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In late 2019, reporters visited the Arak Heavy Water Complex, a potential source of plutonium.

SALAMPIX/ABACA/SIPA USA/AP IMAGES

New tensions dim hopes for salvaging Iran nuclear deal

Since U.S. President Donald Trump pulled the United States out of the Iran nuclear deal 2 years ago, other signatories have tried to salvage the agreement in hopes of constraining Iran’s ability to resurrect a nuclear weapons program. They haven’t given up yet. And although Iran has resumed activities proscribed by the deal, including stepping up uranium enrichment, it has kept the door open to a reversal. But a series of disputes has continued to fray the agreement.

This week, questions about Iran’s past clandestine atomic research program—including the disappearance of a missing uranium disk that could be used in a bomb, and illicit explosives testing—took center stage during a meeting of the governing board of the International Atomic Energy Agency (IAEA). And recent moves by the Trump administration have threatened to derail the conversion of Iranian nuclear facilities to reduce the risk they could contribute to a weapons program.

The Joint Comprehensive Plan of Action (JCPOA), as the 2015 deal is called, offered Iran relief from economic sanctions in exchange for dismantling large pieces of its nuclear program. Although experts generally agree the JCPOA worked, the Trump administration withdrew in May 2018, arguing it didn’t go far enough. New U.S. sanctions have since battered Iran’s economy.

“It hasn’t been easy to watch the deal get dismantled,” says a European diplomat who requested anonymity because talks with Iran are at a sensitive stage. Yet, “So far, Iran has been notably measured in building up its nuclear capabilities,” Christopher Ford, assistant secretary for international security and nonproliferation at the U.S. State Department, recently told journalists.

An IAEA report shared with the governing board last week said Iran has been enriching uranium hexafluoride gas to 4.5% of the fissile isotope uranium-235 (U-235) over the past year. By 20 May, it had stockpiled 1572 kilograms of enriched uranium, ostensibly for use in civilian reactors. Nuclear bombs require enrichment levels exceeding 90% of U-235. “They could have made a lot more uranium at a higher enrichment level, but they haven’t,” says Richard Johnson of the nonprofit Nuclear Threat Initiative.

An enriching pursuit

Iran has revved up uranium enrichment, decreasing the time needed to produce a bomb’s worth of uranium-235.

May 2019 Aug. 2019 Nov. 2019 Feb. 2020 May 2020 0 400 800 1200 1600 May 2019 Aug. 2019 Nov. 2019 Feb. 2020 May 2020 0 400 800 1200 1600 kg 174 1572 Enriched uranium up to 5%
GRAPH: M. ENSERINK/SCIENCE; (DATA) David Albright, Sarah Burkhard, Andrea Stricker/Institute for Science and International Security

But Iran has greatly ramped up R&D on advanced centrifuges, which could speed up enrichment and reduce the “breakout time” needed to enrich a bomb’s worth of weapons-grade uranium to 3 months. The JCPOA ensured the breakout time would exceed 1 year; the Western diplomat estimates it is still more than 6 months.

IAEA and outside analysts have also been poring over a cache of documents Israeli agents spirited out of Iran in early 2018. The nuclear archive, as it’s called, has yielded fresh insights into Iran’s past R&D on nuclear weapons and its plans for underground testing that IAEA says call into question the “correctness and completeness” of declarations Iran made in 2003, when it agreed to come clean on its nuclear program and permit inspectors broad access to sites.

Iran had hoped the deal would end questions about its shuttered bomb effort. But IAEA now wants to know the whereabouts of a disk of uranium metal that could be used to generate neutrons for triggering fission in a bomb’s U-235 core. Evidence suggests it was housed at a site called Lavizan-Shian in Tehran, which Iran razed and sanitized in 2003 and 2004. In January, IAEA asked Iran to give its inspectors access to two unnamed sites to verify the absence of undeclared nuclear material and activities. According to a report last week from the nonprofit Institute for Science and International Security, one site appears to be a testing range for high explosives near Abadeh, in central Iran. During a September 2019 press conference, Israeli Prime Minister Benjamin Netanyahu showed satellite images indicating that site was razed only in July 2019.

In a 28 January letter to IAEA, Iran rebuffed the agency, declaring it “will not recognize any allegation on past activities and does not consider itself obliged to respond to such allegations.” The dispute has raised fresh questions about Iran’s intentions and gives the United States another cudgel to try to persuade the United Nations Security Council to reimpose nuclear related sanctions.

Other components of the JCPOA are also foundering. Before the agreement, Iran was building a heavy water research reactor in Arak that would accumulate several kilograms of plutonium a year in spent fuel—enough for one or two bombs. The deal mandated a redesign of the Arak reactor to sharply curtail generation of plutonium. Even after walking away from the JCPOA, the United States had supported the redesign by waiving sanctions on other countries taking part in the work—until May, when the State Department decided to let the waivers expire as of 27 July. The move perplexed observers. “I cannot stress enough how bizarre it is to me that we demanded that the Iranians convert the reactor—and now we insist they must not convert it,” says Jeffrey Lewis of the Middlebury Institute of International Studies at Monterey.

If the Arak redesign falls through, Iran could claim that Western powers are out of compliance with the JCPOA, the diplomat says. Work will continue at Arak, which Iran has renamed Khondab, says Ali Akbar Salehi, president of the Atomic Energy Organization of Iran. “Soon the international community will witness our new achievements at the Khondab Research Reactor,” Salehi told Science. “Although sanctions impose some constraints, it invigorates us.” He did not provide details, and analysts are not sure what Iran’s plans are for the reactor.

U.S. withdrawal from the JCPOA has also scuttled a grand plan to turn an underground facility near the holy city of Qom into an international research center. Under the deal, Iran mothballed 700 uranium enrichment centrifuges at the Fordow site and worked with Russia to convert 328 others to producing isotopes for medicine. JCPOA negotiators floated other ideas, including installing a particle accelerator in the cramped space. But late last year, Iran resumed uranium enrichment in one Fordow hall. “That created a bit of a conundrum,” says Johnson, who was involved in the deal’s implementation during the Obama administration. Even minute traces of uranium would contaminate the medical isotope centrifuges. Worsening matters, a few weeks later, the United States canceled a sanctions waiver for the medical isotope work, prompting Russia to back away. Iran will continue to operate a dozen Russian-modified centrifuges on its own.

The failure to convert Fordow to a civilian research center “is a missed opportunity,” says Andrea Stricker, a nonproliferation analyst at the nonprofit Foundation for Defense of Democracies.

Despite the nuclear deal’s slow-motion collapse, observers don’t expect Iran to open up the throttle on its program—at least not before the U.S. elections in November. If Democratic presidential candidate Joe Biden wins, the next administration “may try to resurrect some form of the JCPOA,” Stricker says. “And the Iranians would probably want to test and see what they can get.”