. Almost 80 percent indicated that the attack was more likely to be carried out by terrorists than a nation-state. The following year, scholar Matthew Bunn devised a mathematical model to quantify the probability of an act of nuclear terrorism, which coincidentally suggested a 29 percent likelihood of attack within the next decade.
Mercifully, no such tragedy has occurred, and the haunting question we must ask ourselves is, Why not? Although there may be a temptation to chalk up earlier dire predictions to alarmism, a more compelling explanation is that the U.S. government simply took to heart its vulnerability to nuclear terrorism and responded accordingly. Even prior to 9/11, the United States and many of its international partners had begun enacting an extraordinary range of policies that dramatically reduced the threat of nuclear terrorism. These efforts have addressed both sides of the supply and demand equation, reducing access to the materials and technology needed to build a nuclear device and methodically targeting the terrorists who covet them.
Simply put, the United States has been systematic in disrupting or neutralizing al-Qaeda’s and ISIS’ leadership, as well as specialists in logistics, bombmaking, and other technical disciplines with relevance to weapons of mass destruction (WMD). A sophisticated global intelligence apparatus was erected to monitor terrorists’ communications and activities and disrupt their financing, training, and operational plots. The United States placed particular emphasis on preventing terrorists from acquiring the knowledge and infrastructure needed to produce WMD. That terrorist attacks have been limited in recent years to car bombs, small arms, and even running people over with trucks can be explained in part by the fact that we have so thoroughly decimated their capacity to conduct more sophisticated operations.
On the supply side, U.S. initiatives to secure vulnerable nuclear weapons and materials date back more than 40 years. First begun in earnest with the Cooperative Threat Reduction program in the states of the former Soviet Union, one such operation was Project Sapphire, in which the United States and Kazakhstan cooperated in 1994 to remove more than a half-ton of highly enriched uranium (HEU) from a poorly guarded warehouse. These efforts expanded to a much larger number of countries under former President Obama’s Nuclear Security Summit process. To date the United States and its foreign partners have removed, eliminated, downblended, or confirmed the disposition of over 500,000 kilograms of plutonium and HEU – the indispensable ingredients of a nuclear weapon – from 48 countries and Taiwan. We have also converted over 100 research reactors and isotope production facilities from the use of HEU to low enriched uranium or verified their shutdown altogether. The United States has also made major investments to upgrade the security of foreign nuclear facilities, furnishing security system upgrades, underwriting insider threat mitigation programs, enhancing transportation security, and offering training to strengthen regulatory regimes, cybersecurity, and overall security culture.
Notwithstanding these efforts, however, it cannot be excluded that the building blocks of a nuclear device will somehow fall into the hands of terrorists. Weapons-usable nuclear material has been interdicted on roughly two dozen occasions since the 1990s, and we must assume some quantity of this material exists outside of regulatory control. Consequently, the United States has deployed an array of radiation detectors worldwide to identify and interdict smuggled nuclear weapons and materials. More than 60 countries have received such equipment, as well as training and technical assistance to counter nuclear smuggling. Some 57,000 radiation detectors have also been distributed domestically, ranging from static portal monitors that scan cargo at ports-of-entry to mobile and handheld devices operating at border crossings and within the United States.
“Weapons-usable nuclear material has been interdicted on roughly two dozen occasions since the 1990s, and we must assume some quantity of this material exists outside of regulatory control”
As a last line of defense against nuclear terrorism, the United States maintains a suite of counter-WMD capabilities to search for, diagnose, and defeat nuclear devices on its own soil. In particular, highly trained teams in more than a dozen major cities are equipped to respond rapidly to nuclear threats, using advanced tools to image a threat device and take decisive action to protect public safety. Additionally, aerial and ground-based NEST assets are used to protect major public events such as the presidential inauguration and Super Bowl by detecting radiation anomalies. Expanded employment of these capabilities represents a dramatic improvement over the U.S. posture at the time of the 9/11 attacks.
In short, the nuclear terrorism threat appears far less menacing today than it did in the fall of 2001. Various attempts by al-Qaeda and other terrorist groups to achieve a nuclear capability, we now know, made little progress. In all likelihood, terrorists have concluded that the considerable resources and technical skill needed to construct a nuclear device are simply beyond their capabilities, and nuclear security enhancements have deterred them from attempting to acquire nuclear material in the first place. Yet, as it is exceptionally difficult to prove a negative, the United States cannot rest on its laurels and assume these conditions will hold. Rather, we must maintain the intelligence community’s focus on WMD terrorism and sustain a robust nuclear counterterrorism and incident response posture in perpetuity.
Although the United States has made tremendous progress to protect weapons-usable nuclear material from outright theft, we cannot discount the possibility that a hostile government or corrupt insiders might provide such material to terrorists. To deter states from facilitating nuclear terrorism, the United States has invested in nuclear forensic capabilities to attribute the source of any material found outside of regulatory control or used in a terrorist attack. These scientific tools underpin the credibility of U.S. threats to retaliate against any state sponsors of nuclear terrorism.
Here there is much work to be done. Beyond improving the speed of forensics analysis, additional investments are required in scientific disciplines that would allow the United States to better determine the enrichment processes used to produce the nuclear material used in a terrorist device, which can aid in attribution. The U.S government must also foster global confidence in its forensic capabilities, in part by pursuing the establishment of scientific data collection methodologies that are internationally agreed upon before a nuclear incident occurs.
Additionally, efforts to secure nuclear material around the world have succeeded only where the political will exists to do so, and modest vulnerabilities persist. As of 2021, there are still nearly 40 states party to the amended Convention on the Physical Protection of Nuclear Material – the bedrock of the international nuclear security regime – that have not yet ratified the Amendment. Adopted in 2005 to expand the original requirements for protecting nuclear material during international transport, the Amendment adds protections for this material in domestic use, storage, and transport. Achieving universal ratification of the Amendment, as well as ensuring consistent implementation of its provisions, is crucial to reducing any remaining vulnerability of nuclear materials worldwide.
Finally, several countries that possess large stocks of weapons-usable nuclear material have rebuffed international entreaties to eliminate excess material or make security improvements for materials that remain, and such material continues to accumulate for both military and civil purposes around the world. Several states have evinced interest in enrichment and reprocessing technologies, and global competition in the commercial nuclear sector may incentivize suppliers with more elastic nonproliferation standards to service this demand. Absent ironclad nonproliferation safeguards, these trends threaten to reverse hard-won progress on nuclear security and nonproliferation since the end of the Cold War.
Although the national security commentariat has correctly shifted its attention to the resumption of great power competition, attentiveness to the threat of nuclear terrorism must not be the casualty of a zero-sum allocation of national security bandwidth. The mere knowledge that nuclear weapons can be built ensures that active measures to prevent terrorists from obtaining them will always be necessary, and protecting fissile material from malicious use is an imperative that will simply never go away. In all likelihood the worst nuclear fears of the post-9/11 era have not come to pass because of the nuclear security and counterterrorism initiatives launched in the mid-1990s, many of which continue to this day. If our success in preventing nuclear terrorism is to continue, the United States and its international partners must remain committed to keeping nuclear material beyond the reach of terrorists and detecting, disrupting, and responding to nuclear threats as they emerge.