February 28, 2013

The Iranian Nuclear Program: Timelines, Data, and Estimates V6.0


This assessment is the eighth version of a recurring analysis of Iran’s nuclear program.


Start of Advanced Centrifuge Installation

  • International Atomic Energy Agency (IAEA) inspectors observed that Iran installed 180 IR-2m centrifuges at the Natanz enrichment facility. These machines have an output rate several times greater than first-generation centrifuges. The deployment of IR-2m centrifuges in significant quantities will drastically reduce the time required for weapons-grade (~90% enriched) uranium production and, therefore, increase the risk that Iran will be able to produce such material undetected.

Significant Installation of First-Generation Centrifuges

  • Iran increased its enrichment capacity by installing more than 2,200 additional first-generation centrifuges at the Natanz enrichment facility between November 2012 and February 2013. This mass installation will further cut the time needed to produce weapons-grade uranium. It also indicates that Iran is still able to produce centrifuges in significant quantities despite sanctions and interdiction efforts. 

Stockpiling for Second Bomb’s Worth of ~20% Enriched Uranium

  • Iran is producing near-weapons grade (~20% enriched) uranium at rate of about 10 kilograms per month. It has converted to powder and sent to the Tehran Research Reactor only a small fraction of this material thus far. Iran has stockpiled, in gas and powder forms, enough 20% uranium to rapidly convert to fuel for one bomb. It is now on its way to accumulating a second bomb’s worth of 20% uranium.     

Stonewalling the IAEA

  • Iran failed to cooperate with IAEA officials regarding the IAEA’s investigation into weaponization activities over the course of 3 meetings held since November 2012. The IAEA has said that its information indicates that some weaponization-related activities continued after 2003 and that some activities may still be ongoing.

Alternative Fissile Material Acquisition Path

  • The IAEA observed continued installation work at the Arak (IR-40) reactor, scheduled to “go hot” in 2014. This reactor, once operational, will be capable of producing plutonium for two weapons every year after reprocessing.



  • Obtaining fissile material in the form of weapons-grade uranium or plutonium is the most technically demanding step in developing a nuclear weapon. The parallel steps of designing an explosive device and a delivery system are comparatively less technically challenging.
  • Iran, due to its enrichment program expansion since 2009, can now produce one bomb’s worth of fissile material faster than estimates of the time needed to build a nuclear device to mate the material with. Potential timelines for weapons-grade uranium production could contract further due to increasing centrifuge numbers and types. Iran’s low-enriched uranium stockpile is currently adequate for fueling a small arsenal of nuclear weapons after further conversion to weapons-grade.  
  • Enrichment up to weapons-grade uranium (~90% enriched) is one key indicator of Iranian weaponization. Evidence of enrichment beyond research reactor-grade uranium (~20% enriched), material that is 90% of the way to weapons-grade, will strongly suggest not only that the decision to weaponize has been made, but also that the Iranians believe they have (or will shortly have) a viable device. 


Time needed to produce fuel for 1 nuclear weapon:

  • Iran needs 3.6 months to produce 25 kg of weapons-grade uranium and 1.9 months to produce 15 kg weapons-grade uranium at the hardened Fordow enrichment facility.* It can cut these times significantly using the centrifuges installed but not yet operating at the Fordow facility.
  • Iran needs 4-10 weeks to produce 25 kg of weapons-grade uranium and 1-5 weeks to produce 15 kg of weapons-grade uranium at the main Natanz enrichment facility.* The higher end of the range accounts for a three-step conversion process.

Estimates of the time Iran needs to build a nuclear device to use this fissile material are generally longer than the timelines above.

The existence of undeclared (covert) enrichment sites would have a significant impact on breakout estimates.

*All enriched uranium figures are given in terms of solid uranium (where 1 kg uranium hexafluoride is equal to ~0.67 kg elemental uranium). Estimates assume Natanz and Fordow are used with the operational capacity reflected in the November 2012 IAEA report. Iran may need 15-25 kg of weapons-grade uranium for an implosion-type bomb design depending on its level of technical ability (high technical ability would require less material).

This product is an exposition of the technical data contained in numerous IAEA reports informed by the discussions of experts in the field of nuclear proliferation. It is a work in progress in that it will be revised continuously based on new information from the IAEA reports and other sources and on feedback from readers. We welcome your informed commentary on the technical considerations presented in this document. Please send your comments, with references to source-date or documentation, to [email protected].