How quickly will Iran be able to build a nuclear bomb?

Iranian officials say they could accelerate nuclear activities and start enriching uranium but they also have incentives not to.

Iran could quickly ramp up its nuclear activities now that President Donald Trump pulled out of the 2015 international agreement designed to curtail them. But experts and former officials differ over how long Tehran would need to build a bomb.

Some, pointing to Iran’s slow past progress and independent analyses, believe Iran would need several years to produce a nuclear weapon. Others think Tehran could build one in little over a year.

Iranian officials have said they could accelerate nuclear activities and start enriching uranium within days.

Separate from the technical question is the political one. US officials have voiced skepticism that Iran would quickly return to work on a bomb.

“Iran wasn’t racing to a weapon before the deal,” Secretary of State Mike Pompeo told lawmakers last month. “There is no indication that I’m aware of that if the deal no longer existed that they would immediately turn to racing to create a nuclear weapon today.”

Many observers believe Iran has incentives not to expand its nuclear activities or expel international inspectors even if the U.S. exits the deal.

Iranian officials hope to maintain trade with Europe—which is mainly supportive of the pact—and an outright return to nuclear activities would likely stop that. Attempting to relaunch its nuclear program secretly would slow Iran’s path significantly and carry major risks.

Donald Trump delivers his statement on the Iran nuclear deal. Picture: AP.

Iran worked on three aspects of a nuclear program—enriching uranium, obtaining plutonium and trying to acquire the know-how to build a nuclear weapon—before the 2015 deal, which lifted most international sanctions in exchange for strict but temporary limits on its program. Tehran says its nuclear program was always for peaceful purposes.

Iran had amassed a large stock of low-enriched uranium and produced nuclear fuel enriched to 20% purity. That is several steps from producing weapons-grade uranium enriched to 90% purity. Still, US officials said in 2015 that Iran was just two or three months from amassing enough fuel for a bomb.

Iran was also building a plutonium reactor at Arak, in its northwest. When completed, it could have produced material for a couple of nuclear weapons annually, US officials say.

The International Atomic Energy Agency concluded in 2015 that Tehran— despite denials—pursued a concerted weaponization program until 2003 and continued some of that work until 2009.

The 2015 agreement was structured around restrictions to ensure Iran would need at least 12 months to gather enough nuclear fuel for a bomb.

Most experts believe that the accord largely ensured that by removing roughly 98% of Iran’s enriched uranium stockpile, mothballing two-thirds of its uranium-spinning centrifuges, limiting research and development, and removing the core of the Arak reactor.

“It would take many years for Iran to have a working nuclear arsenal,” said Daryl Kimball, executive director of the Arms Control Association, a Washington based group that supports the deal.

Hassan Rouhani. Picture: AP.

One critic of the deal, Olli Heinonen, a former senior IAEA official who works for the Foundation for Defense of Democracies think tank, said Iran may have gathered the parts for more advanced centrifuges than Tehran had declared. That could speed the production of weapons-grade uranium and shorten the time to build a bomb. There is no evidence, however, that Iran lied to the IAEA about this additional hardware.

Experts and former officials say Iran would need at least 18 months to reconstitute the Arak reactor, whose core was filled with concrete as a consequence of the deal.

It’s also unclear how much Iran knows about assembling a bomb. The IAEA in 2015 concluded that Iran’s weaponization work “did not advance beyond feasibility and scientific studies” and knowledge of “certain relevant technical competences and capabilities.”

The report was controversial. The IAEA spoke to some scientists and experts but not at length. Access to key sites was limited.

But it’s also unclear whether Iran​ has the technical ability to reliably deliver a nuclear warhead with its existing missile technology.

Last month, Israeli Prime Minister Benjamin Netanyahu said his country had obtained 100,000 pages of documents from a secret location in Tehran showing Iran had safeguarded its nuclear know-how. He said the material showed Tehran intended to resume its activities. Israeli leaders have vowed to stop Iran from getting the bomb.

While no new information has emerged publicly from that archive, the IAEA has called out Iran for seeking to erase possibly crucial work at the sprawling military site of Parchin. The agency said in 2015 that Iran’s explanation for its activities didn’t add up.

Iran is believed to have carried out work there on high explosives—materials that detonate very quickly. Mr. Heinonen said these could have been “an important step in the design and mock-up of a nuclear weapon.”

Jeffrey Lewis, a non-proliferation expert at the Middlebury Institute of International Studies, said Iran was “quite far along” on its weaponization work with access to sophisticated designs from abroad. Stopping that effort was one reason why concluding the 2015 deal made sense, he argued.

“What we don’t know is how well they [the Iranian efforts] would work on a first test,” he said.

The Wall St Journal