Fordow was built inside a mountain, apparently to protect it from aerial bombardment, and the 2015 deal does not allow enrichment there.
Iran has breached the deal’s 3.67 per cent limit on the purity to which it can enrich uranium, but it has only gone up to 4.5 per cent so far, well short of the 20 per cent it achieved before the deal and the 90 per cent that is weapons-grade.
The deal’s main aim was to extend the time Iran would need to produce enough fissile material for a nuclear bomb, if it chose to, to at least a year from roughly two to three months. It also lifted international sanctions against Tehran.
U.S. intelligence agencies and the IAEA believe Iran had a secret, coordinated nuclear weapons programme that it halted in 2003. Iran denies ever having had one.