The Iranian Nuclear Program: Timelines, Data, and Estimates V4.1


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

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The Iranian Nuclear Program: Timelines, Data, and Estimates V4.1

  1. The Iranian Nuclear Program Timelines, Data, and Estimates Maseh Zarif Deputy Director and Iran Team Lead AEI Critical Threats Project Version 4.1 OCTOBER 2012 Current as of OCT 29 2012 using data from IAEA report dated AUG 30 2012 Copyright © 2012 by the AEI Critical Threats Project
  2. Key Points IRAN’S ENRICHMENT CAPABILITIES ARE NO LONGER THE PRIMARY BOTTLENECK IN A NUCLEAR BREAKOUT SCENARIOIran can produce one bomb’s worth of fissile material faster than it likely can deploya functioning nuclear device. Tracking Iran’s uranium enrichment activities nowaddresses only Iran’s intentions and the size of its projected arsenal. Obtaining fissile material in the form of weapons-grade uranium or plutonium is the most technically demanding step in acquiring a nuclear weapons capability. Designing an explosive device (which consists of non-nuclear components) and a delivery system for the device are comparatively less technically challenging. Those efforts can also proceed parallel to enrichment. Iran has the infrastructure and material to produce weapons-grade uranium. It has enough enriched uranium to produce fuel for five nuclear weapons after conversion to weapons-grade. Its expanding enrichment activities have significantly reduced the time required for it to produce weapons-grade uranium. The key accelerants for this shrinking timeline have been its growing stockpiles of low- and medium-enriched uranium, which is 90% of the way to weapons- grade, and an increasing number of centrifuges enriching. Page 2 Copyright © 2012 by the AEI Critical Threats Project
  3. Nuclear Program ExpansionIran has installed many more centrifuges at the hardened Fordow facility than arenow actually spinning, providing a reserve and/or surge capacity that will bedifficult for Israel to destroy.The recent installation of 1,076 additional centrifuges at Fordow has more thandoubled capacity at that facility.Iran’s uranium enrichment is at historically high rates despite increasing sanctionsand damage to the Iranian economy.Iran will likely have enough near-20% enriched uranium to rapidly produce fissilematerial for 2 nuclear weapons by late 2013/early 2014.Iran recently told the International Atomic Energy Agency (IAEA) that it plans tobegin operating the Arak heavy water reactor in Q3 2013. This reactor will becapable of producing two warheads’ worth weapons-grade plutonium per yearonce operational. Page 3 Copyright © 2012 by the AEI Critical Threats Project
  4. Breakout TimelinesIran needs 3.7 MONTHS to produce 25 kg of weapons-grade uranium and 1.9 MONTHSto produce 15 kg weapons-grade uranium at the buried Fordow and pilot Natanzenrichment facilities.* It can cut these times significantly using the newly-installedcentrifuges at Fordow.Iran needs 0.8-2.2 MONTHS to produce 25 kg weapons-grade uranium and 1-4 WEEKSto produce 15 kg weapons-grade uranium at the main Natanz enrichment facility.* Thehigher end of the range accounts for a three-step conversion process.The existence of undeclared (covert) enrichment sites would have a significant impacton breakout estimates.Estimates of the time Iran needs to build a nuclear device to use this fissile material areall longer than these timelines.Evidence of significant Iranian enrichment beyond 20% will strongly suggest not onlythat the decision to weaponize has been made, but also that the Iranians believe thatthey will shortly have a viable warhead in which to place weapons-grade uranium.*Estimates assume Natanz and Fordow are used with the operational capacity reflected in the August 2012 IAEAreport. Iran may need 15-25 kg weapons-grade uranium for an implosion-type bomb design depending on its level oftechnical ability (high technical ability would require less material). See page 19 for further detail. Page 4 Copyright © 2012 by the AEI Critical Threats Project
  5. Fordow Facility Expansion: What Is The Impact?Iran installed 1,076 IR-1 centrifuges at Fordow between May and August 2012, bringing its total centrifuges at the facility to 2,140 (12 cascades of 174 centrifuges each and 1 cascade under construction with 52 centrifuges). TIME REQUIRED TO PRODUCE ONE BOMB’S WORTH OF WEAPONS-GRADE URANIUM FROM 141 KG NEAR-20% ENRICHED URANIUM: Pre-expansion Post-expansion 95 DAYS 47 DAYS Fordow Enrichment Capacity 2500 2000 # centrifuges 1500 1000 500 0 Nov-11 Feb-12 May-12 Aug-12 ENRICHING NOT ENRICHING Page 5 Copyright © 2012 by the AEI Critical Threats Project
  6. Iran’s Declared 3.5% LEU Production and IR-1 Centrifuges at NatanzAssessment: Stuxnet derailed the 2009 Iranian effort to expand enrichment capability for roughly one year, but the enrichment expansion effortrecovered in mid-2010. Neither direct actions nor sanctions have had a visible effect on the enrichment program. Even the Stuxnet success does notappear to have derailed the steady growth of the Iranian 3.5% LEU stockpile. Iran is running its highest number of centrifuges and production ratessince the enrichment program began. New U.S./ 10000 UN/EU sanctions 9000 Stuxnet # centrifuges being fed UF6 and kg of 3.5% LEU produced Launched 9,156 8000 centrifuges Iranian Scientist 7000 Killed 6000 (cumulative) Centrifuges enriching at 4,607 kg Natanz 5000 4000 3000 +455 kg since May (2nd largest increase Cumulative production of in a single reporting 2000 period) 3.5% LEU 1000 0 Jun-08 Nov-08 May-09 Nov-09 May-10 Nov-10 May-11 Nov-11 May-12 Nov-12 Enrichment data source: IAEA Page 6 Copyright © 2012 by the AEI Critical Threats Project
  7. Near-20% Enriched Uranium Production and Projected Growth at Fordow/Natanz 705 ~20% enriched uranium Amount needed for: production enough to produce weapons-grade uranium for three nuclear bombs by late 2013. Iran 4 564 would need to begin enriching weapons Iran will have produced 282 kg gradually in installed Fordow ~20% enriched uranium by late cascades to meet this threshold.Kilograms 19.75% LEU 423 2013/early 2014 under steady-state 3 conditions--enough to produce weapons weapons-grade uranium for two nuclear bombs designed with a low 2 282 level of technical capability. weapons 1 141 weapon 126.9 kg (as of AUG 2012) 0 May-12 Jul-12 Oct-12 Jan-13 May-13 Jul-13 Oct-13 Jan-14BLACK: Reported productionRED: Steady-state enrichment (a)GREEN: Enrichment in all currently installed centrifuges (b)PURPLE: Rapid expansion at Fordow (c)*The two lines for each colored scenario represent a range based on different calculations of demonstrated centrifuge efficiency.(a) 1,024 centrifuges currently enriching (2 cascades with 328 total IR-1 centrifuges at PFEP and 4 cascades with 696 total IR-1 centrifuges at Fordow)(b) Same as (a) but Iran began turning on 2 additional cascades every month in SEP and will do so until all 12 currently installed cascades at Fordow areenriching.(c) Iran began enriching in the 8 additional cascades present at Fordow beginning in SEP. It will install and begin operating 2 additional cascades in NOVand in JAN 2013, at which time Fordow will be operating at full capacity with 16 cascades). Page 7 Copyright © 2012 by the AEI Critical Threats Project
  8. Near-20% Enriched Uranium: At The Threshold 141 kg ~126.9 kg needed produced* to produce 25 kg (mid-AUG estimate) weapons-grade uranium for one warhead ~20% enriched uranium produced Iran has likely closed this gap since the release of the August 2012 IAEA report*Iran has allocated some of its near-20% enriched uranium for conversion to reactor fuel plates. Thisallocation, thus far, has a minimal impact on Iran’s stockpiles usable for conversion to weapons-gradeuranium. The process of recovering this allocated material could be completed within the currentlyprojected windows for the development and deployment of a working warhead design. See page 9 fora more detailed explanation.Note: Amounts in elemental uranium Page 8 Copyright © 2012 by the AEI Critical Threats Project
  9. Impact of Near-20% Enriched Uranium Conversion to U3O8The IAEA reported that, between December 2011 and August 2012, Iran had fed the equivalent of 47.7kg near-20% LEU (in the form of 71.25 kg near-20% UF6) into a process for conversion to U3O8 (page 8,August 2012 IAEA report). This converted material is being used to produce fuel plates for use in theTehran Research Reactor (TRR).Some analysts and commentators have said that this 47.7 kg near-20% LEU is no longer usable in abreakout scenario for producing weapons-grade uranium and, thus, should be subtracted permanentlyfrom calculations of Iran’s near-20% LEU stockpile. This assumption is false from a technicalstandpoint.Near-20% LEU in the form of U3O8 can be converted back into a gas suitable for producing weapons-grade uranium. The conversion methods for doing so “are standard processes in the nuclear industryand Iran uses them as part of its uranium ore processing.”1 The time required to execute thisconversion, which requires specialized facilities, can be measured in “days to weeks.”2The near-20% LEU can only be classified as unusable in a breakout once the fuel assemblies containingthe U3O8 are inserted and irradiated in the TRR core. Only a small fraction of Iran’s near-20% LEU in theform of U3O8 has been manufactured into fuel plates and assemblies (4.83 kg) and an even smalleramount has been placed into or irradiated in the TRR core (3.38 kg). The remaining near-20% LEU is, asa result, recoverable.Even if the remaining material is assumed to be “off the table” for a breakout, Iran will likely replenishthe 47.7 kg near-20% LEU in less than 3 months from now using only the centrifuges that were enrichingas of August 2012.1) Gregory Jones, “Fueling the Tehran Research Reactor: Technical Considerations on the Risks and Benefits,” NPEC, October 12, 2009.2) Ibid. Page 9 Copyright © 2012 by the AEI Critical Threats Project
  10. Key Upcoming Events Italicized dates are estimates; bold dates are fixed Listed inspection windows are approximate. The IAEA may be 10/9/2012 conducting inspections outside Approx. date by which Iran of these windows.produced enough near-20% enriched uranium to convert 12/11/2012 to weapons-grade fuel for 1 bomb Review of CBI sanctions waivers granted JUN 2012 10/1/2012 11/1/2012 12/1/2012 1/1/2013 2/1/2013 3/1/2013 11/29/2012 3/4/2013 IAEA BOG IAEA BOG meets meets 10/21/2012 - 11/11/2012 1/25/2013 - 2/15/2013 IAEA Inspection Window IAEA Inspection Window 11/19/2012 2/22/2013IAEA BOG = International Atomic IAEA Report IAEA ReportEnergy Agency Board of Governors Page 10 Copyright © 2012 by the AEI Critical Threats Project
  11. Making an Atomic Bomb (Concept) Acquire Weapons-grade Parallel processes Design Parallel processes Acquire delivery Uranium warhead vehicle Centrifuge Acquire weapon cascade design LEU gas Fed back into produces UF6 gas Shahab-3(3.5% U-235) 19.75% U-235 missile Fed back into produces Develop detonator technology Centrifuge Centrifuge cascade Two-step cascade Test design uranium Fed through produces and engineering enrichment then UF6 gas process UF6 gas 0.7% U-235 90% U-235 Build weapon Converted to Processed into Test weapon Mate warhead with delivery vehicle Natural uranium High-enriched elemental uranium (Process complete) solid metal (90% U-235) Page 11 Copyright © 2012 by the AEI Critical Threats Project
  12. Making an Atomic Bomb (Status as of OCT 2012) ay ay w Acquire Weapons-grade Design Acquire delivery w ne Parallel processes Parallel processes r r de warhead vehicle de Uranium Do Un Un Centrifuge Acquire weapon cascade design ay Shahab-3 w ne ne ne LEU gas Fed back into produces UF6 gas r (3.5% U-235) 19.75% U-235 missile Do Do de Do Un Fed back into produces NB: All estimates of Iran’s Develop detonator ay nuclear status and technology w Centrifuge capabilities assume that Centrifuge r there are no clandestine de cascade cascade facilities, and that the Un IAEA has full access to all Test design Fed through produces declared facilities. The and engineering first assumption is impossible to verify. The d then te second assumption is or ne UF6 gas known to be false. UF6 gas ep 0.7% U-235 Do 90% U-235 tr Build weapon d te No or Converted to Processed ep into tr No Mate warhead with g ne Test weapon in g d in Do te delivery vehicle ar or Natural uranium ar ep ep High-enriched (Process complete) ep Pr tr elemental uranium Pr No solid metal (90% U-235) Page 12 Copyright © 2012 by the AEI Critical Threats Project
  13. Why Enrichment Accelerates at Higher Concentration of U-235 Centrifuge 1,373 kg cascade 116 kg LEU gas Fed back into produces UF6 gas (3.5% U-235) 19.75% U-235 559 SWU The work and time required to Fed back into 37 days enrich uranium from its natural produces concentration (0.7%) to 3.5% Centrifuge 5,060 SWU 115 SWU Centrifuge LEU is an order of magnitude cascade 331 days 8 days cascade greater than that required to enrich 20% LEU to weapons- Fed through produces grade concentrations (~90% U- 235). 14,187 kg 15 kg That is because centrifuges UF6 gas UF6 gas 0.7% U-235 90% U-235 must spin more than 14,000 kg of uranium ore to produce Processed Converted to 1,373 kg of 3.5% LEU, but only into 116 kg of 20% LEU to produce 15 kg of weapons-grade uranium. Natural uranium High-enriched elemental uraniumSWU = Separative work unit, a measure of the amount of effort solid metal (90% U-235)required to process nuclear material. The SWU requirement isused to determine the time needed to enrich uranium with a givennumber of centrifuges operating at a given efficiency. Page 13 Copyright © 2012 by the AEI Critical Threats Project
  14. Iran’s Declared Uranium Enrichment FacilitiesFordow Fuel Enrichment Plant (FFEP)As of 18 AUG 2012: 696 IR-1 centrifuges producing near- 20% LEU 1444 additional IR-1 centrifuges installed Facility producing near-20% low- enriched uraniumAs of 12 AUG 2012: 322.9 kg 3.5% LEU converted to 43.8 kg near-20% LEU Unknown quantity 3.5% LEU stored here*Notes* The IAEA reported in November 1452011 that “one large cylinder” of 3.5%LEU was transferred from Natanz to kmFordow, but did not specify the Natanz Fuel Enrichment Plant (FEP)precise amount of UF6 in that cylinder. As of AUG 2012:**The IAEA reported that some 9156 IR-1 centrifuges producing <5%19.75% material is now in the form of LEUU3O8. 174 additional IR-1 centrifuges reported installed Facility producing 3.5% enriched LEU Pilot Fuel Enrichment Plant (PFEP) As of 21 AUG 2012: 3557 kg 3.5% LEU stored here* 328 IR-1 centrifuges enriching near- 20% LEU 162 IR-2m and 133 IR-4 centrifuges reported installed and intermittently fed Facility producing near-20% LEU ` 727 kg 3.5% LEU converted to 83.1 kg near-20% LEU** Unknown kg 3.5% LEU stored here Page 14 Copyright © 2012 by the AEI Critical Threats Project
  15. Natanz Enrichment FacilitiesPilot Fuel Enrichment Plant (PFEP)As of 21 AUG 2012: 328 IR-1 centrifuges enriching near- Natanz Fuel Enrichment Plant (FEP) 20% LEU As of AUG 2012: 162 IR-2m and 133 IR-4 centrifuges 9156 IR-1 centrifuges producing <5% reported installed and intermittently LEU fed 174 additional IR-1 centrifuges Facility producing near-20% LEU reported installed 727 kg 3.5% LEU converted to 83.1 kg Facility producing 3.5% enriched LEU near-20% LEUe** 3557 kg 3.5% LEU stored here* Unknown kg 3.5% LEU stored hereNotes* The IAEA reported in November 2011that “one large cylinder” of 3.5% LEU was Underground halls under construction FEB 2003transferred from Natanz to Fordow, butdid not specify the precise amount of UF6in that cylinder.**The IAEA reported that some 19.75%material is now in the form of U3O8. Page 15 Copyright © 2012 by the AEI Critical Threats Project
  16. Fordow Enrichment Facility: Status and Construction Image taken 14 SEP 2012 Image from 24 MAR 2005 (Google Earth)Pleiades, Apollo Mapping Fordow Fuel Enrichment Plant (FFEP) Areas covered in 2005 appear as entrances to New above- As of 18 AUG 2012: underground facilities in 2009 ground 696 IR-1 centrifuges producing near- facility 20% LEU appears 1444 additional IR-1 centrifuges between installed 2005 and Facility producing near-20% low- 2009 enriched uranium Ridgeline rises As of 12 AUG 2012: 322.9 kg 3.5% LEU converted to 43.8 kg roughly 200 feet near-20% LEU from entrances Unknown quantity 3.5% LEU stored to peak. here* Note *The IAEA reported that “one large cylinder” of 3.5% LEU was transferred from Natanz to Fordow, but did not specify the precise amount of UF6 in that cylinder. Image from 24 NOV 2009 (Google Earth) Page 16 Copyright © 2012 by the AEI Critical Threats Project
  17. Scope, Assumptions and Technical Points Page 17 Copyright © 2012 by the AEI Critical Threats Project
  18. ScopeThis product is an exposition of the technical data contained in numerousIAEA reports informed by the discussions of experts in the field of nuclearproliferation. It is a work-in-progress in that it will be revised continuouslybased on new information from the IAEA and other sources and on feedbackfrom readers.We welcome your informed commentary on the technical considerationspresented in this document. Please send your comments, with references tosource-data or documentation, to INP@AEI.ORG.This product does NOT contain policy recommendations. It is intended solelyto inform the policy community and the American public about the natureand progress of the Iranian nuclear program.This product does NOT assess Iran’s intentions to weaponize or to pursuebreakout scenarios. It is focused entirely on technical feasibility. Page 18 Copyright © 2012 by the AEI Critical Threats Project
  19. Breakout ScenariosWorst-case The worst-case scenarios assume that Iran devotes all operational centrifuges at Natanz (as of 21 AUG 2012) to producing first additional 19.75% LEU and then 90% highly-enriched uranium (HEU), ceasing production of 3.5% LEU. Such actions would be visible to inspectors and so would most likely occur between inspections. Iranian nuclear policy and strategy does not appear to be going down this road. The scenarios assume 9,156 centrifuges spinning (the number being fed uranium as of 21 AUG 2012) operating with an efficiency of 0.9 separative work units (SWU)/centrifuge/year (roughly the efficiency they have demonstrated). 15 kg requirement: Iran begins to race to breakout by producing 116 kg total of 19.75% LEU and then enriching that material to 90% HEU. 25 kg requirement: Iran begins to race to breakout by producing 193 kg total of 19.75% LEU and then enriching that material to 90% HEU. If Iran breaks out using a three-step process, it would need to produce 240 kg total of 19.75% LEU in total, then enrich to 60% HEU and then to 90% HEU to yield 15 kg. Using this three-step process, Iran could acquire fuel for 1 weapon in 1 month. Assuming Iran needs 25 kg 90% HEU, it would need to produce 399 kg total of 19.75% LEU before it could convert to 60% and then 90%; this process would take approximately 2.5 months. These calculations assume tails assays of 2.0% and 9.3% for the two steps in the first process and 2.0%, 12.0%, and 41.1% for the three steps in the second process (see page 23). These data are derived from the Natanz facility; the Fordow installations are notably more efficient with lower tails assays.Most Likely The 9,156 centrifuges being fed in the main cascade hall at Natanz continue to produce 3.5% LEU and are not diverted to higher-level enrichment. Iran uses 85 kg 19.75% LEU to produce 15 kg 90% HEU or continues enriching to 19.75% until it has amassed approximately 141 kg 19.75% LEU, which can yield 25 kg 90% HEU. Enrichment to 19.75% occurs in 4 cascades totaling 696 IR-1 centrifuges at Fordow (2 sets of 2 interconnected cascades) and 2 cascades totaling 328 IR-1 centrifuges at the Natanz PFEP (all currently operational). Enrichment from 19.75% to 90% occurs in 6 cascades at Fordow in one step using a tails assay of 4.6%. The difference in the tails between the worst-case and most likely breakout scenarios reflects the fact that the cascades at Fordow, like the ones at Natanz PFEP, are interconnected in pairs. Page 19 Copyright © 2012 by the AEI Critical Threats Project
  20. Atomic Weapons DataSmall atomic weapons can be built from cores consisting of 10-25 kg of uranium enriched to 90% U-235 (weapons-grade HEU). We use 15 kg and 25 kg to assess breakout timelines.The explosive yield of a 15 kg core is on the close order of 15 kilotons.Uranium can be enriched to HEU in a two-step or a three-step process.Both processes begin by enriching natural uranium (0.7% U-235) to 3.5% LEU.The two-step process enriches from 3.5% LEU to 19.75% LEU, and then from 19.75% LEU directly to90% HEU.The three-step process proceeds from 3.5% LEU to 19.75% LEU, from 19.75% LEU to 60% HEU, andthen from 60% HEU to 90% HEU.The most important difference between these processes is the amount of LEU required initially—thetime required to enrich from 19.75% to 90% is virtually the same for either process.The two-step process for producing 15 kg weapons-grade HEU requires 85 kg of 19.75% LEU usinginterconnected cascades (such as at Fordow) or 116 kg using non-interconnected cascades (such asthose at Natanz). Producing 25 kg weapons-grade HEU in a two-step process requires 141 kg of19.75% LEU using interconnected cascades or 193 kg using non-interconnected cascades. The three-step process requires significantly more in non-interconnected cascades (such as at Natanz).There is disagreement among experts about Iran’s ability to execute a two-step process with itscurrent technology and cascade configuration.If Iran were forced to use a three-step process, the primary delay would result from the timerequired to produce the additional 19.75% LEU, a factor that Iran could affect either by bringing morecentrifuge cascades online or by beginning to enrich with more efficient centrifuges, some of whichare already installed but not yet producing enriched uranium. Page 20 Copyright © 2012 by the AEI Critical Threats Project
  21. Comparison of Estimated Breakout Times 10/29/2012 11/15/2012 11/22/2012 12/19/2012 2/10/2013 10/22/2012 2-step at Natanz (15 kg) 2-step at Natanz (25 kg) 3-step at Natanz (15 kg) 15 kg 90% HEU 12/27/2012 25 kg 90% HEU Start At Fordow 3-step at Natanz (25 kg) at FordowMaseh Zarif, AEI RED boxes denote scenarios using all 10/22/2012 11/5/2012 1/3/2013 or majority of available cascades Start 2-step at Natanz FEP and 3-step at Natanz FEP, BLUE boxes denote scenarios not clandestine facility (20 kg) Fordow, and PFEP (20 kg) using cascades in the main halls at NatanzGregory Jones, NPEC 10/22/2012 Note that some analyst estimates are Start 11/17/2012 2/1/2013 all based on the earlier IAEA report 2-step at Natanz (20 kg) 3-step at Natanz (20 kg) and do not take account of the new information. Assumptions, including efficiency rates and tails, vary across the estimates.Bipartisan Policy Center 10/22/2012 Start 12/22/2012 2/22/2013 25 kg 90% HEU 25 kg 90% HEUDavid Albright, ISIS 12/9/2012 10/22/2012 Natanz 9,156 centrifuges 1/29/2013 Start 16 kg 90% HEU At Fordow with 1392 centrifuges 16 kg 90% HEUWisconsin Project onNuclear Arms Control Page 21 Copyright © 2012 by the AEI Critical Threats Project
  22. Projections for the November 2012 IAEA Report IR-1 centrifuges being fed at Natanz FEP: 9,430 (low confidence) Total 3.5% LEU produced at Natanz FEP: 5,105 kg (moderate confidence)* IR-1 centrifuges being fed for 19.75% enrichment at Natanz and Fordow: 1,372 (low confidence) Total 19.75% LEU produced at Natanz PFEP and Fordow FEP: 149.4 kg (moderate confidence)* PREVIOUS PROJECTIONS 3.5% LEU We previously estimated that Iran would produce an additional 324 kg of 3.5% enriched uranium at Natanz during the last reporting period. The IAEA reported that Iran produced about 450 kg 3.5% enriched uranium during the period. The difference was largely due to a recent increase in Iran’s production rate (with a roughly constant number of centrifuges) that was not previously accounted for in the model. November 2012 estimates have been adjusted accordingly. 19.75% LEU We previously estimated that Iran would produce an additional 26.85 kg of 19.75% enriched uranium at Natanz and Fordow during the last reporting period. The IAEA reported that Iran produced about 29.35 kg 19.75% enriched uranium. This error is due to Iran’s increased rate of production at Fordow.*Assuming IAEA measurement on 4 NOV 2012 Page 22 Copyright © 2012 by the AEI Critical Threats Project
  23. SourcesInternational Atomic Energy Agency (IAEA) – The IAEA publishes quarterly reports on Iran’s nuclear program and enrichment progress. Enriched uranium stockpile,centrifuge count, potential inspection windows, and other technical data provided by the IAEA are used in our analysis to determine historical rates of productionand to serve as a basis for building projections. IAEA reports on Iran are available at Information Service Project on Energy (WISE) – WISE provides a uranium enrichment calculator for calculating the separative work required to achieve specificlevels of U-235 concentration. The calculator uses manual inputs of feed, product, and tails figures to calculate separative work units (SWU). The resultant SWUserves as the basis for calculating time requirements. This assessment uses the WISE calculator to determine the SWU required for enriching at various levels. Theonline calculator is accessible at Jones, Nonproliferation Education Policy Center (NPEC) – Gregory Jones provided the estimated tails percentage figures for enriching to weapons-gradeuranium levels for two-step and three-step batch recycling methods (starting with 3.5% LEU) at the Natanz FEP and two-step batch recycling (from 3.5%) at NatanzPFEP/Fordow FEP, where cascades are interconnected. Jones has written that the technical assumption underlying an Iranian attempt to break out using two-stepbatch recycling without reconfiguration (from 3.5%) may not be feasible. The alternative Iranian breakout approach he suggests, adding an intermediary stepbetween 19.75% and 90% enrichment, is one that we have relied on in our analysis. Jones’s analyses are available at has written that the process for Iran to convert the U3O8 enriched up to 20% created for fuel plates back to 20% enriched UF6 gas for use in a breakout“involves dissolution by nitric acid, followed by purification by solvent extraction. These are standard processes in the nuclear industry and Iran uses them as part ofits uranium ore processing...The time required from the removal of the fresh TRR fuel from safeguards to the time to produce 19.75% enriched uranium hexafluoridewould be only ‘days to weeks.’ [citing Albert Wohlstetter et al, Swords from Plowshares, Chicago University Press, 1979]” The report is available at on this topic, Henry Sokolski, NPEC, has written that Iran could withdraw 19.75% enriched uranium from fuel plates in the form of UF6 gas in 1-2 weeks. See for Science and International Security (ISIS) – ISIS has contributed to a technical debate among experts regarding the feasibility of two-step and three-stepbatch recycling methods. ISIS analyses are available at Glaser, “Characteristics of the Gas Centrifuge for Uranium Enrichment and Their Relevance for Nuclear Weapon Proliferation,” Science and Global Security(16:1-25, 2008) – Glaser’s analysis of the P-1 centrifuge—the foundation of Iran’s IR-1 centrifuge program—is the basis for two-step batch recycling projections forenriching to weapons-grade uranium. A key aspect of Glaser’s analysis in this paper was that 90% HEU can be produced in one step from 19.7% LEU without theneed to reconfigure the arrangement of cascades. In October 2011, according to Gregory Jones, Glaser said he had “been made aware of certain phenomena thatare not taken into account” in his 2008 analysis and that “We now find that the most credible scenarios involve some kind of cascade reconfiguration.” See GregJones, “Earliest Date Possible for Iran’s First Bomb,” Nonproliferation Education Policy Center, December 6, 2011, Glaser’s original analysis, see Commission on Nuclear Non-Proliferation and Disarmament (ICCND) – The ICCND notes that a basic implosion-type nuclear weapon design with anexplosive yield of 15 kilotons would require 15 kg of weapons-grade uranium. We use this figure as the minimum 90% HEU Iran would produce to fuel one bomb.See B. Cochran and Christopher E. Paine, “The Amount of Plutonium and Highly-Enriched Uranium Needed for Pure Fission Nuclear Weapons,” NationalResources Defense Council, April 13, 1995. – Cochran and Paine assert that the “significant quantity” measurement of 25 kg weapons-grade HEU used by the IAEAgreatly overestimates the amount of fissile material required to fuel a basic implosion-type nuclear explosive device. They estimate that a state with a low technicalcapability can produce a bomb with an explosive yield of 20 kilotons with 16 kg weapons-grade HEU. See: Page 23 Copyright © 2012 by the AEI Critical Threats Project