Location of Iran’s Highly Enriched Uranium Uncertain — but It Likely Cannot Build Nuclear Weapons Now

Iran may have relocated its highly enriched uranium (HEU) — key stocks for fueling a nuclear weapon — to secret sites prior to U.S. or Israeli airstrikes targeting its nuclear facilities. While recovering this HEU is imperative, Iran likely lacks the option to build nuclear weapons in the short term due to Israel’s earlier strikes on Iran’s weaponization assets, which would have enabled Tehran to construct a nuclear device.

How Much HEU Is Missing?

The International Atomic Energy Agency (IAEA) stated on June 22 that “a few days before the military conflict began” on June 13, the agency verified the presence of at least 408 kilograms of 60 percent HEU in highly fortified tunnels next to the Esfahan nuclear complex. Until Israel began striking Iran, Tehran was storing this material in easily moveable canisters. As of the IAEA’s previous formal reporting in May, Iran also possessed some 275 kilograms of 20 percent HEU. Tehran may have stored or housed some of the HEU at the deeply buried Fordow facility.

To produce nuclear weapons, Iran would prefer to enrich the 60 percent material to 90 percent to achieve optimal atomic weapons-grade material. However, the 60 percent HEU stock alone is enough material to fuel at least nine nuclear weapons without further enrichment to weapons grade. While these more rudimentary, or “crude,” weapons would be too large to mount on a ballistic missile, Tehran could still test them and threaten Israel with attack by delivering them via truck or shipping container.

If Iran sought to enrich HEU to weapons grade, it would need a secret enrichment plant operating a few hundred advanced centrifuges, such as IR-6 centrifuges, to make 90 percent enriched uranium.

Surviving HEU

On June 21, the United States targeted the Isfahan tunnel facility with 30 Tomahawk missiles and hit the Fordow enrichment plant with 12 30,000-pound Massive Ordnance Penetrators (MOPs) — bombs designed to reach and destroy deeply buried facilities. While U.S. and Israeli battle damage estimates are ongoing, if HEU survived at either site, it may be entombed and inaccessible for months. Reportedly, Israel struck the Fordow entrances on June 22 to ensure Iran could not engage in any recovery efforts at the site.

Whether Iran moved all or some of its HEU stocks prior to the U.S. strike that targeted the Isfahan tunnels and Fordow is unclear. Trucks were visible in commercial satellite imagery, meaning Tehran could have moved nuclear assets just prior to the U.S. attack. Apart from the HEU, Iran may have sought to detach and relocate some 1,700 IR-6 centrifuges, yet they could be difficult to relocate promptly.

On June 13, Israel eliminated the above-ground Natanz pilot fuel enrichment plant and reportedly damaged the underground main Natanz enrichment plant, which the United States struck with two MOPs on June 21 to ensure its destruction. The Fordow enrichment site is likely too damaged to be operable after successive MOP strikes since centrifuges are delicate machinery and would be significantly damaged from bombing shock waves.

Weaponization May Be Impossible for Foreseeable Future

Positively, Iran likely cannot weaponize any HEU and construct nuclear devices any time soon. During its strikes, Israel damaged Tehran’s weaponization capabilities extensively, meaning Iran may not have the ability to construct nuclear devices in the immediate term, even if it sought to. Jerusalem struck numerous weaponization facilities, equipment, atomic weapons components, and documentation and assassinated at least 14 nuclear scientists.

Netanyahu also noted on June 22 that Israel has intelligence on the whereabouts of the missing HEU. Thus, Israel or the United States may conduct further strikes to eliminate the material. Jerusalem has penetrated Iran’s atomic weapons program and activities so deeply that Israel would likely detect Iran building nuclear weapons, an action that would probably invite additional, massive U.S. and Israeli strikes. Still, Washington and Jerusalem must act swiftly to eliminate any of Tehran’s remaining HEU stocks, advanced centrifuges, and weaponization capabilities.

Andrea Stricker is a research fellow and deputy director of the Nonproliferation and Biodefense Program at the Foundation for Defense of Democracies (FDD). For more analysis from the author and FDD, please subscribe HERE. Follow Andrea on X @StrickerNonpro. Follow FDD on X @FDD and @FDD_Iran. FDD is a Washington, DC-based, nonpartisan research institute focused on national security and foreign policy.