There is an ongoing debate about just how much of a setback Iran’s nuclear program experienced during its recent conflict with Israel and the United States. But there is little doubt that Iran already has sufficient nuclear material to make a radiological weapon known as a dirty bomb. The question is whether it has sufficient strategic motivation to attempt building—and using—such a device.
Michael Rubin, a former U.S. Defense Department official who is now a senior fellow at the American Enterprise Institute, warned of the possibility in a recent op-ed. If Iran’s supreme leader, Ayatollah Ali Khamanei, “wants to make good on his threats, his next step will likely be to hit Israel with dirty bombs to spread radiation over large sections of its urban areas,” he wrote.
In a June interview with NPR, Mark Warner, the leading Democrat on the Senate Intelligence Committee, expressed his concerns: “How do we make sure that there’s not Iran racing now to a dirty bomb? These are questions that we and frankly, the American people, deserve answers to.”
A dirty bomb is not a nuclear weapon but rather a “radiological dispersal device” that consists of a standard explosive, such as dynamite, in conjunction with a radioactive material, such as cesium-137, which is commonly used in cancer treatment; cobalt-60, in industrial radiography; and others that are used in Iran, as in most modern states, for medical and industrial use.
Such a weapon would spread vast panic were it to be used. But every expert that Foreign Policy spoke with said it would also label Iran as a pariah perhaps even among its allies, including Moscow and Beijing. Andreas Krieg, a senior lecturer at King’s College London’s School of Security Studies, said that if Iran were to build and deploy one, it would amount to “strategic suicide.”
At The Hague last month, U.S. President Donald Trump expressed his personal assessment that Iran was done with its nuclear program after the U.S. bombing of key nuclear sites. Yet Iran hasn’t yet said anything that confirms that belief. It hasn’t yet agreed to giving up its nuclear program or reducing uranium enrichment to zero. However, Trump has threatened that if Iran does not abandon its nuclear ambitions, attacks on its nuclear infrastructure may resume.
In such a scenario—and especially if the attacks escalate to involve the threat of regime change or to jeopardize the life of Khamanei—it is possible, if unlikely, that Iranian strategists may consider it worthwhile to build a dirty bomb. This could be a matter of simply combining its highly enriched uranium with conventional explosives. (Although other, less valuable radioactive materials derived from medical and industrial sources are more easily available and could be used instead.)
Iran would then need to determine how to deploy the bomb. Some experts suggest that Iran could use such a bomb against Iran via proxies in the Palestinian territories or transport it to the United States through Hezbollah’s network in Latin American countries, to Persian Gulf countries through their vast shared coastlines, or to Europe though shipping containers or even via land routes through the Eastern Balkans.
A dirty bomb would not qualify as a weapon of mass destruction (WMD), but its potential for causing disruption is vast. Experts said the extent of the damage depends on how much conventional explosive it is packed with, not so much on the radioactive material, since the explosion itself does not undergo fission. But the resulting psychological terror triggered by its dispersal of radioactive material is difficult to measure.
“If you would detonate this device, you would have effects of a conventional bomb, which could be very bad of course, but the radioactivity will be over a very small area and won’t cause casualties,” said Pavel Podvig, a senior researcher at the United Nations Institute for Disarmament Research. “But contamination and, yes, panic.” The effects could be mass hysteria and economic disruption. Contamination of property could result in evacuation and be time-consuming and expensive to clean. Disinformation online could further exacerbate panic.
“A nuclear bomb creates an explosion that is millions of times more powerful than that of a dirty bomb. The cloud of radiation from a nuclear bomb could spread tens to hundreds of square miles, whereas a dirty bomb’s radiation could be dispersed within a few blocks or miles of the explosion,” according to the U.S. Nuclear Regulatory Commission.
“A dirty bomb isn’t a WMD,” said Marion Messmer, an expert in nuclear weapons policy at Chatham House. “WMDs are called such because of the severe impact they would have. … A nuclear weapon destabilizes and unleashes destruction. The radioactivity is much higher than just scattering some radioactive material,” as in a dirty bomb. “The scope and scale of WMDs is much bigger—whether nuclear, biological, or chemical weapons.”
Experts said the talk around the possibility of Iran making and using a dirty bomb is causing more stress and unwittingly extending leverage to the Iranian regime, which was weakened by Israeli-U.S. attacks. They added that deploying such a weapon would inflict a heavy reputational, political, and military cost on Iran, which presents itself as a reasonable and righteous nation fighting merely for its sovereign rights.
“Iran can build a dirty bomb—so can Germany. Any modern state can,” Messmer said. “But my question is that why are we assuming it wants to?” She added that Iran is currently contemplating its options and is most likely to go for a secret program to build a nuclear deterrent, rather than a weapon associated with terrorist groups.
Others said Iran could deploy its proxy groups that have been weakened but survived Israeli attacks or even potentially create a new group to transport and explode a dirty bomb, but any such activity would be traceable, especially as some of the top intelligence agencies are watching Iran’s every move. A link would eventually be established and likely invite a much wider military response from the United States.
Moreover, use of such a weapon could instigate a regional crisis as the Gulf states feel threatened and, despite China-mediated rapprochement between Riyadh and Tehran, exacerbate anxieties. Even friends in the region such as Qatar and favorable constituencies in Iraq and Lebanon could turn against Iran, viewing it as a step too far or panicking if radioactivity spills over into Arab territory. At home, the fear of a return of war, and more punitive sanctions, may worsen the regime’s standing and encourage people to take to the streets.
In the risk-benefit calculus, a dirty bomb fares poorly. It is a losing proposition for a country that has managed to avert a full-blown war and decimation at the hands of a superior military power—in some part owing to the fear that if a country of 92 million is destabilized, it would have far-reaching consequences.
The main reason, perhaps, that the Iranian regime isn’t looking at a dirty bomb yet is because more than ever before, it sees an actual nuclear bomb as its only credible deterrent. It sees North Korea as an example to follow, rather than Libya’s Muammar al-Qaddafi, who got rid of his nuclear program and was attacked by the West and ultimately overthrown and killed.
It remains possible that rather than fall back on the idea of a dirty bomb, Iran could build a conventional nuclear weapon using the stocks of enriched uranium it already possesses—assuming it successfully hid them from Israeli and U.S. attack. Although 90 percent enrichment is often mentioned as the level required to turn uranium into a workable device, that refers to what is needed for a sophisticated, moldable missile warhead. A more old-fashioned, inevitably much larger conventional nuclear bomb could be built out of the stocks of 60 percent enriched uranium Iran already has.