UN nuclear chief reveals secret Syrian reactor could have produced weapons-grade material

A nearly complete nuclear reactor built secretly during the rule of the toppled Syrian leader Bashar al-Assad would have been able to produce fissile material for possible use in nuclear weapons, the chief of the UN nuclear watchdog has revealed.

Inspectors from the International Atomic Energy Agency (IAEA) last month visited two sites, one in Deir ez-Zor and a second in an undisclosed location identified to them by Syrian authorities.

The IAEA head, Rafael Grossi, said on Monday it was “obvious that the previous government was pursuing a number of clandestine” activities.

“They didn’t want the world to know what they were doing,” he told reporters after opening the Vienna-based agency’s quarterly board of governors meeting.

“Given the configuration, the technical features of that type of reactor, this is a reactor that is very efficient in the production of fissile material that could be used directly for the fabrication of nuclear weapons,” he said, adding that building the reactor was a “very important step”.

Syria was believed to have operated an extensive undeclared nuclear programme under Assad that included a nuclear reactor built by North Korea in the eastern Deir ez-Zor province.

After Assad was ousted in December 2024, the new government agreed to give IAEA inspectors access to suspected former nuclear sites.

During a visit to Syria in August, IAEA inspectors confirmed that “the cooling infrastructure which has now been uncovered is consistent with that of a nuclear reactor”. Grossi and a team of senior inspectors also visited a previously undeclared site in the country.

In 2018, Israel admitted carrying out a top-secret air raid on the site 11 years earlier.

In 2008, less than a year after the strike, US officials accused Syria of having sought to build a secret nuclear reactor and acknowledged that Israel had destroyed it in the raid.

Syria notified the agency of the site’s existence in a 17 July letter and invited the IAEA “to cooperate with the Syrian authorities in the inspection and verification of the site and of any nuclear material to be potentially found”.

The IAEA said in its confidential report circulated to member states last Tuesday and seen by the Associated Press that this new site contained “natural uranium metal in the form of fuel rods with cladding”. The agency verified the material and confirmed “the presence of around 73 tonnes of natural uranium metal”.

Grossi said that when the inspectors visited the site in August they had to “tear down walls” and go through “very difficult and narrow passages” to reach the nuclear material that had been hidden. The site had boxes scattered all over the place, he said.

Grossi said “the important thing is that this material now is under safeguards” of the IAEA, adding that agency inspectors had managed to install cameras at the location.

Asked if the nuclear material would remain in Syria or be removed, Grossi said this was “a matter that the Syrian government will have to decide”. He added: “We are not requesting them to do this or to do that. For us what’s important is that we know all the time where this [material] is until the last gram.”

Logan Mintz, a director for nuclear materials security at the Washington-based Nuclear Threat Initiative, said natural uranium metal was not directly usable for a nuclear weapon but could be “diverted to a covert weapons programme that further processes it into plutonium for a nuclear weapon”.

She said that once deemed safe to move, the material could be “transported in certified containers” to a third country that could “safely and securely disposition it into a more chemically stable and more widely used form” for possible use in nuclear power plants.

“As with any transport of nuclear material, this movement would require robust security from theft or sabotage,” she said.

Associated Press and Agence France-Press contributed reporting