Analysis of IAEA Iran Verification and Monitoring Report - May 2023

by David Albright, Sarah Burkhard, Spencer Faragasso, and Andrea Stricker [1]

June 6, 2023

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  • This report summarizes and assesses information in the International Atomic Energy Agency’s (IAEA’s) quarterly report for May 31, 2023, Verification and monitoring in the Islamic Republic of Iran in light of United Nations Security Council resolution 2231 (2015), including Iran’s compliance with the Joint Comprehensive Plan of Action (JCPOA).


  • Iran can now break out and produce enough weapon-grade enriched uranium for a nuclear weapon in 12 days, using only three or four of its advanced centrifuge cascades and little more than one-third of its existing stock of 60 percent enriched uranium. This breakout could be difficult for the IAEA to detect promptly, if Iran took steps to delay inspectors’ access.

  • Using more of its remaining stock of 60 percent enriched uranium in the same three or four cascades and much of its stock of near 20 percent enriched uranium in the vast bulk of its production-scale cascades, Iran could produce enough weapon-grade uranium (WGU) for an additional four nuclear weapons within the first month of a breakout.

  • In the second month, using its further remaining stocks of 20 and 60 percent material and part of its stock of less than 5 percent low enriched uranium (LEU), Iran could produce enough WGU for another two weapons. Using its residual stock of less than 5 percent low-enriched uranium (LEU), Iran could produce enough WGU for an eighth weapon by the end of the third month.

  • In summary, Iran could produce enough WGU for five nuclear weapons in one month, seven in two months, and a total of eight in three months.

  • Iran’s stockpile of 60 percent highly enriched uranium (HEU) was 114.1 kg (Uranium mass, or U mass) or 168.8 kg uranium hexafluoride mass (hex mass) as of May 13. With a monthly average production rate of 9 kg (U mass) per month, Iran could amass enough 60 percent HEU for three nuclear weapons by mid-June.

  • Iran is producing 60 percent HEU from 5 percent LEU feed in advanced centrifuge cascades at the above-ground Pilot Fuel Enrichment Plant (PFEP) and the below-ground Fordow Fuel Enrichment Plant (FFEP); the latter includes an IR-6 centrifuge cascade that is easily modifiable to change operations. This cascade was at the center of an IAEA-detected undeclared mode of operation in January 2023, interconnected with another IR-6 cascade to produce HEU, and subsequently, the IAEA detected the presence of near-84 percent HEU particles at the cascade’s product sampling point.

  • The IAEA assessed that Iran’s explanation for its production of 83.7 percent enriched uranium — which Iran claimed was the result of “unintended fluctuations” — was “not inconsistent” with “additional information and supporting operational data” Iran provided during meetings with the IAEA and “had no further questions on the matter at that stage.”

  • The IAEA did not provide any details of its findings, or report whether it checked if any of Iran’s information was falsified, but notes that it did investigate the information’s consistency. The IAEA has used the more mathematical double negative “not inconsistent,” rather than “consistent,” in the past to express a finding for which it has a lower confidence level because of insufficient basis to confirm information made available by the state. As such, the IAEA may revisit a “not inconsistent” finding. Nonetheless, this episode has left an indelible impression that Iran can quickly and perhaps secretly produce 90 percent enriched uranium, if it chooses to do so.

  • The IAEA has been seeking increased access and intensification of verification activities at the FFEP. In its separate report on Iran’s compliance with the Nuclear Non-Proliferation Treaty (NPT), the IAEA reported that it installed enrichment monitoring devices (EMD) at both the FFEP and at the PFEP to “monitor the enrichment level of the HEU being produced by Iran.” These monitors are not JCPOA-related but are installed pursuant to Iran’s comprehensive safeguards agreement (CSA) with the agency. IAEA Director General Rafael Grossi confirmed in a press conference that the EMD data will notify the IAEA of “another oscillation or otherwise” in the enrichment level in “real-time.”

  • Iran continues to keep the majority (60 percent) of its stock of 60 percent HEU at the Esfahan site, where it maintains a capability to make enriched uranium metal.

  • As of May 13, 2023, Iran had an IAEA-estimated stock of 470.9 kg of 20 percent enriched uranium (U mass and in the form of UF6), equivalent to 696.6 kg (hex mass). Iran also had a stock of 38.8 kg (U mass) of 20 percent uranium in other chemical forms.

  • The average production rate of 20 percent enriched uranium at the FFEP remained steady at 12.2 kg (U mass) or 18 kg (hex mass) per month.

  • At the Natanz Fuel Enrichment Plant (FEP), Iran has a total of 36 cascades of IR-1 centrifuges, 21 cascades of IR-2m centrifuges, four cascades of IR-4 centrifuges, and three cascades of IR-6 centrifuges installed. It did not install any additional centrifuge cascades at the FEP during this reporting period, although it has additional eight IR-4 centrifuge cascades planned and the installation of one IR-4 cascade was ongoing.

  • Iran did not install any additional advanced centrifuge cascades at the FFEP, where it is currently operating six IR-1 centrifuge cascades and two IR-6 centrifuge cascades, although it plans to install up to 14 additional IR-6 centrifuge cascades.

  • Iran installed one IR-4 centrifuge cascade at the PFEP since the last reporting period. It is unclear why Iran has not installed additional centrifuge cascades per its announced plans, especially following a spike in advanced centrifuge deployment from August 2022 to February 2023. It is unclear whether this means Iran produced fewer centrifuges than expected, implying possible manufacturing difficulties, or is keeping newly produced machines in storage instead.

  • Iran’s current, total operating enrichment capability is estimated to be about 19,100 separative work units (SWU) per year, a slight increase over the end of the last reporting period, largely due to the added cascade at the PFEP. As of this reporting period, Iran was not yet using its fully installed enrichment capacity at the FEP.

  • Iran’s stockpile of near 5 percent LEU was 1340.2 kg (U mass) or 1982.5 kg (hex mass). Average production of near 5 percent LEU at the FEP decreased, but despite large amounts of 5 percent LEU being used as feedstock for 20 and 60 percent uranium production, Iran’s overall near 5 percent LEU stock increased slightly.

  • Despite the increase during this reporting period in the amount of uranium enriched between two and five percent, Iran has not prioritized stockpiling this material over the past two years. In addition, it has not made planned progress on the Enriched Uranium Powder Plant, a key civil facility to convert less than five percent enriched uranium hexafluoride into a uranium oxide powder for use in nuclear power reactor fuel. These two choices are at odds with Iran’s contention that its primary goal is to accumulate 4-5 percent enriched uranium for use in nuclear power reactor fuel. Instead, Iran has used this stock extensively to produce near 20 percent and 60 percent enriched uranium, far beyond any of Iran’s civilian needs.

  • Iran’s overall reported stockpile of enriched uranium increased by 983.7 kg (U mass), largely due to an increase in uranium enriched to less than 2 percent.

  • The IAEA reported unsatisfactory progress by Iran on resolving a discrepancy in Iran’s natural uranium inventory at the Uranium Conversion Facility (UCF). It reported a shortfall in Iran’s declaration, which may indicate that Iran mixed into the UCF inventory undeclared uranium it used in the past at the Lavisan-Shian site during its early-2000s nuclear weapons program.

  • The IAEA reports that Iran provided an updated design information questionnaire (DIQ) for the Arak reactor indicating that it is reorienting the reactor consistent with the conceptual design set out in the JCPOA. The reactor will have a power of 20 MW(th). Iran informed the IAEA that it expects to commission the reactor in 2023 and start operations in 2024, although the reported status of the reactor construction raises doubts about whether these milestones will be reached.

  • The IAEA underscores that “for two and a quarter years Iran has not provided updated declarations and the Agency has not been able to conduct any complementary access under the Additional Protocol to any sites and locations in Iran.”

  • The IAEA reports that in line with an IAEA/Iran Joint Statement from March 2023, in May, “the Agency installed surveillance cameras at workshops in Esfahan where centrifuge rotor tubes and bellows are manufactured.” However, despite reinstalling surveillance cameras, Iran is still not turning over the video footage to the IAEA, nor has Iran provided past footage from nuclear-related sites from February 2021 to June 2022. Moreover, there remain other Iranian centrifuge manufacturing and assembly facilities where Iran has still not permitted the IAEA to reinstall cameras.

  • The IAEA urges Iran to hasten its cooperation. It writes, “The process of implementing the activities set out in the Joint Statement needs to be sustained and uninterrupted in order that all of the commitments contained therein are fulfilled. In addition, the Agency has informed Iran that for these activities to be effective the Agency needs to re-establish a satisfactory understanding of Iran’s inventory of centrifuge rotor tubes and bellows, including those in assembled centrifuges.”

  • The absence of monitoring and surveillance equipment, particularly since June 2022, has caused the IAEA to doubt its ability to ascertain whether Iran has diverted or may divert advanced centrifuges. A risk is that Iran could accumulate a secret stock of advanced centrifuges, deployable in the future at a clandestine enrichment plant or during a breakout at declared sites. Another risk is that Iran will establish additional centrifuge manufacturing sites unknown to the IAEA. Iran has proven its ability of moving manufacturing equipment to new, undeclared sites, further complicating any future verification effort and contributing to uncertainty about where Iran manufactures centrifuges.

  • The IAEA concluded previously that “Iran’s decision to remove all of the Agency’s equipment previously installed in Iran for surveillance and monitoring activities in relation to the JCPOA has [had] detrimental implications for the Agency’s ability to provide assurance of the peaceful nature of Iran’s nuclear programme.”

  • Concern about Iran’s installation of advanced centrifuges at an undeclared site increases as its 60 percent HEU stocks grow. Such a scenario is becoming more worrisome and viable, since a relatively small number of advanced centrifuge cascades would suffice for the rapid enrichment of the 60 percent enriched material to weapon-grade. This hybrid strategy involves the diversion of safeguarded HEU and the secret manufacture and deployment of only three or four cascades of advanced centrifuges. With greater uncertainty about the number of advanced centrifuges Iran is making, there is a greater chance of Iran hiding away the requisite number of advanced centrifuges to realize this scenario.

  • Combined with Iran’s refusal to resolve outstanding safeguards violations, the IAEA has a significantly reduced ability to monitor Iran’s complex and growing nuclear program, which notably has unresolved nuclear weapons dimensions. The IAEA’s ability to detect diversion of nuclear materials, equipment, and other capabilities to undeclared facilities remains greatly diminished.

Read the full report in pdf here

1. Andrea Stricker is deputy director of the Foundation for Defense of Democracies’ (FDD) Nonproliferation and Biodefense Program and an FDD research fellow.

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