How much enriched uranium does Iran have left to make nuclear weapons?

The US attack and Israeli airstrikes of recent days leave an unsolved mystery as important as the status of the attacked nuclear facilities: where are the 400 kilograms of enriched uranium Iran possesses ? The International Atomic Energy Agency (IAEA) has told Bloomberg that it has not known its whereabouts for more than a week. There are fears on the part of Israel and the US that Tehran wants to end the enrichment process , which currently stands at 60%, in order to manufacture atomic weapons to be launched by its ballistic missiles.

According to US Secretary of State Marco Rubio, Iran could make up to ten nuclear warheads with that amount of uranium: "They have enough highly enriched uranium to make nine or ten bombs. All they have to do is spend a couple of days enriching it from 60 to 90 percent." Should the Persian nuclear program fail, this material risks ending up in the hands of militias and terrorist groups who would use it to make radiological bombs.

Enriched uranium is a raw material used to fuel nuclear reactors and produce atomic weapons . It is not the only available source, but it is one of the most important. On Earth, uranium usually occurs in the form of two isotopes: uranium -238 and uranium-235 . The latter is the only one of the two that can generate the atomic fissions used in nuclear reactors and weapons.

In nature, uranium-235 is very rare, often less than 1% of the total chemical element. A mechanism for separating isotopes produces "clean" uranium-235. Conceptually, it pursues a goal similar to other chemical processes used to obtain "purity" in elements such as silver, gold, etc. For nuclear power plants, the level of enriched uranium varies depending on the type of reactor, but in no case does it exceed 20% . However, for the development of atomic weapons such as the bomb dropped on Hiroshima, an enrichment level of 90% is required.

Rubio told CBS that "no one will know for sure for days" whether Iran attempted or was able to move highly enriched uranium . A member of the Iranian government told the Financial Times that it would have been "very naive to keep our enriched uranium" at the facilities attacked by the US. "The enriched uranium is intact now," he added. A senior Iranian official confirmed to Reuters that most of the 60% enriched uranium had been moved to an undisclosed location before the US attack. If confirmed, this movement would imply that Iran is hiding nuclear materials and equipment beyond the reach of Israeli, US, and IAEA oversight.

Several countries have developed their own atomic programs independently of the West, shrouded in great secrecy. These include China, North Korea, India, and Pakistan . Given Iran's level of enrichment, both Israel and the US fear that Iran will join the list of nuclear powers.

A second, yet unclear, risk is whether Iran had enriched uranium to 90% before the attack on the Fordow plant, the country's main facility bombed by the United States on Saturday. In that case, analysts cited by the Financial Times estimate they could develop a pair of nuclear warheads within a few months.

There is a third risk: the collapse of the Iranian regime could lead to enriched uranium ending up in the hands of Iranian-allied militias or terrorist groups through the black market. The material could be used to develop radiological bombs (popularly known as dirty bombs), which are much less destructive but still potentially dangerous.