The Iranian Nuclear Program: Timelines, Data, and Estimates V2.1

This assessment is version 2.1 of a recurring analysis of Iran’s nuclear program. 

Iran is at the threshold of a nuclear weapons capability. Sanctions, direct action, and diplomatic tools have neither changed Iran’s nuclear policy nor had a visible effect on the enrichment program, including the growing stockpile of 19.75% LEU. Obtaining weapons-grade high-enriched uranium (HEU) is the most difficult and technically challenging obstacle to acquiring a nuclear weapon. Assessing the “breakout” time—the time required to convert low-enriched uranium (LEU) to weapons-grade HEU—is therefore a critical component of determining progress toward a nuclear weapons capability.    

AEI's Critical Threats Project has produced a capabilities-assessment of the time required for Iran to acquire enough weapons-grade uranium to fuel one nuclear weapon if it proceeds to break out in 2012. It does not assess Iran’s intentions to weaponize or to purse break-out scenarios, but rather focuses entirely on technical feasibility. The assessment also provides scenarios for the growth of Iran’s 19.75% LEU stockpile, background data on processes involved in a nuclear weapons program and Iran’s reported progress, and imagery of the primary enrichment facilities at Natanz and Fordow.  

This product is an exposition of the technical data contained in numerous International Atomic Energy Agency (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].

KEY FINDINGS 

• Iran is developing a rapid nuclear weapons breakout capability. Its expanding uranium enrichment activities at Natanz and Fordow are reducing the time it would need to break out and produce fuel for an atomic weapon.

• Iran is increasing its total stockpile of uranium enriched up to 20%—which can be converted to weapons-grade levels of 90% in a short amount of time—at the Natanz Pilot Fuel Enrichment Plant (PFEP) and, now, at the buried Fordow Fuel Enrichment Plant (FFEP) where it began producing that material in December 2011. It has taken steps to prepare for a further expansion of the FFEP by building the infrastructure required to install and operate over two thousand additional centrifuges.

• It is also increasing its stockpile of uranium enriched around the 3.5% level; that material is the feedstock for producing uranium enriched to 20%. During the past reporting period, Iran sharply increased the number of centrifuges being fed natural uranium gas for the production of 3.5% fuel and began installing equipment to operate several thousand additional centrifuges at the large Natanz Fuel Enrichment Plant (FEP).

• We assess that Iran, continuing to operate PFEP and FFEP under the current conditions described by the International Atomic Energy Agency, will have 85 kilograms of uranium enriched up to 20% in April 2012. This amount will be enough for Iran to produce 15 kg of weapons-grade uranium for one bomb within 3 months using the more-efficient interconnected cascades installed at FFEP for the final enrichment step to 90%. If Iran required 25 kg of weapons-grade uranium to fuel one bomb, it would take 4.7 months after September when it is projected to have 141 kg uranium enriched to 20%.

• A more immediate breakout scenario, in which Iran races to produce additional material enriched to 20% at FEP and then enriches to 90% there in its operational centrifuges, would result in a drastically shorter timeline for Iran’s acquisition of bomb fuel.

VERSION HISTORY

April 6, 2012: Version 2.1

• Added estimates to account for the possibility that Iran would require 25 kg weapons-grade uranium to fuel one bomb given its level of technical capability. The breakout thresholds for 19.75% LEU and the time required for production of weapons-grade HEU were updated accordingly.

February 27, 2012: Version 2.0

• All figures and data were updated where possible using the updated IAEA report dated February 24, 2012.

• Added an evaluation section to explain the differences between previously projected data and the figures reported by the IAEA in February 2012.

• Adjusted the timelines for breakout to account for the increased production of uranium enriched to 20% at PFEP and FFEP.

• Adjusted the growth scenarios for Iran’s 19.75% LEU to reflect the current situation described by the IAEA and the pattern of cascade installation for enrichment at that level. Iran appears to be building out the FFEP facility with sets of 2 interconnected IR-1 centrifuges and has installed infrastructure there for more than two thousand additional IR-1 centrifuges. Thus, we replaced the scenario of Iran using advanced centrifuges there with one that projects 19.75% LEU growth if Iran were to install and operate two additional IR-1 cascades every two months beginning in June.

• The most likely breakout scenario was adjusted to include enrichment up to weapons-grade at the expanded FFEP facility only.

• Graphs and images depicting enriched uranium stockpiles and centrifuge totals were adjusted to reflect the new IAEA data.

• The comparison slide depicting estimates produced by other analysts was updated to reflect the new data (page 18). These other estimates are all based on the earlier IAEA reports and do not take account of the new information available. Assumptions, including efficiency rates and tails, vary across the estimates.

January 31, 2012: Version 1.1 (with gratitude to Greg Jones, NPEC, for feedback) 

• Clarified scenarios on p. 3.

• Previous version had erroneously noted that Hiroshima bomb had used 15 kg HEU; in fact, that gun-type device had used 50 kg HEU.

• Feedback noted that Iran is installing 2 interconnected cascades of IR-1 centrifuges at Fordow (174 each), where this assessment adds only one of 164 in March 2012. Iran is more likely to bring the centrifuges online in pairs, but we will await the next IAEA report to verify the status of the additional cascades and incorporate adjustments in the February assessment.

• Timeline start date on p.14 adjusted to 2/1/12 to match scenario assumptions.

• The time required for the final two steps of the three-step process at Natanz FEP in the Worst Case scenario was adjusted based on feedback noting that separative work calculators do not provide accurate calculations for assessing higher enrichment levels at the Natanz FEP.

• Estimates attributed to Greg Jones adjusted on timeline on p.14. Greg Jones's calculations indicate that Iran does not have enough 3.5% LEU now to complete a 3-step process to 90% at Natanz; the last tick on his estimate timeline was therefore removed because it is beyond the range of the timeline. 

January 26, 2012: Version 1.0

• Release.