Why the U.S. Bombed a Bunch of Metal Tubes − a Nuclear Engineer Explains the Importance of Centrifuges to Iranian Efforts to Build Nuclear Weapons
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 is Professor of Nuclear and Radiological Engineering, Georgia Institute of Technology. This article is published courtesy of The Conversation.
