Iran's Nuclear Timetable
Updated February 1, 2010
Iran’s bank of rapidly spinning centrifuges at the Natanz Fuel Enrichment Plant 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. The Project further estimates that by the end of 2009, Iran had enough U-235 to fuel a second bomb. "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 February 1, 2010 is estimateda below:
- Amount of U-235 contained in Iran’s stockpile of low-enriched uranium:
47.7 kg b
- Amount of this U-235 produced each month:
2 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 probably had enough U-235 to fuel a second bomb:
December 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:
2,018 kg j
- Average daily production rate of this low-enriched UF6:
2.77 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:
3,936 o
- Average number of SWUs each centrifuge now appears to be producing per year:
.5 p
- Average number of SWUs each centrifuge produced per year between December 2007 and November 2008:
.5 q
- Total number of centrifuges installed at Natanz:
8,692 r
- Number of SWUs these 8,692 centrifuges are assumed to be capable of producing per year:
8,600 s
- Number of months needed for these 8,692 centrifuges operating at such a capacity to produce 840 SWUs:
1.2 t
Comments:
- Though Iran has not increased the number of centrifuges enriching uranium at Natanz, it has made steady progress in increasing the plant’s enrichment capacity by installing additional centrifuges. Iran is close to having three operational units (of about 3,000 machines each) at the plant, though as of early November 2009 it was enriching uranium in only about half of these machines.
- Iran appears to be operating its centrifuges well below their estimated capacity. Iran’s monthly production rate of low-enriched uranium now appears stable. An increase in the production rate earlier in 2009 can be attributed to the fact that more machines were operating, not because these machines were operating more efficiently.
- Following start-up, centrifuge cascades must be operated for a time without product withdrawal. The low production rate at Natanz may be, in part, due to the fact that Iran continues to add new centrifuges.
- The amount of low-enriched UF6 produced from November 2008 through the end of October 2009 (about 924 kg) is an estimate provided by Iran to the IAEA. Through independent readings, the IAEA calculates that Iran produced 814 kg of this material over roughly the same period. Under the current inspection arrangement, the Agency only verifies Iran's estimate once a year, when a physical inventory verification is done. The next inventory at Natanz is planned for late November 2009, and the results of this inventory can be expected in early 2010. It should be noted that the results of the previous inventory revealed that Iran had underestimated by about one third the amount of low enriched UF6 actually produced.
Additional information: Number of centrifuges deployed over time
| Date of IAEA inventory | Centrifuges being fed with UF6 | Other 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 |
6/1/2009 |
4,920 |
2.296 |
8/12/2009 |
4,592 |
3,716 |
11/2/2009 |
3,936 |
4,920 |
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 1,179 kg of this material for a total of 2,018 kg (see note j) (http://www.iranwatch.org/international/IAEA/iaea-iranreport-111609.pdf). Of that amount, 1,364 kg is uranium; 1,364 kg of uranium enriched to 3.5% contains 47.7 kg of U-235.
(c) Iran is estimated to produce about 2.77 kg of low-enriched UF6 each day (see note k), for an average monthly production rate of 84 kg, 57 kg of which is uranium; enriched to 3.5%, this 57 kg contains 1.99 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, at the time, 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 8,300 SWUs per year (see note s), 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 has maintained its current monthly production rate of U-235 at 2 kg, then Iran would have accumulated the requisite 21.6 kg for a second bomb by December 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, 329 kg between February 1, 2009 and May 31, 2009, 169 kg between June 1, 2009 and July 31, 2009, and 255 kg between August 1, 2009 and October 30, 2009. This gave Iran a total of about 1,763 kg of low-enriched UF6 by November 1, 2009. Assuming a daily production rate of 2.77 kg (see note k) since then, Iran produced a further 255 kg of low-enriched UF6, bringing its total stockpile to 2,018 kg. (http://www.iranwatch.org/international/IAEA/iaea-iranreport-111609.pdf).
(k) Iran estimates that it produced 255 kg of low-enriched UF6 over 92 days, from July 31, 2009 to the end of October 2009, for an average daily production rate of 2.77 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, as of early November 2009 Iran was 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/iaea-iranreport-111609.pdf).
(p) Iran is operating its IR-1 centrifuges at well below their estimated capacity. For instance, between February 2009 and October 2009, during which Iran was operating an average of 4,376 machines, an estimated 753 kg of low enriched UF6 were produced. Assuming a product assay of 3.5% U-235 and tails of .4% U-235, this amounts to about 1,851 SWU over 9 months (2,468 SUW over one year), or just over .5 SWU per machine.
(q) Between December 2007 and November 2008, during which Iran was operating an average of 3,375 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.
(r) 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 twelve cascades (1,968 machines) at unit A26 and seventeen cascades (2,788 machines) at unit A28 have been installed. The installation of another cascade (164 machines) at unit A28 is ongoing (http://www.iranwatch.org/international/IAEA/iaea-iranreport-111609.pdf).
(s) Iran’s IR-1 centrifuge is widely estimated to have an annual enrichment capacity of about two SWUs. Iran, however, has been achieving a much lower output (see note p). If Iran were to increase the efficiency of its centrifuges to one SWU per machine, the machines at the Natanz Fuel Enrichment Plant would produce about 8,600 SWUs per year.
(t) 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 were to produce approximately 8,600 SWUs per year, or 716 SWUs per month, then it would probably take less than two months to achieve 840 SWUs.