Publication Type:
- Weapon Program Background Report
Weapon Program:
- Nuclear
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. 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.
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, 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: 7267 at FEP:[11] 6204 |
Total: 7266 at FEP:[11] 6204 |
|
IR-2m |
~4-5[8] |
Maraging steel + carbon fiber |
2009
|
Total: 3749 at FEP:[12] 3654 |
Total: 1482 at FEP:[12] 1392 |
|
IR-4 |
~4-5[8] |
Carbon fiber |
2009
|
Total: 887 |
Total: 712 |
|
IR-5 |
6-10[9] |
Carbon fiber[10]
|
2013
|
Total: 41 at FEP: 0 |
Total: 40 at FEP: 0 |
|
IR-6 |
6-10[9] |
Carbon fiber[10] |
2013 |
Total: 1052 |
Total: 1047 |
|
IR-6s |
3-6[9] |
Carbon fiber[10] |
2013 |
Total: 39 at FEP: 0 |
Total: 39 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-s |
8-12[9] |
Carbon fiber[10] |
2019 |
Total: 0 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 to5 percent concentration of U-235 is suitable for nuclear reactors. Weapons-grade uranium is usually defined as 90 percent U-235.
[2] As of February 28, 2023.
[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] 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, which corresponds to the 36 cascades reported to be installed and in production mode in GOV/2023/8 Para. 21.
[12] The IR-2m and IR-4 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 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 GOV/2023/8 Para. 21 to be installed and/or in production mode. Likewise, the initial Iranian DIQ specified 174 IR-6 machines per cascade. Although Iran subsequently increased the number of planned IR-2m, IR-4, and IR-6 cascades in its updated DIQ as reported in GOV/INF/2022/17 Para. 7, GOV/INF/2022/23 Para. 3, GOV/INF/2022/24 Para. 2, and GOV/2023/8 Para. 18, there is no indication that it altered the number of centrifuges contained in each cascade.
[13] Figures for IR-5 and IR-6s centrifuges in R&D Line 5 at PFEP are calculated using the IAEA's most recent reporting on the number of centrifuges comprising the cascade in R&D Line 1, verified on August 15, 2021 (see GOV/INF/2021/40 Para. 4). Iran informed the IAEA on August 2, 2022, that it had swapped the numbering of R&D Lines 1 and 5 (see GOV/2022/39 Para. 23). Therefore, R&D Line 5 after August 2, 2022, corresponds to R&D Line 1 before that date.
[14] Figures for IR-4 and IR-6 numbers installed and in production mode at PFEP are an undercount, as the exact number of IR-4 and IR-6 centrifuges installed in R&D Line 5 (first reported in GOV/INF/2022/25) has not been specified by the IAEA; these centrifuges are therefore not accounted for in this table.