Since October 2012 when ISIS last published detailed breakout assessments about Iran’s gas centrifuge uranium enrichment program, Iran has steadily expanded the number of IR-1 centrifuges installed at both its Fordow and Natanz gas centrifuge plants.2 Additionally, it has started installing its more advanced centrifuge model, the IR-2m centrifuge, at the Natanz Fuel Enrichment Plant (FEP). These substantial changes merit updating our previous breakout estimates of the time Iran would need to produce one significant quantity (SQ) of weapon-grade uranium (WGU), taken as 25 kilograms of WGU, using its existing safeguarded nuclear facilities and low enriched uranium (LEU) stocks as of August 2013.

For several years, experts at ISIS and the School of Engineering and Applied Science at the University of Virginia (UVA) have quantified Iran’s ability to adapt its enrichment program to produce WGU. Iran maintains a number of options should it choose to breakout of the Nuclear Nonproliferation Treaty (NPT). This report evaluates those options in various realistic combinations to examine Iran’s current ability to produce WGU. We also look for the first time in this report at breakout times in the case of Iran having a covert centrifuge plant of advanced centrifuges.

As in the October 2012 iteration, the estimates in this report do not include the additional time that Iran would need to convert WGU into weapons components and manufacture a nuclear weapon. This extra time could be substantial, particularly if Iran wanted to build a reliable warhead for a ballistic missile. However, these preparations would most likely be conducted at secret sites and would be difficult to detect. If Iran successfully produced enough WGU for a nuclear weapon, the ensuing weaponization process might not be detectable until Iran tested its nuclear device underground or otherwise revealed its acquisition of nuclear weapons. Therefore, the most practical strategy to prevent Iran from obtaining nuclear weapons is to prevent it from accumulating sufficient nuclear explosive material, particularly in secret or without adequate warning. This strategy depends on knowing how quickly Iran could make WGU.