Publication Type:
- Weapon Program Background Report
Weapon Program:
- Nuclear
Update: Between June 12 and 24, Israel carried out a campaign of military strikes against Iran’s nuclear program. The United States also struck multiple Iranian nuclear sites on June 21. The full extent of damage from the strikes is not yet clear. The figures in this publication reflect the status of Iran’s nuclear program on the eve of the strikes.
Iran possesses thousands of gas centrifuges that are the mainstay of its nuclear program. Gas centrifuges spin uranium hexafluoride gas (UF6) to separate uranium isotopes suitable for nuclear fuel, a process known as uranium enrichment.[1] The number and capacity of these machines determine Iran’s "breakout" time: how long it would take Iran—if it decided to do so—to produce the fuel for a small nuclear arsenal. The machines are also key to Iran's ability to "sneakout" by producing nuclear weapon fuel at secret sites.
In recent years, Iran has developed and deployed centrifuge models that can enrich greater amounts of uranium with fewer machines relative to its original IR-1 design. In early 2025, the number of these advanced centrifuge models enriching uranium at declared sites surpassed the number of IR-1 machines known to be in production mode. Iran’s increasing mastery of centrifuge design and manufacturing raises the risk of a "sneakout," and it reflects an acquisition of knowledge that cannot be reversed.
The table below sets out the capacity and primary materials of each of Iran’s currently-deployed centrifuge models, as well as the number of each model known from publicly-available IAEA reports[2] to be installed and/or enriching uranium at Iran’s three declared enrichment sites: the Fuel Enrichment Plant (FEP) and Pilot Fuel Enrichment Plant (PFEP) at Natanz and the Fordow Fuel Enrichment Plant (FFEP) at Fordow. It is not an inventory of all centrifuges in Iran. Iran has not permitted the IAEA to monitor or verify centrifuge production since early 2021. Consequently, according to a June 2024 joint statement by France, Germany, and the United Kingdom, “The IAEA does not know how many centrifuges Iran has and where they are located.”
In addition to the models listed in the table, Iran has developed several other centrifuge designs that are not currently installed at any of its declared sites, including the IR-2, IR-3, IR-6m, IR-6sm, IR-6smo, IR-8s, IR-s, and IR-9s.
The information in the table about the number of centrifuges installed or operating is based on IAEA reports. The information on centrifuge capacity and rotor material is based on a November 2021 Iran Watch report, Beyond the IR-1: Iran’s Advanced Centrifuges and their Lasting Implications, which contains analysis of each centrifuge model.
|
MODEL |
CAPACITY (SWU/yr)[3] |
ROTOR ASSEMBLY MATERIAL[4] |
FIRST TESTED[5] |
# INSTALLED |
# IN PRODUCTION MODE[6] |
|---|---|---|---|---|---|
|
IR-1 |
~0.8[7] |
Aluminum + maraging steel |
Late 1990s |
Total: 7260 at FEP:[12] 6204 |
Total: 7260 at FEP:[12] 6204 |
|
IR-2m |
~4-5[8] |
Maraging steel + carbon fiber |
2009
|
Total: 7060 at FEP:[13] 6786 |
Total: 5666 at FEP:[13] 5394 |
|
IR-4 |
~4-5[8] |
Carbon fiber |
2009
|
Total: 4321 at FEP:[13] 3914 |
Total: 2489 at FEP:[13] 2088 |
|
IR-5 |
6-10[9] |
Carbon fiber[10]
|
2013
|
Total: 30 at FEP: 0 |
Total: 28 at FEP: 0 |
|
IR-6 |
6-10[9] |
Carbon fiber[11] |
2013 |
Total: 3256 |
Total: 2552 |
|
IR-6s |
3-6[9] |
Carbon fiber[10] |
2013 |
Total: 20 at FEP: 0 |
Total: 20 at FEP: 0 |
|
IR-7 |
11-20[9] |
Carbon fiber[10] |
2019 |
Total: 1 at FEP: 0 |
Total: 0 at FEP: 0 |
|
IR-8 |
16-24[9] |
Carbon fiber[10] |
2017 |
Total: 1 at FEP: 0 |
Total: 0 at FEP: 0 |
|
IR-8B |
10-15[9] |
Carbon fiber[10] |
2019 |
Total: 1 at FEP: 0 |
Total: 0 at FEP: 0 |
|
IR-9 |
34-50[9] |
Carbon fiber[10] |
2021 |
Total: 1 at FEP: 0 |
Total: 0 at FEP: 0 |
Footnotes:
[1] Natural uranium contains about 0.7 percent of the fissionable isotope U-235. Uranium is considered enriched when the concentration of U-235 is increased. Uranium enriched up to 5 percent concentration of U-235 is suitable for nuclear reactors. Weapons-grade uranium is usually defined as 90 percent U-235.
[2] As of May 27, 2025 (for PFEP) and May 28, 2025 (for FEP and FFEP).
[3] The capacity of a centrifuge is measured in “separative work units” (SWU) per year. SWU reflect the effort needed to separate the two uranium isotopes (U-235 and U-238) in the enrichment process. A centrifuge with a higher SWU per year can enrich greater quantities of uranium to higher levels in shorter periods of time than a less efficient centrifuge.
[4] The rotor of a centrifuge is what spins the uranium hexafluoride (UF6) gas to separate uranium isotopes. Centrifuges use “bellows” between rotors to form a rotor assembly that allows for flexibility when spinning at higher speeds. The bellows and the rotors themselves must be made with strong, lightweight material. Carbon fiber is an ideal material for this purpose, but aluminum and specialty steels such as maraging steel can also be used.
[5] Fed with UF6; excludes mechanical testing.
[6] Accumulating enriched uranium
[7] Calculated from output data contained in IAEA reports.
[8] Based on the capacity of the Pakistani P2 centrifuge, the base model for the IR-2m and IR-4.
[9] The low end of the range is based on estimates contained in "A Comprehensive Survey of Iran's Advanced Centrifuges" by David Albright, Sarah Burkhard, and Spencer Faragasso, published by The Institute for Science and International Security on December 2, 2021 and available at https://isis-online.org/isis-reports/detail/a-comprehensive-survey-of-ir... the high end of the range consists of nominal claims made by Iranian officials or Iranian media (possibly referring to kg UF6 SWU/yr, which has a value 1.47 times higher than the more standard kg U SWU/yr).
[10] Due to technological progression, centrifuges developed after the IR-4 are assumed to have their rotor assembly made entirely from carbon fiber even when not explicitly confirmed as such.
[11] Although Iran originally claimed the IR-6 rotor assembly to be made entirely of carbon fiber, the IAEA verified in January 2021 that Iran had manufactured metal bellows for IR-6 centrigues, which were subsequently displayed in a video released by the Atomic Energy Organization of Iran (AEOI). See: GOV/2021/10 Para. 38 and "The IR-6 Centrifuge Needs Further Development" by David Albright and Sarah Burkhard, published by The Institute for Science and International Security on July 14, 2022.
[12] The figures for IR-1 centrifuges are arrived at by adding the number of additional machines installed (120) as reported in GOV/2023/8 Para. 18 to the total planned for 36 cascades in the initial Iranian DIQ (6084) as reported in GOV/INF/2021/27 Para. 3.
[13] The IR-2m figures for FEP are an estimate based on an average of 174 machines per cascade, obtained by dividing the total number of machines planned in the initial Iranian DIQ reported in GOV/INF/2021/27 Para. 3 (1044) by the number of planned cascades (6). That average (174) is multiplied by the number of cascades reported in the most recent Verification and Monitoring report to be installed and/or in production mode. Although Iran subsequently increased the number of planned cascades, there is no indication that it altered the number of centrifuges contained in each cascade. For the IR-4, we similarly estimate an average of 174 machines per cascade for the 12 planned cascades in the initial DIQ. In GOV/2025/8 Para. 16, Iran announced plans for 18 additional IR-4 cascades containing up to 166 machines each; thus, we use an average of 166 machines per cascade for those additional cascades. For the IR-6, the IAEA confirmed 174 machines per cascade in GOV/INF/2022/19 Para. 2.
[14] In November 2022 (as reported in GOV/INF/2022/24 Para. 8), Iran announced its intention to install 14 new cascades of IR-6 centrifuges in addition to the two interconnected cascades of IR-6 centrifuges that were already installed. In February 2025 (GOV/2025/8 Para. 13), the IAEA reported that five of the new cascades then in production mode contained up to 870 centrifuges, indicating an average of 174 machines per cascade. The figure in this table thus reflects an assumption of 174 machines per new cascade, the sum of which is added to the 350 machines reported in GOV/2025/8 Para. 13 as comprising the two existing interconnected cascades.