Jeffrey LewisP3 and P4 Centrifuge Data

Mark Hibbs has published specifications for Pakistan’s P3 and P4 centrifuges based on “Western government data.”

I haven’t seen this anywhere else, so here it is (with rough data on the P1 and P2 for comparison):

Desig. Derivation Rotor Velocity (m/s) Length SWU
P1 SNOR/CNOR Aluminum 350 1-2 1-3
P2 G2 Maraging Steel 500 1 5
P3 URENCO 4M Maraging Steel 485 2 11.6
P4 SLM/Unknown Maraging Steel 508 3.2 21

Source for P3 and P4: Mark Hibbs, “Pakistan developed more powerful centrifuges,” Nuclear Fuel, January 29, 2007, 1, 15-16.

I find it interesting that Pakistan remained committed to maraging steel, rather than carbon fiber, as the material for its centrifuge rotors. Sources told Hibbs that “procurement breakthroughs” were partially responsible for Pakistan obtaining maraging steel with higher tensile strength necessary for the P4 centrifuge.

I am fascinated by procurement networks. Recently, I wrote an article in The Bulletin entitled, “A Crisis of Confidence,” arguing that the principal challenge facing the nonproliferation regime is not a crisis of compliance, but rather confidence among US policymakers about our ability to detect clandestine gas centrifuge programs.

It is my hypothesis that US policymakers were late to recognize the challenge posed by gas centrifuges, and may be over-reacting (ALUMINUM TUBES! THE END IS NIGH!). Despite the understandable panic, options for controlling sensitive components and monitoring national programs may still be feasible, if difficult.

At the very least, it is way too early to conclude that such efforts are futile and throw in the towel.

That argument, by the way, will form the basis of my presentation on Tuesday, February 20 at the Belfer Center on “Gas Centrifuges and the Future of the Nonproliferation Regime.”


  1. Robot Economist (History)

    The Bush administration’s verification pessimism isn’t just limited to gas centrifuges. Wasn’t their justification for torpedoing talks on a BWC verification protocol was that it wouldn’t be “adequately verifiable”?

  2. Derek

    Mark Hibb’s latest article notes that Pakistan’s P-1 had a throughput of less than 1 SWU/year. Far lower than has been reported elsewhere. Can anyone comment on this discrepancy or put it in context?

  3. Richard F.

    Derek: Read carefully Mark’s sentence. He said less than one SWU PER SEGMENT, and the P1 has at least four SEGMENTs or rotors, making it 2.5 SWU or so altogether. Jeffrey got it right above. Cheers…

  4. John Field (History)

    You know, I remain confused about the centrifuges. I can see that once you get them set up you are sitting in gravy, but getting there seems to be such a difficult road. As I have said before, it seems like the laser AVLIS system is the fastest, easiest and maybe even cheapest route to a bomb. For the clandestine route, it seems better than MOLIS even. Worse, it is getting easier all the time. The only problem is that you only get one or a few devices.

    The drawbacks:1)export controlled CV and dye lasers2)will require constant maintenance and attention to keep the windows clean, evaporator running, etc. etc.3)a prototype setup will be slow and not achieve ultimate separation factor4)UHV, laser, and e-beam evaporator experience required

    But, on the other hand:Advantages:1)no UF6, UF4, or high U purity req’d2)distributable concealable garage scale operations3)not subject to catastrophic failure4)little or no exotic precision manufacturing

    After that, it’s just a handful of watt-years of tuned light between you and your irresponsible goal. All the talk about getting implosion designs light enough to get on a missile is balderdash if you’ve got HEU and are willing to use some excess. Watch out for spalling and otherwise you’re good to go.

    The very last thing you do before declaring war on your chosen ally of the US is to take apart the microwave oven in the coffee break room and build it into your initiator.(Cold coffee is no good after all)

    Maybe the point is that the DPRK route of a few bombs is a dead end politically. You have to have a bottomless supply of bombs for credibility.

  5. yale (History)

    One difficulty in hoping to “Manage by Monitoring” procurement networks is when these networks are unneeded.

    Altho useless for economically creating powerplant fuel, low-tech, non-exotic centrifuges may be just the thing for undetectable bomb production.

    Consider a centrifuge that, instead of the 2.5 SWU per year production rate of a P1 design, is only a tenth as productive, or only 0.25 SWU per year.

    Starting with the globally ubiquitous “proliferation-resistant” LEU powerplant fuel as feedstock, only 2,000 machines will enrich a bomb’s worth of HEU in a single year.

    Building many, many thousands of low-tech centrifuges in just a few months is a no-problem.

    As Lovins pointed out more than a quarter century ago (see Foreign Affairs June 80):

    … centrifuges now entering commercial service… are relatively large, very high-technology devices which use exotic materials to achieve the high efficiency, high output, and long lifetime that led Pakistan to steal their design…

    But these exacting commercial criteria are not the only imaginable ones. Natural uranium can also be gradually enriched to bomb-usable concentrations using low-technology centrifuges. The task is three-fifths easier if the starting material is LEU (7/8ths easier with VVER-1000 LEU – yale), and nearly a hundred times easier still if it is a mixture of uranium-233 and -238 from the front end of a proposed “denatured” thorium cycle. An effective centrifuge design was published twenty years ago. Better versions—much less efficient than the high-technology commercial versions, but still adequate—have been made by a good machinist in a few weeks. … the centrifuges are simple, modular, concealable, relatively cheap, and highly accessible.

  6. Robert Merkel (History)

    Assuming it works reliably and these numbers are accurate, would the P4 design be cost-competitive with, say, Urenco’s centrifuge technology for enriching uranium for light-water power reactors?

  7. John Field (History)

    Amory Lovins may have won a MacArthur fellowship, but he’s also an idiot.

    The centrifuge hall would be hot as hell using the Thorium fuel cycle.SEE for example, pp. 83-84 in discussion of daughter products:

    You can’t make 233 without making 232 and that plus the daughter products is going to fill the room with gamma rays and subsequent compton scattered X-rays.

    Let’s do some numbers…Say the centrifuges are spinning 200 m/s rimspeed and the U233 is contaminated with 1000 ppm U232. I get on order of 1.4 gm U233 per centrifuge – e.g 1.4 mg U232.Using the U233 LD-50 table from the above citation and assuming that the cascade has 2 machines per meter and maybe the radiation penetrates 3 cascade rows deep, that works out to a lethal dose in about 60 hours for someone standing 10 feet in front of the(enriched end of the) cascade.

    Read what he has to say about the hydrogen economy to see for yourself.Or, try:“Nuclear weapons and power-reactor plutonium” Nature, Vol 283 #5750 pp.817-823 for an exercise in idle speculation.

  8. yale (History)

    John F.Calling Amory Lovins an idiot is rather misguided.


    BTW… for those interested in all things Non-Proliferation, at the end of Feb, Lovins will be one of the three featured experts in the inaugural Online Rountable Discussion being started by the Bulletin of Atomic Scientists.

    The Bulletin Online: Global Security News & AnalysisNuclear Power and Climate Change

    When considering ways to limit carbon dioxide emissions, experts argue that all options should be considered—including nuclear power. But with nuclear power comes concerns about proliferation, waste disposal, and cost. Starting in late February, R. Stephen Berry, the former Special Advisor to the Director of Argonne National Laboratory for National Security, Amory Lovins, the CEO of the Rocky Mountain Institute, and Peter Bradford, a former member of the U.S. Nuclear Regulatory Commission, will consider the feasibility of nuclear power as a remedy to climate change in the Bulletin Online’s inaugural roundtable.


    As to your points:John F. Wrote:

    …the U233 is contaminated with 1000 ppm U232.

    Only some Thorium cycles produce such high levels of U232.

    As your IAEA source points out:

    In the BN–350 fast neutron reactor, the 232U content in irradiated thorium blankets has been significantly minimized by locating the thorium blankets some 15 to 20 cm away from the core border. The 232U content was only 2 to 11 ppm in 233U obtained by irradiation of thorium blanket away from the core in BN-350,until about 1.3g233U per kg of thorium was obtained

    A proliferating country of course would use a range of techniques to produce u233 with any arbitrarily low content of u232 .

    An excellent overview of the proliferation (non)-resistance of Thorium-U233 is the von Hippel and Kang article:

    U-232 and the Proliferation-Resistance of U-233 in Spent Fuel

    Thus the proliferation resistance of thorium fuel cycles depends very much uponhow they are implemented.

    Also see:

    Amory B. Lovins, “Thorium cycles and proliferation,” Bulletin of the Atomic Scientists, February 1979


    John F. wrote:Read what he has to say about the hydrogen economy to see for yourself.

    Good idea!

    Excellent essays here

    John F. wrote:

    “Nuclear weapons and power-reactor plutonium” Nature, Vol 283 #5750 pp.817-823 for an exercise in idle speculation.

    This mystifies me. This is as mainstream as anything could be. What could you possibly consider “idle speculation”?

    Here’s the article

  9. John Field (History)

    OK, I agree that’s rude to call Lovins an idiot. Let me be more professional. Lovins has done a good job of bringing a message to the people, and for that he should be praised. I am really sorry I called him an idiot.

    But, I think criticisms of Amory Lovins break down into the following categories:

    A) he is saying things that are obvious and that have long been said by othersB) he is saying things that are so overoptimistic as to being misleadingC) he is saying things that are flat wrongD) his scientific expertise is thin

    To A) let me say that energy conservation is a great thing. Most of the CO2 reductions we will see in the next 20 years will come from this route. “Natural Capitalism” and the idea that there are environmental externalities is almost as old as economics itself. So, I hardly think this is visionary.

    B)Hydrogen has the serious problem of extremely low volumetric energy density. It also appears that it has an unacceptably deleterious effect on the ozone layer. I think at a minimum these two factors deserve careful consideration.

    C)Lovins has published in the proliferation field quite a bit. Unfortunately, much of what he is written is wrong or completely misleading. For example, I think the fact that the centrifuges would be wildly radioactive in a U233 system makes such a system impractical.

    In the Nature article on implosion mechanisms, his Level III description of a converging shock is wrong as is the main conclusion that preinitiation is easy to overcome.See for example Chap. 12, Zel’dovich and Raizer, Physics of Shock Waves and High Temp Hydro Phenom. It’s really a matter a matching the driver to the load. If you hit it too hard on the initial hit, the entropy created will cause the pit to fall apart. More entropy and you get less compression. You have to hit it softly, bring up the pressure steadily, and make it bounce off at the last possible moment. It’s all in the timing, and so you need to know the equation of state to get the wave velocities. The bounce greatly increases the speed, and the weak initial hit prevents all the kinetic energy from being dissipated into internal heat.

    When I publish scientific articles, I try hard to get the conclusions right. Why is it that if you publish on nuclear weapons, the entire peer review process goes out the window?

    Finally, as to D), I think I should point out that Lovins doesn’t actually have an earned PhD as far as I can tell. He seems to have flunked out of both Harvard and Oxford at a very young age. I’m not quite sure what the stuff about Bates College is. And, you know if you look around the RMI staff list, it seems light on technical PhDs. That’s OK with me, but gosh, wouldn’t a visionary who was going to change the world of energy attract PhDs from the four corners of the globe? I only count two out of dozens and dozens of people – Swisher and Koomey, probably Wilkinson doesn’t count. The engineering lead for Hypercar seems to only have a bachelor’s degree. Maybe Lovins has something against PhDs? Look, undoubtedly Lovins is a smart guy, but I think bearing in mind the above, we should consider the possibility that he is precocious sensationalist.

    I shouldn’t be insulting about him though. Sorry.

  10. yale (History)

    I don’t think Lovin’s needs me to defend him against you. lol

    My point was not that you are rude, its that its ridiculous to call him an idiot.

    However, as to your claims:

    a) John wrote:So, I hardly think this is visionary

    Ummm… no.. One look at the Bush energy policy demonstrates that Lovin’s ideas are not yet commonplaces.

    The fact that Articles 4 and 5 of the NPT treaty still exist in their present form demonstrates that Lovin’s ideas are not yet commonplaces.

    b) John wrote:Hydrogen has .. problem of… low volumetric energy density…. unacceptably deleterious effect on the ozone layer.

    You didn’t even take the effort to READ his words! Those issues are EXTENSIVELY and in specific detail covered in those papers.

    As to the ozone problem – READ the essays. The authors of that claim miscalculated by over an order of magnitude. Don’t you ever read primary sources??

    c) John wrote:centrifuges would be wildly radioactive in a U233 system makes such a system impractical

    Obviously, the gamma emitting products are chemically washed out in the reprocessing line and the virtually non-radioactive uranium is enriched from the U238 before the daughter products ingrow. The u233 is already nearly HEU in the reactor and a VERY quick enrichment will strip the U238 denaturant.

    The same chemical cleaning occurs prior to warhead manufacture. This is standard knowledge.

    BTW – In a threat not widely written about, the protactium-233 can be stripped from the targets and in just a few weeks automagically converts itself into pure u233.

    John wrote:..Level III description of a converging shock is wrong as is the main conclusion that preinitiation is easy to overcome


    The level 3 he was discussing (in 1980 it was not open) is simply a levitated core. In use for the last SIXTY years, it does EXACTLY as he describes. As he points out, it greatly exceeds the 2 km/s implosion, providing the preinitiation resistance.

    Remember- anything that exists is possible.

    d) your stuff in D is pointless, but I will post about it later if I have some dead-end time.

    ============================================Finally, from the man who created the largest, smallest, and most efficient pure fission bombs produced:

    Utility of Reactor Grade Plutonium in Nuclear WeaponsTheodore B. TaylorVisiting FellowCenter for Energy and Environmental StudiesPrinceton University, Princeton NJ 08544June 10, 1998

    Contrary to opinions expressed by many nuclear engineers that are not familiar with the still secret intimate details of nuclear weapon design and operation, plutonium extracted from all types of spent fuel removed from nuclear power plants or research reactors can be used for making modern fission or thermonuclear weapons that are reliabily predictable in performance, over a very wide range of yields, from fractions of a kiloton to megatons of high explosive equivalent. This has been true for decades, and confirmed by numerous nuclear weapon tests.

    It is true that the first generation of implosion type fission bombs, such as the one that destroyed Nagasaki in 1945, could “fizzle” and produce much lower than the design yields if the plutonium they contained were of “reactor grade.” This could be the result of premature initiation of a fission chain reaction by spontaneous fission neutrons emitted by Pu-240 or other isotopes that are more abundant in reactor grade than weapon grade plutonium. But ways to avoid this problem, by use of plutonium in different designs that could be reliably used for fission and thermonuclear weapons were developed and demonstrated before the end of the 1950s. The performance of these weapons is not significantly degraded by using reactor grade plutonium instead of weapon grade plutonium.