IAEA report names Isfahan tunnel as storage site for 60% enriched uranium

The International Atomic Energy Agency circulated a confidential report on Feb. 27 saying some of Iran’s most highly enriched uranium was stored in an underground tunnel complex at the Isfahan nuclear site. The report identified material enriched to roughly 60 percent U‑235 and to up to 20 percent at the same location and said satellite imagery showed “regular vehicular activity around the entrance to the tunnel complex at Isfahan in which (uranium) enriched up to 20% and 60% U‑235 ... was stored.”

The agency estimated that, before last year’s U.S.-Israeli strikes on Iranian nuclear sites, Iran held 440.9 kilograms of uranium enriched to up to 60 percent. Using the IAEA’s own yardstick, the report said that quantity would be “enough, if enriched further, for 10 nuclear weapons.” The Jerusalem Post cited the agency’s conversion figure that about 42 kilograms of 60 percent material, if enriched further, could in theory yield one bomb.

The disclosure is the first time the UN nuclear watchdog has publicly named a specific location for material enriched as high as 60 percent. The report warns that inspectors must be allowed access and calls such access “indispensable and urgent.” It also said a successful outcome to Iran‑U.S. negotiations would have a “positive impact on the effective implementation of safeguards in Iran.”

The IAEA emphasized its verification limits, noting it does not currently have access to any of Iran’s four declared uranium enrichment facilities and therefore cannot confirm the present size or whereabouts of Iran’s enriched uranium stock or whether enrichment has been suspended. The agency confirmed technical discussions in Vienna in the week beginning March 2 between Iran and U.S. officials intended to “hammer out safeguards implementation.”

Diplomats cited in reporting said the entrance to the Isfahan tunnel complex was targeted in U.S. and Israeli strikes in June, but that the underground facility “appears largely undamaged” or “largely unharmed.” Satellite images dated Jan. 30 and Feb. 1 show new roofs over previously destroyed buildings at Natanz and Isfahan respectively, a sign that facilities hit last year are being repaired or rebuilt.

The revelation arrives amid a renewed diplomatic push. Iran and the United States have completed a third round of indirect, Oman‑mediated talks in Geneva; Iran’s Deputy Foreign Minister Abbas Araghchi described those sessions as “most intense” and said negotiators made “very good progress.” Araghchi added that continued advancement would require a “realistic approach” and the avoidance of “excessive demands,” and warned that reaching an agreement requires “seriousness and realism from the other side.”

The security implications are immediate. Sixty percent enrichment is not weapons grade by common definitions, which typically place weapons grade near 90 percent U‑235, but it is materially closer to that threshold and can shorten the time and work needed to produce weapons‑grade uranium. U.S. President Donald Trump used his State of the Union to warn that Iran is developing missiles capable of reaching the United States and vowed he would never allow Tehran to obtain a nuclear weapon, underscoring the political stakes in Washington.

The IAEA sent its confidential report to member states ahead of a quarterly meeting of its 35‑country board next week. With the agency barred from declared enrichment facilities and repairs visible at multiple sites, the report is likely to intensify calls from capitals for on‑site verification and will complicate both regional security calculations and the delicate diplomacy aimed at restoring more stringent safeguards.