The killing of Iranian nuclear scientists in U.S.-Israeli military strikes has raised fears that, if the regime destabilizes, weakened control over uranium stockpiles and the spread of nuclear expertise could increase proliferation risks.
While Iran can replace its lost personnel, experts say the lost expertise will be harder to rebuild and undisclosed sites in the country may also leave dangerous materials and knowledge vulnerable.
"Currently, the risk of nuclear terrorism or nuclear material moving to the black market remains low," said Kelsey Davenport, director of nonproliferation policy at the Iran’s nuclear facilities between 2025 and 2026.
Among them is Hossein Jabal Amelian, head of the Organization of Defensive Innovation and Research (SPND), who was killed in 2026 during Operation Rising Lion and Operation Epic Fury.
SPND is seen as the successor to Iran’s pre-2004 nuclear weapons program and plays a key role in new weaponization research.
Others killed in 2025 include Mohammad Mehdi Tehranchi, Akbar Motallebizadeh and Said Borji, all linked to weaponization work.
"The full impact of this campaign on Iran’s weaponization capabilities remains unclear," Jim Lamson, a senior research associate at the targeted strikes have also hit a network of sites tied to their work, creating extra obstacles for Iran’s program in the near term, he said.
"We have identified at least 11 weaponization-related sites that have been hit since 2024," Lamson said.
"These include SPND headquarters, a newly identified site called Min-Zadayi in northeast Tehran, SPND’s Taleghan and Sanjarian explosives testing sites, the Defense Ministry’s Shahid Meisami complex in western Tehran and several research universities."
These facilities were all involved in neutronics, explosives, metallurgy and nuclear physics — all tied to nuclear weapons development, he said.
Despite the scale of the latest strikes, Iran retains enriched nuclear material, with President Donald Trump saying April 17 that the U.S. would work with Iran to recover "nuclear dust" — enriched uranium — from sites, adding that both countries would use heavy machinery to remove it.
The Israeli and U.S. strikes, and harder to assess their actual impact on Iran's capabilities and intentions to produce a nuclear weapon," Lamson clarified.