Iran's Nuclear Timetable
Updated March 1, 2009
Iran’s bank of rapidly spinning centrifuges has produced a stockpile of low-enriched uranium, able to fuel nuclear reactors, but able also to fuel nuclear weapons if further enriched by re-circulating it through the centrifuges. The re-circulation raises the concentration of the uranium isotope U-235, which fissions in nuclear weapons such as the one dropped on Hiroshima.
Based on the amount of low-enriched uranium Iran has stockpiled, and the amount it is believed to be producing each month, the Wisconsin Project estimates that by December 2008, Iran had accumulated enough U-235 to fuel one bomb quickly. "Quickly," in this context, means two to three months – about the time it would take Iran to raise the level of U-235 in its uranium stockpile from 3.5 percent to over 90 percent.
As Iran increases the number of centrifuge machines it is operating, and increases its stockpile of low-enriched uranium, it will consolidate its status as a "virtual" nuclear weapon state.
Iran's progress towards this status as of March 1, 2009 is estimateda below:
- Amount of U-235 contained in Iran’s stockpile of low-enriched uranium:
25.4 kg b
- Amount of this U-235 produced each month:
1.6 kg c
- Date by which Iran probably had stockpiled the above:
December 2008 f
- Number of additional months needed to convert this low-enriched uranium to weapon-grade g:
Two to three h
- Date by which Iran may have enough U-235 to fuel a second bomb:
October 2009 i
Additional estimates: Moving from reactor-grade to weapon-grade uranium
- Amount of uranium hexafluoride (UF6) enriched to 3.5 percent U-235 now on hand:
1,074 kg j
- Average daily production rate of this low-enriched UF6:
2.28 kg k
- Amount of this low-enriched UF6 needed to produce a bomb’s worth of weapon-grade UF6:
914 kg l
- Number of first generation IR-1 centrifuges being fed with UF6 at the Natanz Fuel Enrichment Plant as of February 1, 2009:
3,936 o
- Number of SWUs these centrifuges appear to be producing per year:
2,000 p
- Total number of centrifuges installed or being installed at Natanz, as of February 1, 2009:
5,904 q
- Number of SWUs these 5,904 centrifuges are assumed to be capable of producing per year:
6,000 r
- Number of months needed for these 5,904 centrifuges operating at such a capacity to produce 840 SWUs:
1.7 s
Additional estimates: Low-enriched uranium production
- Amount of UF6 produced through February 9, 2009:
357 metric tons t
- Approximate number of first-generation implosion bombs that this amount of UF6 could fuel if enriched to weapon grade:
45-50 u
Additional information: Number of centrifuges deployed over time
| Date of IAEA inventory | Centrifuges being fed with UF6 | Centrifuges installed or being installed |
|---|---|---|
2/17/2007 |
0 |
656 |
5/13/2007 |
1,312 |
820 |
8/19/2007 |
1,968 |
656 |
11/3/2007 |
2,952 |
0 |
12/12/2007 |
2,952 |
? |
5/7/2008 |
3,280 |
2,624 |
8/30/2008 |
3,772 |
2,132 |
11/7/2008 |
3,772 |
2,132 |
2/1/2009 |
3,936 |
1,968 |
ENDNOTES
(a) The following estimates are based on information in quarterly reports by the International Atomic Energy Agency (IAEA), which is responsible for nuclear inspections in Iran.
(b) According to the IAEA, Iran had produced a total of 839 kg of low-enriched UF6 as of November 17, 2008. Since then, Iran has produced approximately 235 kg of this material for a total of 1,074 kg (see note j) (http://www.iranwatch.org/international/IAEA/documents/iaea-iranreport-021909.pdf). Of that amount, 726 kg is uranium; 726 kg of uranium enriched to 3.5% contain 25.4 kg of U-235.
(c) Iran is estimated to produce about 2.28 kg of low-enriched UF6 each day (see note k), for an average monthly production rate of 69 kg month, 46 kg of which is uranium; enriched to 3.5%, this 46 kg contains 1.6 kg of U-235.
(d) Sixteen kilograms are assumed to be sufficient for an implosion bomb. This was the amount called for in the implosion device Saddam Hussein was trying to perfect in the 1980’s, and the design for such a device has circulated on the nuclear black market, to which Iran has had access. The critical mass of a sphere of U-235 metal is only 15 kg with a Beryllium reflector. See Gunter Hildenbrand, Nuclear energy, nuclear exports and the proliferation of nuclear weapons, AIF Conference on International Commerce and Safeguards for Civil Nuclear Power, March 1977. For a schematic diagram of an implosion bomb, see: www.wisconsinproject.org/bomb-facts/images/nw-1.jpg.
(e) Because of losses during the enrichment and weaponization processes, Iran would need about 914 kg (see note l) of UF6 enriched to 3.5% U-235, of which about 618 kg would be uranium, in order to achieve 16 kg of weapon-grade uranium. 618 kg of uranium enriched to 3.5% U-235 contains 21.6 kg of U-235. See the SWU calculator published by URENCO, a European uranium enrichment consortium: web.archive.org/web/20021226100607/www.urenco.de/trennarbeit/swucal_e.html.
(f) Assuming 19.9 kg of U-235 on hand as of November 17, 2008, a requirement of 21.6 kg for a first bomb, and a production rate of 1.6 kg of U-235 each month, Iran would have had enough in December 2008.
(g) Once enriched to weapon-grade, this material would still need to be converted from gas to metal and then machined into a form suitable for a bomb.
(h) The IAEA estimates the conversion time for low-enriched uranium to weapon-grade uranium metal to be approximately 3-12 months (www-pub.iaea.org/MTCD/publications/PDF/nvs-3-cd/PDF/NVS3_prn.pdf). However, if it would take approximately 840 SWUs to produce 16 kg of U-235 from a stockpile of 3.5% enriched uranium (see note n), and if Iran is capable of producing 6,000 SWUs per year (see note r), then a conversion time at the lower end of this range is probable. Therefore, Iran could have weapon-grade UF6 within 2-3 months, even assuming a delay in processing.
(i) If Iran were to add by April 1, 2009 the 1,476 centrifuges it has installed and placed under vacuum, the monthly production rate of U-235 would increase by about 37% to 2.2 kg per month, and if by June 2009 Iran operates all 5,904 centrifuges that are currently either in use or being installed, and adds no additional centrifuges, the monthly production rate of U-235 would increase by about 9% to approximately 2.4 kg per month. These production rates would allow Iran to accumulate the requisite 21.6 kg for a second bomb by October 2009.
(j) According to the IAEA, Iran had an inventory of 839 kg of low-enriched UF6 as of November 17, 2008, based on production from the beginning of operations (http://www.iranwatch.org/international/IAEA/documents/iaea-iranreport-021909.pdf); Iran has estimated that it produced 171 kg of this material from November 18, 2008 through January 31, 2009; and at an average daily production rate of 2.28 kg, Iran produced about 64 kg in February, for a total of 1,074 kg of low-enriched UF6 by March 1, 2009.
(k) Iran estimates that it produced 171 kg of low-enriched UF6 over 75 days, from November 18, 2008 to January 31, 2009, for; an average daily production rate of 2.28 kg.
(l) This is assuming uranium tails of 1% U-235, a feed assay of 3.5% U-235, a product assay of 93% U-235, a 5% loss of material during bomb manufacture, and that 16 kg of this product are needed for a bomb. See the SWU calculator published by URENCO, a European uranium enrichment consortium: web.archive.org/web/20021226100607/www.urenco.de/trennarbeit/swucal_e.html.
(m) The Separative Work Unit is the standard measure of the effort required to increase the concentration of the fissionable U-235 isotope. See www.urenco.com/Content/89/Glossary.aspx.
(n) Based on the assumptions set forth above (see footnote l), Iran would need approximately 840 SWUs to bring 914 kg of low-enriched UF6 to weapon grade. See the SWU calculator published by URENCO, a European uranium enrichment consortium: web.archive.org/web/20021226100607/www.urenco.de/trennarbeit/swucal_e.html.
(o) According to the IAEA, Iran is operating an 18 cascade unit (A24) of 2,952 machines and six cascades (984 machines) in a second unit (A26) at the Natanz Fuel Enrichment Plant (http://www.iranwatch.org/international/IAEA/documents/iaea-iranreport-021909.pdf).
(p) Iran has not been operating its IR-1 centrifuges at their estimated capacity. For instance, between December 2007 and November 2008, during which Iran was operating an average of 3,444 machines, 764 kg of low enriched UF6 were produced. Assuming a product assay of 3.5% U-235 and tails of .4% U-235, this represents about 1,880 SWU, or just over .5 SWU per machine.
(q) According to the IAEA, Iran is operating an 18 cascade unit (A24) of 2,952 machines and six cascades (984 machines) in a second unit (A26); a further nine cascades (1,476 machines) at unit A26 are installed and under vacuum and the three remaining cascades (492 machines) are being installed (http://www.iranwatch.org/international/IAEA/documents/iaea-iranreport-021909.pdf)
(r) Iran’s IR-1 centrifuge is widely estimated to have an annual enrichment capacity of about two SWUs. Iran, however, has been achieving a lower output (see note p). If Iran were to increase the efficiency of its centrifuges to one SWU per machine, two units operating at the Natanz Fuel Enrichment Plant would produce about 6,000 SWUs per year.
(s) If 840 SWUs are needed to bring a bomb’s worth of Iran’s stockpiled low-enriched UF6 to weapon-grade, and if Iran’s centrifuges produce approximately 6,000 SWUs per year, it would probably take less than two months.
(t) According to the IAEA, 357 metric tons is the total amount of UF6 produced by Iran at its Uranium Conversion Facility from the beginning of operations in March 2004, to February 9, 2009 (http://www.iranwatch.org/international/IAEA/documents/iaea-iranreport-021909.pdf).
(u) natural uranium feed, a product assay of 93%, and tails of .4%, 357 metric tons of UF6 would yield approximately 800 kg of uranium enriched to 93% U-235; if 16 kg of 93% material are required to fuel one first-generation implosion device, then this 800 kg of uranium would be enough to fuel 45-50 such weapons.