The UN’s nuclear inspectors still cannot say where Iran’s Isfahan enrichment plant is, 17 months after they were due to visit

The world’s nuclear inspectors have told governments they cannot say where one of Iran’s uranium enrichment plants is, let alone what is inside it.

In its confidential quarterly report to member states, dated Friday 13 November, the International Atomic Energy Agency (IAEA) says it is “increasingly concerned” about the Isfahan Fuel Enrichment Plant. The agency does not know the plant’s exact location, its status for safeguards purposes, or whether it contains nuclear material, the report says. Iran has not allowed inspectors to visit it or to see its design plans.

The report calls this “a matter of serious proliferation concern” that needs to be rectified “with the utmost urgency”. It asks Iran to declare the status of its enrichment plants and its stock of highly enriched uranium, some of it close to weapons grade, and to let inspectors back into the sites that were bombed.

Why does one plant matter so much?

Because it may be where the uranium is. Iran declared the plant to the IAEA on 12 June 2025, and inspectors planned to see it on 13 June. That morning Israel began a 12-day bombing campaign, later joined by the United States, that destroyed or badly damaged Iran’s other enrichment plants. Diplomats believe the Isfahan plant sits inside a tunnel network at Isfahan that was itself targeted.

In March, IAEA Director General Rafael Grossi said the agency believed a significant amount of Iran’s most highly enriched uranium was inside that tunnel complex.

How much uranium is unaccounted for?

The IAEA estimates Iran had 440.9 kilograms of uranium enriched to 60 per cent when the strikes began. Weapons grade is around 90 per cent, and 60 per cent material can be taken there quickly. Iran has not let inspectors back into any bombed site since, so no one outside Iran can say how much of that stock still exists or where it is.

What is Iran saying?

Iran’s security chief, Mohsen Rezaei, has said not a single particle of enriched material will leave the country, and that Tehran has told Moscow the same. Russia has offered to take the uranium as part of any deal but says the decision is Iran’s. Rezaei has also said no negotiations are under way with Washington.

Why now?

The report arrives as the war heats up again. On Friday Iran’s Revolutionary Guards claimed to have destroyed a US radar in Bahrain, the first claimed hit on US forces in the Gulf in about two months. A report that the agency has lost sight of near-weapons-grade material gives both sides another argument.

VNN will update this story as more is confirmed.