The status of Iran's uranium enrichment programme

VIENNA — U.S. Vice President JD Vance told Reuters on Tuesday Iran must make a "meaningful" reduction in its uranium enrichment capacity to satisfy U.S. demands and end the countries' seven-month war.

While it is not clear what exactly he meant, below is a summary of what is known, and not, about the current status of Iran's uranium enrichment programme, which is at the heart of its nuclear infrastructure.

What did Iran have before the U.S. and Israel bombed?

Israel launched airstrikes on Iran's nuclear facilities on June 13 of last year, soon followed by the United States. In a 12-day campaign, they destroyed or badly damaged the three uranium-enrichment facilities that were known to be operating in Iran at the time.

They argued that Iran was getting too close to being able to produce a nuclear weapon, but the UN nuclear watchdog, the International Atomic Energy Agency, said it had no credible indication of a coordinated weapons programme.

Iran was, however, enriching uranium to up to 60 percent purity, a short step from the roughly 90 percent of weapons grade.

The IAEA, which had access to all Iran's declared nuclear sites, including its enrichment plants, until the U.S.-Israeli bombing campaign, estimates Iran had 440.9 kg of uranium enriched to up to 60 percent when the first bombs fell.

That is enough, if enriched further, for 10 nuclear weapons, according to an IAEA yardstick. Iran also had stocks of uranium enriched to lower levels.

No other country has enriched uranium to such a high level without producing nuclear weapons. The U.S. and its European allies say there is no civil justification. The IAEA said the enrichment level and quantity produced were of serious concern.

What remains?

Iran has not told the IAEA how much of its enriched uranium survived the attacks or informed it of its whereabouts. It has also not let IAEA inspectors return to the bombed sites since they were attacked.

Of the three enrichment plants, the only above-ground one, at the sprawling Natanz nuclear facility, was destroyed, the IAEA has said. The other two, at Natanz and Fordow, were at least badly damaged and are widely believed to be out of action.

The day before Israel attacked, Iran informed the IAEA it was opening a new enrichment plant at Isfahan, which diplomats say is in a network of tunnels there that appears largely unscathed from U.S. bombing. The IAEA says it does not know the status of that plant or whether it contains nuclear material.

While some of Iran's enriched uranium will have been destroyed in the U.S.-Israeli strikes, IAEA chief Rafael Grossi said in March his agency believes "a bit more than 200 kg" of Iran's uranium enriched to up to 60 percent remains in the tunnel complex at Isfahan, with some also still at Natanz.

Where does that leave Iran's enrichment capacity?

Not even Iran's arch-foe Israel alleges Iran is currently enriching uranium. How long it would need to restart is an open question, but as long as a significant portion of its 60 percent stock remains, it could in principle enrich to weapons grade with relatively little effort and few machines known as centrifuges.

A 2015 deal between Iran and major powers gave the IAEA extra inspection powers, including oversight of the number of centrifuges and parts for them.

U.S. President Donald Trump's withdrawal from that deal in 2018 prompted its collapse and the IAEA lost track of those machines. Their current number and whereabouts is unknown.

Then how can Iran reduce its capacity?

Given that Iran is not currently known to be enriching, any reduction is likely to be compared to its previous capacity, which was significant. A reduction could refer to purity, output or the number of enrichment sites.