How to make a nuclear bomb? Assembling a nuke isn’t hard part, getting the uranium is. Here’s how Iran could do it

The head of the UN’s nuclear agency has warned that Iran could begin enriching uranium again for a potential nuclear bomb within months. Rafael Grossi, Director-General of the International Atomic Energy Agency (IAEA), said US airstrikes on Iranian sites had done “severe but not total” damage, pushing back on Donald Trump’s claim that Iran’s nuclear programme had been “totally obliterated”.

“Frankly speaking, one cannot claim that everything has disappeared and there is nothing there,” Grossi told CBS News on Saturday. He added that Iran retains the “industrial and technological capacities” needed to restart uranium enrichment if it chooses to.

Iran’s nuclear facilities hit by US and Israel

On 13 June, Israel carried out strikes on several of Iran’s nuclear and military sites, claiming Tehran was nearing the development of a nuclear weapon. The United States later joined in, targeting key locations including Fordo, Natanz, and Isfahan with B-2 bombers and precision munitions. Despite these attacks, Grossi said Iran could have “a few cascades of centrifuges spinning and producing enriched uranium” in a matter of months. But how can one make a nuclear bomb?

Note: Don't try this at home, or you might risk ‘pre-emptive’ strikes.

How to make a nuclear bomb?

In principle, building a nuclear bomb requires reaching a critical mass of radioactive material to trigger a chain reaction. But the main challenge lies in acquiring the required material, plutonium or enriched uranium.

How to enrich Uranium?

Uranium is naturally found as uranium-238 and uranium-235. Only uranium-235 can sustain a nuclear chain reaction. But since less than 1% of natural uranium is uranium-235, it must be enriched to increase its concentration.

To do this, uranium is converted into a gas, typically uranium hexafluoride, and spun through centrifuges to separate the lighter uranium-235 from the heavier uranium-238. This process is repeated thousands of times until the desired enrichment level is achieved.

How enriched uranium fuels both power and weapons?

Civilian nuclear reactors typically use uranium enriched to 3%–5%, just enough to generate electricity. For a nuclear bomb, uranium must be enriched to 80%–90% a level called “weapons-grade”. Around 50 kilograms of this enriched uranium can be enough for a bomb.

Alternatively, plutonium, produced as a by-product in nuclear reactors, can also be used. Only 10 kilograms is needed for a bomb, and it’s often the preferred material for missile-mounted warheads due to its lighter weight.

How much-enriched uranium Iran has?

According to the IAEA, Iran has already enriched uranium to 60% purity. While that isn’t weapons-grade, the jump from 60% to 90% is technically easier than reaching the initial 60% from natural uranium. This has sparked international concern, especially since the same centrifuge technology used for peaceful nuclear energy can be repurposed for weapons development.

Civilian use versus military use of nuclear technology

Nuclear technology isn’t only for warfare. Controlled chain reactions in nuclear reactors produce around 9% of global electricity and are vital in medicine, particularly for diagnostics and treatment of diseases. However, the dual-use nature of uranium enrichment has made it one of the most tightly monitored processes in international security, with the IAEA playing a key role in oversight.