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"[Arms Control Today is] Absolutely essential reading for the upcoming Congressional budget debate on the 2018 #NPR and its specific recommendations ... well-informed, insightful, balanced, and filled with common sense."

– Frank Klotz
former Administrator of the National Nuclear Security Administration
March 7, 2018
Iran’s Nuclear Program Remains on Steady Trajectory

Arms Control NOW


A Sept. 4 report by the International Atomic Energy Agency (IAEA) confirms that Iran continues to exceed limits on its uranium enrichment program imposed by the 2015 nuclear deal (JCPOA) and is incrementally expanding its stockpile of uranium enriched up to 4.5 percent.

While Iran’s persistent violations of the deal are troublesome, its rate of enriched uranium production has not increased over the course of 2020, indicating that Tehran is not actively dashing toward a bomb nor accelerating its production of fuel. This carefully calibrated approach supports assertions by Iranian leaders that its breaches of the JCPOA are a response to the U.S. reimposition of sanctions in violation of the accord and that Tehran will return to compliance with the nuclear deal if its conditions on sanctions relief are met.

The IAEA’s Sept. 4 report notes that Iran’s stockpile grew by 533 kilograms since the Agency’s June 5 report, a change slightly smaller than the 550-kilogram increase between the March and June quarterly reports and the 648-kilogram increase between the November 2019 and March reports. Importantly, the IAEA report also confirms Iran has not exceeded a 4.5 percent uranium-235 enrichment level since it first breached the 3.67 percent limit in June 2019.

A move to higher enrichment level would pose a more immediate proliferation risk and would more significantly erode Iran’s breakout, or the time it would take for the country to produce enough weapons-grade nuclear material for a bomb.

Given that Iran has not increased its enrichment level or brought additional centrifuges online since the last report, the current breakout estimate for Iran to produce one bomb’s worth of highly enriched uranium, if it chose to do so, is about 3-4 months, down from the 12 months when the JCPOA was fully implemented. However, Iran has now produced about enough uranium enriched from 2-4.5 percent for a second bomb.

Based on the Agency’s report, there are no indications that Iran is planning to ramp up its production of enriched uranium in the near term. While Iran informed the IAEA of its intention to install three advanced centrifuge cascades—or chains of centrifuges arranged to optimize enriched uranium output —at its main fuel enrichment plant at Natanz, the Sept. 4 report notes that Iran clarified to the Agency its intent to cease operations of identical cascades at the pilot fuel enrichment plant once the new machines are installed and operational.

This does, however, suggest that Iran has ramped up its manufacturing of advanced centrifuges and that it may expand production of enriched uranium using advanced machines in violation of the JCPOA’s provision that it employ only 5,060 first-generation IR-1 centrifuges at Natanz for enrichment purposes. Such a step would further decrease breakout.

The Sept. 4 report also details Iran’s ongoing cooperation with the verification and monitoring measures imposed by the deal and notes that Iran continues to provisionally apply the additional protocol to its safeguards agreement. (For more on the IAEA’s request to access undeclared sites as part of its investigation into past possible undeclared nuclear materials and activities, see our Sept. 10 post IAEA Report Notes Progress on Investigation.)

It was reported Sept. 8 that Iran has begun to construct a hall for the manufacturing of centrifuges in “the heart of the mountains” near Natanz, according to comments from Ali Akbar Salehi, who heads the Atomic Energy Organization of Iran. There was no direct mention of the new facility in the IAEA report, but Iran’s centrifuge manufacturing is subject to continuous monitoring and verification under the JCPOA.

Iran’s decision to build the new, underground facility appears to be a direct response to an act of sabotage that damaged its advanced centrifuge production building at Natanz in July.

This announcement underscores the risks of attempting to disrupt Iran’s nuclear program using sabotage or military strikes. Such acts might set back Iran’s nuclear program, but they are also likely to push Tehran to build new facilities at hardened locations that are more difficult to target. Military strikes may also push Iran to determine that the benefits of pursuing nuclear weapons outweigh the costs, and either withdraw from the nuclear Nonproliferation Treaty to openly pursue nuclear weapons or attempt a covert program, the latter of which is much more likely to be detected with the JCPOA’s intrusive monitoring mechanisms in place.—JULIA MASTERSON, research assistant and KELSEY DAVENPORT, director for nonproliferation policy

Key Details from the Sept. 4 Report

The IAEA does not determine Iran’s compliance with the JCPOA, but the Agency’s most recent report indicates that Iran has violated the following restrictions on its nuclear activities that were agreed to in the JCPOA:

  • Breached the limit on enriching uranium to no more than 3.67 percent uranium-235 for 15 years. The IAEA first verified that Iran exceeded the 3.67 percent uranium-235 enrichment limit and began enriching uranium to 4.5 percent in June 2019. According to the Sept. 4 report, Iran continues to enrich uranium up to 4.5 percent.
  • Breached the stockpile limit of 300 kilograms of uranium hexafluoride gas (UF6) enriched to 3.67 percent (about 202 kilograms of uranium by weight) for 15 years. In May 2019, Iran stated it would no longer be bound by the JCPOA’s 300-kilogram stockpile cap and the IAEA verified that Iran breached that limit July 1, 2019. According to the IAEA’s Sept. 4 report, Iran’s total enriched uranium stockpile equates to 2105.4 kilograms of uranium by weight (of which 2073.8 kilograms is in gas form), comprised of 215.1 kilograms enriched up to 3.67 percent, 1251.5 kilograms enriched to between 2 and 4.5 percent, and 638.8 kilograms enriched up to 2 percent.
  • Breached restrictions on the number of advanced centrifuges installed and the 10-year prohibition on accumulating enriched uranium from advanced machines. The IAEA’s Sept. 4 report notes that Iran continues to install, test, operate, and accumulate enriched uranium from advanced model centrifuges at the Natanz enrichment facility. The number of centrifuges per cascade differs slightly from the prior June report Specifically, the IAEA reported that:
    • Six smaller cascades of 15 IR-4 centrifuges, 10 IR-5 centrifuges, 9 IR-6 centrifuges, 20 IR-6 centrifuges, 10 IR-6s centrifuges, and 10 IR-s centrifuges are operational and producing uranium enriched up to 2 percent.
    • Three longer cascades of 156 IR-4 centrifuges, 164 IR-2m centrifuges, and 129 IR-6 centrifuges are operational and producing enriched uranium.
    • Iran will begin testing IR-5 and IR-6 centrifuges in a full cascade of 172 centrifuges, or in two smaller cascades of 84 centrifuges each. The IAEA verified that Iran is preparing to install IR-5 and IR-6 centrifuges for this purpose.
    • Iran conducted several rounds of mechanical testing on IR-4 centrifuges at the Tehran Research Centre.

The IAEA also verified that Iran plans to install three cascades of IR-4, IR-2m, and IR-6 centrifuges equivalent to production cascades currently used for research and development. According to the Agency, Iran will cease operation of the three equivalent cascades at the pilot facility once the new cascades are operational. However, if the cascades remain installed Iran could use them to ratchet up its enrichment down the road.

  • Breached the prohibition on any uranium activities, including enrichment, at Fordow for 15 years. Iranian President Hassan Rouhani directed the Atomic Energy Organization of Iran to begin enriching uranium to 4.5 percent uranium-235 at Fordow in November 2019. Since then, the IAEA has verified that Iran continues to enrich uranium at the Fordow facility using 1,044 IR-1 centrifuges. The Agency’s Sept. 4 report also notes the installation of a chain of 12 IR-1 centrifuges and an additional standalone IR-1 machine at Fordow, for the stated purpose of conducting “initial research and R&D activities related to stable isotope production.” There are now 1057 IR-1 centrifuges installed at Fordow, according to the Sept. 4 report, a slight increase over the 1,044 IR-1 machines permitted at the site by the JCPOA

The Sept. 4 IAEA report also notes areas where Iran continues to meet its obligations under the accord:

  • Monitoring Activities: According to the IAEA, Iran continues to cooperate with the continuous monitoring measures put in place by the deal, including by allowing on-line enrichment monitors and electronic seals which would detect any deviations to Iran’s uranium enrichment levels or the operational status of its nuclear infrastructure under safeguards. The Agency’s Sept. 4 report also notes that Iran continues to provisionally apply the additional protocol to its safeguards agreement and that Iran has cooperated with Agency requests for clarification on, or access to, declared or undeclared locations. The report says the IAEA “has conducted complementary access under the Additional Protocol to all the sites and locations in Iran which it needed to visit, except for a location at which complementary access will be conducted later in September 2020,” but adds that “the Agency has recently informed Iran that there are a number of other findings for which further clarifications and information need to be provided and questions need to be answered.” (For more on the IAEA’s safeguards investigation into possible undeclared materials and activities, see our Sept. 10 post IAEA Report Notes Progress on Investigation.)
  • Numerical Limit on Operational IR-1 Centrifuges at Natanz: The IAEA report details that Iran continues to use no more than 5060 IR-1 centrifuges installed in 30 cascades at the Natanz fuel enrichment plant, as specified by the deal.
  • Conversion of the Arak Reactor: The IAEA notes that Iran has not taken steps to pursue the construction of the Arak heavy water research reactor based on its original design. Under the deal, Iran agreed to convert the reactor into a light-water design that would produce significantly less weapons-grade plutonium for a bomb on an annual basis than the Arak reactor would, when operational, under its original design. The United States terminated its sanctions waiver supporting the reactor’s conversion May 27, and that waiver expired in late July, following a sixty-day wind-down period. The report does not indicate if any work on the modified reactor has occurred since that time. The IAEA did mention that Iran has installed the refueling machine at the site, which will be modified for the redesigned reactor.
  • Heavy Water Production: Iran’s heavy water stockpile is 128.5 metric tons, below the JCPOA’s 130 metric ton limit. The IAEA’s Sept. 4 report reflects a moderate decrease in Iran’s heavy water stockpile since the Agency’s June 5 report, when Iran’s stockpile equated to 132.6 metric tons. The heavy water production plant is operating, but the overall stockpile decreased as a result of 4.9 metric tons being shipped out and the use of 2.3 metric tons for domestic research and development since the June report.