The Geneva agreement is designed to freeze Iran's nuclear programme for six months, pending a final settlement. The essential goal is to increase the amount of time that Iran would need to "breakout" and build a nuclear weapon.
So the deal imposes strict controls on Iran's most sensitive nuclear work.
– Today, Iran has 19,462 centrifuges inside two uranium enrichment plants. These machines could be used to make fuel for nuclear power stations – or the core of a nuclear weapon. Making sure they never do the latter is the agreement's key aim.
– The deal says that the 9,500 centrifuges which are currently standing idle will stay idle. Iran agrees to leave them unused. That includes 1,008 advanced machines, which will stay out of commission, thereby achieving a key Western goal.
– As for the almost 10,000 working centrifuges, the agreement allows Iran to continue using them to enrich uranium, in breach of six United Nations resolutions. But there are crucial restrictions. In particular, Iran will stop enriching uranium to the 20 per cent purity that is close to weapons grade. Its existing stockpile of this material will be converted into harmless oxide.
– In addition, Iran will not increase its store of uranium processed to the 5 per cent level needed for nuclear power stations. If its scientists make any more of this material, it will have to be converted into oxide. There will be no net increase in its stockpile.
– Iran is building a new plutonium reactor at Arak, which could give the country an alternative path to the ability to build a nuclear weapon. Under the deal, Iran will not fuel or commission this facility – and essential work will be halted. In effect, this should prevent Iran from being able to operate Arak.
– As for verification, inspectors from the International Atomic Energy Agency will be allowed to pay daily visits to Iran's nuclear plants.
– In return, the P5+1 will ease sanctions in what the White House has described as a “limited, temporary, targeted, and reversible” manner to the tune of around $7 billion.
The United Nations Security Council and European Union will not impose any new nuclear-related sanctions for six months, while the US and EU will suspend sanctions on Iran’s petrochemical exports and associated services such as insurance or transportation, and on gold and precious metals and associated services. US trade restrictions on Iran’s car industry and associated services will be lifted and licenses given for the supply and installation in Iran of spare parts for flight safety. An agreed amount of revenue from sanctioned Iranian oil sales held abroad will be repatriated.
Experts believe the agreed controls will stop Iran's nuclear programme in its tracks.
Mark Fitzpatrick, a non-proliferation expert at the International Institute for Strategic Studies, said: "It's better than I thought it would be. I didn't realise that the verification would be this extensive. It caps every aspect of their programme."
Mr Fitzpatrick added: "They're extending the time that Iran would need to breakout to build a nuclear weapon: they are at least doubling it, I would say. And if they hadn't done this, the time needed would have halved. Instead of the Iranians halving the breakout time, it will double."
But there are key concerns.
Iran would, in theory, be able to reverse the process of converting its medium-enriched uranium into oxide. In addition, the country has built secret plants in the past. It may possess unknown facilities where work could continue regardless.