The UN atomic agency said as recently as June 2 that Tehran is sticking to the terms of the deal, having neither...
Struck in Vienna by the five permanent members of the United Nations Security Council (Britain, China, France, Russia and the United States) plus Germany, the deal established controls to prevent Tehran from developing an atom bomb.
The UN atomic agency said as recently as June 2 that Tehran is sticking to the terms of the deal, having neither enriched uranium to prohibited levels, nor built up illegal stocks of low-enriched uranium or heavy water.
The objective of the accord is bring to a minimum of one year, for at least 10 years, the "breakout time", or the time Iran needs to produce enough fissile material to make an atom bomb. It is also meant to ensure that any moves to do so will be easily detectable.
Under the deal, Tehran agreed to slash the number of uranium centrifuges, which can enrich uranium for nuclear fuel as well as for nuclear weapons, from more than 19,000 to 5,060, maintaining this level for 10 years.
All enrichment takes place at the Natanz facility. The Fordo site, containing an additional 1,044 centrifuges, is no longer allowed under the accord to enrich uranium.
Iran's pre-deal stockpile of 12 tonnes of low-enriched uranium -- enough for several nuclear weapons if further enriched -- is under the deal reduced to 300 kilogrammes (660 pounds), a ceiling that will last for 15 years.
Only enrichment to low purities is allowed, also for 15 years.
Iran's Arak reactor is also to be redesigned so that it does not produce weapons-grade plutonium, the alternative to highly enriched uranium for a nuclear weapon.
Tehran will not build another heavy water reactor for 15 years.
A so-called Additional Protocol is applied, allowing for closer inspections, including potentially of military bases.
The International Atomic Energy Agency (IAEA) also employs high-tech surveillance equipment and has access to facilities such as uranium mines and centrifuge workshops for periods of up to 25 years.
The accord, adopted by the UN Security Council on July 20, 2015, came into force on January 16, 2016, opening the way for a partial lifting of international sanctions on Iran.
UN embargos on conventional arms and on ballistic missiles have been maintained up to 2020 and 2023 respectively.
Many international sanctions have since been lifted, opening the door for foreign investors. In early July, French group Total, heading an international consortium, signed $4.8-billion deal with Iran.
However, Washington has imposed new measures targeting Iran's ballistic missile programme and activities in the region.