Iran has enough LEU, in the form of 2 to 3 percent LEU and near 20 percent enriched uranium, to produce weapon-grade uranium (WGU) for three nuclear weapons without using any natural uranium as feedstock, a fact that reduces breakout timelines.
This report assesses information in the International Atomic Energy Agency’s (IAEA’s) quarterly safeguards report for May 31, 2021, 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).
The IAEA report is also the first update on the status of Iran’s uranium enrichment program since an attack on the Natanz Fuel Enrichment Plant (FEP) on April 11, which caused major damage to the underground enrichment hall’s electricity supply and emergency backup power. 2 The IAEA report reflects apparent significant post-explosion damage to about half of the enriching cascades operating at the time of the power outage. Enriched uranium output also decreased by over half post-explosion.
Highlights and Worst-Case Breakout Estimate
- On April 17, 2021, Iran started to produce near 60 percent enriched uranium at the Pilot Fuel Enrichment Plant (PFEP) and as of May 22, 2021, has produced 2.4 kg of near 60 percent enriched uranium (in uranium mass).
- Iran continued to grow its near 20 percent enriched uranium stock and as of May 22, 2021, has produced a stock of 62.8 kg (in uranium mass), or 92.9 kg (in uranium hex mass, or hex mass for short).
- Iran experimented with skipping typical enrichment steps as it enriched up to 60 percent uranium 235, going from a level below 5 percent low enriched uranium (LEU) directly to near 60 percent in one cascade, rather than using two steps, a slower process entailing the intermediate production of 20 percent enriched uranium. As such, Iran is experimenting with multi-step enrichment while seeking to shortcut the process, and is likely learning important lessons, all useful if Iran decides to break out and produce weapon-grade uranium.
- Iran continued to produce uranium metal and has increased its yield of uranium metal significantly from when it first converted uranium tetrafluoride to uranium metal in February 2021.
- Half of the IR-1 and IR-2m cascades (translating to 15 cascades and 3 cascades, respectively) installed at the Natanz Fuel Enrichment Plant (FEP) appear to have been destroyed by the April 11 attack, based on consideration of which cascades the IAEA reports are now being fed with uranium.
- Iran’s production of low enriched uranium at the FEP likewise slowed after the explosion, its rate dropping by at least one half.
- Iran’s usable stock of below 5 percent LEU did not grow this reporting period, because of slower production and use of it as feed into cascades to produce 20 and 60 percent enriched uranium.
- Iran has enough LEU, in the form of 2 to 3 percent LEU and near 20 percent enriched uranium, to produce weapon-grade uranium (WGU) for three nuclear weapons without using any natural uranium as feedstock, a fact that reduces breakout timelines.
- Iran started using an existing workshop at Natanz to conduct mechanical testing of centrifuges, a workshop noted by the IAEA noted as not listed under the JCPOA. This likely means that this work is not subject to IAEA video surveillance and suggests that any work done at this workshop will not be included in the set of data and recordings being held by Iran under the temporary monitoring agreement.
- The report does not discuss Iran’s construction of a new advanced centrifuge assembly facility in a tunnel near the main Natanz complex.
- A worst-case breakout estimate, which is defined as the time to produce enough WGU for one nuclear weapon, is as short as 2.3 months. Iran could produce a second significant quantity of WGU early in the fifth month after breakout commences, and a third quantity could be produced early in the seventh month. For comparison, if no explosion had occurred at the FEP, the minimum breakout timeline would have been 1.75 months, reflecting a longer breakout by one month. However, it should be noted that the post-explosion breakout estimate has additional uncertainties that suggest that it may be lengthier.
- Iran’s suspension of the Additional Protocol (AP) and JCPOA monitoring arrangements has severely limited the IAEA’s ability to verify the peacefulness of Iran’s nuclear program. Iran’s threat to destroy IAEA monitoring data underscores the recent dramatic reduction in its transparency, at a time when it is carrying out many activities related to nuclear weapons applications.
- As noted in a companion report, 3 and independent of the problems caused by Iran’s suspension of the AP and JCPOA monitoring, Iran has failed to cooperate with the IAEA regarding the IAEA’s findings of undeclared uranium at at least three sites, leading Director General Grossi to state, “The lack of progress in clarifying the Agency’s questions concerning the correctness and completeness of Iran’s safeguards declarations seriously affects the ability of the Agency to provide assurance of the peaceful nature of Iran’s nuclear program.”
