What is Iran’s Fordow nuclear facility that the US has bombed?

The United States bombed three major Iranian nuclear facilities early on Sunday, with President Donald Trump claiming that they had been “totally obliterated”.

The targets included Iran’s main uranium enrichment site at Natanz, which Israel had also struck on June 13 at the start of its current bombing campaign on Iran; a nuclear complex in Isfahan that Israel had also hit previously, and Fordow, home to another facility where nuclear fuel can be purified.

While Israeli missiles had also hit Fordow, on June 13, the facility – unlike Natanz and Isfahan – had not suffered any real damage in the earlier attack, according to the United Nations nuclear watchdog, the International Atomic Energy Agency (IAEA). Fordow is deep underground and much harder to access than Natanz.

Trump had indicated in recent days that he was considering Israeli requests to help in the bombing of Fordow, with weapons that its Middle Eastern ally does not have.

Then, he gave himself a two-week timeline within which he said he would decide whether to attack Iran. On Sunday, it became clear that he had made up his mind. His answer: Yes.

“FORDOW IS GONE”, said a social media post that Trump shared on his Truth Social platform after the strikes.

So what is known about the Fordow plant, and why was it at the heart of US considerations over whether to join Israel’s military strikes against Iran?

So what is known about the Fordow plant, and can it be destroyed?

What is the Fordow nuclear facility?

Fordow was originally built as a military facility for the Islamic Revolutionary Guard Corps. It is located 30km (18.5 miles) northeast of the city of Qom in northwestern Iran, and is reportedly hundreds of metres inside a mountain.

Iran disclosed its conversion to a nuclear site in a letter to the International Atomic Energy Agency (IAEA), the global nuclear watchdog, on September 21, 2009, after learning that Western intelligence services already knew about it.

Days later, the US, United Kingdom and France confirmed publicly that they were indeed aware of a secret fuel enrichment plant at Fordow. Conclusive intelligence that Iran was trying to install 3,000 centrifuges at the site was gathered in early 2009. By September, Fordow’s conversion was nearing completion.

Fordow is the only Iranian facility at which IAEA inspectors have found particles of uranium purified to near weapons-grade purity. That happened during an unannounced inspection in 2023.

The site is designed to hold up to 2,976 spinning centrifuges, the IAEA said, a fraction of the capacity for the approximately 50,000 in Natanz, Iran’s main nuclear site, which Israel struck the day it began its air strikes on Iran.

Was Fordow destroyed in the US attack on Sunday?

We do not independently know.

While Trump has claimed that the facility was destroyed, Iran has so far not officially described the extent of damage at the site, though it has confirmed the hit.

IRNA, Iran’s official news agency, said that residents near Fordow “did not feel any signs of a major explosion” after the US strike.

“Conditions in the area were completely normal,” the agency said. “Further details of the incident will be reported by official experts.”

The Crisis Management Headquarters in the province of Qom, where Fordow is located, issued a statement saying that “there is no danger to the people of Qom and the surrounding area”.

Earlier, Mahdi Mohammadi, an adviser to Iran’s Parliament speaker, Mohammad Bagher Ghalibaf, said that Iran had moved its nuclear infrastructure from Fordow in anticipation of an attack. “The site has long been evacuated and has not suffered any irreversible damage in the attack,” Mohammadi wrote in a social media post.

On June 16, after the Israeli attack, IAEA Director General Rafael Grossi said: “No damage has been seen at the site of the Fordow Fuel Enrichment Plant or at the Khondab heavy water reactor, which is under construction.”

What is known about nuclear development at Fordow?

After the presence of the Fordow site became public in 2009, the US and Iran began their first direct talks in 30 years.

“The goal for these negotiations is to reach a mutually agreed long-term comprehensive solution that would ensure Iran’s nuclear programme will be exclusively peaceful,” the IAEA said.

While Iran submitted information on Fordow to the IAEA in October 2009, it refused to submit a timeline for its design, construction and original purposes, saying that information lay outside its reporting obligations under the safeguards agreement with the UN agency.

Two years later, in September 2011, then-IAEA Director General Yakiya Amano revealed that Iran had “installed centrifuges in Fordow with the stated objective” of producing uranium enriched up to 20 percent.

By March 2012, Amano reported that monthly production of 20 percent-enriched uranium at Fordow had tripled as four cascades of centrifuges had started simultaneous operation for the first time.

Uranium enrichment is the process of increasing the concentration of the uranium-235 isotope in natural uranium, which normally contains only about 0.7 percent U-235. To build a nuclear weapon, uranium must be enriched to about 90 percent U-235. Once enriched to those levels, uranium is considered “weapons-grade”.

In 2015, Iran, China, Russia, the US, France, Germany, the UK and the European Union signed the Joint Comprehensive Plan of Action (JCPOA). The deal put strict curbs on Iran’s nuclear programme in exchange for lifting sanctions.

In 2015, Iran was believed to have 2,700 centrifuges installed at Fordow.

What did Iran agree to under the JCPOA?

As the JCPOA talks progressed, Iran stopped production at Fordow by January 2014 and did not conduct “any further advances” there, the IAEA reported, for the rest of the year. Iran also diluted its enriched uranium stockpile to 5 percent purity.

The JCPOA banned enrichment at Fordow and allowed only peaceful development of nuclear technology in Iran for energy production in return for a complete lifting of sanctions.

Iran agreed to refrain from any uranium enrichment and research into uranium enrichment at Fordow for 15 years. It also agreed not to keep any nuclear material there but instead “convert the Fordow facility into a nuclear, physics and technology centre”.

A little more than 1,000 of the facility’s centrifuges were allowed to remain there, with the rest moving to Natanz – something the IAEA said was done by January 2017.

Are there concerns about clandestine nuclear development at Fordow?

Despite the JCPOA, concerns and speculation over the Fordow facility continued.

In 2016, Iran placed a Russian S-300 air defence system above the facility, indicating that it feared a direct air strike there.

After Trump unilaterally withdrew from the JCPOA in 2018, Iran gradually slid free of its constraints too, even though European partners tried to salvage the agreement.

During the unannounced inspection in January 2023, the IAEA discovered that Iran had connected two sets of centrifuges at Fordow, allowing it to enrich uranium to 60 percent purity, in contravention of Tehran’s safeguards agreement with the UN agency.

“Iran implemented a significant change to the declared design information for the Fordow Fuel Enrichment Plant (FFEP) without informing the agency in advance. This was contrary to Iran’s obligations under its safeguards agreement,” Grossi said.

The IAEA also said it had found uranium particles at Fordow enriched to 83.7 percent purity – close to the 90 percent enrichment needed for weapons-grade uranium.

“At the Fordow Fuel Enrichment Plant, we found particles of high enriched uranium with enrichment levels well beyond the enrichment level declared by Iran,” Grossi said on March 6, 2023.

Iran denied this. On June 3 this year, Iran told the IAEA that it had “exhausted all its efforts to discover the origin of such particles in those locations. According to the extensive investigations and examinations, relevant Iranian security authorities have recently discovered further clues confirming that sabotage and/or malicious act have been involved in the contamination of those locations.”

What could destroy the Fordow facility?

It is widely believed that Israel lacks the means to penetrate the facility unless it deploys a commando unit to go inside it and physically plant explosives – a risky operation.

The Fordow Fuel Enrichment Plant is considered a much more difficult target than Natanz because it is located inside a mountain.

The US, however, has a bomb that could theoretically destroy Fordow. The Massive Ordnance Penetrator weighs 13,600kg (30,000lbs). If enough of these bombs are dropped from a B-2 bomber, they could possibly collapse Fordow’s underground bunkers.

The Trump administration has confirmed that B-2 bombers were used in the Sunday attack. However, the US has so far not spelled out what bombs were used.