Donald Trump never tires of calling for a comprehensive deal Iran to put in prospect. The nuclear question is particularly important – if only because Trump has to prove that he is achieving more than Barack Obama did ten years ago with the nuclear agreement, which Trump later undermined.
According to American media reports, there are, among other things, intensive discussions between Washington and Tehran about the duration of a possible moratorium on uranium enrichment. Even before the war, Iran had offered to suspend uranium enrichment for five years. According to US media reports, the USA is currently demanding a significantly longer moratorium and a permanent ban on enriching uranium to more than four percent, as well as extensive control rights for the International Atomic Energy Agency (IAEA).
What fissile material does Iran have?
According to an April 9 report from the usually well-informed Institute for Science and International Security (ISIS), Iran has produced a total of about 1,235 kilograms of enriched uranium over the past 15 years. “Most of the uranium produced since the beginning of 2021 was used for further enrichment to 60 percent. Of the 933 kilograms, 731 kilograms, i.e. 78 percent, were enriched to 60 percent between December 2024 and June 2025,” the report says.
Why are the thresholds of 20 and 60 percent relevant?
Beyond 20 percent we speak of highly enriched uranium. Material that has already been enriched to 20 percent can be processed comparatively quickly into weapons-grade uranium. While uranium enriched to less than four percent is sufficient to produce fuel rods for common light water reactors to generate energy, material that has already been enriched to 20 percent can quickly be enriched even more. This applies even more to the material enriched to 60 percent. An enrichment level of a good 90 percent is required for weapon capability.
The ISIS analysts state that Iran produced around 230 kilograms of uranium enriched to 60 percent from April 2021 to December 2024. By the time the facilities were bombed in June 2025, this inventory had increased to 440 kilograms in just six months. This dynamic increases the suspicion that Iran wanted to build a nuclear weapon.
What is “nuclear dust”?
Trump has often used the word “nuclear dust.” In doing so, he seems to be alluding to the fact that Iran’s stocks of enriched uranium are probably completely or largely buried beneath the enrichment facilities bombed in June 2025, as the IAEA assumes. The United States and Israel have attacked Iran’s three main nuclear facilities, Nathan, Fordo and Isfahan. Some of their production halls are located deep under mountains.
Trump last suggested in April that Iran had agreed to hand over its stockpile of enriched uranium to the United States. “They agreed to give us back the nuclear dust,” Trump told reporters. Tehran immediately rejected this. The US President had previously even talked about the US and Iran being able to dig up and ship the material together.
Why does Iran need the uranium?
The Iranian side says it needs uranium for civilian purposes. Uranium enriched to 20 percent is necessary for the operation of a research reactor in Tehran (TRR), where radionuclides are primarily produced. These are needed for cancer treatments, for example. However, Rafael Grossi, director general of the IAEA, said in a March 2026 interview that the research reactor that the IAEA regularly inspects was a “reactor that could potentially be used to produce radioisotopes. There was very, very little… There was only limited use.”
The ISIS report also refers to the actual fuel consumption of the reactor. In four years, a total of only ten standard fuel elements and one control fuel element were used in the reactor core – this would require around 15.4 kilograms of uranium, which was enriched to 20 percent. In addition, Russia supplies Iran with fuel components. These “were sufficient to operate the reactor,” according to the analysis.
ISIS concludes: Iran’s justification for needing 20 percent uranium for medical purposes and energy supplies in the TRR “has proven to be grossly exaggerated.” Rather, Iran concealed the actual low use of the research reactor.
