New Estimates of Iran’s Breakout Capabilities at Declared Sites Using a New, Simple-to-Use Breakout Calculator

September 3, 2019

Weapon Program: 

  • Nuclear


David Albright with Sarah Burkhard


Institute for Science and International Security

A new Institute breakout calculator is presented and applied to several theoretical cases where Iran increases its stocks of low enriched uranium (LEU) above the limits allowed in the Iran nuclear deal, or Joint Comprehensive Plan of Action (JCPOA). In addition, breakout times for Iran’s August 2019 inventory of LEU are developed.

If Iran decided to build nuclear weapons, it could use its existing, declared production-scale gas centrifuge plants, the Natanz Fuel Enrichment Plant and the Fordow Fuel Enrichment Plant, and low enriched uranium already produced there to make weapon-grade uranium (WGU), defined as uranium enriched to at least 90 percent U-235. This report introduces a new, easy-to-use calculator developed by the Institute to evaluate scenarios, commonly called “breakout times,” by which Iran could produce enough WGU for one or more nuclear weapons. In line with previous conventions used by the Institute, 25 kilograms of WGU represents the amount sufficient for a single nuclear weapon.

In this report, the new breakout calculator estimates realistic, minimum breakout times given Iran’s current enrichment capabilities under the Joint Comprehensive Plan of Action and a set of additional, potential capabilities as it reduces its commitment to the JCPOA’s centrifuge-related limits. Here, with one exception, the focus is on Iran’s potential growth in its stocks of LEU hexafluoride rather than a systematic increase in the enrichment capacity at Natanz and Fordow, in further violation of JCPOA limits. Other scenarios will be addressed in future reports, as events and interests develop.


Read the full report at the Institute for Science and International Security.