How long will it take for Iran to produce a nuclear weapon?  

On April 11, 2006, Iran announced that it had enriched a small quantity of uranium to 3.5 percent in its experimental 164-centrifuge test cascade.  It also announced plans to begin building a 3,000-centrifuge cascade by the end of 2006.

 

The best estimates indicate that Iran is 5-10 years away from the ability to enrich enough weapons-grade uranium for a nuclear weapon. But there are major uncertainties with these estimates. One worst-case scenario could have Iran with a nuclear bomb at the end of 2009, but that assumes that Iran does not encounter any of the technical problems that typically plague such programs.  

 

As reported in August 2005 by the Washington Post, the National Intelligence Estimate on Iran concludes that Iran is closer to 10 years from having a nuclear bomb. The IISS (International Institute for Strategic Studies) hypothesizes that it would “likely require a few years to complete and operate a pilot-scale test facility of several thousand centrifuges” and “likely a few years to produce enough HEU for a single nuclear weapon.” One of the most comprehensive reports to date has been published by David Albright and Corey Hinderstein at ISIS (the Institute for Science and International Security).  The report speculates that it may be possible for Iran to build a nuclear weapon by 2009.

This analysis explores this worst-case estimate. It concludes that carefully tracking the Iranian progress over the next two years and giving IAEA inspectors the authority and ability to fully investigate all facilities will be the key to determining when, or if, Iran could achieve the ability to produce the material for a nuclear bomb.

 

How to Make a Bomb

The start-to-finish process of producing weapons-grade uranium involves the extraction of natural uranium from deposits, milling to produce uranium concentrate (more commonly referred to as “yellowcake”), uranium conversion to UF6 gas, and centrifuge enrichment to low-enriched (LEU) and then to highly-enriched uranium (HEU) or directly from UF6 to HEU.

 

The IAEA Director General noted in his March report to the IAEA Board of Governors that by February 2006, Iran had already produced 85 metric tons of UF6 at the Uranium Conversion Facility (UCF). Albright and Hinderstein estimate that this supply would be enough to manufacture 15 nuclear bombs. There are serious questions, however, about the quality and purity of this gas.  Impurities in the mixture could prevent its use in the delicate centrifuges.

 

How quickly Iran could produce significant quantities of enriched uranium depends on several factors, including the number of available centrifuge parts, the rate of centrifuge installation, the necessary cascade testing period, and then the method used to enrich UF6 into HEU. In October 2005, Iran proclaimed that it would no longer adhere to the Additional Protocol, indicating that nuclear inspectors would not be able to visit nuclear sites on short notice.

 

Albright and Hinderstein estimate that Iran has enough working components for 1,000-2,000 centrifuges and, based on Iran’s previous rates of installation, predict that 1,500 centrifuges could be installed by the end of 2006 at a rate of 70-100 centrifuges per month. (Albright, 6)  Based on ISIS and IAEA data, it appears unlikely that Iran could achieve its stated goal of operating 3,000 centrifuges by the end of the year. The Wall Street Journal reports on April 13 that the Iranians have clarified that they will begin to install these 3,000 centrifuges by the end of the year.

 

The Iranian program is based on P1 centrifuges. These are the original Pakistani design.  The general rule of thumb is that it would take 1500 P1 centrifuges operation for a year to produce 28 kilograms of highly-enriched uranium (90 percent Uranium-235).  This is enough for one weapon.  The Department of State on April 12 estimated that 3000 centrifuges could produce enough HEU for one nuclear bomb in about 9 months.

 

Pilot Fuel Enrichment Plant (PFEP)

The Pilot Fuel Enrichment Plant, located at Natanz, 200 miles south of Tehran, was built to hold six 164-centrifuge cascades. Iran began the PFEP in 2001, and assembled up to 200 gas centrifuges during 2002-2003.  The November 2004 IAEA Board Report states that prior to the November 22, 2004 suspension, Iran assembled 1,275 centrifuges. Albright and Hinderstein assumed that Iran continued to assemble centrifuges at past rates of assembly and may have reached a total of 1,345 by the end of March 2006. However, the IAEA verified that since the suspension, only about 30% of the centrifuges are still in good condition. Albright and Hinderstein outline that problems leading to the breakdown of the remaining centrifuges could “include excessive vibration of the centrifuges, motor or power failures, pressure and temperature instabilities, or breakdown of the vacuum.”

 

The Iranian reports of April 11, 2006 that Iran had begun enriching uranium using a completed 164-centrifuge test cascade indicate that they have successfully rebuilt this assembly.  IAEA officials will report soon on their observations of the assembly, possibly including information on how much uranium Iran has enriched.  After operation for only a few days, it is likely that Iran could enrich only a miniscule quantity.  Assistant Secretary of State for Security and Nonproliferation Steven Rademaker noted that with a 164 centrifuge cascade, it would take Iran 13.6 years to produce enough HEU for a nuclear weapon.

 

Operating a test cascade will allow Iran to test and improve its centrifuge technology, a necessary stage before it can duplicate the assembly for a larger cascade.  It is possible that Iran could skip some of this testing and verification work in order to install the 3,000-centrifuge hall as soon as possible, but that increases the chances that the larger assembly would suffer a catastrophic failure.

 

Breakout at FEP

The ISIS worst case estimate is based on the possible break-out capability that even a partially complete enrichment facility could give Iran.  

 

Iran is building a Fuel Enrichment Plant (FEP) at Natanz to house 54,000 centrifuges.  This is designed to produce LEU for nuclear reactor fuel.  The plant, however, could be modified to produce HEU for nuclear weapons.  Such modifications would be observable by international inspectors.  It would then be up to the international community to act before Iran could complete its operations.

 

For example, Iran could reconfigure its centrifuges to enrich UF6 to HEU. Albright and Hinderstein indicate that if 3,000 of these centrifuges were so reconfigured Iran could produce 20 kilograms—or about one bomb’s worth--of HEU in roughly 4-6 months. Using either reconfiguration or another method (called batch recycling), Albright and Hinderstein estimate that Iran “is not likely to have enough HEU for a nuclear weapon until 2009.” However, they note that these estimates assume that there are no technical difficulties or breakdowns.  The estimate further assumes that Iran has actually assembled the 3,000 centrifuges by 2008. 

 

Carefully tracking the Iranian progress over the next two years and giving IAEA inspectors the authority and ability to fully investigate all facilities will be the key to determining when, or if, Iran could achieve the ability to produce the material for a nuclear bomb.

 

Related Links:

 

The Clock is Ticking, But How Fast?
David Albright and Corey Hinderstein, Institute for Science and International Security, 27 March 2006

 

Iran's Strategic Weapons Programmes
International Institute for Strategic Studies, 6 September 2005

 

IAEA Reports on Iran, International Atomic Energy Agency website