Iran fortifies buried uranium as talks advance

In recent weeks, Iran has undertaken deliberate steps to seal off an underground cache of near bomb-grade, highly enriched uranium. Multiple U.S. intelligence sources report that tunnels have been intentionally collapsed and entrances booby-trapped with explosive mines. These measures are designed to make reaching the buried material far more difficult, dangerous and time-consuming.

International assessments cited in the reporting indicate that most of this enriched uranium is believed to be located in collapsed tunnels at the Isfahan nuclear complex in central Iran. The stockpile is described as roughly half a ton of highly enriched uranium, placing a premium on secure handling and removal if any operation proceeds.

Experts and officials indicate that the new fortifications sharply increase the complexity of any effort to secure or remove the material. Heavy excavation equipment would be required to open collapsed tunnels and reach the storage areas. De-mining teams would first need to clear explosive devices placed at access points, adding further risk and time to any mission.

Reporting also describes the likely need for a specialized mobile uranium facility organized under the National Nuclear Security Administration. Such a unit, associated with capabilities at Oak Ridge National Laboratory in Tennessee, would be needed on site to safely process, stabilize and prepare the highly enriched uranium for destruction and transport.

While physical access to the material has become more challenging, diplomatic efforts have advanced in parallel. A senior U.S. administration official has said that the United States and Iran are "inching closer" to a deal focused on the enriched uranium. Under the emerging understanding, Iran would be required to turn the material over to the United States.

The official outlined a concept in which the highly enriched uranium would first be destroyed on site in Iran and then taken out of the country. This framework aligns with broader descriptions that nuclear material is to be eliminated and removed as part of ongoing talks. However, the hardened conditions around the stockpile could complicate verification that all material has been accessed and processed.

The combination of collapsed tunnels and explosive mines poses significant verification challenges. With portions of the Isfahan complex now more difficult to access, confirming the exact size and completeness of the stockpile may be harder for any international or bilateral inspection effort. Different reports describe the buried highly enriched uranium as roughly half a ton, while other accounts cite about 970 pounds, underscoring uncertainties around precise quantities.

The increased physical risk from mines and unstable tunnels adds to the political and technical sensitivity of any mission to secure the material. Negotiators must account for these on-the-ground realities when defining procedures for destruction, removal and confirmation that no enriched uranium remains inaccessible in the sealed areas.