UN inspectors confirm Assad-era Syria secretly built a nuclear reactor, find 73 tonnes of uranium

The International Atomic Energy Agency has confirmed that Syria's government under Bashar al-Assad secretly built a nuclear reactor at Deir ez-Zor and left roughly 73 tonnes of undeclared natural uranium at a related site, closing out one of the longest-running mysteries in global nonproliferation enforcement. The findings, laid out in a confidential report circulated to the agency's member states and reviewed by wire services this week, mark the first time inspectors have been able to fully verify what they had long suspected but could never confirm on the ground.

Inspectors who visited Syria in August found that cooling infrastructure at the Deir ez-Zor site is "consistent with that of a nuclear reactor," according to the agency's assessment of the facility, and identified it specifically as a gas-cooled, graphite-moderated design. The reactor was destroyed before it could be completed, in a September 2007 Israeli airstrike known as Operation Orchard, but Damascus spent the following years bulldozing the site and rebuffing IAEA questions about it.

The numbers

The material now verified and placed under IAEA containment includes approximately 73 tonnes of natural uranium metal, of which about 55 tonnes are in the form of some 8,800 fuel rods, with the remainder consisting of uranium scrap and manufacturing waste. Inspectors identified three previously undeclared locations tied to the program: the reactor itself under construction at Deir ez-Zor, a fuel-fabrication plant where the reactor's fuel rods were manufactured, and a separate storage site holding the fuel, scrap and waste. Two additional locations visited by inspectors on August 19 were found to contain no nuclear material or equipment.

The reactor design matters as much as the tonnage. A gas-cooled, graphite-moderated reactor of the type identified at Deir ez-Zor is the same class North Korea operates at Yongbyon, where roughly 300 tonnes of graphite slow neutrons inside the core and carbon dioxide gas carries away heat. Its principal attraction to a proliferator is that it runs on natural, unenriched uranium metal fuel rather than the enriched uranium most power reactors require, meaning a state with no enrichment infrastructure of its own can still generate weapons-usable material. Spent fuel from such a reactor, once reprocessed, yields plutonium suitable for a weapon; North Korea's Yongbyon unit has been estimated to produce on the order of six kilograms of plutonium annually when operating and reprocessing continuously. Independent analysts note the volume recovered at Deir ez-Zor — described by nuclear-security researcher David Albright as enough for roughly one full reactor core plus surplus — points to a sustained production effort rather than a single isolated batch, and to work on a parallel facility to separate plutonium from spent fuel, according to an analysis of the agency's findings.

How the case broke open

The Deir ez-Zor reactor, believed to have been built with North Korean assistance, was a closely guarded secret until Israeli jets destroyed it in 2007. Syria denied for years that the site was ever nuclear in nature, and demolished and graded the ruins before inspectors could take environmental samples. When the IAEA finally assessed in a May 2011 report that the demolished building was "very likely" an undeclared nuclear reactor, its Board of Governors voted 17 to 6 the following month to find Syria in non-compliance with its safeguards obligations and to refer the case to the UN Security Council, a decision Russia and China opposed. The Security Council took no action, and Syria's descent into civil war later that year made further access all but impossible; the file sat largely dormant for more than a decade, revisited by the agency's Board mainly as a recurring, unresolved line item, as its successive briefings to its own Board of Governors show.

The breakthrough came only after Assad's government collapsed in December 2024 and a transitional administration led by Ahmed al-Sharaa took power. Syria's new authorities notified the IAEA in a July 17 letter of an undeclared site containing leftover nuclear material and invited inspectors in — a reversal from the previous government's stonewalling. IAEA Director General Rafael Grossi traveled to Damascus in mid-August to inspect the site alongside Syrian officials, part of a broader nuclear-safeguards agenda that had already been raised at the agency's June meeting in Vienna.

Who is affected

The disclosure carries the heaviest weight for the region's already fragile security balance. Israel has watched the file closely for years out of concern that residual material could end up in a radiological device, and Israeli and American officials had spent more than a year discussing how to deal with a separate clandestine storage facility, referred to as "Site 99," where the Assad government is believed to have kept uranium yellowcake and other residue from the abandoned reactor project. An Israeli official involved in the talks said Jerusalem made clear it would not allow nuclear material to remain there and warned it would strike the facility again if the material was not removed or if Syria showed any sign of trying to access it. Washington and Jerusalem ultimately settled on securing Damascus's cooperation rather than acting unilaterally, and the resulting three-way understanding among Syria, Israel and the United States, with the IAEA overseeing the technical work, was confirmed by officials involved in the negotiations in mid-August. As of that reporting, the material at Site 99 had not yet been physically removed and the operation was still described as ongoing.

For Syria's transitional government, the episode is also a test case: it is trying to demonstrate, to Washington and to the IAEA's board, that it is a fundamentally different actor than its predecessor on questions of proliferation, even as it insists on retaining the uranium for a future civilian energy program. Syria's Atomic Energy Commission chief, Mudar al-Okla, said Damascus had given inspectors full access to every site and document requested, according to a statement carried by the state news agency SANA, and that all nuclear material and facilities are now subject to IAEA safeguards.

"We are talking about a few tons of nuclear material that could be put to bad use," Grossi told reporters in Damascus, while also praising Syria's "courageous decision" to disclose the site.

Reaction and what happens next

Syria's Foreign Minister, Asaad al-Shaibani, has said the recovered material "does not pose a risk" and will remain in Syrian national custody while under international safeguards, framing the disclosure as evidence of a clean break from the Assad era rather than a lingering weapons ambition. Outside analysts are more circumspect. Mark Hibbs of the Carnegie Endowment for International Peace said the findings underscore the importance of sustained international monitoring in a region where nuclear ambiguity has repeatedly fed conflict, while Susi Snyder of the International Campaign to Abolish Nuclear Weapons noted that the cooperation at least reduces the risk of further environmental contamination from the abandoned site. Nonproliferation specialists who tracked the original 2011 Board of Governors dispute have also pointed out that the political dynamics look markedly different this time: where Russia and China blocked consensus on referring Syria to the Security Council fifteen years ago, no government has publicly objected to the current findings, a reflection of how thoroughly Assad's fall has changed the diplomatic terrain around the file.

The IAEA's Board of Governors is scheduled to convene in Vienna from September 7 to 11, and Grossi's findings are expected to be a central agenda item, with the stated goal of a full resolution of the safeguards case that has shadowed Syria's file since 2011. How the board characterizes Syria's years of concealment — and whether it presses for further verification of the Site 99 removal or additional undisclosed locations — will shape not only Syria's rehabilitation within the nonproliferation regime but also the wider question of how the international community accounts for weapons programs inherited from fallen governments.