Joshua PollackIR-1 Estimates Revisited

[Update | Feb. 11, 2010. Estimates from the new ISIS analysis by David Albright and Christina Walrond, “Iran’s Gas Centrifuge Program: Taking Stock,” now appear at the end of the table. The paper contains a number of different estimates derived from different sources; the summary in the last two lines of the table doesn’t fully do them justice. So read it for yourself.]

Note: Two previously overlooked estimates have been added to the data table, and the “observations” section updated accordingly.

Last week, at an event sponsored by AAAS (depicted above*), I had the privilege of giving a presentation on “Expert Opinion on Iran’s IR-1 Centrifuge.” The session was off the record, but I can share with you, Dear Reader, a data table assembled for the occasion, along with a few observations.

This table is an amended version of the data previously assembled by the Federation of American Scientists (see Table 1 in this report). I’ve tinkered with this dataset before (see: Estimating SWU with Expert Opinion, December 6, 2009). The amended table covers every published estimate of the separative power of the IR-1 centrifuge that I could find, running from March 2003 to December 2009. Explicit repetitions of previous estimates [or estimates explictly derived from earlier estimates] are not included.

(N.B. “Actual” indicates the mean performance of actual devices. “Nominal” indicates the maximum power of the device on paper. Despite some ambiguities, it’s usually apparent from context which type of estimate is intended, when not stated directly. For example, I’ve tagged as “nominal” those estimates that relate to the machines believed by different experts at various points to be ancestors of the IR-1.)

There are 29 31 now 33 estimates, although some of the “nominal” estimates from ISIS appear to be repetitions. (More on this point in a few moments.) Here it is: the whole megillah.

Note: Thanks to Scott Kemp for the clarification on his 5/27/08 estimate, which was actually two estimates. Thanks also to Andreas Persbo for the similar observation about his estimate of 2/27/09. I’ve corrected the table to reflect both of these inputs. I’ve also corrected a few minor errors and inconsistencies.

Author(s) Data source(s) kg SWU/yr Estimate of Date
Hibbs Official sources 7 to 15 Actual 3/13/03
Hibbs IAEA sources 12 to 14 Actual 5/12/03
Hibbs AEOI data 6 to 7 Actual 5/12/03
Albright & Hinderstein (ISIS) Senior Western officials 2 Actual 9/1/03
Albright & Hinderstein (ISIS) Senior IAEA officials (stated subsequently) 3 Nominal (based on 4M) 3/1/04
Gilinsky, Miller, & Hubbard Unclassified sources (and educated guesses) 1 to 3 Actual 10/22/04
Hibbs IAEA and Western governments 2 Nominal (based on SNOR & CNOR) 1/31/05
Glaser (not stated) 2 Nominal (estimate of P-1) 6/14/05
Lewis Rademaker (USDOS) statement 2 < and < 3, closer to 2 Actual 4/15/06
Lewis Aghazadeh (AEOI) statement 2.3 Actual 4/18/06
“Feynman” via Lewis Aghazadeh (AEOI) statement 1.46 Actual 5/12/06
“Feynman” via Lewis Aghazadeh (AEOI) statement 2.3 Nominal 5/12/06
Albright (ISIS) Aghazadeh (AEOI) statement 1.4 to 2.7 Actual 5/17/06
Albright (ISIS) (not stated) 2.5 to 3 “the high end of the possible” 7/1/06
Albright & Shire (ISIS) Level Pakistan is said to have achieved 2 Actual of P-1 11/1/07
Garwin Aghazadeh (AEOI) statement 1.362 Actual 1/17/08
Glaser (not stated) 2.5 Nominal (hypothetical max. of P-1) 4/16/08
Kemp via Lewis Observed efficiency of 42% 1 Actual 5/27/08
Kemp via Lewis (not stated) 2.5 Nominal 5/27/08
ISIS NuclearIran FAQ (not stated) 1 to 2 Actual ~9/1/08 (n.d.)
ISIS NuclearIran FAQ (not stated) 3 Nominal ~9/1/08 (n.d.)
Persbo Cascades operating between 27 and 36% of total capacity 0.59 to 0.79 Actual 2/27/09
Persbo (not stated) 2.2 Nominal (based on SNOR) 2/27/09
Salehi (AEOI) (not stated) 2.1 Unclear; nominal? 9/22/09
Oelrich & Barzashka (FAS) IAEA reports 0.5 Actual 9/25/09; see also 11/23/09
Wisconsin Project IAEA reports 0.5 Actual 11/16/09
Albright & Brannan (ISIS) IAEA reports 1.0 to 1.5 Actual 11/30/09
Albright & Brannan (ISIS) (not stated) 3 Nominal 11/30/09
Oelrich & Barzashka (FAS) IAEA reports 0.44 to 0.88 (0.88 is highly unlikely) Actual 12/1/09
Kemp IAEA reports 0.6 to 0.9 Actual 12/1/09
Wood via Kemp Max. of P-1 based on validated hydrodynamic codes from the U.S. program 2.1 to 2.2 Nominal (max. of P-1) 12/1/09
Albright & Walrond (ISIS) Multiple sources 0.5 to 1.0 Actual 2/11/10
Albright & Walrond (ISIS) Multiple sources 1.60 to 3.76 Nominal 2/11/10

Four Observations

First, as noted previously, the trend of the estimates declines with time. This effect only becomes more pronounced with the inclusion of the estimates reported by Mark Hibbs in NuclearFuel and Nucleonics Week in early 2003: now the trend of the decline is follows an exponential curve. These reports appeared when IAEA inspectors had just put eyes on the IR-1 (then called the P-1 in IAEA reports) for the first time. Their initial frame of reference presumably involved more up-to-date machines, rather than centrifuges whose design heritage extends back to the 1960s.

[Update | 22:54. See Mark Hibbs’ account in the comments below.]

Second, the decline comes in bursts, coinciding with the availability of new information. This effect is loosely similar to the influence of news on stock prices, as documented in event studies. The effect tends to be prompt in finance; a bit less so here.

  • From mid-2003 into 2005, which covers the first period of centrifuge operations at PFEP in Natanz, we see the gradual sorting-out of the design heritage of the IR-1.
  • The next wave comes in mid-2006, right after AEOI chief Gholamreza Aghazadeh gave some detailed figures during an interview with Iranian TV. Here we start to see some divergence between “actual” and “nominal” estimates, with “actual” figures falling below 2 kg SWU/yr.
  • Next come the estimates of late 2007 to early 2009 2008, after the commencement of enrichment work at the FEP in Natanz, whose results were periodically documented in IAEA reports.
  • A final burst of estimates, explicitly derived from the ever-accumulating IAEA reports, takes place in late 2009. Here, “actual” estimates fall below 1 kg SWU/yr.

Third, in most cases, a “new entrant” tends to lead the way in pushing “actual” estimates down. That is, someone who wasn’t previously in the game seems to take hold of the new information and bring it to light, with the rest shortly catching up. In 2003 and 2004, it was David Albright and Corey Hinderstein of ISIS. In 2006, it was Jeffrey Lewis and a pseudonymous correspondent here at ACW. In 2009, it was Ivan Oelrich and Ivanka Barzashka of FAS.

[Update | 23:51. In hindsight, Andreas Persbo was the first to present an “actual” estimate below 1, using recent IAEA reports. This contribution may have been overlooked because it was couched as a range of percentages of a nominal figure.]

Fourth, there are lingering differences between experts in both “actual” and “nominal” figures. Much of the basis of the “actual” differences was laid bare in the FASISIS debate of late 2009. The “nominal” differences seem to originate with early reports about the design heritage of the IR-1. In March 2004, ISIS related that the IR-1 was copied from URENCO’s 4M centrifuge; both designs have four aluminum tube rotor segments. In January 2005, Hibbs reported that the IR-1 was derived from URENCO’s SNOR and CNOR machines.

Both 4M and CNOR are said to have been capable of about 3 kg SWU/yr. The CNOR had six segments, each responsible for about 0.5 kg SWU/yr, according to Hibbs. Since the Pakistani P-1 and the Iranian IR-1 have four segments, their nominal output, if they are understood to be CNOR derivatives, is about 2 — or, according to some recent figures, 2.1 or 2.2. Most experts seem to agree with Hibbs, or wind up close to his figure. But Albright and colleagues persist in viewing 3 as the real ceiling.

Should you, Dear Reader, notice any other subtle patterns in the data, well, that’s what the comments feature is for!

*Actually, the picture at the top of this post does not show me giving a presentation.


  1. R. Scott Kemp

    My 5/27/08 estimate should be read as 2.5 swu/yr nominal capacity, with the actual performance at 42% of this value, or about 1 swu/yr.

  2. mark hibbs

    On March 7 2003—a few days after Mohamed ElBaradei stepped off the plane in Vienna following the IAEA’s initial visit to Iran’s Natanz enrichment plant—I published in Nuclear Fuel the first open-source description of the IR-1 centrifuge. Most of the statements in this article were correct, but the throughput estimate we were given turned out to be way too high by a factor of about four or five.

    In retrospect, given the size of the throughput discrepancy, and efforts by the IAEA’s board of governors to accurately assess Iran’s capabilities, shortly after the IAEA visit to Natanz, it took surprisingly long for the record to be corrected in the open literature.

    On March 5, 2003, a few Western government officials, who had in turn obtained some data from the IAEA trip to Natanz in February, agreed to discuss with me some characteristics of the IR-1. On the basis of this information, two days later I published the article “Iran Has Developed an Advanced Supercritical Aluminum Centrifuge.”

    Right after I was briefed, and a day before I wrote the article, I left phone, e-mail, and fax messages for David Albright, providing him main claims imparted to me about IR-1, including the surprising conclusion that the throughput might be as high as 10 SWU/y. Albright did not respond to any of these messages, and so we published the account based primarily on the data I had been given.

    The March 7, 2003 article did raise questions about the credibility of the high throughput estimate. A Western enrichment official told me for the article that, in his view, “for Iran to get an aluminum machine to work at 10 SWU/y would be a stunning accomplishment.” Unless Iran had prior experience in enriching uranium, he said, “I can’t believe they could do it.”

    The article also pointed out that subcritical aluminum centrifuges developed by Urenco had throughputs of only about 0.5 SWU/y and that supercritical Urenco machines based on that template might have a throughput of 3 SWU/y and not higher than 5 SWU/y.

    Some of the confusion during the first half of 2003 concerning the throughput of IR-1 was abetted by Iran. In May, two months after my first estimate was published, I was told that AEOI officials in Vienna had advanced the claim that the throughput of IR-1 was between 6 and 7 SWU/y.

    At about the same time, some European officials began muddying the non-classified expert discourse about the pedigree of centrifuges in Libya and Iran. Sources for the original March 2003 article informed me that, during initial briefings to IAEA member states held after ElBaradei had returned from Natanz in February, IAEA officials assured them that the Iranian machine was not a replication of any known centrifuge. Only in 2005 were official sources willing to firmly assert that design information from CNOR and SNOR, obtained by Iran through interlocutors in Pakistan, which had previously stolen the design from Urenco, had served as the design basis for critical IR-1 parameters. It is not a surprise that, as the range of throughput estimates for IR-1 over the years has narrowed down, IR-1’s capability seems to broadly track with the empirical results of the CNOR/SNOR program.

  3. Andreas Persbo

    You may add that my estimate (actual) in the post was 0.59-0.79 kg SWU/year. Or, as I put it then, 27-36 per cent of total capacity.

  4. nick (History)

    I wonder why the Agency (IAEA) has not made any reports on the SWU for IR-1. After all they have access to exact feed amount and tail assay per unit and most likely detailed IR-1 design specs.

  5. Josh (History)

    Thanks to both Scott and Andreas for explaining what I should have realized in the first place.

    As an aside, it appears that Scott may have been the first analyst to take advantage of the data in the IAEA reports on operations at FEP.

    Thanks also to Mark for the detailed insights into how his early reports on the P-1/IR-1 came to be written as they were.

    If any other authors would like to add further clarification about their work, or if anyone has spotted additional estimates that aren’t explicitly repetitions of earlier estimates, or explicitly derived from earlier estimates, please drop a line in the comments.


    I’m not sure the IAEA has access to design specifications. As for why they don’t quantify the performance of the machines, all I can tell you is what I’ve heard: this sort of number is considered to be proprietary, competition-sensitive information. We might speculate, too, that from a pure safeguards perspective, it’s not considered germane.

  6. Milton Hoenig (History)

    Maybe the value of 1.362 kgSWU/yr calculated by Garwin and others, based on the 2006 interview with Aghazadeh, should be replaced 0.92 kgSWU/yr because the feed and product values cited by Aghazadeh are likely for UF6, not U.

  7. Andreas Persbo

    Another thing that might be interesting is to see where all analysts have set tails. I came to the conclusion that tails were set high 0.39wt% for the figures to make sense. I seem to recall that FAS also came to that conclusion.

  8. Pete (History)

    Some may find this nitpicking, but I disagree with the statement “now the decline is exponential” for a few reasons.

    1. Stating that the decline is exponential is misleading because it implies that the mechanism behind the decline is understood. The data may have been fit to an exponential curve, but that does not mean that the behavior is actually exponential.

    2. The “exponential” behavior is highly dependent on the 2003 data point. How does the curve change if that data point is omitted? One data point should not define a curve.

    3. Geek alert on this one. Calculus required. The derivative of the exponential function is itself. Saying that the function of SWU vs time is an exponential function also says that the change in SWU vs time is also an exponential function. This contradicts the second point that the decline comes in bursts.

    It is a small correction in an otherwise very nice piece of work.

  9. Josh (History)


    I salute your fussiness!

  10. Josh (History)

    Ivan Oelrich and Ivanka Barzashka have made a case for considering their estimate exclusively. I’m not quite ready to go there…

  11. Josh (History)

    David Albright and Christina Walrond of ISIS have produced a new report on the IR-1. I’ve incorporated their estimates into the table in summary form. There’s much more detail in the report itself.