"I greatly appreciate your very swift response, and your organization's work in general. It's a terrific source of authoritative information."

– Lisa Beyer
Bloomberg News
August 27, 2018

Appendix D: Understanding Breakout Calculations


Table of Contents

As the U.S. intelligence community has consistently noted since 2007, Iran has the scientific, technical, and industrial capacity to produce nuclear weapons if it chooses to do so. The U.S. intelligence community has also assessed that if Iran were to make a decision to build nuclear weapons, it is more likely that it would seek to do so by means of undeclared, secret facilities, a scenario sometimes called a “sneak-out.”

Thus, the realistic goal of the P5+1 for the final deal was not to make breakout impossible but to make it a more difficult and unattractive policy option for Iran.

The JCPOA accomplishes this core goal by putting in place restrictions on its uranium-enrichment capacity, the level of uranium enrichment, its uranium stockpile, and research and development in a way that lengthens the time it would take for Iran to amass enough bomb-grade nuclear material to no less then 12 months for more than a decade, by eliminating its ability to produce and separate plutonium for at least 15 years, and by putting in place stringent monitoring and verification mechanisms to quickly detect and deter any attempt to pursue a covert program.

The JCPOA will limit Iran’s installed centrifuges to 6,104 IR-1 centrifuges, of which 5,060 will be used to enrich uranium for 10 years. This, combined with the 300-kilogram limit on Iran’s stockpile of 3.5 percent enriched uranium gas, increases the time it would take Iran to accumulate enough material for one bomb to more than a year, if such an effort were not detected.

Other restrictions limit Iran’s breakout potential through the uranium route. For 15 years, Iran’s low-enriched uranium stockpile cannot exceed 300 kg. Agreed limits on Iran’s deployment of advanced centrifuge machines in years 11-13 of the JCPOA will ensure that its overall enrichment capacity remains the same. Given other reporting requirements and monitoring of Iran’s centrifuge program through year 20 of the agreement, Tehran will not have the ability to quickly ramp up its enrichment capacity without prompt detection.

It is important to remember that the milestone being measured in this definition of “breakout” is the accumulation of enough uranium hexafluoride gas for one bomb, not the bomb’s actual construction or initial operating capability. Although the production of fissile material is arguably the most resource intensive and difficult step toward building nuclear weapons, there are several additional technical hurdles, including designing and constructing an explosive device and integrating it into a delivery system (most likely a ballistic missile) so it would reliably detonate.

Iran would need to convert the material into powder form, fabricate the metallic core of the weapon from the powder, assemble other weapons components that had been previously developed or acquired on an independent track, and integrate the weapons package into a delivery vehicle.

This process could be more easily hidden, but it would require several months or longer.

States developing nuclear weapons typically conduct multiple, large-scale nuclear test explosions to perfect their warhead designs, particularly the smaller, lighter, and more efficient designs needed for missiles.

With existing U.S. national means of intelligence and the International Monitoring System established to verify compliance with the Comprehensive Test Ban Treaty, any Iranian test would very likely be detected. If Iran were to try to “sneak out” to build nuclear weapons, Tehran would have to accept a lower confidence level concerning its warhead design or risk detection.

Iran is very unlikely to break out of the nuclear Nonproliferation Treaty to acquire only one nuclear weapon.

Even if Iran were willing to tolerate the large uncertainties deriving from an untested nuclear weapons design, a single weapon would add additional uncertainties regarding missile performance and the ability of the warhead to penetrate the sophisticated missile defenses deployed in the region. Tehran would be staking everything on the perfect performance of one untested system. It is highly improbable that Iran would plan to break out of the NPT by building only one nuclear weapon. Calculating timelines based on a one-device scenario therefore compounds the misimpression already left by using a breakout definition that falls short of actually building a weapon.

However, if Tehran were to choose to increase the odds of success by planning to build multiple weapons, it would increase the need for fissile material, thus lengthening the breakout timelines and increasing the chances of international detection and blocking actions.

The robust inspection regime in the JCPOA would include increased reporting requirements for Iran on its nuclear activities and grant the right of timely, on-site inspections at undeclared sites to the International Atomic Energy Agency. While designed to detect clandestine enrichment activities, such a regime will also significantly enhance the collection of information relevant to the identification of post-enrichment activities that could be targeted to disrupt a weapons program.

Country Resources:

Solving the Iranian Nuclear Puzzle: The Joint Comprehensive Plan of Action

August 2015

For well over a decade, the sensitive nuclear fuel-cycle activities of the Islamic Republic of Iran have been at the center of international concerns about the further spread of nuclear weapons.

Download this report.

Strengthening Stability in Turbulent Times

A new report by a 21-member commission consisting of experts from Germany, Russia, and the United States, “Strengthening Stability in Turbulent Times,” recommends several new arms control and confidence-building-measures to reverse the deterioration in Russia’s relations with U.S. and European governments.

The immediate objective of the fifteen recommendations is to achieve a verified termination of the violent conflict in Ukraine, arresting the slide of NATO and Russia toward a potentially more dangerous situation. 

Download this report.

The Nuclear Security Summit: Progress Report on Joint Statements

March 2015

A year out from the final Nuclear Security Summit, a report from the Arms Control Association (ACA) and the Partnership for Global Security (PGS) concludes that multilateral collaborative efforts targeting key areas are improving global nuclear material security. However, narrowly focused commitments at the 2016 Nuclear Security Summit (NSS) will only result in incremental improvements, not a sufficiently cohesive global nuclear security system and lasting legacy for the summit process.

Download this report.

The Unaffordable Arsenal: Reducing the Costs of the Bloated U.S. Nuclear Stockpile

The United States currently plans to spend some $355 billion to maintain and rebuild its Cold War-era nuclear arsenal over the next decade, even as the overall U.S. defense budget is declining and U.S. military planners and the president have determined that the United States can deter nuclear threats against the United States and its allies with far fewer nuclear weapons.

Download this report.

Solving the Iranian Nuclear Puzzle: Toward a Realistic and Effective Comprehensive Nuclear Agreement

June 2014

For well over a decade, the sensitive nuclear fuel cycle activities of the Islamic Republic of Iran have been at the center of international concern about the further spread of nuclear weapons.

In November 2013, after years of on-and-off negotiations, Iran and six world powers concluded an interim agreement that pauses the some of Iran’s most proliferation sensitive activities and opened the way for further talks on a long-term, comprehensive solution to would ensure Iran’s nuclear program will be exclusively peaceful.

Download this report.

Preparing for Deep Nuclear Cuts: Options for Enhancing Euro-Atlantic and International Security

A new report by a 21-member experts commission recommends practical, modest steps that the United States, NATO and Russia could take to further reduce nuclear arms, both strategic and non-strategic, and to resolve long-standing differences over missile defense and the regulation of conventional military forces in Europe.

Incooperation with the Deep Cuts Commission

Download this report.

The Nuclear Security Summit: Assessment of Joint Statements

By Michelle Cann, Kelsey Davenport and Sarah Williams

As 53 states prepare to meet in The Hague March 24-25 for the third Nuclear Security Summit, a new report released today by the Arms Control Association (ACA) and the Partnership for Global Security (PGS), finds that multilateral initiatives from the 2012 Nuclear Security Summit are improving targeted areas of nuclear security, but more ambitious initiatives are needed to address the lack of transparency and regime cohesion in the global nuclear security system.

Download this report.

Solving the Iranian Nuclear Puzzle: Updated ACA Briefing Book

The election of Hassan Rouhani as President of Iran presents an important opening to reinvigorate negotiations with Tehran over its nuclear program. As the United States and its partners continue to pursue a range of strategies to guard against the possibility of a nuclear-armed Iran, the non-partisan Arms Control Association has updated its comprehensive, entry-level guide to Iran’s nuclear program and its capabilities, and the risks, benefits, and limitations of the available policy options.

Download this report.

The Nuclear Security Summit: Progress Report

By Michelle Cann, Kelsey Davenport and Sarah Williams

A new report released by the Arms Control Association (ACA) and Partnership for Global Security (PGS), finds that the Nuclear Security Summit (NSS) process has catalyzed action to secure nuclear weapons-usable materials, but the largely nationally-focused efforts to date are inadequate, and leading governments must begin building the framework for a cohesive international nuclear security governance system.


Subscribe to RSS - Reports