Iran’s Last Atomic Gambit Could Make Crafting a Bomb Harder

Iran’s decision to cast its stockpile of 20% enriched uranium into metal for a research reactor reduces the risk that the Islamic Republic will move swiftly to build an atomic bomb, according to Robert Kelley, a U.S. nuclear-weapons engineer and former senior inspections official.

The International Atomic Energy Agency reported late Wednesday that Iran took another step to bring the country further out of compliance with its 2015 nuclear agreement with world powers. The country produced 3.6 grams of natural uranium metal -- about the size of an eraser on a pencil -- at its fuel plate fabrication facility on Feb. 6, according to a restricted two-page document seen by Bloomberg.

The move witnessed by IAEA inspectors is the first toward fuel production at a facility in Esfahan. Iran outlined last month how it will turn its stockpile of 20%-enriched uranium into metal plates for its research reactor, which in turn produces isotopes used for medicine and industry.

“They are taking material out of the pipeline,” said Kelley, the former manager of the U.S. Department of Energy’s centrifuge and plutonium metallurgy programs at the Lawrence Livermore National Laboratory. “It takes the uranium out of the weapons-usable inventory.”

Iran’s Last Atomic Gambit Could Make Crafting a Bomb Harder

Iran has been ratcheting up pressure since early December, when its parliament passed a law ordering engineers to begin enriching uranium at higher levels and then cast the metal into fuel for the Tehran Research Reactor.

But the activities don’t just make reviving the moribund nuclear agreement harder for the Biden administration, which is open to doing so once Iran returns to compliance. They also could make it tougher for Iran -- which wants the U.S. to first lift sanctions imposed by the Trump administration -- to sprint toward weaponization, according to Kelley.

Most of Iran’s current enriched-uranium stockpile is held in gaseous form, where it can be run through cascades of centrifuges at short notice. Those machines, which spin at supersonic speeds, separate the uranium-235 isotope required to set off the chain reactions in power plants and bombs. Most nuclear weapons use uranium enriched to 90% purity. Iran’s stockpile is between 3% and 20% enriched.

Iran told IAEA inspectors that they intend to mix their uranium metal with silicon in order to produce uranium silicide fuel, a source of energy used in atomic energy for decades that typically takes the form of small pellets.

“This is hardly an enabling step for a weapon,” Kelley said. “A uranium-silicon compound is very unsuitable for further enrichment in a centrifuge.”

The assessment could give the Biden administration space to engage with Iran as the clock ticks toward the next deadline on Feb. 21 -- the day when IAEA inspectors have been told they’ll have some monitoring powers curtailed unless U.S. sanctions are lifted.

“Until that day, Iran continues to be subject to full IAEA monitoring, which allows good insight into Iran’s fuel-cycle activities,” said Andreas Persbo, a nuclear nonproliferation analyst who is research director at the European Leadership Network. Even though casting uranium into metal could complicate a sprint toward a weapon, the message Iran is sending is still troubling.

“The Iranians are masters of operating in the gray zone,” Persbo said. “They are hewing to the letter of their safeguards agreement, but it’s clear this isn’t the kind of behavior that is desirable or expected.”

©2021 Bloomberg L.P.

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