IAEA Report Shows Iran’s Stockpile of Uranium Grows


The International Atomic Energy Agency’s (IAEA) June 5 report assessing Iran’s compliance with the 2015 nuclear deal noted that Tehran’s stockpile of low enriched uranium continues to increase beyond limits set by the accord, known as the Joint Comprehensive Plan of Action (JCPOA).

Iranian workers smile at the nation’s newly opened heavy water production plant in Arak in 2006. Iran has moved closer to storing more heavy water than allowed by the 2015 nuclear deal. (Photo: Atta Kenare/AFP/Getty Images)

While the stockpile growth is concerning, the IAEA report states that Iran continues to comply with the JCPOA’s monitoring and verification measures, which provide assurance that if Tehran were to take further steps to violate the deal or dash toward a bomb, its activities would be quickly detected.

In short, Iran continues to transparently breach the nuclear deal to create leverage in response to the U.S. sanctions campaign and the failure of the remaining P4+1 parties (China, France, Germany, Russia, the United Kingdom, and the EU) to deliver meaningful economic relief. The breaches are troubling, but do not indicate a decision to pursue nuclear weapons and are quickly reversible should Iran decide to return to compliance with the JCPOA.

Specifically, the June 5 report noted that Iran’s stockpile of enriched uranium increased by about 551 kilograms since the March report, bringing the total stockpile to 1,571 kilograms of uranium enriched to less than 4.5 percent uranium-235, nearly all of which is in the form of uranium hexafluoride gas (UF6). Of the 551 kilograms produced over the past three months, 214.6 kilograms consists of uranium enriched to less than 2 percent. That brings the total amount of uranium enriched to less than 2 percent to 483 kilograms.

While any uranium enriched in excess of the stockpile limit (300 kilograms of uranium enriched to 3.67 percent UF6) is still a concerning breach of the restrictions established by the JCPOA, producing enriched uranium at the 2 percent enrichment level poses far less risk and does not significantly alter the so-called breakout time, or time it would take to produce enough weapons-grade uranium for one bomb (25 kilograms of uranium enriched to greater than 90 percent uranium-235).

Setting aside the 483 kilograms of uranium enriched to less than 2 percent uranium-235, Tehran has produced about 1,088 kilograms of uranium enriched to between 2 and 4.5 percent, mostly in the form of UF6, which is enough reactor-grade material for one bomb. If Iran were to further enrich this material to weapons-grade using its IR-1 centrifuges currently installed and enriching at Natanz and Fordow, it would likely take at least 3-4 months to produce enough weapons-usable nuclear material for one bomb.

While this timeline is short in comparison with the 12-month breakout when the JCPOA was fully implemented, Iran does not appear to be making a “dash” to try to acquire a nuclear weapon and the IAEA has said there is no evidence that Iran is diverting nuclear material for covert purposes. Even if Iran did decide to pursue nuclear weapons, further time would be needed to weaponize the material and any move by Iran to enrich to higher levels would be quickly detected by the IAEA.

Also, while it is clear that Iran undertook activities in the past related to developing a nuclear explosive device, Tehran has not verified its design with a nuclear test, and it is unlikely that Tehran would “breakout” to produce only one bomb. So, while the increase in the stockpile of low enriched uranium is concerning, it is not yet an urgent proliferation risk and there remains time to restore full compliance with the JCPOA.

The June 5 report confirmed that while Iran is breaching the 3.67 percent uranium-235 enrichment level set in the JCPOA by enriching to 4.5 percent, there is no enrichment up to 20 percent. The U.S. decision to terminate the sanctions waiver allowing Iran to import 20 percent enriched uranium fuel for its Tehran Research Reactor in May raises concern that Iran may use fueling for the TRR as a justification to resume 20 percent enrichment down the road. Uranium enriched to 20 percent poses a far more significant proliferation risk as it can be much more quickly enriched to weapons-grade. However, the IAEA noted that Iran received a shipment of fuel for the TRR in April 2020, which should allay any immediate need for 20 percent enriched fuel. Iran last received a shipment of 20 percent enriched fuel in 2018.

The report also noted that Iran has not taken steps to act on its Jan. 5 announcement that the country’s nuclear program would no longer be “subject to any restrictions” and that there have been no changes to JCPOA-related monitoring and verification activities. The IAEA “maintained its verification and monitoring activities” during the Covid-19 crisis, according to the report.

According to the IAEA report, Iran continues to breach:

  • The stockpile limit of 300 kilograms of uranium gas enriched to 3.67 percent and the 3.67 percent uranium-235 enrichment limit. Iran’s enriched uranium stockpile was 1,571 kilograms on May 20, an increase from the 1,020 kilograms reported by the IAEA in the March 3 report. Of the 551-kilogram increase since the last report, about 215 kilograms is uranium enriched to less than 2 percent, a level that poses less of a proliferation risk. The enrichment level of the other 336 kilograms produced since March is not specified. In total, the 1,571-kilogram stockpile includes:
    • 215 kilograms of uranium enriched to 3.67 percent produced prior to Iran’s decision to breach the enrichment limit set by the JCPOA in July 2019, mostly in the form of UF6
    • 1,356 kilograms of uranium enriched up to 4.5 percent in gas form, produced since July 2019, of which is 483 kilograms of uranium is enriched to up to 2 percent in gas form, produced by some of the advanced centrifuges at Natanz. Presumably, the balance of 873 kilograms of uranium is enriched to levels between 2 and 4.5 percent. That, plus the 215 kilograms enriched to 3.67 percent before July 2019, puts Iran’s stockpile of uranium enriched between 2 and 4.5 percent uranium-235 totals to about 1,088 kilograms.
  • Restrictions on advanced centrifuge research and development. According to the report, Iran continues to produce enriched uranium using its advanced machines at Natanz in violation of the deal and has installed and operated more advanced machines than permitted by the JCPOA. Specifically, the June 5 IAEA report noted that Iran is producing enriched uranium using a 164 cascade of IR-4 centrifuges, a 164 cascade of IR-2m centrifuges, and a cascade of 135 IR-6 centrifuges. Iran was enriching using the IR-4 and IR-2m cascades as of the last report. However, Iran has expanded its IR-6 cascade from 72 centrifuges in February to 135 noted in the June report. Iran also continues to produce 2 percent enriched uranium using small cascades of 20 or less IR-4, IR-5, IR-6, and IR-6s centrifuges. Iran continues testing other models, including the IR-8 and IR-9, with uranium, but not withdrawing any enriched material. These tests all involve one or two machines.
  • The prohibition on enrichment at Fordow. The IAEA noted that Iran continues to enrich uranium using 1,044 IR-1 centrifuges at Fordow in violation of the 15-year ban on enrichment at that site. The IAEA noted on May 30 that Iran has also breached the limit on 1,044 machines at the site. According to the agency, 13 IR-1 centrifuges are installed for research and development of stable isotope production, which was the specified activity for Fordow under the JCPOA, bringing the total number of IR-1s at the site to 1,057.
  • The 130 metric ton limit on heavy water. As of May 11, Iran’s stockpile of heavy water was 132 metric tons, according to the report. The IAEA also noted that 5.1 metric tons were shipped out of Iran and had used 1.4 metric tons since the March report. Iran’s shipment of heavy water out of the country suggests that the Trump administration is not sanctioning the shipment and storage of heavy water, as it threatened to do in May 2019.

Iran is still abiding by some provisions of the JCPOA. According to the IAEA report:

  • Iran has not resumed construction at the Arak heavy-water reactor based on the original design. The report does not indicate if any activity related to modifying the reactor, as required by the JCPOA, is taking place. The current U.S. sanctions waiver allowing cooperative activity on the reactor will lapse around July 27 and it is unclear if conversion activities will continue at that time. Iran has threatened to pursue construction based on the original design if conversion efforts cease. Under the original design, the Arak reactor would have produced an estimated 10-13 kilograms of plutonium a year, enough for about two nuclear weapons. The modified reactor will produce less than one bomb's worth per year, and Iran will ship that material out.
  • Iran has not installed additional IR-1 centrifuges at Natanz in excess of the 5,060 machines allowed by the JCPOA.
  • Iran continues to provisionally implement the additional protocol to its safeguards agreement and monitoring and verification mechanisms specified by the JCPOA. According to the IAEA report, monitoring and verification activities were not interrupted by the Covid-19 crisis, although inspectors had to rely on charter flights to visit Iran. Inspectors still have regular access to all declared sites, including on a daily basis, and continue to monitor enrichment in real time.


The IAEA issued a second report June 5 on Iran's implementation of its safeguards agreement. That report is discussed in "Iran’s Failure to Comply with IAEA Investigation Raises Concerns."