How Close Is Iran to Building a Nuclear Bomb?

January 7, 2020, 5:05 PM UTC

In the second half of 2019, after the U.S. withdrew from a landmark nuclear agreement with Iran and set out to wreck its economy, Tehran took modest steps violating the accord. After the U.S. killed the country’s most prominent military commander in a drone strike in Baghdad Jan. 2, Iran’s government said it was no longer bound by any of the atomic limits imposed by the deal. While officials stressed its nuclear sites remain open to international inspectors and said their decision was reversible, the escalation has deepened concern in world capitals from Beijing to Berlin.

1. How close is Iran to making a bomb?

It would take a while to accumulate the necessary materials. Under the multilateral 2015 accord, Iran forfeited some 97% of its enriched uranium, which can fuel a nuclear weapon, and mothballed some three-quarters of the centrifuges needed to refine the heavy metal. When the accord was negotiated, U.S. officials estimated that if Iran abandoned its provisions, the country would need a year to restore the material needed for a bomb. Iran’s 2019 violations and pledge to bring new enrichment capacity online will shorten the period. Before the accord, Iran had material to potentially build more than a dozen bombs. And while the country always maintained its program was civilian, world powers pursued the deal because they doubted that claim.

2. So is the Iran nuclear deal now dead?

Technically not, though it’s in critical condition. The deal stipulates Iran can cease performing commitments “in whole or in part” should a dispute over the legality of sanctions arise. Hundreds of International Atomic Energy Agency inspectors continue to receive access to Iranian nuclear facilities, which are visited daily and monitored. Seals and cameras help ensure that material isn’t diverted for weapons. Iran remains subject to snap inspections occurring at a rate of three a month. The accord’s Joint Commission continues consultations at its headquarters in Vienna and could eventually refer Iran’s nuclear file back to the United Nations Security Council to face even stiffer sanctions.

3. How does Iran benefit from the accord’s survival?

Iran has good reason to maintain the nuclear deal because of the access it will eventually be afforded to conventional weapons. The agreement stipulated that a UN arms embargo would be lifted within five years of the pact. That’s now become a top concern at the U.S. State Department, which has published a live ticker counting down the days until the Iranians can buy new weapons. Russia, seeing prospects for multi-billion dollar sales, has already ruled out extending the embargo. Should the pact now survive until October, Iran will be able to buy new generations of fighter jets, tanks and air-defense systems on global markets.

4. How might Iran escalate the crisis?

Most notably by increasing the quantity and quality of fuel needed for atomic bombs, kicking out IAEA monitors or following through on threats to abandon the nuclear Non-Proliferation Treaty — the bedrock agreement that regulates the spread of material needed to induce fission. Nuclear bombs are most commonly fueled with uranium-235 or plutonium-239. Uranium-235 makes up less than 1% of the matter in uranium ore, which necessitates separating it out through the process known as enrichment, usually using thousands of centrifuges spinning at supersonic speeds. IAEA inspectors are legally bound to keep track of gram-level changes in uranium inventories worldwide to ensure material produced for nuclear power plants isn’t diverted for weapons.

5. What are the enrichment worries?

Under the nuclear accord, Iran agreed that for 15 years it would not refine uranium to more than 3.7% enrichment — the level needed to fuel nuclear power plants — and would limit its enriched-uranium stockpile to 300 kilograms. It broke those promises in July and by November had accumulated more than 372 kilograms of low-enriched uranium. That’s about half of the 630 kilograms of material that would be needed to make a single weapon if further enriched to weapons grade. Iran has begun enriching some uranium to a level of 4.5%, which still qualifies as low-level. It would be more worrisome if Iran were to produce, as it did before the accord, uranium enriched to 20%, which can be purified to weapons-grade material at short notice.

6. What’s the plutonium concern?

Even before the U.S. killed General Qassem Soleimani, commander of the expeditionary branch of the Revolutionary Guard Corps, Iran was talking about restarting construction of a heavy-water reactor that could produce plutonium. That decade-long project in Arak was disabled by the accord and would need significant work to resume. The U.K. and China took over the U.S.’s role of modernizing the reactor after Washington abandoned the nuclear pact in May 2018. As part of the deal, Iran removed the original reactor core and rendered it unusable in 2016.

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