Analysis of IAEA Iran Verification and Monitoring Report — May 2024

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

May 29, 2024

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● This report summarizes and assesses information in the International Atomic Energy Agency’s (IAEA’s) quarterly report, dated May 27, 2024, 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 produce more weapon-grade uranium (WGU) since the IAEA’s last report in February 2024 due to increased stocks of enriched uranium.

● Iran’s stocks of enriched uranium and its centrifuge capacity combined are sufficient to make enough WGU, taken as 25 kilograms (kg) of WGU, for almost eight nuclear weapons in one month, ten in two months, 12 in three months, 13 in four months.

● With Iran’s growing enrichment experience and using only a portion of its stock of 60 percent highly enriched uranium (HEU), Iran could produce its first quantity of 25 kg of WGU in about one week. This breakout could be difficult for the IAEA to detect promptly, if Iran delayed inspectors’ access.

● The IAEA’s efforts to verify Iran’s nuclear activities, particularly its uranium enrichment activities, continue to be seriously affected by Iran’s decision last fall to withdraw the designation of several experienced inspectors. Despite repeated calls by the IAEA that Iran reconsider this inappropriate, political act, as of the end of May 2024, Iran has failed to reverse course.

● As of May 11, the net overall enriched uranium stock, including all levels of enrichment and all chemical forms, increased by 675.8 kg, from 5525.5 kg to 6201.3 kg (Uranium mass or U mass).

● Iran’s stockpile of 60 percent HEU was 142.1 kg (U mass) or 210.2 kg uranium hexafluoride mass (hex mass) as of May 11, 2024, an increase of 20.6 kg (U mass) since February 2024.

● However, the IAEA report states in a footnote that sometime after May 11, 2024, Iran downblended 5.9 kg of uranium enriched up to 60 percent U-235 by mixing it with 2 percent enriched uranium, producing 20 percent enriched uranium. Taking into account newly produced 60 percent HEU from May 11 to the end of May, using average production rates during this reporting period, the estimated 60 percent HEU stock as of the end of May is approximately 140.5 kg (U mass).

● The average production rate of 60 percent HEU was 6.4 kg (U mass) per month, slightly lower than the 7.1 kg (U mass) during the previous reporting period. At this rate, Iran can produce about 78.4 kg of 60 percent HEU (U mass) annually.

● Iran continued to produce 60 percent HEU from 5 percent low enriched uranium (LEU) feed in two pairs of interconnected advanced centrifuge cascades at the above-ground Pilot Fuel Enrichment Plant (PFEP) and at the below-ground Fordow Fuel Enrichment Plant (FFEP). The FFEP pair includes two IR-6 centrifuge cascades, one of which is easily modifiable to change operations and enrich uranium to higher levels. In January 2023, the IAEA detected the presence of near-84 percent HEU particles at the cascade’s product sampling point after Iran failed to declare a change in the cascade’s mode of operation. While Iran temporarily reversed the configuration over the summer of 2023, it began using this configuration again after December 2023. The current IAEA report does not provide any new details on this issue, other than stating that two interconnected IR-6 cascades continue to make 60 percent enriched uranium.

● According to previous reports, Iran was storing the majority of its 20 percent enriched uranium and 60 percent HEU stocks at the Esfahan Fuel Plate Fabrication Plant (FPFP), which may not be as thoroughly monitored as Natanz and Fordow. The stocks require enhanced IAEA safeguards to detect and prevent Iran’s diversion of enriched uranium to a secret enrichment plant. For example, there should be stepped-up inspector presence and remote camera surveillance at the facility.

● As of May 11, 2024, Iran had an IAEA-estimated stock of 751.3 kg of 20 percent enriched uranium (U mass and in the form of UF6), equivalent to 1111.4 kg (hex mass), representing an increase of 39.1 kg (U mass). Iran also had a stock of 30 kg (U mass) of 20 percent enriched uranium in other chemical forms.

● The average production rate of 20 percent enriched uranium at the FFEP was 12.6 kg (U mass) per month or 18.6 kg (hex mass) per month, slightly lower but similar to the previous reporting period.

● In addition to regular production of 20 percent enriched uranium, after May 11, when Iran downblended 5.9 kg of 60 percent HEU, it produced an additional 18.4 kg of 20 percent enriched uranium (U mass), resulting in a further increase of Iran’s stock of 20 percent enriched uranium.

● Iran’s deployment of advanced centrifuges has not changed from the last IAEA report in February 2024. Iran now has nearly 7400 advanced centrifuges installed at Natanz and Fordow, where most are deployed at the Natanz Fuel Enrichment Plant (FEP) (see Figure 1). The FEP now has all near-term planned centrifuge cascades installed, pending less firm Iranian plans.

● Including the installed IR-1 centrifuges at the FEP and FFEP brings the total number of installed centrifuges to about 14,600. It should be noted that many advanced centrifuges are deployed but not enriching uranium, and the IR-1 centrifuges have a reduced ability to enrich uranium.

● During the reporting period, 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 an additional 14 IR-6 centrifuge cascades.

● The quantity of Iran’s enriching centrifuges decreased during this reporting period to around 10,000 centrifuges. In a footnote, the IAEA draws a distinction between operating and enriching centrifuges, where operating centrifuges include those that have enriched uranium previously and enriching centrifuges are those that are enriching uranium at the time of inspection.

● Iran’s current, total operating enrichment capability is estimated to be about 19,000 separative work units (SWU) per year, where only cascades enriching uranium during the reporting period are included in the estimate. As of this reporting period, Iran was not yet using its fully installed enrichment capacity at the FEP, which, if operational, would increase the total SWU per year by about 80 percent, for a total of about 34,500 SWU.

● Iran’s stockpile of near 5 percent LEU decreased by 19.9 kg (U mass) to 2376.9 kg (U mass), or 3516.1 kg (hex mass). Average production of near 5 percent LEU at the FEP was about 75 percent of the last reporting period’s total, consistent with the IAEA’s reporting that Iran used fewer centrifuge cascades.

● Iran has not prioritized stockpiling uranium enriched between two and five percent. It also has not made planned progress on the Enriched Uranium Powder Plant, a key civil facility to convert less than 5 percent enriched uranium hexafluoride into 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 Iran’s civilian needs.

● The IAEA again reports that Iran has not started commissioning the Arak reactor, now called the Khondab Heavy Water Research Reactor (KHRR), or IR-20. Iran previously informed the IAEA that it expected to commission the reactor in 2023 and start operations in 2024. The IAEA reports that construction efforts on the reactor continue, and Iran has provided no new update.

● The IAEA underscores that it has been “more than three years since Iran stopped provisionally applying its Additional Protocol and, therefore, since it provided updated declarations and the Agency was able to conduct complementary access to any sites and other locations in Iran.”

● The IAEA reports no new progress on installing new surveillance cameras at Iran’s nuclear-related facilities, including centrifuge manufacturing and assembly sites. Iran has also said it will not turn over data or footage associated with monitoring devices and cameras, as it committed in an IAEA/Iran Joint Statement from March 2023, unless sanctions are removed, essentially holding the IAEA hostage to political developments outside the agency’s control.

● 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 to secretly move manufacturing equipment to new, undeclared sites, further complicating any future verification effort and contributing to uncertainty about where Iran manufactures centrifuges.

● The IAEA concludes that “Iran’s decision to remove all of the Agency’s equipment previously installed in Iran for JCPOA-related 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 [program].”

● The IAEA reiterates, “The Agency has lost continuity of knowledge in relation to the production and inventory of centrifuges, rotors and bellows, heavy water and [uranium ore concentrate] UOC.”

● Concern about Iran’s installation of advanced centrifuges at an undeclared site increases as the 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 HEU to weapon-grade. This hybrid strategy involves Iran diverting safeguarded HEU and enriching the material to weapon-grade using three or four secretly manufactured and deployed cascades of advanced centrifuges. With greater uncertainty about the quantity of advanced centrifuges Iran is making, there is a greater chance of Iran hiding away the requisite number of advanced centrifuges to carry out 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.

Figure 1. The total number of advanced centrifuges installed at all three enrichment facilities. No new centrifuge cascades were added during this most recent reporting period. There were only minor fluctuations in the quantities of deployed centrifuges at the PFEP. As can be seen, centrifuge installation accelerated during the previous reporting period, following relatively small incremental increases during most of 2023.

Read the full report as pdf here.

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

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