Iran-U.S. nuclear negotiations in Vienna: Why it’s critical to understand what breakout capacity means.

How a Widely Misunderstood Term Could Doom the Iran Nuclear Negotiations

How a Widely Misunderstood Term Could Doom the Iran Nuclear Negotiations

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June 18 2014 11:54 PM

The Trouble With “Breakout Capacity”

How a widely misunderstood term could doom the Iran nuclear negotiations.

Talks with Iran at the UN headquarters in Vienna.
Vice President of the European Commission Catherine Margaret Ashton and Iranian Foreign Minister Mohammad Javad Zarif attend P5+1 talks with Iran at the U.N. headquarters in Vienna on June 17, 2014.

Photo by Dieter Nagl/AFP Photo/Getty Images

For better or worse—and probably for worse—negotiations to peacefully resolve the standoff over Iran’s nuclear program may hinge on a single technical term: “breakout capacity.”

“Breakout capacity” refers to the time it would take to produce enough highly enriched uranium for a nuclear weapon, should Iran at some point decide to build one. The term isn’t formally part of the negotiations that resumed in Vienna this week between Iran and the P5+1 (the five permanent members of the U.N. Security Council, plus Germany). Rather, negotiators discuss things like how many centrifuges Iran should be allowed to keep as part of a peaceful nuclear energy program. But back in Washington, when people in Congress and elsewhere argue over what constitutes an acceptable deal, they talk in terms of breakout: How much breakout capacity would Iran have if left with a given number of centrifuges, or a given amount of some other variable under negotiation?

It’s a valid question. All the more unfortunate, then, that so many people—including politicians, pundits, and policy analysts—are so confused about it. Some misunderstand the literal meaning of “breakout capacity.” Others misunderstand its practical meaning; they fail to see that how threatening a given “breakout time” is depends heavily on other aspects of a negotiated deal—and so they pay too little attention to those crucial aspects. The result of Washington’s muddled preoccupation with breakout capacity is that negotiations in Vienna may well be heading toward an outcome that damages America’s interests and makes war with Iran more likely.


There are several big issues to be resolved if a deal is to be had by the July 20 target date, but one of the biggest is about centrifuges. Iran has roughly 19,000 centrifuges for enriching uranium, about 10,000 of which are operating, and it has signaled that it won’t accept cuts in that inventory and will eventually need to expand it. How firmly Iran will stick with this position is unknown, but it’s true that Iranian President Hassan Rouhani, like President Obama, has hard-line critics that he needs to mollify, and he can’t afford to be seen by the Iranian people as consenting to Iran’s humiliation.

These 10,000 operational centrifuges, given existing stockpiles of low-enriched uranium, imply an estimated breakout time of two to three months. That’s about twice as long as the estimated breakout time last year, before Iran started reducing its stockpile of medium-enriched uranium in compliance with an interim deal reached in November.

The P5+1 countries, most conspicuously the United States, want Iran’s centrifuge infrastructure to shrink. The exact U.S. negotiating position isn’t known, but various indicators, including statements by former Obama administration officials, suggest a willingness to leave Iran with about 4,000 of its existing centrifuges. That number (depending on other dimensions to be negotiated, such as limits on enriched uranium stockpiles) implies an estimated breakout time of six months to a year.

A big unknown on both sides is negotiating flexibility. How much compromise is acceptable, and at what point do you decide that no deal would be better than the deal on offer? Here is where prevailing American thinking about breakout capacity could damage America’s interests. Before deciding what is and isn’t acceptable in the way of breakout capacity, it would help to understand what the term means, both in the abstract and in the context of these negotiations.

Perhaps the most common misconception about breakout capacity is that it refers to the time it would take to actually build a nuclear weapon. Though Iran’s estimated breakout time is now about two months, if Tehran tomorrow embarked on a headlong effort to build a weapon, the project would take much longer than two months.

Having produced enough weapons-grade uranium hexafluoride, or UF6, for one bomb—the part that would take two months—Iran would need to convert the UF6 to powder form, fabricate the metallic core of the weapon from the powder, develop and assemble other components, and finally integrate the weapons package into a delivery vehicle. Estimates used by the White House have this process taking up to a year, and even the most alarming estimates coming from other sources have it taking several months.

And it’s worth noting that these and other American estimates related to Iran’s breakout speed may have a kind of bias. As a former U.S. official told the journalist Laura Rozen, “What everyone tends to forget is that, when U.S. government and academic experts speak on breakout timelines, they are usually describing a worst-case scenario … where Iran gets everything right the first time around, even if they are completing procedures they have never attempted before.”  

Once a bomb is built, there’s testing to be done. States with nuclear weapons typically conduct multiple test explosions—particularly for the smaller, more efficient designs needed for missile warheads. Eight out of the nine countries that have nuclear weapons openly conducted tests before deployment—and the ninth, Israel, seems to have conducted a clandestine test off of South Africa. Preparing, conducting, and evaluating a test would take months—and would also mean that a new bomb had to be built, since the test would have eliminated the first one.

In short, even if “breakout time,” as conventionally defined, is only a few months, or even a few weeks, what you might call the “effective breakout time”—the time it takes to produce a deliverable weapon—is closer to a year, maybe longer.