Vantor Technologies imagery from September 13 shows extensive construction at Taleghan 2 in southeastern Tehran, with Iran erecting a large tarp over the destroyed underground structure that obscures work beneath it from satellites and aerial reconnaissance, the Institute for Science and International Security said in a report published Thursday.
The imagery shows dump trucks, bulldozers, concrete pump trucks, mixers and cranes operating across the site, according to the institute. Iran has also added concrete reinforcement on one side of the facility, while a similar structure identified in July appears to have been completed on the other side, measures the institute said would provide additional blast protection against aerial attack.
Repair work began in June, initially focused on sealing three penetration holes left by bunker-buster weapons used in an attack three months earlier. High-resolution imagery reviewed by the institute in June and July showed the holes being excavated, covered with reinforcing steel and prepared for permanent concrete caps.
The reconstruction marks Iran's second effort to rebuild Taleghan 2 in less than two years.
The original facility was destroyed in an Israeli strike in October 2024. Iran began rebuilding it in May 2025, eventually constructing a reinforced structure encased in concrete and covered with earth. By early 2026, the site had effectively become a hardened bunker, with additional defensive features including concrete barriers and protection against drones.
In November, satellite images of the reconstruction showed a large cylindrical object inside the facility resembling a high-explosive containment chamber. The institute estimated it at about 36 meters long and at least 12 meters wide and said such a chamber could be used for explosive experiments relevant to nuclear weapons development, though imagery alone could not establish its purpose.
The rebuilt facility was struck again in early March 2026. Satellite images afterward showed three large penetration holes over the portion of the buried structure where the suspected cylindrical chamber had been installed. The Institute for Science and International Security assessed that the internal structure and probable chamber were likely destroyed.
The institute said the pace of the latest reconstruction raises questions about why Tehran has repeatedly restored a facility with a history tied to work relevant to nuclear weapons.
Ties to past nuclear weapons research
Taleghan 2's significance predates the recent attacks. The institute says the facility was used during Iran's AMAD Plan, a program that Western governments and nuclear experts have linked to work on a nuclear explosive device in the early 2000s.
According to the institute's reconstruction of material from Iran's nuclear archive, Taleghan 2 once housed a specially designed high-explosive chamber and flash X-ray equipment used to study explosive compression.
It says a scaled-down test of a multipoint initiation system — technology relevant to triggering an implosion-type nuclear weapon — was conducted there in 2003. The institute says the International Atomic Energy Agency (IAEA) never inspected the Taleghan 2 building itself.
The IAEA's own 2015 assessment found that before the end of 2003 Iran had an organizational structure capable of coordinating a range of activities relevant to developing a nuclear explosive device.
Information available to the agency indicated that those activities became concentrated in the early 2000s under projects known as the AMAD Plan and were halted in late 2003.
The IAEA found that some related activities continued afterward but were not part of a coordinated effort. Iran denied both that it had a coordinated nuclear weapons program and that the AMAD Plan existed as such.
The agency revisited Iran's past nuclear work in a comprehensive safeguards assessment last year. It concluded that Lavizan-Shian, Varamin and Marivan, along with potentially related locations, had been part of an undeclared structured nuclear program until the early 2000s and that some activities involved undeclared nuclear material.
At the same time, the IAEA said it had no credible indications of an ongoing undeclared structured program of that kind. Tehran rejected the findings and maintained that it had declared all nuclear material required under its Safeguards obligations.
IAEA not able to monitor Iran’s nuclear program
The renewed work at Taleghan 2 comes as the IAEA says its ability to monitor Iran's current nuclear program has deteriorated sharply.
IAEA Director General Rafael Grossi said this week that the agency had conducted almost no in-field verification in Iran for more than six months, apart from an inspection of the Bushehr nuclear power plant in June.
The agency has also been unable for more than a year to maintain continuity of knowledge over previously declared stocks of enriched uranium at facilities affected by military strikes.
Before losing access, the IAEA estimated that Iran possessed 440.9 kilograms of uranium enriched to as much as 60% purity. The agency has been unable to verify how much remains or its current location and has also said it still cannot establish the status of Iran's fourth declared enrichment facility at Isfahan.
Grossi called the lack of information and access a “serious proliferation concern” requiring urgent action.
Last week, the IAEA Board of Governors also reported Iran to the UN Security Council over safeguards non-compliance, after the agency said Tehran had failed to provide inspectors with information and access necessary to account for nuclear material. Iran called the move politically motivated and has argued that US and Israeli attacks on its facilities have made normal inspections impossible.
The Institute for Science and International Security said the purpose of the new Taleghan 2 facility still cannot be established from satellite imagery alone. But after two attacks and two reconstruction campaigns, it said Iran's continued investment in the site demonstrates its determination to restore the facility despite its sensitive history.
