Uranium enriched to 60% sits one step below the roughly 90% used in weapons. That single number explains most of the alarm around Iran’s nuclear program.
What the percentages mean
The Council on Foreign Relations lays out the ladder. Mined uranium holds less than 1 percent of the uranium-235 isotope that drives fission, and centrifuges raise that share. Power plants run on uranium enriched to 5 percent. At 20 percent it serves research reactors and medical uses. Weapons need around 90 percent.
The 2015 nuclear deal, the JCPOA, capped Iran’s enrichment level, its centrifuge numbers and types, and the size of its enriched stockpile. Iran also agreed to let inspectors from the International Atomic Energy Agency, the UN’s nuclear watchdog, into its facilities and potentially into undeclared sites. The aim, in the CFR’s account, was to stretch the time Iran would need to build a bomb to at least one year, so other powers could respond.
How the limits came apart
President Trump pulled the United States out of the agreement in 2018. A year later Iran began exceeding the cap on its low-enriched stockpile and moved to higher concentrations, though still far short of weapons grade. In January 2020, after the US killing of General Qasem Soleimani, Tehran said it would stop limiting its enrichment at all. Talks to revive the deal opened in April 2021 and went on and off without result.
Inspection access shrank over the same period. Iran pledged in March 2023 to cooperate more with the IAEA. That came months after inspectors found uranium particles enriched to 83.7 percent at Fordow, which set off international concern. UN inspectors had reported in early 2023 that Iran had enriched trace amounts to nearly weapons-grade levels.
Tehran’s explanation
Iran’s account is that 60% was a response, not a goal. President Ebrahim Raeisi told CNN’s Fareed Zakaria in September 2023 that the country had not set out to reach that level. European states, he said, “trampled upon their commitments.” He rejected any military dimension, and Iranian state media Press TV reported that he repeated Tehran’s position that it does not plan to acquire a bomb.
Europe and the United States reject that reading. They argue there is no civilian justification for enrichment at that purity and say the purpose is bomb-making, according to DW. Iran has repeatedly denied it.
The IAEA’s warning
IAEA chief Rafael Grossi later told reporters at the Manama Dialogue in Bahrain that Iran was “dramatically” increasing its enrichment up to 60% purity. He said monthly production of highly enriched uranium was expected to jump from 4.7 kilograms to more than 34 kilograms (75 pounds). “This is a message,” Grossi said. “This is a clear message that they are responding to what they feel is pressure.” He called the plan “very concerning” and said that if Iran ran all of its centrifuges, it would be “a huge jump.”
The agency asked Iran for “timely and technically credible assurances” that its facility was not being misused to produce uranium above the declared level. A German foreign ministry source told Reuters the step was “a serious escalatory step by Iran.”
Sources
- What Is the Iran Nuclear Deal? (Council on Foreign Relations backgrounder)
- Iran 'dramatically increasing' enrichment, IAEA warns (DW)
- Raeisi: 60% uranium enrichment came after Europeans trampled on JCPOA commitments (Press TV, Iranian state media)
