When U.S. forces attacked Iran’s nuclear facilities on June 21, 2025, the main target was metal tubes in laboratories deep underground. The tubes are centrifuges that produce highly enriched uranium needed to build nuclear weapons.

Inside of a centrifuge, a rotor spins in the range of 50,000 to 100,000 revolutions per minute, 10 times faster than a Corvette engine’s crankshaft. High speeds are needed to separate lighter uranium-235 from heavier uranium-238 for further collection and processing. Producing this level of force means the rotor itself must be well balanced and strong and rely on high-speed magnetic bearings to reduce friction.

Over the years, Iran has produced thousands of centrifuges. They work together to enrich uranium to dangerous levels – close to weapons-grade uranium. Most of them are deployed in three enrichment sites: Natanz, the country’s main enrichment facility, Fordow and Isfahan. Inside of these facilities, the centrifuges are arranged into cascades – series of machines connected to each other. This way, each machine yields slightly more enriched uranium, feeding the gas produced into its neighbor to maximize production efficiency.

As a nuclear engineer who works on nuclear nonproliferation, I track centrifuge technology, including the Iranian enrichment facilities targeted by the U.S. and Israel. A typical cascade deployed in Iran is composed of 164 centrifuges, working in series to produce enriched uranium. The Natanz facility was designed to hold over 50,000 centrifuges.

Iran’s early intentions to field centrifuges on a very large scale were clear. At the peak of the program in the early 2010s it deployed over 19,000 units. Iran later scaled down the number of its centrifuges in part due to international agreements such as the since scrapped Joint Comprehensive Plan of Action signed in 2015.

Legacy of enrichment

Iran has a long history of enriching uranium.

In the late 1990s, it acquired a Pakistani centrifuge design known as P-1. The blueprints and some components were supplied via the A.Q. Khan black market network – the mastermind of the Pakistani program and a serious source of nuclear proliferation globally. Today, the P-1 design is known as IR-1. IR-1 centrifuges use aluminum and a high-strength alloy, known as maraging steel.

About one-third of the centrifuges that were deployed at the sites of the recent strike on June 21 are IR-1. Each one produces on the order of 0.8 separative work units, which is the unit for measuring the amount of energy and effort needed to separate uranium-235 molecules from the rest of the uranium gas. To put this in perspective, one centrifuge would yield about 0.2 ounces (6 grams) of 60%-enriched uranium-235 per year.

A typical uranium-based weapon requires 55 pounds (25 kilograms) of 90%-enriched uranium. To get to weapons-grade level, a single centrifuge would produce only 0.14 ounces (4 grams) per year. It requires more work to go higher in enrichment. While capable of doing the job, the IR-1 is quite inefficient.

More and better centrifuges

Small yields mean that over 6,000 centrifuges would need to work together for a year to get enough material for one weapon such as a nuclear warhead. Or the efficiency of the centrifuges would have to be improved. Iran did both.

Before the strike by U.S. forces, Iran was operating close to 7,000 IR-1 centrifuges. In addition, Iran designed, built and operated more efficient centrifuges such as the IR-2m, IR-4 and IR-6 designs. Comparing the IR-1 with the latest designs is like comparing a golf cart with the latest electric vehicles in terms of range and payload.

Iran’s latest centrifuge designs contain carbon fiber composites with exceptional strength and durability and low weight. This is a recipe for producing light and compact centrifuges that are easier to conceal from inspections. According to the international nuclear watchdog International Atomic Energy Agency, before the strike Iran was operating 6,500 IR-2m centrifuges, close to 4,000 IR-4 centrifuges and over 3,000 IR-6 centrifuges.

With each new generation, the separative work unit efficiency increased significantly. IR-6 centrifuges, with their carbon fiber rotors, can achieve up to 10 separative work units per year. That’s about 2.8 ounces (80 grams) of 60%-enriched uranium-235 per year. The International Atomic Energy Agency verified that the IR-6 cascades have been actively used to ramp up production of 60%-enriched uranium.

The most recent and advanced centrifuges developed by Iran, known as IR-9, can achieve 50 separative work units per year. This cuts down the time needed to produce highly enriched uranium for weapon purposes from months to weeks. The other aspect of IR-9 advanced centrifuges is their compactness. They are easier to conceal from inspections or move underground, and they require less energy to operate.

Advanced centrifuges such as the IR-9 drive up the risk of nuclear weapons proliferation significantly. Fortunately, the International Atomic Energy Agency reports that only one exists in testing laboratories, and there is no evidence Iran has deployed them widely. However, it’s possible more are concealed.

Bombs or talks?

Uranium enrichment of 60% is far beyond the needs of any civilian use. The International Atomic Energy Agency confirmed that Iran stockpiled about 880 pounds (400 kilograms) of highly enriched uranium before the attack, and it might have escaped intact. That’s enough to make 10 weapons. The newer centrifuges – IR-2m, IR-4 and IR-6 – would need a bit over eight months to produce that much.

It’s not clear what the U.S. attack has accomplished, but destroying the facilities targeted in the attack and hindering Iran’s ability to continue enriching uranium might be a way to slow Iran’s move toward producing nuclear weapons. However, based on my work and research on preventing nuclear proliferation, I believe a more reliable means of preventing Iran from achieving its nuclear aims would be for diplomacy and cooperation to prevail.

Anna Erickson receives funding from Department of Energy National Nuclear Security Administration (NNSA) related to nuclear nonproliferation technologies. She has previously served on the Board of Directors of the American Nuclear Society.