Missing uranium: US air strikes on Iran's nuclear sites set up 'cat-and-mouse' hunt

IAEA had regular access and used to watch enrichment sites closely; earlier there was detailed accounting of enrichment, but now doubts linger whether fate of all batches can be determined

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The US and Israeli bombing of Iranian nuclear sites creates a conundrum for UN inspectors in Iran: how can you tell if enriched uranium stocks, some of them near weapons grade, were buried beneath the rubble or had been secretly hidden away?

Following last weekend's attacks on three of Iran's top nuclear sites at Fordow, Natanz and Isfahan President Donald Trump said the facilities had been "obliterated" by US munitions, including bunker-busting bombs.

But the UN nuclear watchdog, the International Atomic Energy Agency, which monitors Tehran's nuclear programme, has said it's unclear exactly what damage was sustained at Fordow, a plant buried deep inside a mountain that produced the bulk of Iran's most highly enriched uranium.

IAEA chief Rafael Grossi said on Monday it was highly likely the sensitive centrifuges used to enrich uranium inside Fordow were badly damaged. It's far less clear whether Iran's 9 tonnes of enriched uranium - more than 400 kg of it enriched to close to weapons grade were destroyed.

Western governments are scrambling to determine what's become of it.

Reuters spoke to more than a dozen current and former officials involved in efforts to contain Iran's nuclear program who said the bombing may have provided the perfect cover for Iran to make its uranium stockpiles disappear and any IAEA investigation would likely be lengthy and arduous.

Olli Heinonen, previously the IAEA's top inspector from 2005 to 2010, said the search will probably involve complicated recovery of materials from damaged buildings as well as forensics and environmental sampling, which take a long time.

"There could be materials which are inaccessible, distributed under the rubble or lost during the bombing," said Heinonen, who dealt extensively with Iran while at the IAEA and now works at the Stimson Centre think-tank in Washington.