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The Iranian Uranium-Enrichment Challenge
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Daryl G. Kimball

A long-sought deal between Iran and six world powers on a comprehensive, multiyear agreement to ensure Iran’s nuclear program is exclusively peaceful is within reach if the parties pursue realistic solutions on the major issues. The two sides appear to have found common ground in some areas, such as modifying Iran’s Arak heavy-water reactor to significantly reduce its plutonium output and expanding International Atomic Energy Agency (IAEA) monitoring.

But time is running short. China, France, Germany, Russia, the United Kingdom, and the United States, known collectively as the P5+1, and Iran have but a few weeks to close the gaps on other issues by their July 20 target date.

The most challenging issue may be setting limits on Iran’s uranium-enrichment capacity. Iran’s enrichment program has been the focus of international concern for more than a decade because gas centrifuge machines can be used to enrich uranium not only to normal reactor grade—with 3.5 percent fissionable uranium-235—but also to weapons grade, which is 90 percent U-235.

After talks between European powers and Iran broke down in 2005, Iran increased its centrifuge capacity from 300 first-generation IR-1 machines at one site to about 19,000 installed IR-1 machines at two sites. Today, about 10,200 are operating; 1,000 advanced IR-2M centrifuges are installed at the Natanz enrichment plant, but are not operational.

Iran and the P5+1 should be able to agree that Iran will limit uranium enrichment to levels of less than 5 percent, keep stocks of its enriched uranium near zero, and halt production-scale work at the smaller Fordow enrichment plant and convert it to a research-only facility.

Yet, the two sides must find a formula that limits Iran’s uranium-enrichment capacity at the Natanz site in a way that precludes an Iranian dash to produce enough highly enriched uranium (HEU) for weapons without being detected and disrupted but allows for Iran’s “practical” civilian needs, as the Nov. 24 interim agreement between Iran and the P5+1 puts it.

Iran’s operating IR-1 machines, with about 9,000 separative work units (SWU) per year of combined capacity, could allow Tehran to enrich natural uranium stock into a sufficient quantity of HEU (25 kilograms) for one nuclear bomb in about six months if such an effort were not detected first.

If Iran tried to build a militarily significant nuclear arsenal, it would take considerably more than a year to amass enough material for additional weapons, assemble and perhaps test a nuclear device, and mate the bombs with an effective means of delivery.

An agreement that significantly reduced Iran’s present-day enrichment capacity would increase the time even further and still would provide Iran with more than sufficient capacity for its nuclear fuel needs, which are very limited for the next decade or more. Iran’s Tehran Research Reactor produces medical isotopes, and Iran already has enough material to fuel that reactor for years to come. If the Arak reactor is modified to use 3.5 percent enriched uranium fuel, it might require no more than 1,000 SWU.

Iran also operates a 1,000-megawatt electric light-water power reactor at Bushehr, which uses fuel supplied by Russia under a 10-year arrangement that could be renewed in 2021. The arrangement obliges Russia to continue supplying fuel unless Iran chooses not to renew the fuel supply contract. Iran is in talks with Russia to build and supply up to four additional nuclear power reactors, with the first possibly completed eight years from now.

Yet, Iranian negotiators insist that Iran’s nuclear fuel needs may increase and say they cannot depend on foreign suppliers given the unreliability of these suppliers in the past. It is estimated that Iran would need about 100,000 SWU of enrichment capacity to provide fuel for Bushehr.

Negotiators can square the circle in several ways. The comprehensive agreement could allow for appropriate increases in Iran’s uranium-enrichment capacity in the late stages of the deal. Such adjustments could be conditioned on Iran providing sufficient information to the IAEA to show that any past experiments with possible military dimensions have been discontinued and demonstrating that it cannot obtain foreign nuclear fuel supplies for the new nuclear power reactors that it builds.

As researchers from Princeton University propose in a forthcoming article, it would be in Iran’s interest to replace its less efficient IR-1 machines with a smaller number of more-efficient IR-2M centrifuges, holding total operating SWU capacity constant, and to continue research and development and even stockpile components for more advanced centrifuges but not assemble them until there is a demonstrable need for commercial-scale enrichment. This would increase the time it would take Iran to operate the machines, providing added insurance against rapid breakout scenarios. As part of the final agreement, the P5+1, particularly Russia, should also make clearer fuel supply guarantees to Iran to reduce its rationale for greater enrichment capacity by 2022.

Concluding an effective comprehensive agreement will require difficult compromises on the major issues for both sides. But solutions that prevent a nuclear-armed Iran and still provide Iran with the means to pursue a civil nuclear program are achievable.