Iran Declares It Is Doing More Nuclear Enrichment After I.A.E.A. Rebuke

Iran said Friday it would begin operating new machines to enrich more uranium, which could bring it closer to having a weapon. The move came in response to a censure by the International Atomic Energy Agency for failing to cooperate fully with atomic inspectors.

The announcement did not say how many of the machines began spinning, nor how much uranium they will produce. But Western experts said Iran’s act could initiate a significant escalation in the moves and countermoves between Tehran and the U.N. nuclear inspectors based in Vienna, who have struggled for decades to keep the nation from getting the means to make an atom bomb.

Iran will activate “a substantial number of advanced centrifuges of various models,” which are able to produce highly enriched nuclear fuel, read a joint statement from Iran’s Foreign Ministry and its Atomic Energy Organization. It condemned the censure as “politicized and destructive,” saying it undermined “the positive momentum” achieved between Iran and the I.A.E.A.

Behrouz Kamalvandi, a spokesman for Iran’s Atomic Energy Organization, said Friday in an interview with media in Iran that the country began accelerating its enrichment right after the order was announced. “We immediately started,” he was quoted as saying. “We will significantly increase enrichment.”

Having a supply of highly enriched uranium fuel is just one step of many it would take to build a deliverable atom bomb. Other crucial steps include turning the material into a metallic sphere and making arrays of explosive detonators, and may take many more months to complete.

Late Thursday in Vienna, the Board of Governors of the International Atomic Energy Agency voted 19 to 3, with 12 abstentions, for Iran’s censure. The move could lead to penalties against Tehran, including new economic sanctions. The agency sees the censure step as exercising its mandate to try to keep the world’s peaceful nuclear programs from crossing lines that would let them make warheads.

The technical aspect of the current impasse involves Iran’s enrichment of uranium to a purity of 60 percent — very close to the level needed for a weapon. Iran had offered to freeze its enrichment at that level if the censure move was abandoned. It is now racing ahead.

Critics objected to the freeze, arguing that Iran could restart nuclear fuel enrichment quickly. The country already has enough material in its stockpile to rapidly make fuel for four or five nuclear weapons. Iran insists that its nuclear program is for peaceful purposes only. But uranium enriched to 5 percent is used to fuel most civilian nuclear reactors, while the purity level must be raised to roughly 90 percent for atom bombs.

Iran agreed to give up much of its enriched uranium stock in 2015 under an international accord, but that fell apart in 2018 after President Donald J. Trump said the deal was inadequate for curbing Iran’s nuclear ambitions and regional influence.

Then, in early 2021, Iran began a push to raise its enrichment levels to 60 percent. That level is considered quite threatening. As the purity level rises, the tricky process of enrichment becomes far easier and requires fewer centrifuges. In other words, it’s much less complicated to get to 90 percent purity from a starting point of 60 percent than from 30 or 20 percent.

“The higher the concentration, the easier it gets,” said Houston G. Wood III, a professor of mechanical and aerospace engineering at the University of Virginia who specializes in nuclear enrichment.

In an interview, David Albright, president of the Institute for Science and International Security, a private group in Washington that tracks nuclear proliferation, said Iran had “put in place a very large capacity” to enrich uranium “and they’re now expanding their use of it.”

The basic measure of Iran’s capacity for making nuclear fuel is its number of centrifuges — tall machines that spin at supersonic speeds to raise concentrations of the rare form of uranium needed to fuel reactors and atom bombs. That process is known as enrichment.

Mr. Albright said Iran has installed 19,000 centrifuges at its main enrichment plants, based at its Natanz and Fordo sites. The Fordo plant is inside a mountain to shield it from aerial attack. All the country’s major nuclear sites are ringed by barbed wire and antiaircraft guns. As of earlier this week, Mr. Albright added, 5,200 of the installed centrifuges were in a standby state — deployed and ready to go but not yet enriching.

The quick Iranian response to the censure, Mr. Albright said, is undoubtedly throwing some unknown number of those thousands of idle machines into action.

“They already have a huge amount of activity,” he said. “Now they’re adding to that.” Mr. Albright said his group laid out the centrifuge numbers and other Iranian nuclear developments in a report published Thursday.

In July, Secretary of State Antony J. Blinken said Iran’s breakout time — the period of rapid enrichment needed to make enough weapon-grade material for a single nuclear weapon — “is now probably one or two weeks.” His estimate appeared to be one of the shortest breakout estimates that American officials had ever made in public.

Mr. Albright has estimated that if Tehran pulled out all the stops, it could make a crude atom bomb in about six months.