http://www.iranwatch.org/ourpubs/articles/iranucleartimetable.html
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Iran's Nuclear Timetable

Updated June 9, 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 June 1, 2009 is estimateda below:

Additional estimates: Moving from reactor-grade to weapon-grade uranium

Comments:

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
6/1/2009
4,920
2.296



 

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 500 kg of this material for a total of 1,339 kg (see note j) (http://www.iranwatch.org/international/IAEA/iaea-iranreport-060509.pdf). Of that amount, 905 kg is uranium; 905 kg of uranium enriched to 3.5% contain 31.68 kg of U-235.

(c) Iran is estimated to produce about 2.75 kg of low-enriched UF6 each day (see note k), for an average monthly production rate of 84 kg, 56 kg of which is uranium; enriched to 3.5%, this 56 kg contains 1.96 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 7,000 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, by July 2009, Iran were to add the 2,132 centrifuges it has installed and placed under vacuum, the monthly production rate of U-235 would increase by about 43% to 2.86 kg per month. This production rate 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 329 kg between February 1, 2009 and May 31, 2009, for a total of 1,339 kg of low enriched UF6 (http://www.iranwatch.org/international/IAEA/iaea-iranreport-060509.pdf).

(k) Iran estimates that it produced 330 kg of low-enriched UF6 over 120 days, from February 1, 2009 to May 31, 2009, for an average daily production rate of 2.75 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 twelve cascades (1.968 machines) in a second unit (A26) at the Natanz Fuel Enrichment Plant (http://www.iranwatch.org/international/IAEA/iaea-iranreport-060509.pdf).

(p) Iran is operating its IR-1 centrifuges at well below their estimated capacity. For instance, between November 2008 and May 2009, during which Iran was operating an average of 4.346 machines, an estimated 500 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 1,230 SWU, or nearly .3 SWU per machine.

(q) 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.

(r) According to the IAEA, Iran is operating an 18 cascade unit (A24) of 2,952 machines and twelve cascades (1,968 machines) in a second unit (A26); a further six cascades (984 machines) at unit A26 and seven cascades (1,148 machines) at unit A28 are installed and under vacuum (http://www.iranwatch.org/international/IAEA/iaea-iranreport-060509.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 operating at the Natanz Fuel Enrichment Plant would produce about 7,000 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 produce approximately 7,000 SWUs per year, or 583 SWUs per month, then it would probably take less than two months to achieve 840 SWUs.