Two types of radioactive material can be used to manufacture a nuclear bomb, uranium and plutonium, both produced from uranium ore.
Raw uranium contains less than 1% of U-235, the substance (isotope) needed to fuel reactors and make bombs. In a process called enrichment, centrifuges are used for separating the U-235 from the rest of the uranium, and to raise its concentration.
Meanwhile, plutonium is made by irradiating uranium in a nuclear reactor.
For most power reactors in the West, uranium is enriched up to 5%, according to the New York Times. However, Iran had been enriching ore up to 20%.
Also, Iran has been constructing a nuclear reactor at Arak to produce Pu-239, the type of plutonium that can be used to manufacture bombs.
The framework of the Iranian deal
Iran shall decrease enrichment levels to 3.7% and cut its stockpile of low-enriched uranium from 10,000 kg to 300 kg.
Iran shall reduce the number of centrifuges installed by about two-thirds.
About 5,000 centrifuges would remain spinning to enrich uranium at the main nuclear site at Natanz, about half the number currently running.
Iran shall convert the underground enrichment site at Fordo into a centre for nuclear physics and technology research.
Iran shall redesign and rebuild the Arak reactor base in a manner that will not produce weapons-grade plutonium.
Iran shall not build any additional heavy water reactors for 15 years.
Iran shall allow the International Atomic Energy Agency better access and information regarding its nuclear programme, and to the supply chain that supports that programme.