What you need to know about Iran’s nuclear program as Israel ramps up strikes

When Israel attacked Iran last week, it said nuclear scientists working on the bomb were the target, and has since launched waves of missiles targeting Iranian nuclear facilities.

Global alarm has been increasing as Iran enriched uranium to almost weapons-grade, and Israel claimed the Islamic republic was just days away from building nuclear weapons.

But is Iran actually close to making a nuclear bomb? What’s the fallout when a nuclear workshop is blown up? And does Israel have its own stockpile of nuclear weapons?

What is enriched uranium, and how does it make nuclear weapons?

Enriched uranium, specifically uranium-235, is an essential component in many nuclear weapons. Scientists take naturally occurring uranium, of which less than 1 per cent is uranium-235, and expertly draw out (or enrich) the substance to increase the proportion of uranium-235 while removing uranium-238.

They do this by using centrifuges, a kind of scientific salad spinner which rotates uranium, in gas form, thousands of times a minute and separates the lighter uranium-235 from the base uranium.

This is an incredibly difficult process because both forms of uranium are nearly identical in their make-up, says Edward Obbard, Nuclear Innovation Centre director at the University of New South Wales. Most nuclear reactors are powered by uranium that is enriched by no more than 5 per cent, according to the World Nuclear Association.

But once uranium is enriched by 90 per cent, it is deemed weapons-grade. “That’s incredibly difficult, in that you need to enrich it for a very long time, and push it through this process again and again and again,” Obbard says.

Is Iran enriching uranium?

Iran is enriching uranium under what it claims is a civilian energy program reliant on enriched uranium. Iran is also a signatory to the Nuclear Non-Proliferation Treaty.

But the International Atomic Energy Agency, the global nuclear watchdog, has reported that Iran has enriched uranium to 83.7 per cent and had a stockpile of 60 per cent-enriched uranium.

Uranium enriched to this level has no civilian application, and the process for enriching uranium from 60 per cent to weapons-grade is much faster than the initial enrichment steps.

Stephan Frühling, nuclear weapons expert at the Australian National University, says Iran has given some “concoctive excuses” for possessing such highly enriched uranium, but that “nobody believes that stuff ... they’re [Iran] just claiming that they’re civilian applications”.

The day before Israel attacked, the International Atomic Energy Agency board censured Iran for refusing to co-operate with inspectors and announcing it would build a third enrichment site and update its centrifuges.

In the hours after the attack, Israeli Prime Minister Benjamin Netanyahu said Iran was just days away from being able to build several nuclear weapons, and Israel’s airstrikes were an act of preventative self-defence. CNN reported that US intelligence had indicated Iran was still years away from being able to make the weapons, quoting unnamed officials.

Where are Iran’s nuclear facilities?

There are several nuclear sites in Iran – including power plants and reactors – but the nuclear enrichment plants Natanz and Fordow are central to Israel’s war against the Islamic republic.

The Natanz facility is Iran’s biggest enrichment plant and where thousands of centrifuges diffuse uranium.

The Natanz nuclear enrichment facility, south-east of Tehran in January, and on Saturday, after Israeli airstrikes destroyed several buildings.Credit: AP

The International Atomic Energy Agency said Israel had directly hit the underground enrichment halls at the Natanz facility, leaving them “severely damaged, if not destroyed altogether”.

Israel Defence Forces spokesman Effie Defrin said: “We’ve struck deep, hitting Iran’s nuclear, ballistic and command capabilities.”

Fordow is Iran’s secret, deep-underground enrichment site. It was completed and unveiled to the public in 2009, although US intelligence claims to have been aware of its existence earlier.

Fordow is smaller than Natanz and, because of its depth and secrecy, is probably where Iran tries to diffuse uranium to weapons-grade, says Frühling. “[Fordow] really has no civilian application that makes sense,” he says.

What happens if a nuclear facility is blown up?

The main health risk from destroying an enrichment plant is releasing the harmful uranium hexafluoride gas contained in the centrifuges. “[It] is one of the most corrosive substances on Earth, and so that poses a lot of challenges,” says Frühling.

“So if you destroy one of these enrichment plants, you will create very nasty local contamination of a highly corrosive and highly toxic gas that you really do not want to get in contact with.”

Obbard says: “It’s not what people generally think of as a kind of nuclear accident,” referencing the explosion at Chernobyl, Ukraine, in 1986. “It makes a mess, but it’s not gonna be a kind of nuclear mess”, due to the low radioactivity of the uranium.

But the International Atomic Energy Agency’s director-general, Rafael Mariano Grossi, said armed attacks on nuclear facilities “could result in radioactive releases with grave consequences”.

Inside the missile-struck Natanz facility, there was radiological and chemical contamination, and the radiation “poses a significant danger if uranium is inhaled or ingested”, Grossi said. But outside the facility, radiation remained unchanged, the agency said.

How can Israel destroy Fordow?

If Israel continues attacking Iran until it cripples the country’s nuclear capability, destroying the Fordow nuclear enrichment site is essential, since nuclear energy experts believe it to be the most likely place the Islamic republic would build weapons.

Fordow is located inside a mountain, 90 metres underground. It can be reached only by American “bunker-busting” bombs, which Israel does not possess. These bombs punch through the earth before detonating to penetrate deep underground.

So far, the US has not agreed to supply its ally with the bombs, but according to CBS News, the White House is considering joining Israel in striking Iran’s nuclear facilities.

Does Israel have nuclear weapons?

Israel is believed to have its own stockpile of nuclear weapons, though it refuses to confirm or deny their existence.

The Centre for Arms Control and Non-Proliferation says Israel is believed to possess 90 nuclear warheads. It is the second-smallest collection of the nine nuclear-armed nations.

Israel is not a signatory of the Nuclear Non-Proliferation Treaty.

Get a note directly from our foreign correspondents on what’s making headlines around the world. Sign up for the weekly What in the World newsletter here.