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François Diaz-Maurin
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François Diaz-Maurin

Bulletin of the Atomic Scientists nuclear editor whose satellite analysis found Iran may have pre-moved 540 kg of 60%-HEU before strikes.

Last refreshed: 19 May 2026 · Appears in 1 active topic

Key Question

If Iran pre-moved 540 kg of 60%-HEU before the strikes, can any deal verify what was actually destroyed?

Timeline for François Diaz-Maurin

#10218 May

Published satellite analysis of Isfahan truck movement estimating 540 kg HEU upper bound

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Common Questions
What did the Bulletin of the Atomic Scientists find about Iran's hidden uranium?
Editor François Diaz-Maurin's March 2026 satellite analysis estimated Iran moved up to 540 kg of 60%-enriched uranium to the Isfahan complex on 9 June 2025, four days before Israeli airstrikes. This is 100 kg above the 440 kg figure in the US MOU.Source: Bulletin of the Atomic Scientists
How much Iranian uranium survived the June 2025 strikes?
The exact amount is unverified. The Bulletin of the Atomic Scientists estimates up to 540 kg of 60%-HEU was pre-moved to Isfahan before the strikes. IAEA has had no inspector access to Isfahan since June 2025.Source: Bulletin of the Atomic Scientists / IAEA
Why does the 540 kg figure matter for Iran nuclear talks?
The US MOU is built on a 440 kg baseline. If Diaz-Maurin's 540 kg estimate is correct, the deal's verification framework understates the actual stockpile by 100 kg, undermining any agreement that does not account for the pre-moved material.Source: Bulletin of the Atomic Scientists

Background

François Diaz-Maurin is the Editor for Nuclear and Radiological Threats at the Bulletin of the Atomic Scientists, based in Chicago. His satellite-image analysis, published in March 2026, became one of the most consequential pieces of open-source nuclear intelligence produced since the Iran conflict began. The analysis concluded that Iran may have moved up to 540 kg of 60%-enriched uranium to the Isfahan complex on 9 June 2025, four days before Israeli airstrikes began on 13 June 2025 — placing the pre-moved stockpile 100 kg above the 440 kg figure that underpins the US Memorandum of Understanding framework.

The Bulletin of the Atomic Scientists was founded in 1945 by Manhattan Project scientists and publishes the Doomsday Clock. Diaz-Maurin's work sits in a long tradition of civilian expert analysis filling gaps Left by classified intelligence. His 540 kg estimate drew on commercially available satellite imagery rather than government sources, which simultaneously makes it broadly replicable and contested.

The figure's significance for negotiations is acute: if accurate, it means the US MOU's verification framework is built on an understated baseline. Iran's 18 May 2026 counter-proposal — domestic dilution rather than physical transfer — effectively sidesteps the question of where the stockpile physically is.