The Institute for Science and International Security (ISIS) citing satellite imagery reported apparent construction at Taleghan 2, a former nuclear weapons development facility within Iran's Parchin military complex.
“The imagery, captured between September and November 2025, shows a large cylindrical vessel - approximately 36 meters long and 12 meters in diameter—housed inside a new domed building,” the report said on Tuesday.
"What exactly the object is cannot be completely determined from the satellite imagery alone, however, its shape and metal structure are consistent with previous high-explosive test chambers Iran has built," the report added. "The facility is likely entering an advanced stage of construction."
Taleghan 2 is located near Taleghan 1; both are part of the Parchin military complex, about 20 miles southeast of Tehran.
“Reconstruction began as early as May 2025 and has progressed quickly despite the prior damage,” the report said.
The institute said both Taleghan sites were part of Iran’s AMAD Plan, an alleged covert project aimed at developing nuclear weapons.
The AMAD Plan ran from the late 1990s until 2003, according to the International Atomic Energy Agency (IAEA).
Iran denies the existence of the AMAD Plan, insisting its nuclear program is purely peaceful and that nuclear weapons are forbidden by a religious decree from Supreme Leader Ali Khamenei.
The institute which monitors sites activity satellite imagery, reported last month on Iran’s renewed activity in Taleghan 2 site.
“By June 12, groundwork and foundations had been laid, and by late August, a new arch-roofed structure about 45 by 17 meters was under construction over the temporary cover, with two smaller buildings nearby,” the institute added.
The UN nuclear watchdog said on Wednesday it needs more Iranian cooperation to restore full inspections at sites hit in June’s strikes, warning that verification of enriched uranium stocks is “long overdue.”
In his opening statement to the IAEA Board of Governors, UN nuclear chief Rafael Grossi said the agency urgently needs access to Iran’s inventories of low-enriched and high-enriched uranium, which have not been checked for five months.
Grossi said he is in regular contact with Iranian officials following a September agreement in Cairo that set inspection procedures after the attacks, but added that “further constructive engagement is needed” to implement the deal in full.
The remarks come as the United States and three European allies have submitted a draft resolution demanding that Iran promptly restore cooperation and provide comprehensive nuclear-material accountancy.
Diplomats told Reuters on Tuesday that the measure is expected to pass at the board meeting later this week.
The text calls on Iran to grant the agency “all access it requires” and to fully implement the Additional Protocol without delay.
Tehran has warned that such a resolution could undermine the September understanding reached with Grossi.
Earlier this week, Iran’s Deputy Foreign Minister Kazem Gharibabadi said the Western push would compromise the agreement, while Iranian officials have linked stalled access to the reimposition of UN sanctions in late September under the snapback mechanism.
Iran has yet to allow inspectors to visit the facilities damaged during Israeli and US strikes in June, according to a confidential IAEA report seen by Reuters earlier this month.
The report said the agency has not been able to verify Iran’s enriched-uranium stockpile since the attacks, when inspectors last confirmed about 440 kg of uranium enriched to 60% purity.
Access granted to unaffected sites
Grossi told the board on Wednesday that establishing the status of Iran’s enriched material “needs to be addressed urgently,” warning that extended gaps in verification increase risks to the safeguards system.
“It is critical the agency be able to verify this material as soon as possible,” he said.
The IAEA chief added that Iran has facilitated access with advanced notice to “almost all unaffected facilities,” calling this step welcome but insufficient.
The renewed push for cooperation follows a turbulent year in which Israeli and US attacks on Iranian nuclear facilities during the 12-day war in June left parts of the program damaged.
Iranian officials say the strikes undermined the credibility of the IAEA and have accused the agency of failing to condemn the attacks.
The IAEA board will continue discussions this week as Western governments seek to pressure Tehran back into full compliance, while Iran argues that sanctions and security concerns must also be addressed.