Yet assessments by nuclear specialists and officials show the strikes have slowed but not stopped Iran's nuclear progress. One central issue remains the fate of Iran's stockpile of highly enriched uranium. Despite numerous Israeli and U.S. attacks on key nuclear facilities in 2025 and 2026, experts say Iran still has enough uranium enriched to 60% purity—almost weapons-grade—to build up to 10 nuclear bombs with further processing.
The International Atomic Energy Agency estimates that around 440 kilograms of uranium enriched to 60% remains stored at Isfahan, a central city in Iran. This quantity alone could be further refined into bomb-making material in a matter of weeks. Iran has consistently blocked IAEA inspectors from accessing its most secretive nuclear sites, raising concerns among international monitoring groups and nuclear experts alike.
Stockpiles and storage
Most of the enriched uranium is stored in the form of uranium hexafluoride gas. This substance is contained in relatively small cylinders. This makes it easier to transport through underground tunnels. U.S. intelligence reports suggest that Iranian personnel may still have access to the Isfahan site. This is through a limited access point, despite the extensive damage sustained during the 2025 attacks.
According to a recent analysis by the Institute for Science and International Security, between 265 and 287 kilograms of highly enriched uranium may still lie buried at Isfahan. An additional 80 kilograms could be located at Fordo, though these estimates lack independent verification from international inspectors. The rest is likely stored at Natanz, Iran's largest enrichment site.
Damage and recovery
Natanz, hidden beneath the ground for years, suffered major damage during the 2025 attacks. Both above-ground and underground structures were struck, with entrances to the enrichment halls severely damaged in later strikes. Nearby, a new facility called Kuh-e Kolang, also known as
Fordo, long considered the most secure of Iran's nuclear sites due to its deep, mountainous location, sustained serious damage when 12 U.S.-launched bunker-buster bombs hit the site in June 2025. Tunnel entrances remain blocked, and recent satellite images show added obstacles on access roads, likely intended to deter further attacks. However, recent strikes in the area targeted air-defense systems and a research center rather than the enrichment facility itself, indicating a shift in focus.
Ellie Geranmayeh, an Iran nuclear expert at the European Council on Foreign Relations, highlighted in an interview with The New York Times that while the attacks have disrupted Iran's nuclear infrastructure, the core capabilities remain intact. The so-called
Daryl Kimball, who leads the Arms Control Association, has argued that military strikes alone cannot erase Iran's nuclear capabilities. Even with damaged facilities, Iran's expertise and stockpiles remain intact, making it possible for the country to revive its program quickly. Kimball’s view echoes broader concerns that military action is insufficient to guarantee lasting deterrence.
Capacity for rapid restart
Currently, Iran has not restarted uranium enrichment, and the destruction of its above-ground centrifuge production facilities appears to have reduced the immediate threat. However, the real concern remains Iran's ability to ramp up nuclear enrichment rapidly should it choose to do so.
Satellite analysis has shown no signs of rebuilding at the damaged sites. But the presence of large uranium stockpiles and construction activity at Kuh-e Kolang means the country could significantly advance its nuclear capabilities in a short period. This reality underscores the limited effectiveness of the military campaign. It highlights the need for alternative strategies to address Iran's nuclear ambitions.
