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– Lisa Beyer
Bloomberg News
August 27, 2018
Iran’s Accumulation of Enriched Uranium Slows

Arms Control NOW


Although the troubling growth of Iran’s uranium enrichment stockpile continues, the most recent report from the International Atomic Energy Agency (IAEA) indicates that Tehran’s accumulation of enriched uranium slowed over the past quarter. It is concerning that Iran continues to breach limits set by the nuclear deal, but the slower stockpile growth and no indication of new violations suggests Tehran is showing restraint so as not to cross any red lines that might imperil a U.S. re-entry into the nuclear deal and return to full compliance by all parties down the road.

Iran’s stockpile of uranium gas enriched to less than 4.5 percent is now 2,443 kilograms—roughly 12 times the 202 kilograms of 3.67 percent enriched uranium limit set by the deal, known as the Joint Comprehensive Plan of Action (JCPOA). According to the Nov. 11 IAEA report, Iran accumulated  338 kilograms over the last quarter, down significantly from the 533 kilograms increase from June to September, 550 kilograms from March to June, and 648 kilograms from November 2019 to March.

Of the 338 kilograms produced, about 284 are enriched to 2-4.5 percent and 54 are enriched to less than 2 percent. In the last quarter, Iran accumulated about 100 kilograms more of each category of material. The stockpile of uranium enriched to less than 2 percent, while still a violation of the JCPOA, is not significant from a risk perspective as it would not decrease the time it would take Iran to produce enough weapons-grade uranium for a bomb if Tehran chose to do so.

According to the November report, the IAEA has “not observed any change in the level of cooperation by Iran” on JCPOA monitoring and verification activities. Tehran’s continued compliance with the JCPOA’s transparency measures is particularly critical as the stockpile grows. Iran has now produced about 1,716 kilograms of uranium gas enriched from 2-4.5 percent which, if enriched to weapons-grade (greater than 90 percent uranium-235), would be enough material for two bombs. Given the JCPOA’s transparency measures, including real-time monitoring of enrichment, any move to enrich the uranium to weapons-grade would be quickly detected. Iran’s continued adherence to these more intrusive monitoring measures further supports Tehran’s assertion that its violations are a transparent attempt to pressure parties to the JCPOA to deliver on sanctions relief and not intended to kill the deal.

If Iran were to make the political decision to violate its international obligations and develop a nuclear weapon, it would still take about 3-4 months for Tehran to produce the weapons-grade material. This 3-4 month period, known as the breakout timeline, is roughly unchanged from the prior report because Iran’s centrifuge enrichment capacity has remained about the same since the last reporting period. After producing the weapons-grade material, Iran would then need to convert the gas and pair the material with an explosives package, a process that could take about 18 months, according to Israeli assessments. The 3-4 month breakout is significantly less than the 12 months established by full implementation of the JCPOA, but it is still enough time to negotiate a return to compliance to the deal in January when President-elect Joe Biden takes office. Biden has expressed his intention to return the United States to compliance with the JCPOA if Iran is willing to do the same.

The assessment that Iran has stockpiled enough uranium enriched between 2-4.5 percent which, when enriched to weapons-grade is enough for a bomb, may appear to contradict an interview that IAEA Director-General Rafael Mariano Grossi gave with AP in October. Grossi told AP that Iran does not at the moment possess a “significant quantity” of uranium.

The assessments are not necessarily incompatible, however, as  Grossi may have been referring to the IAEA’s definition of the quantity of nuclear material from which the “possibility of manufacturing a  nuclear explosive device cannot be excluded.” The IAEA assesses this quantity as 25 kilograms of uranium enriched to greater than 90 percent uranium-235. The IAEA reports have consistently noted that Iran has breached the 3.67 percent uranium-235 enrichment limit, but has not exceeded 4.5 percent. That would be consistent with an interpterion of Grossi’s comments as meaning that Iran does not possess 25 kilograms of uranium gas enriched to greater than 90 percent.

Interestingly, the IAEA report indicates that Iran reverted to its original plan to transfer advanced centrifuges from the pilot plant to the main enrichment hall at Natanz, rather than build equivalent cascades. Originally, Tehran notified the IAEA in July of its intent to move three cascades, one each comprised of IR-2, IR-4, and IR-6, centrifuges, from the pilot plant to the enrichment facility at Natanz. In the September IAEA report, the agency noted that Iran had decided to install equivalent cascades in the fuel enrichment plant and cease operation of the corresponding centrifuges at the pilot plant. According to the November IAEA report, “Iran informed the Agency that it had decided to transfer the existing cascades at [the pilot plant] to [the Natanz enrichment plant], rather than install cascades at [the pilot plant] equivalent to those installed at [Natanz].” Only the cascade of IR-2 centrifuges has been moved as of the November report, and it is not yet enriching uranium. From a breakout perspective, the decision to transfer existing centrifuges is positive, as it reduces the number of installed machines available should Iran seek to ramp up its production of enriched uranium down the road.

Iran told the IAEA that it is moving the cascades from the pilot plant “with the aim that eventually all of the enrichment [research and development] activities will be concentrated in this area.” Tehran may also be motivated to move the cascades after the July attack on its centrifuge assembly facility at Natanz. The below-ground fuel enrichment plant is likely more secure and more difficult to sabotage.

While the IAEA report said that Tehran continues to adhere to the required monitoring and verification requirements for its declared program, the agency noted frustration with Tehran’s failure to provide satisfactory and timely answers to its investigation into uranium particles found at an undeclared site in February 2019, which U.S. officials have said was the Turquzabad warehouse. The IAEA was able to access the site and take samples per the additional protocol to Iran’s safeguards agreement, which Tehran is provisionally implementing as part of the JCPOA.

According to the IAEA, the agency’s assessment of the particles was “not inconsistent” with the information provided by Iran, but that Tehran’s response to additional follow-up questions is “unsatisfactory because it was not technically credible.” Iran did provide the IAEA with additional information Nov. 5, but the agency said Nov. 9 that the response is still “not technically credible.”

While the IAEA has made clear these particles date back to pre-2003 activities, when Iran had a nuclear weapons program according to IAEA and U.S. assessments, and therefore unlikely to alter current assessments of Iran’s proliferation risk, Tehran’s failure to provide satisfactory and credible answers to the agency’s inquiries is concerning. Iran’s timely cooperation is necessary for the integrity of the safeguards regime and would bolster Tehran’s credibility.

Furthermore, inadequate cooperation with IAEA safeguards inquiries may complicate U.S. efforts to re-enter the JCPOA and return to compliance alongside Iran after Biden’s Jan. 2021 inauguration. It may be politically difficult for the United States to rejoin the deal if Iran is perceived as failing to cooperate or stonewalling IAEA investigations.—KELSEY DAVENPORT, director for nonproliferation policy, and JULIA MASTERSON, research assistant

Key Details from the Nov. 11 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 Nov. 11 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 Nov. 11 report, Iran’s total enriched uranium stockpile equates to 2,442.9 kilograms of uranium by weight (of which 2,408.5 kilograms is in gas form), comprised of 215.1 kilograms enriched up to 3.67 percent, 1,535.1 kilograms enriched to between 2 and 4 percent, and 692.7 kilograms enriched up to 2 percent. The uranium enriched to less than 2 percent is being produced by Iran’s advanced centrifuge machines and does not factor in to breakout.
  • Breached the prohibition on any uranium activities, including enrichment, at Fordow for 15 years. Iran began enriching uranium to 4.5 percent uranium-235 at Fordow in Nov. 2019. Since then, the IAEA has verified that Iran continues to enrich and stockpile uranium at the Fordow facility using 1,044 IR-2 centrifuges arranged into six cascades. The agency’s Nov. 11 report notes the installation of 12 IR-1 centrifuges and one single IR-1 centrifuge, for the stated purpose of conducting “initial research and R&D activities related to stable isotope production,” which is the intention for the facility under the JCPOA.There are now 1,057 IR-1 centrifuges installed at Fordow, according to the Nov. 11 report. This number is consistent with the last reporting period and marks a slight increase over the 1,044 IR-1 machines permitted at the site by the JCPOA.
  • Breached restrictions on the number of advanced centrifuges installed and the 10-year prohibition on accumulating enriched uranium from advanced machines. The IAEA’s Nov. 11 report notes that Iran continues to install, test, operate, and accumulate enriched uranium from advanced model centrifuges at the Natanz enrichment facility. Specifically, the IAEA reported that:
    • Five smaller cascades of up to nine IR-4 centrifuges, eight IR-5 centrifuges, six IR-6 centrifuges, 20 IR-6 centrifuges, 10 IR-6s centrifuges, and 10 IR-s centrifuges are operational and accumulating enriched uranium at the pilot fuel enrichment plant.
    • Two longer cascades of 152 IR-4 centrifuges and 110 IR-6 centrifuges are operational and accumulating enriched uranium at the pilot fuel enrichment plant. These cascades will be transferred to the main fuel enrichment plant, according to the report (see below).
    • One IR-1 centrifuge, four IR-2m centrifuges, one IR-4 centrifuge, two IR-5 centrifuges, two IR-6s centrifuges, one IR-8 centrifuge, one IR-8B centrifuge, one IR-s centrifuge, and one IR-9 centrifuge are being tested with UF6 at the pilot fuel enrichment plant, but are not accumulating enriched uranium.
    • Iran conducted mechanical testing of three IR-4 centrifuges for 42 days at the Tehran Research Center.

The IAEA also verified that Iran plans to transfer three cascades of IR-4, IR-2m, and IR-6 centrifuges from the pilot fuel enrichment plant to the fuel enrichment plant at Natanz. According to the report, the cascade of IR-2ms has already been moved and installed at the main plant. The cascades are not yet enriching. The move violates the provision of the JCPOA that allows for only 5,060 IR-1s to be installed in the fuel enrichment facility at Natanz.

The Nov. 11 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. The agency’s Nov. 11 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.
  • Numerical Limit on Operational IR-1 Centrifuges at Natanz: The Nov. 11 IAEA report details that Iran continues to use no more than 5,060 IR-1 centrifuges installed in 30 cascades at the Natanz fuel enrichment plant, as specified by the JCPOA. However, as noted above, Iran has installed a cascade of IR-2m centrifuges in the fuel enrichment plant at Natanz, in violation of the limit of only 5,060 IR-1s. As of Nov. 9, the IAEA reported that the cascade was connected to feed lines but was not enriching uranium.
  • 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. However, consistent with the last reporting period, the IAEA’s report did mention that Iran has installed the refueling machine at that site, which will be modified for the redesigned reactor.
  • Heavy Water Production: Iran’s heavy water stockpile is 128 metric tons, below the JCPOA’s 130 metric ton limit. The IAEA’s Nov. 11 report reflects a minor decrease in Iran’s heavy water stockpile since the agency’s Sept. 4 report, when Iran’s stockpile equated to 128.5 metric tons. The report noted that Iran shipped out heavy water and used some for domestic purposes during the reporting period.