The other day, I observed that US public statements imply that Iran’s centrifuges operate closer to 2 kg SWU/year than 3.
That is a little lower than previous public estimates by David Albright and Corey Hinderstein (The Centrifuge Connection, Bulletin of the Atomic Scientists 60:2, March/April 2004, 61-66) but within the range generally suggested for a P1-type centrifuge. Here is a handy chart produced by Marvin Miller at MIT:
Basic Parameters of Contemporary Centrifuges
Source: Marvin Miller, “The Gas Centrifuge and Nuclear Proliferation,” in A Fresh Examination of the Proliferation Dangers of Light Water Reactors (Washington, DC: The Nonproliferation Policy Education Center, October 22, 2004), p. 38.
Technical information provided by Iran Atomic Energy Organization Director Gholam-Reza Aqazadeh fits perfectly: Aqazadeh claims Iran’s centrifuges are 1.8 m long and rotate at a linear speed of 350 m/s.
Aqazadeh also provides enough technical information to estimate the capacity of Iran’s centrifuges, stating the 48,000 centrifuges could produce 30,000 metric tons of 3.5 percent LEU per year with a 10:1 feed to product ratio.
Let’s do some math!
We can figure out the tails assay (how much U235 ends up in the waste) from the feed to product ratio.
xt=[(F/P)xf – xp]/(F/P-1)
Where xt is the tails assay, F/P is the feed-to-product ratio, xf is the percentage of U235 in feed, and xp is the percentage of U235 in the product.
Once we have xt, we can use the FAS SWU calculator figure out how many SWU you need to produce 1 kg of 3.5 percent U235. (Rather than do the math by hand, which I would screw up). Multiply that by the product, divide by the numbers of centrifuges and … behold:
(3.64 SWU/kg)(30,000kg/y)/48,000 = 2.3 SWU/y
(My calculations were much messier—these orderly equations belong to a physicist who corrected an early error on my part. Live and learn.)
So, each machine operates at about 2.3 SWU per year—about what I figured the US uses in public estimates.
So why are the estimates so much lower than Albright and Hinderstein?
One possibility—suggested in Albright and Hinderstein, The Clock is Ticking, But How Fast?—is that impurities in Iran’s uranium hexafluoride “can interfere with the operation of centrifuges and reduce their output”—although they are careful to note “most IAEA experts believe that Iran can overcome this problem…”