Paul K. Kerr
Analyst in Nonproliferation
Iran’s nuclear program began during the 1950s. The United States has expressed concern since the mid-1970s that Tehran might develop nuclear weapons. Iran’s construction of gas centrifugebased uranium enrichment facilities is currently the main source of proliferation concern. Gas centrifuges enrich uranium by spinning uranium hexafluoride gas at high speeds to increase the concentration of the uranium-235 isotope. Such centrifuges can produce both low-enriched uranium (LEU), which can be used in nuclear power reactors, and weapons-grade highly enriched uranium (HEU), which is one of the two types of fissile material used in nuclear weapons.
Obtaining fissile material is widely regarded as the most difficult task in building nuclear weapons. As of May 2012, Iran had produced an amount of LEU containing up to five percent uranium-235 which, if further enriched, could theoretically produce enough HEU for several nuclear weapons. Iran has also produced LEU containing up to 20 percent uranium-235, but, as of May 2012, this amount was not sufficient to yield a sufficient amount of weapons-grade HEU for a weapon.
Although Iran claims that its nuclear program is exclusively for peaceful purposes, the program has generated considerable concern that Tehran is pursuing a nuclear weapons program. Indeed, the UN Security Council has responded to Iran’s refusal to suspend work on its uranium enrichment program by adopting several resolutions that imposed sanctions on Tehran. Despite evidence that sanctions and other forms of pressure have slowed the program, Iran continues to enrich uranium, install additional centrifuges, and conduct research on new types of centrifuges.
Tehran has also continued work on a heavy-water reactor, which is a proliferation concern because its spent fuel will contain plutonium—the other type of fissile material used in nuclear weapons. However, plutonium must be separated from spent fuel—a procedure called “reprocessing.” Iran has said that it will not engage in reprocessing.
The International Atomic Energy Agency (IAEA) monitors Iran’s nuclear facilities and has been able to verify that Tehran’s declared nuclear facilities and materials have not been diverted for military purposes. But the agency still has concerns about the program, particularly evidence that Iran may have conducted procurement activities and research directly applicable to nuclear weapons development. The United States has assessed that Tehran has the technical capability eventually to produce nuclear weapons, but has not yet mastered all of the necessary technologies for building such weapons. Whether Iran has a viable design for a nuclear weapon is unclear.
Whether Iran has a nuclear weapons program is also unclear. A National Intelligence Estimate made public in December 2007 assessed that Tehran “halted its nuclear weapons program” in 2003. The estimate, however, also assessed that Tehran is “keeping open the option to develop nuclear weapons” and that any decision to end a nuclear weapons program is “inherently reversible.” U.S. intelligence officials have reaffirmed this judgment on several occasions. For example, Director of National Intelligence James Clapper stated in January 2012 that Iran “is keeping open the option to develop” nuclear weapons.
Secretary of Defense Leon Panetta stated in January 2012 that Iran would probably need “about a year” to produce a nuclear weapon and “possibly another one to two years” to incorporate it into a delivery vehicle. However, Director Clapper indicated in February 2012 that it would likely take Iran longer than a year to produce a nuclear weapon after making a decision to do so. These estimates apparently assume that Iran would use its declared nuclear facilities to produce fissile material for a weapon. However, Tehran would probably use covert facilities for this purpose; Iranian efforts to produce fissile material for nuclear weapons by using its known nuclear facilities would almost certainly be detected by the IAEA.
Date of Report: September 26, 2012
Number of Pages: 54
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