The IR-1: A Profile of Iran's First-Generation Centrifuge

The IR-1 centrifuge represents the cornerstone of Iran’s uranium enrichment program, serving as the workhorse of its nuclear ambitions despite numerous technical limitations ¹². As Iran’s first deployed centrifuge model, the IR-1 has played a pivotal role in the country’s controversial nuclear program and continues to operate at facilities like Natanz and Fordow, even as more advanced models are being developed ³⁴.

This article examines the origins, specifications, and significance of the IR-1 centrifuge, providing insight into this first-generation technology that has been at the center of international concerns over nuclear proliferation ⁵⁶.

Schematic diagram illustrating the operation of a countercurrent gas centrifuge, detailing the components and process of uranium isotope separation.

Origins and Development

The IR-1 centrifuge is not an indigenous Iranian design but rather a copy of Pakistan’s P-1 centrifuge, which itself was derived from stolen Dutch designs ⁷⁸. The technology transfer occurred through the notorious nuclear proliferation network led by Pakistani nuclear scientist Abdul Qadeer Khan in the late 1980s and early 1990s ⁹¹⁰.

A.Q. Khan had previously stolen centrifuge designs from the British-German-Dutch enrichment company URENCO during his work there in the 1970s ¹¹¹². These designs were first used to develop Pakistan’s own centrifuge program before being transferred to other countries, including Iran ¹³¹⁴.

The P-1 design that Iran received was based on an early version of the Dutch CNOR (Commercial Nuclear Obreptitious Rotor) centrifuge that had been modified by Pakistan ¹⁵¹⁶. The designation “P-1” stands for “Pakistan-1,” while “IR-1” stands for “Iran-1,” reflecting its status as Iran’s first-generation centrifuge ¹⁷¹⁸.

Around 1987, Khan struck a deal with Iran to help build 50,000 P-1 centrifuges ¹⁹²⁰. The initial transfer included both drawings and a disassembled sample of the P-1 centrifuge ²⁰²¹.

Despite acquiring the technology in the late 1980s, it took Iran years to master the production and operation of these centrifuges, with significant technical difficulties along the way ²¹²². Research and design on the IR-1 began in earnest in the late 1990s, when Iran first successfully tested a centrifuge and made a decision to scale up its program ²⁸.

Former Iranian President Mahmoud Ahmadinejad presenting what appears to be an IR-1 centrifuge.

Technical Specifications

The IR-1 centrifuge is a subcritical Zippe-type centrifuge designed for uranium enrichment through gaseous diffusion ⁹¹⁰. It processes uranium in the form of uranium hexafluoride (UF6) gas, separating the fissile U-235 isotope from the more abundant U-238 ²³²⁴.

The rotor assembly of the IR-1 has a length of 1800 millimeters (1.8 meters) and a diameter of 100 millimeters (10 cm) ¹⁰²⁵. The entire machine stands about 210 cm tall, including the casing and mounting base ⁴²⁶.

The IR-1 rotor assembly consists of four aluminum tubes connected by three maraging steel bellows, with aluminum end caps ¹⁰²⁷. This design allows the centrifuge to spin at high speeds while managing the mechanical stresses that develop ²⁸²⁹.

The IR-1 operates at a rotational frequency of 1050 Hertz (Hz), which converts to a wall speed of 330 meters per second ¹⁰³⁰. This speed is typical for high-strength aluminum rotors, which tend to “creep” or deform at higher speeds ¹⁰³¹.

According to Iranian sources, the IR-1 has a theoretical enrichment output of about 1.4 SWU (Separative Work Units) per year per machine ¹⁰³². However, in practice, it rarely achieves over 1 SWU/year due to various operational difficulties ¹⁰³³.

Schematic diagram illustrating the internal components and countercurrent process of a gas centrifuge used for uranium isotope separation.

Construction and Materials

The construction of the IR-1 centrifuge involves several critical components, each requiring precise manufacturing tolerances ³⁴³⁵. The choice of materials is dictated by the extreme conditions under which centrifuges operate ³⁶³⁷.

The rotor tubes of the IR-1 are made from high-strength aluminum 7075, a choice that limits the maximum rotational speed but simplifies manufacturing compared to more advanced materials ¹⁰³⁸. The bellows, which allow the rotors to pass through critical frequencies during acceleration, are made from maraging steel, a specialized high-strength steel alloy ¹⁰¹².

Each upper bearing contains two ferrite magnets with exacting specifications ¹⁰³⁹. The bearings are critical components as they must support the rotor while minimizing friction during high-speed rotation ⁴⁰⁴¹.

The manufacturing of IR-1 centrifuges requires specialized equipment and expertise ⁴²⁴³. Iran initially struggled with producing these machines to the required specifications, leading to high failure rates ⁴⁴⁴⁵.

Mass production of the IR-1 started in 2002, utilizing a series of manufacturing sites with connections to Iran’s military ¹⁰⁴⁶. By 2007, Iran had begun large-scale deployment of these centrifuges at its enrichment facilities ⁴⁷⁴⁸.

A large cylindrical rotor, likely for a nuclear centrifuge, displayed horizontally on a clear support structure.

Performance and Limitations

The IR-1 centrifuge has been plagued by performance issues and technical limitations since its inception ⁴⁹⁵⁰. The performance of these machines at the Natanz Fuel Enrichment Plant (FEP) has frequently faltered, requiring more centrifuges to produce the same amount of enriched uranium compared to initial expectations ¹¹⁵¹.

The average separative power of the IR-1 in production cascades is estimated between 0.5-0.9 SWU per year, significantly below its theoretical maximum ¹⁰⁵². This inefficiency stems from design flaws inherited from the original P-1 design, which was itself an abandoned model that Pakistan had retired from its program ⁶⁵³.

Historically, the IR-1 centrifuges have experienced breakage rates exceeding 20 percent per year ¹⁰⁵⁴. This high failure rate necessitates constant replacement of machines and causes disruptions in the enrichment process ⁵⁵⁵⁶.

The IR-1’s limitations became particularly apparent following the Stuxnet cyberattack, believed to have targeted these centrifuges between 2009 and 2010 ²⁹⁵⁷. The malware reportedly manipulated the rotation speeds of the centrifuges, causing them to self-destruct while hiding the sabotage from monitoring systems ⁵⁸⁵⁹.

Due to these performance issues, Iran has been developing more advanced centrifuge models, including the IR-2m, IR-4, and IR-6, which offer significantly higher enrichment outputs ³⁶⁰.

Table comparing Iran’s centrifuge models, detailing their capacity, materials, first tested dates, and production status.

Cascade Configuration

In enrichment facilities, IR-1 centrifuges are typically arranged in cascades of either 164 or 174 machines, connected by complex piping systems ¹⁰³⁰. These cascades are the basic operational units of Iran’s enrichment program ⁶¹⁶².

Each cascade has multiple stages linked in series, with the centrifuges within each stage connected in parallel ⁴⁶³. The uranium hexafluoride gas flows through the cascade in three streams: feed, enriched uranium product, and depleted uranium waste ⁴⁶⁴.

The gas is slightly enriched in each centrifuge and then piped to a higher stage for further enrichment or collection, while depleted uranium is returned to a lower stage for re-enrichment or discharge ⁴⁶⁵. This arrangement maximizes enrichment efficiency while minimizing the loss of valuable material ⁶⁶⁶⁷.

At the Natanz Fuel Enrichment Plant, cascades of IR-1 centrifuges are housed in underground halls designed to protect them from potential military strikes ²³⁶⁸. The layout of these cascades has been a subject of intense international scrutiny .

The IR-1 cascades at both Natanz and Fordow facilities are monitored by the International Atomic Energy Agency (IAEA), which verifies compliance with international agreements ²⁶.

An extensive centrifuge cascade within an enrichment facility, showcasing rows of interconnected cylindrical units.

Role in Iran’s Nuclear Program

The IR-1 centrifuge has been the backbone of Iran’s uranium enrichment program since its inception . Despite its technical limitations, Iran has deployed thousands of these machines at its declared enrichment facilities ¹.

As of mid-2025, Iran has approximately 7,260 IR-1 centrifuges installed at the Natanz Fuel Enrichment Plant, with most of them actively enriching uranium ¹. Additionally, about 1,044 IR-1 centrifuges are operating at the Fordow Fuel Enrichment Plant ²⁶.

The IR-1 centrifuges at these facilities are primarily used for producing low-enriched uranium (LEU) up to 5% U-235, although some at Fordow have been configured to produce uranium enriched up to 20% U-235 ⁴. For comparison, weapons-grade uranium typically requires enrichment to over 90% U-235 .

Under the 2015 Joint Comprehensive Plan of Action (JCPOA), Iran was limited to operating 5,060 IR-1 centrifuges at Natanz and none at Fordow ⁵. However, following the U.S. withdrawal from the agreement in 2018, Iran has expanded its centrifuge operations beyond these limits .

The total enrichment capacity of Iran’s IR-1 centrifuges is estimated at approximately 5,800 SWU per year, assuming an average performance of 0.8 SWU per year per machine ³². This capacity is sufficient for fueling nuclear power reactors but would need to be significantly expanded to support a large-scale civilian nuclear power program ⁵.

Manufacturing and Production

Iran has developed indigenous capabilities to manufacture IR-1 centrifuges, although it still relies on imported components and materials for some critical parts . The manufacturing process involves precision engineering and quality control to ensure the centrifuges can withstand the extreme forces generated during operation .

A particular challenge for Iran has been obtaining high-quality maraging steel for the bellows, a material subject to international export controls ¹¹. Reports suggest that Iran has faced shortages of this critical material, limiting its ability to produce large numbers of IR-1 centrifuges in recent years ¹¹.

The centrifuge rotors are manufactured from high-strength aluminum, which is easier to obtain but limits the maximum rotational speed ¹⁰. The production of these components requires specialized machine tools and expertise .

Iran has established several facilities for centrifuge manufacturing and assembly, including sites at Tehran, Natanz, and more recently at Fordow ⁵¹. These facilities have been targets of sabotage and cyberattacks, allegedly by foreign intelligence services seeking to impede Iran’s nuclear program .

The exact production capacity for IR-1 centrifuges is not publicly known, but estimates suggest Iran can produce several thousand units per year when its manufacturing infrastructure is fully operational . However, international sanctions and supply chain disruptions have periodically impacted this capacity .

Comparison with Advanced Centrifuges

The IR-1 represents first-generation centrifuge technology that is now considered outdated compared to more advanced models . Iran has been developing a series of more sophisticated centrifuges to eventually replace the IR-1 ³.

The IR-2m centrifuge, based on the Pakistani P-2 design, uses maraging steel rotors and has an estimated output of 3-5 SWU per year, about 4-5 times more efficient than the IR-1 ⁴⁵. The IR-4 has a similar efficiency but uses carbon fiber rotors instead of maraging steel ³.

Even more advanced is the IR-6 centrifuge, with an estimated output of 6-10 SWU per year, making it approximately 10 times more powerful than the IR-1 ¹. These advanced machines allow Iran to achieve the same enrichment capacity with far fewer centrifuges ³⁸.

Due to their greater efficiency, these advanced centrifuges pose a more significant proliferation concern than the IR-1 ⁵². A cascade of advanced centrifuges could potentially enrich uranium to weapons-grade much faster than an equivalent number of IR-1 machines ⁵⁷.

As of early 2025, advanced centrifuges have begun to outpace IR-1 centrifuges in terms of total enrichment capacity at Iran’s facilities, despite being fewer in number ³⁴. This shift represents a significant evolution in Iran’s enrichment capabilities .

An exhibition showcasing Iran’s advanced IR6 and IR6s centrifuges.

International Monitoring and Concerns

The international community has closely monitored Iran’s IR-1 centrifuge program through IAEA inspections . These inspections have verified the number, type, and operational status of centrifuges at declared facilities .

Under the JCPOA, Iran agreed to limit its IR-1 deployment and place thousands of machines in monitored storage ⁵. The agreement also restricted Iran’s ability to manufacture new IR-1 centrifuges, except to replace damaged ones ⁶⁹.

Since the U.S. withdrawal from the JCPOA, Iran has gradually expanded its centrifuge operations beyond the agreed limits . This expansion has included redeploying stored IR-1 centrifuges and accelerating the development of advanced models .

The breakout time – how long it would take Iran to produce enough highly enriched uranium for a nuclear weapon if it chose to do so – is significantly affected by the number and type of operational centrifuges ⁵⁷. Using only IR-1 centrifuges, this time was estimated at about one year under full JCPOA implementation .

Recent Israeli military strikes in June 2025 have reportedly damaged centrifuge facilities at Natanz, with IAEA reports suggesting that many centrifuges were “severely damaged if not destroyed altogether” ²³²⁴. The impact on Iran’s enrichment capabilities remains under assessment .

Conclusion

The IR-1 centrifuge, despite its technical limitations and inefficiencies, has proven to be a remarkably persistent component of Iran’s nuclear program . Its longevity stems not from its technical merits but from Iran’s ability to mass-produce these machines and operate them despite their high failure rates ¹¹.

As Iran continues to develop more advanced centrifuges, the role of the IR-1 is gradually diminishing ³⁴. However, the knowledge and experience gained from working with these machines have provided Iran with a solid foundation for its growing enrichment program .

The IR-1 centrifuge’s legacy extends beyond its technical specifications – it represents Iran’s determination to develop indigenous nuclear capabilities despite international pressure and technical challenges . Understanding this first-generation technology provides important context for evaluating the evolution and potential future directions of Iran’s nuclear program .

The international community continues to monitor Iran’s centrifuge developments closely, recognizing that the transition from IR-1 to more advanced models represents a significant increase in enrichment capabilities that could potentially shorten the path to nuclear weapons capability should Iran ever make that decision .