Why the World Should Still Worry About Dirty Bombs

In the years after the 9/11 attacks, a new threat loomed large in the minds of policymakers and the public: the dirty bomb. This term describes a radiological weapon that used an explosive to disperse radioactive material over a limited area. A dirty bomb is far less powerful than a nuclear bomb, but it is easier and cheaper to assemble and can cause tremendous panic and disruption. Many analysts feared that terrorist groups would seek to develop and use such weapons: in 2002, U.S. officials announced the detention of Jose Padilla, an American citizen and alleged al Qaeda operative who they insisted intended to detonate a dirty bomb in the United States. Since then, several governments in Europe have claimed to have foiled similar plots by terrorist groups.

But visions of dirty bombs and radiological terrorism obscured the fact that the threat from radiological weapons was not limited to terrorist groups. Indeed, for decades, major countries including the United States and the Soviet Union pioneered the development of these weapons. And now, as the norm against nuclear weapons is weakening and tensions between great powers mount, there is reason to worry that the dangers posed by radiological arms proliferation may be growing again.

In the past, at least five states expressed interest in weapons designed to disperse radioactive material without a nuclear detonation. Four states actively pursued them, and three—Iraq, the Soviet Union, and the United States—tested them on multiple occasions before ultimately choosing not to deploy them. The largely obscure history of the development of radiological weaponry helps to explain its appeal, especially in the context of rising international hostilities, a breakdown in nuclear arms control, and a loss of faith in the credibility of security assurances.

Russian disinformation about a purported covert Ukrainian radiological weapons program has brought renewed attention to the issue. Russia’s war against Ukraine and the attendant escalation in great-power competition have eroded the taboo against nuclear weapons use and undermined the international nonproliferation regime. Additional states may consider the possible deterrent benefits of possessing nuclear arms or, if the costs of acquiring such weapons are prohibitive, other nonconventional weapons. For these states, radiological weapons may appear a more viable option, something akin to “a poor man’s nuclear weapon.” Although U.S.-led diplomatic efforts are now underway to ban them, radiological weapons are not prohibited under international law, which could encourage states to seek them out. Two decades ago, policymakers were haunted by visions of dirty bombs in the hands of terrorists. In the near future, however, they may have to grapple with the more dangerous possibility that states will once again turn to these lethal weapons.

Death dust

Although shrouded in secrecy and largely ignored by both scholars and diplomats, the origins of the pursuit of radiological weapons by states can be traced to World War II. Unsurprisingly, the first two countries to explore these capabilities were also the first two to develop nuclear weapons. In October 1940, a pair of Soviet mathematicians submitted a proposal to the Soviet Union’s inventions bureau on the “use of uranium as an explosive and poisoning substance.” In May of the following year, the initial report of the U.S. National Academy of Sciences’ Advisory Committee on Uranium highlighted the “production of violently radioactive materials” to be carried by airplanes and dispersed over enemy territory as one of three possible military uses of atomic fission.

Within a matter of years, these proposals and reports had turned into something more substantial. Starting in 1949, the U.S. Army’s Chemical Corps oversaw dozens of atmospheric tests of prototypes for radiological munitions. Similarly, the Soviet Union conducted tests of various munitions containing radioactive waste in the mid-1950s. These included experiments on live animals, including rabbits, dogs, and mice, and, inadvertently, on the humans staging the tests themselves.

At virtually the same time, the United Kingdom also began to explore the military potential of radiological weapons. These preliminary investigations led to a more substantial British developmental effort, but by the autumn of 1953, about one year after the country’s first nuclear weapons detonation, its radiological arms program had for all practical purposes been abandoned. There is also circumstantial evidence that in the early 1960s, Egypt flirted with the idea of developing radiological artillery shells and sought to import radioactive isotopes to that end. Two decades later, Iraq undertook a far more serious program, which led to the development and testing of radiological weapons toward the end of its war with Iran in the 1980s.

The rise and demise of radiological weapons

The circumstances differed, but none of these efforts led to the mass production or deployment of radiological weapons. Why, then, did countries want to develop this capability in the first place, and why did they all ultimately decide to abandon these programs?

States were principally motivated to seek radiological weapons for security reasons. In both the United States and, to a lesser extent, the United Kingdom, concerns that Nazi Germany was pursuing radiological weapons prompted explorations of their military potential. In the Soviet Union, meanwhile, knowledge of the United States’ radiological weapons activities—provided, in part, by spies active in the British nuclear weapons program—generated high-level support for the establishment of a Soviet program.

Iraq sought these weapons for tactical reasons during its war with Iran. Specifically, Iraqi leaders thought radiological weapons could be useful in disrupting “human wave” attacks in which Iran hurled massed ranks of infantrymen at Iraqi positions. In contrast to the substantial documentary evidence available about the Iraqi program, much less is known about Egypt’s short-lived flirtation with radiological weapons. Nevertheless, it appears that after the revelation in 1960 that Israel was building its Dimona nuclear reactor in the Negev desert, Egypt sought ways to match and counter Israeli military innovations, in part by experimenting with radiological artillery shells.

In none of the five cases, however, did external threats or internal drivers prove sufficient to move radiological weapons from experimentation or testing to mass production and deployment. Instead, radiological weapons lost traction—and budgetary support—in Washington, Moscow, and London as policymakers in those capitals placed a greater emphasis on developing nuclear weapons, especially hydrogen bombs. In Iraq, the Soviet Union, the United Kingdom, and the United States, the attention of leaders shifted to chemical weapons, which were judged to be more cost-effective.

But perhaps the biggest factor accounting for the demise of radiological weapons was their technological limitations. The weapons could not deliver what their advocates promised. In some cases, it proved too difficult or expensive to produce the sources of radiation from which the weapons were made. Especially challenging were very specific military requirements regarding the half-life of the radioisotopes that would be dispersed by the weapons and the intensity of radioactivity emitted. In other instances, the risks associated with the production, transportation, testing, and delivery of radiological weapons were regarded as outweighing their utility on the battlefield. Over time, the enthusiasm many states had for the weapons waned and ultimately disappeared.

IN SEARCH OF A DEAL

The war in Ukraine has revived interest in the risks of radiological weapons. Shortly after Russia’s invasion in February 2022, Russian media began to disseminate unsubstantiated claims that Russian forces had interrupted a Ukrainian radiological weapons program that some propagandists asserted was based at the defunct Chernobyl nuclear power station. Russia’s subsequent seizure of the Zaporizhzhia nuclear power plant and its shelling of other nuclear facilities in Ukraine raised the specter of the unintended dispersal of radioactive material in a fashion that might have resembled the battlefield effects of radiological weapons.

Ironically, the Soviet Union—along with the United States—had led the initial effort to negotiate a ban on radiological warfare. A draft convention submitted to the Committee on Disarmament—the predecessor to the current Conference on Disarmament, a 65-member multilateral forum based in Geneva—by the two superpowers in 1979 specified that parties to the accord would agree not to develop, produce, stockpile, otherwise acquire or use radiological weapons. Consensus could not be reached, however, because delegations found its scope to be too narrow. (It did not include radiation emitted by nuclear explosions.) What is more, many governments were simply not convinced of the importance of radiological weapons.

It is significant, therefore, that in October 2023, the United States and 38 co-sponsors introduced a remarkably similar draft resolution on radiological weapons at the UN General Assembly. This resolution called on all states not to use radiological weapons and to refrain from developing, producing, or stockpiling devices or materials for use in such weapons. In addition, it urged the Conference on Disarmament to commence negotiations that would result in a prohibition of the use of radiological weapons by states. Although some adversaries of the United States opposed the draft resolution, its final version was adopted by a vote of 159 to 5 with 13 abstentions. (The five naysayers were Belarus, Iran, North Korea, Russia, and Syria. China abstained.)

The war in Ukraine has revived interest in the risks of radiological weapons.

This overwhelming vote in favor of the U.S.-led initiative does not necessarily augur a successful prohibition of radiological weapons. UN General Assembly resolutions are mostly nonbinding and may not spur any meaningful action. Most states do not have well-formed views on radiological weapons. There is also considerable skepticism about the timing of the U.S. initiative and why it was introduced without greater consultation.

Some diplomats, for example, see the initiative as a move to embarrass Russia after its bogus allegations about Ukrainian radiological activities. Many states also question what Washington expects to accomplish at the Conference on Disarmament, which is the sole multilateral negotiating forum on that issue but has been paralyzed for decades. Other states object to the resolution’s emphasis on banning the use of radiological weapons rather than focusing equally on limiting the development, production, and stockpiling of materials that can be used in such devices. A senior diplomat from one state that voted in favor of the resolution raised an interesting question shortly after the vote about what prompted the resolution. Was there new intelligence to suggest that some states were considering the launch of radiological weapons programs?

U.S. officials have yet to respond to the question, but they believe this effort is long overdue. The recent UN vote has convinced them that banning radiological weapons has broad support. The test will now come at the Conference on Disarmament, where prospects for the accord are dim: the body’s consensus-based decision-making process has long stalled negotiations, and several opponents of the U.S. initiative, including Iran and Russia, could exercise a veto. If talks founder there, Washington might support commissioning an international group of government experts who would assess the dangers posed by radiological weapons and make recommendations about how to prevent or mitigate these risks. They could in turn recommend legally binding restraints on the production and use of radiological weapons, as well as the adoption of nonproliferation and nonuse commitments, the creation of radiological weapons-free zones, and the fostering of a taboo against radiological weapons through civil society engagement and public education.

Although these steps could help mitigate the risks posed by radiological weapons, their implementation relies on like-minded states. With little certainty that this will transpire, shedding more light on the impediments faced by past would-be radiological weapons proliferators could discourage new states from investing in them in the first place.