The International Atomic Energy Agency (IAEA) said in a confidential report that part of Iran's stockpile of highly enriched uranium has been stored in an underground tunnel complex at the Isfahan nuclear site, marking the first time the UN watchdog has specified the exact location of material enriched to near-weapons-grade levels.
According to the report, which was seen by Reuters, some of the uranium enriched to 60% purity was kept at the subterranean facility. Uranium enriched to 90% is considered weapons-grade. Western media outlets had previously reported assessments that the material was being stored at the underground complex.
Reuters reported that the entrances to the tunnel system were damaged in US and Israeli strikes in June, though diplomats said the facility itself sustained little damage. During the recent escalation, satellite imagery showed Iranian efforts to block and fortify access points to the underground site.
The agency has previously estimated that Iran possesses approximately 440 kilograms of uranium enriched to 60%. With further enrichment, that amount could be sufficient for about 12 nuclear warheads.
The tunnel complex also housed uranium enriched to up to 20%. Satellite images showed regular vehicle traffic near the entrance to the facility. According to the report, as of June 13, the day Israel launched its attack on Iran, the stockpile of uranium enriched to 20% stood at roughly 184 kilograms.
The International Atomic Energy Agency has expressed growing concern that Iran has never granted it access to the enrichment facility in Isfahan. "This is a matter of proliferation concern," the agency said in the report, calling on Iran to allow verification activities "without further delay."
At the outset of the war in June, Iran announced that it had taken steps to ensure the "security" of its uranium stockpile. Since then, the material has not been under international monitoring.
Satellite images analyzed in early February by the Institute for Science and International Security, a Washington-based research organization, showed that Iran had completely sealed two of the three tunnel entrances with massive piles of earth, using trucks and bulldozers. The third entrance remained open and was reinforced with protective walls designed to prevent the penetration of cruise missiles.
