Iran could still build a dirty bomb – but it would spell disaster for the regime

Iran may still possess the ability to build a “dirty bomb” even after the United States struck its key nuclear sites — but using such a weapon would be “strategic suicide” for the regime, experts have said.

A dirty bomb or “radiological dispersal device” combines conventional explosives with radioactive material rather than being an actual nuclear weapon.

The US conducted precision bunker-buster strikes on Iran’s key nuclear sites – Fordo and Natanz uranium enrichment sites and the Isfahan research centre at the weekend, aiming to delay Tehran’s nuclear programme by destroying critical infrastructure.

However, a leaked report from the Pentagon’s Defence Intelligence Agency suggests that the strikes did not destroy the sites and likely set back Iran’s nuclear programme by only a few months.

Intelligence suggests that over 400 kilograms of uranium enriched to 60 per cent purity was quietly moved out of the Fordo site before it was hit — an amount sufficient for about nine nuclear warheads.

David Albright, president and founder of the Institute for Science and International Security, has also pointed to intelligence evidence that more enriched uranium stocks were in the rubble of the damaged nuclear sites than believed previously.

How would a dirty bomb be assembled? 

Theoretically, Iran retains the technical capacity to build a crude radiological dispersal device because their civilian nuclear infrastructure provides access to isotopes like cobalt-60, caesium-137, and iridium-192 from medical and industrial sources, according to Dr Andreas Krieg, a senior lecturer at the School of Security Studies at King’s College London, Royal College of Defence Studies and fellow at the Institute of Middle Eastern Studies.

Technicians work inside of a uranium conversion facility producing unit March 30, 2005 just outside the city of Isfahan (Photo: Getty Images)

Technical knowledge gained from its missile and drone programmes would support the development of a possible bomb, he said.

“While its main nuclear facilities have been damaged, underground labs and dispersed storage sites may still hold usable material,” Dr Krieg said, adding that “assembling a viable dirty bomb with significant dispersal impact involves logistical, safety, and secrecy challenges”.

However, John Erath, senior policy director at the Washington, DC think-tank, the Centre for Arms Control and Non-Proliferation, points out that if Iran were considering building a dirty bomb, “it’s kind of wasting a lot of enrichment”.

He added: “It would, in theory, potentially put a lot of radiation out in the atmosphere and potentially make people sick over a wide area. So it exists mostly in theory. It’s highly impractical and a little bit difficult to do in practice.”

Dr Marion Messmer, an expert in nuclear weapons policy at the Chatham House think-tank in London, said that although building a dirty bomb was possible for Iran, it would be “a waste” when Iran’s goal is a strategic nuclear arsenal.

‘Strategic suicide for Iran’

Regardless of Iran’s capability to build such a weapon, experts are united in saying that doing so would be hugely risky for Tehran itself, to the point it would be “strategic suicide”.

“Iran is highly unlikely to deploy a dirty bomb in Israel or any foreign country. The costs — political, military, and reputational — would be catastrophic,” said Dr Krieg.

Although a smuggled device could theoretically be used via one of Iran’s proxies, like Hezbollah, “the risk of detection, attribution, and retaliation would be enormous”, he added.

“Iran has historically prioritised strategic ambiguity and deniability. A dirty bomb attack would eliminate those buffers, triggering massive international retaliation and risking regime collapse.”

“Deploying a dirty bomb — even for demonstration — would be unprecedented and strategically reckless,” Dr Krieg continued. If used against a target, “it would cross a major threshold, provoking massive retaliation and possibly unifying global powers,” including China and Russia, against Tehran.

In the region, this would likely unsettle the Gulf, bring an end to mediation attempts by Qatar or Oman, and deepen Iran’s isolation. It might also trigger military action or provide grounds for regime change, Dr Krieg noted.

He continued: “Domestically, the blowback would include economic collapse, sanctions, and possible civil unrest. Even a symbolic detonation would carry high reputational costs and signal desperation, not strength.

“Dirty bombs offer little military utility; their main effect is psychological. Iran already has more effective tools — ballistic missiles, drones, and cyber operations — to project power and retaliate without crossing red lines.”

Furthermore, “a dirty bomb’s traceability removes plausible deniability, a cornerstone of Iran’s asymmetric strategy. For these reasons, the weapon is theoretically possible but practically unusable,” he said. “Using a dirty bomb would be strategic suicide for Iran.”

Could a dirty bomb be used for other purposes?

A dirty bomb could potentially be used for other purposes, “but only in extremely narrow contexts,” Dr Krieg said.

One possibility would be for Iran to detonate a bomb in a remote or controlled area for the purposes of demonstration or signalling rather than for use in warfare or terrorism.

“Iran might consider a controlled detonation as a deterrent signal, demonstrating its capability without direct harm — akin to a nuclear test,” he said.

“However, even that would carry significant risks, including diplomatic fallout, regional panic and intensified sanctions. Dirty bombs are not useful on the battlefield and are unlikely to yield strategic gains. Their main utility is psychological, and Iran’s leaders know that any actual use would trigger responses far beyond what they could control.”

Numerous references to dirty bombs have appeared in recent history, but no country has actually used one in a military conflict.

Expertise gained from Iran’s missile and drone programs could help enable bomb development (Photo: Iranian Presidency/Handout/Anadolu Agency/Getty)

“The most notable case was in 1995, when Chechen rebels planted a caesium-137 device in Moscow that was discovered before detonation. It served more as a psychological threat than a weapon,” said Dr Krieg.

Other dirty bomb terror plots, including the José Padilla case in the US, were foiled. Padilla, originally from Chicago, was arrested in 2002 on suspicion of plotting an attack and labelled by US authorities as an “enemy combatant”. After years of legal battles, Padilla was eventually convicted on terrorism charges.

Nuclear programme back in months

The main question when it comes to Iranian weaponry, experts say, is how much damage was actually done to Iran’s nuclear programme — and how much material may have been preserved.

Regarding the missing 400 kilograms of highly enriched uranium, Pavel Podvig, a senior researcher at the United Nations Institute for Disarmament Research (UNIDIR), said the 60 per cent enrichment of was still enough for “reasonably good weapon material”.

“The critical mass is larger,” he explained, “but it can still be used in a weapon, theoretically.”

While Iran has successfully enriched uranium through centrifuge cascades, Podvig stressed that Iran was still a “long way” off producing warheads. He said Iran would need to convert its current stash of uranium hexafluoride into metal, or uranium metal manufacture, and assemble a complete warhead.

“And then you need to figure out the delivery system,” he said. “So it’s a long way off, and as far as we know, Iran doesn’t have the other components that it needs,” Podvig added, to construct complete nuclear weapons.

Satellite image provided by Maxar Technologies shows damage at the Fordo enrichment facility in Iran after US strikes on June 22 (Photo: Maxar Technologies/AP)

Despite Iran lacking other capabilities, he suggested that it may be able to get its nuclear programme back up and running with “several months to a couple of years”, as the leaked Pentagon intelligence report has suggested.

Podvig said this would depend on whether Iran chooses to pull out of the Nuclear Proliferation Treaty, as it has threatened, while at the same time saying it would not develop nuclear weapons if it did.

Dr Messmer suggested that the only “credible deterrence” for Iran was now a nuclear arsenal following the devastating strikes.

“I’d caution against assuming that it’s a foregone conclusion that Iran will develop a fully blown nuclear weapons programme, though it is likely that nuclear weapons will be seen as the only credible deterrence capability for Iran after this.”

Darya Dolzikova​, senior research fellow in Proliferation and Nuclear Policy at the Royal United Services Institute (Rusi) in London, said: “We didn’t have a complete picture of whether Iran had all the necessary pieces to produce a nuclear weapon before these attacks; that assessment is even harder to make now.

“It is certainly an over-statement to call the Iranian programme ‘obliterated’ but it is true that a number of key facilities – including those that would allow it to enrich uranium or produce uranium metal for the development of a nuclear warhead have been severely damaged or, in some instances, destroyed,” she said.

“What remains unclear is the precise extent of that damage and what materials, equipment and capabilities have been salvaged.”