Uranium at low concentrations can be used to operate nuclear reactors. At higher concentrations, through enrichment, uranium can be used to make nuclear bombs.
Iran began industrial uranium enrichment in 2006 and declared its goal to be peaceful. Reports from the International Atomic Energy Agency (IAEA) show that Iran's uranium reserves gradually increased in the following years.
In 2010, Iran announced it would begin enriching uranium to 20%, believed to be for the production of fuel for a research reactor. This is the official dividing threshold between civilian and military purposes.
The 20% enriched uranium level is worrying because it has moved closer to the level of bomb-making fuel.
As stockpiles continued to increase, the US began negotiations to restrain Iran's nuclear program. In 2015, Iran and 6 US-led powers reached an agreement, limiting the purity of enriched uranium to 3.67% and limiting the scale of stockpiles to below 300kg by 2030.
Iran did not have enough uranium for a bomb in 2018, when the US withdrew from the agreement and re-imposed a series of sanctions on Iran. After that, Iran began enriching beyond the limits of the agreement, first at a low level, then increasing to 20% in early 2021.
During the negotiation of the nuclear deal with the US during the administration of President Joe Biden, Iran enriched uranium to an unprecedented level, up to 60% - only a very short distance from the level used for atomic bombs.
When Donald Trump returned to power in 2025, Iran's enriched uranium stockpile increased at the fastest rate since the IAEA began publishing data.
In June 2025, during the 12-day war, the US bombed Iran's uranium enrichment facilities in Natanz, Fordow, and uranium storage tunnels in Isfahan.
A month later, Iran suspended cooperation with the IAEA, ending monitoring uranium enrichment sites.
In a context where there is no longer direct on-site inspection and although there is still satellite monitoring, the location of Iran's 11-ton uranium depot is still a mystery.
Due to its radioactivity and chemical toxicity, part of the reserve is still hidden or buried under the rubble, making access or destruction difficult. Even confirming that uranium still exists is not easy.
Experts believe that even if Iran digs up this amount of uranium, it will take months, even more than 1 year, to turn it into a nuclear warhead. According to experts, when a conflict breaks out, Iran will not create a close threat because it is still many years away from being able to build nuclear weapons.
The administration of President Donald Trump said that US satellites are monitoring this deep-buried uranium and that stockpile is little or no longer valuable to Iran because nuclear facilities and technical capabilities have been widely destroyed.
However, many analysts believe that last year, Iran may have established an enrichment facility in mountain tunnels connecting the Isfahan area, where Tehran is believed to have stored most of its uranium stockpiles.
If this is true, it raises the possibility that Iran is possessing a secret facility where it can conduct new enrichment waves to produce fuel for atomic bomb manufacturing.
