VIENNA — Iran has converted three quarters of a nuclear stockpile that it could have turned quickly into weapons-grade uranium into less volatile forms and is well on its way to transforming the rest, the U.N. atomic agency reported Thursday.
The development — agreed to by Iran under a nuclear deal it struck late last year with six world powers — leaves Tehran with substantially less of the 20 percent enriched uranium that it would need for a nuclear warhead.
Iran denies any interest in atomic arms. But it agreed to some nuclear concessions in exchange for a partial lifting of sanctions crippling its economy. The deal took effect in January.
Uranium at 20 percent is only a technical step away from weapons-grade material. By the time the agreement was reached late last year, Iran had amassed nearly 440 pounds. With further enrichment, that would have yielded almost enough weapons-grade uranium for one atomic weapon — a threshold that Israel had vowed to prevent Iran from reaching by any means possible.
Under the agreement, Iran agreed to stop enriching to grades beyond 5 percent, the level most commonly used to power reactors. It also committed to neutralizing all of its 20 percent stockpile — half by diluting to a grade that is less proliferation-prone and the rest by conversion to oxide used for reactor fuel.
In line with information given to the Associated Press by diplomats this week, the International Atomic Energy Agency confirmed Thursday that Iran had completed the dilution process.
The confidential IAEA report obtained by the AP also said conversion was well underway, with more than 110 pounds of the 20 percent material rendered into oxide.
Iran has until July to fulfill all of its commitments under the deal. But it has to show progress in exchange for sanctions relief, and it is eager to get its hand on the next tranche of some $4.2 billion of oil revenue funds that were frozen under international sanctions meant to force it into nuclear compromise.