Even a month after the US attacks on three major nuclear sites inside Iran, the effects of the airstrikes on June 22 remain unclear amid conflicting damage assessments. 

The strikes were a part of what US President Donald Trump called "Operation Midnight Hammer" and targeted the nuclear facilities in the cities of Fordo, Natanz and Isfahan.

The operation involved 125 aircraft and specialty B-2 bombers carrying 30,000-pound bombs officially designated as Massive Ordinance Penetrators — and colloquially known as "bunker busters."

Fordo heavily fortified

The strike in Fordo was the most significant. It is the country's most heavily fortified nuclear facility buried deep inside a mountain to shield it from attacks.

It is unclear when Iran began building the plant in Fordo but its existence was revealed to the world in 2009. The facility was designed to house around 3,000 centrifuges, machines used to enrich uranium.

As part of Iran's 2015 nuclear deal — the Joint Comprehensive Plan of Action (JCPOA) — with global powers, Tehran agreed to convert the site into a research facility and halt uranium enrichment there for 15 years.

But after US President Donald Trump, during his first term, unilaterally withdrew from the agreement in 2018, Iran resumed enrichment activity at Fordo.

Iran has been enriching uranium to 60% purity at the site, well beyond what is required for civilian nuclear power generation purposes. Tehran also announced plans to further expand enrichment capacity at the site.

The International Atomic Energy Agency (IAEA )also said it had found uranium particles at Fordo enriched to as high as 83.7% purity — significantly close to the 90% enrichment needed for weapons-grade uranium.

Targeting uranium enrichment facilities

Another target of the US operation was the nuclear facility in Natanz, Iran's largest uranium enrichment hub, located around 140 miles (225 kilometers) south of Tehran. 

Like the one in Fordo, Natanz is also a subterranean nuclear site that can hold around 50,000 centrifuges.

Both the Fordo and Natanz facilities had previously been targeted multiple times in a series of sophisticated attacks.

Iranian officials said these attacks — ranging from the 2010 Stuxnet cyberattack to incidents disabling the Fordo power grid and a remote-controlled explosion in Natanz four years ago — had already caused extensive destruction and severely damaged their enrichment capabilities.

The third nuclear site targeted by the US was the one in Isfahan, which was suspected of hosting near weapons-grade nuclear fuel.

In simple terms, this facility was converting natural uranium into uranium hexafluoride gas, which goes into centrifuges at Natanz and Fordo for uranium enrichment.

Russia provides fuel for Iran's sole nuclear power plant

The sites at Fordo, Natanz and Isfahan are uranium enrichment facilities, and experts estimate that Iran already has more than 400 kilograms (880 pounds) of highly enriched uranium. 

Despite the damage US strikes caused to the three sites, the fate of this enriched uranium remains uncertain.

Iranian government sources mostly claim that the enriched uranium has been moved to "secure" locations.

However, several media outlets have quoted Israeli sources as saying that the uranium was distributed among the three sites and "was not relocated."

A senior Israeli official, who did not want to be named, recently told the BBC that a portion of the enriched uranium was located deep within the Isfahan facility and that Iran could try to retrieve it.

The three targeted sites are believed not to have active nuclear reactors. However, Iran does have an operating nuclear power plant, in Bushehr, some 750 kilometer south of Tehran. The plant, which is monitored by the IAEA, is run by uranium supplied by Russia. Its spent fuel is also returned to Russia to prevent reprocessing into weapons-grade material.

The plant was not targeted in the US strikes.

Monitoring radiation levels in Iran

Following the US attacks, the IAEA said it didn't notice any increase in radiation levels in the region.

As no active reactors were targeted, the potential risk of radiation is limited to leakage of the uranium hexafluoride gas from enriched uranium storage tanks, centrifuge cascades or pipelines.

If released, the gas would react with moisture in the air to form uranyl fluoride and hydrofluoric acid, the latter being a highly corrosive and dangerous acid.

Contact with this acid or inhalation of its vapors can destroy lung tissue, and cause severe and deadly respiratory problems, which could result in suffocation and death.

"There are indeed indications that uranium hexafluoride was released at the facility site. Both radiological hazards and elevated radiation levels, as well as chemical dangers, were mentioned. This can only refer to the release of hydrofluoric acid," Clemens Walther, professor and nuclear expert at the Institute for Radioecology and Radiation Protection at the University of Hanover, told DW.

"However, it was clearly stated that the incident was confined to the site itself. No spread into residential areas has been reported."

Roland Wolff, an expert in radiation protection, medical and radiation physics, said uranium, as a heavy metal, is chemically toxic.

"It can, for example, cause kidney damage. Incorporation increases the risk of cancer as well as the risk of genetic damage due to the short-range alpha radiation. Depending on the scenario, this presents a potential hazard for both workers and the general population," he told DW.

Risk of a Chernobyl-style disaster?

The nuclear meltdowns in Chernobyl in 1986, and Fukushima in 2011, highlighted the radiation risks caused by reactor accidents.

The Fukushima disaster occurred when a magnitude 9 earthquake and tsunami disabled the power supply and cooling systems of three reactors at the Fukushima Daiichi nuclear power plant, on Japan's east coast.

Radioactive material was released from the site, leading to tens of thousands of people being evacuated.

But Wolff said the targeted sites don't pose a Chernobyl-style danger.

"The radioactive inventory in enrichment facilities, unlike in nuclear reactors, does not contain fission products," said the radiation expert. "Furthermore, it was not released into high altitudes by an explosion, as was the case in Chernobyl. Therefore, potential contamination is assumed to be local."

Edited by: Srinivas Mazumdaru