Iran’s Centrifuges: Models and Status

December 16, 2021

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 producing enriched 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, either because they are still under development or have so far proven unsuccessful in operation. These include the IR-2, IR-3, IR-6m, IR-6sm, IR-6smo, IR-8s, and IR-9s. 

This table is based on a November 2021 Iran Watch report, Beyond the IR-1: Iran’s Advanced Centrifuges and their Lasting Implications, which contains detailed analysis of each centrifuge model. The table will be updated periodically as the IAEA releases new information.

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: 6302

at FEP:[11] 5239
at PFEP: 18
at FFEP: 1045

Total: 5794

at FEP:[11] 4732
at PFEP: 18
at FFEP: 1044

IR-2m
 

~4-5[8]

 

Maraging steel + carbon fiber

 

2009

 

Total: 1079

at FEP: 1044
at PFEP: 35
at FFEP: 0

Total: 1077

at FEP: 1044
at PFEP: 33
at FFEP: 0

IR-4
 

~4-5[8]

 

Carbon fiber

 

2009

 

Total: 522

at FEP: 348
at PFEP: 174
at FFEP: 0

Total: 521

at FEP: 348
at PFEP: 173
at FFEP: 0

IR-5
 

6-10[9]

 

Carbon fiber[10]

 

2013

 

Total: 36

at FEP: 0
at PFEP: 36
at FFEP: 0

Total: 34

at FEP: 0
at PFEP: 34
at FFEP: 0

IR-6
 

6-10[9]

 

Carbon fiber[10]

 

2013

 

Total: 398

at FEP: 0
at PFEP: 209
at FFEP: 189

Total: 208

at FEP: 0
at PFEP: 208
at FFEP: 0

IR-6s
 

3-6[9]

 

Carbon fiber[10]

 

2013

 

Total: 41

at FEP: 0
at PFEP: 41
at FFEP: 0

Total: 39

at FEP: 0
at PFEP: 39
at FFEP: 0

IR-7
 

11-20[9]

 

Carbon fiber[10]

 

2019

 

Total: 1

at FEP: 0
at PFEP: 1
at FFEP: 0

Total: 0

at FEP: 0
at PFEP: 0
at FFEP: 0

IR-8
 

16-24[9]

 

Carbon fiber[10]

 

2017

 

Total: 1

at FEP: 0
at PFEP: 1
at FFEP: 0

Total: 0

at FEP: 0
at PFEP: 0
at FFEP: 0

IR-8B
 

10-15[9]

 

Carbon fiber[10]

 

2019

 

Total: 1

at FEP: 0
at PFEP: 1
at FFEP: 0

Total: 0

at FEP: 0
at PFEP: 0
at FFEP: 0

IR-s
 

8-12[9]

 

Carbon fiber[10]

 

2019

 

Total: 10

at FEP: 0
at PFEP: 10
at FFEP: 0

Total: 10

at FEP: 0
at PFEP: 10
at FFEP: 0

IR-9
 

34-50[9]
 

 

Carbon fiber[10]

 

2021

 

Total: 1

at FEP: 0
at PFEP: 1
at FFEP: 0

Total: 0

at FEP: 0
at PFEP: 0
at FFEP: 0

Footnotes: 

[1] Nautral 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 to 3-5 percent concentration of U-235 is suitable for nuclear reactors. Weapons-grade uranium is usually defined as 90 percent U-235. 

[2]  As of November 17, 2021. 

[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-irans-advanced-centrifuges; 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] IR-1 numbers for FEP are estimates based on an average of 169 machines per cascade, obtained by dividing 6064, the total number of machines planned in the April 2021 Iranian declaration, as reported by the IAEA (see GOV/INF/2021/24), by the number of planned cascades (36). That average is multiplied by the number of cascades reported by the IAEA in November 2021 to be installed or in production mode (see GOV/2021/51).