The United Nations' nuclear watchdog confirmed on Saturday that Iran had curbed its nuclear programme as agreed with world powers, paving the way for most international sanctions against Teheran to be lifted. Here are details of what this means.
BREAKOUT: The nuclear deal struck on July 14 last year aims, for the next decade, to extend the amount of time it would theoretically take Iran to produce enough fissile material for an atomic bomb - the so-called breakout time - from several months to a minimum of one year. CENTRIFUGES: Iran agreed to cut the number by two-thirds. It will be allowed to operate up to 5,060 first-generation centrifuges for 10 years at its Natanz plant. It will cap its uranium enrichment level at 3.67 per cent, well below the 90 per cent needed for bomb-grade material.
It will keep 1,044 first-generation centrifuges at its underground Fordow fuel enrichment plant, which will be converted into a nuclear, physics and technology centre. It can continue to conduct enrichment research and development without accumulating enriched uranium, including work with certain types of advanced centrifuges.
ARAK: Heavy water reactors, such as the one Iran had started building at Arak, can produce weapons-grade quantities of plutonium. Iran agreed to convert the Arak reactor so that such a "plutonium pathway" to a nuclear bomb is ruled out.
URANIUM STOCKPILE: Iran had to cut its enriched uranium stockpile from around 10,000kg to 300kg for 15 years. United States officials describe it as a 98 per cent reduction in Iran's stockpile, which would have no material enriched beyond 3.67 per cent. On Dec 28, the US said a ship carrying more than 11,000kg of low-enriched uranium materials had left Iran for Russia.
POSSIBLE MILITARY DIMENSIONS: Iran helped the International Atomic Energy Agency (IAEA) complete an investigation into what Western powers said was past nuclear weapons research, based on an IAEA report that strongly suggested Teheran had a nuclear weapons programme for years.
Last month, having received the extra information, which was not made public, the IAEA board of governors ended its inquiry into the so-called "possible military dimensions" of the programme. Iran denies ever having considered developing atomic weapons.
UN SANCTIONS: All such resolutions passed between 2006 and 2010 are terminated. However, a new resolution adopted on July 20 carries over some UN restrictions.
U SANCTIONS WITH IAEA: With IAEA confirmation that Iran had met its obligations under the deal, the European Union said it was immediately taking formal steps to lift all its nuclear-related economic and financial sanctions.
US SANCTIONS: Under the deal, the US is suspending nuclear-related sanctions against Iran. In practice, this means lifting restrictions that now prevent non-US firms, entities and individuals from engaging in a wide array of transactions with Iran, on pain of sanctions against their activities in the US.
For the most part, restrictions on US actors will remain in place. The most dramatic US sanctions to be eased will be those that prevented non-US actors from buying oil from Iran, except in very limited circumstances, or from investing in its petroleum sector.
SNAPBACK: This mechanism is designed to allay fears that Iran might fail to keep its promises once sanctions are lifted. Under snapback, punitive sanctions will be automatically reintroduced if Iran fails to comply with the deal. A July 20 Security Council resolution allows all UN sanctions to be re-imposed if Iran breaches the deal in the next 10 years.