Jeffrey LewisAQ Khan on the Pak Stockpile

AQ Khan has written an oped in which he defends his efforts to produce nuclear weapons as necessary to “save my country from Indian nuclear blackmail.”

I was going to suggest SEAL Team 6 make an encore performance in Pakistan, when I noticed that Khan said something else very interesting: there is a limit to Pakistan’s fissile material requirements.

Khan has been chatty lately, although largely in the form of an Urdu-language blog that I can’t read.  This time, though, he has chosen an English language venue — Newsweek, which is also the Daily Beast.

After having defended his actions in the op-ed, Khan talks a little about Pakistan’s need for continuing modernization of its nuclear deterrent:

I have little knowledge of the present status of our program, as I left Kahuta, Pakistan’s main nuclear facility, 10 years ago. As the pioneer of the program, my guess is that our efforts have been to perfect the design, reduce the size of the weapons to fit on the warheads of our missile systems, and ensure a fail-safe system for their storage. A country needs sufficient weapons to be stored at different places in order to have a second-strike capability. But there is a limit to these requirements.

“There is a limit to these requirements.” That’s very interesting.  Suddenly, AQ Khan is all Mr. Minimum Deterrence.  Of course, if there is a limit to Pakistan’s requirements, then Pakistan might conceivably support negotiation of a  Fissile Material Cut-off Treaty.  And, as validators go, AQ Khan would be a pretty effective one in Pakistan for a cut-off.

There are obvious reasons, of course, for AQ Khan to suddenly support capping Pakistan’s arsenal.  As David Albright has noted, Pakistan is making significant progress on the construction of a fourth plutonium production reactor.  Pakistan’s rapidly expanding plutonium program is the legacy of AQ Khan’s long-time bureaucratic rival, the late Munir Ahmad Khan. The impending eclipse of the enrichment program at Kahuta Research Laboratories by a PAEC-dominated plutonium program is precisely the last thing AQ Khan would enjoy living long enough to see.

Let’s hold off that SEAL team for now.


  1. Ben (History)

    The singular focus on Pakistan’s stockpile is baffling. Pakistan is replacing its uranium warheads with lighter plutonium ones. It is in increasing at the rate it is because it knows that the FMCT is a geopolitical inevitability (it can’t hold out forever), so it’s
    making a mad dash to minimum credible deterrence. It’s also possible it’s using the new reactors as a bargaining chip for a civil nuclear treaty with the US. I’d be suprised if they are still operating past 2025.

    • sanman (History)

      Well, Pakistan is punching above its weight by trying to “me too” alongside the major world powers, when it’s nuclear budget is dependent upon foreign aid. Perhaps the worry is that their version of credible-minimum-deterrent is soon going to be extended in Saudi Arabia’s direction.

      Nobody knows where the Iranians will draw the line on their nuclear program, and that will naturally tempt Saudi-Pak collusion.

    • FSB (History)

      So Pakistan is replacing its U based devices with ones that incorporate Pu? Looks like Pakistan has its own RRW program.

      Will they need to test these new beasts?

    • Ben (History)

      I don’t think India will sign the CTBT without another round of testing, particularly after their two-stage design fizzled in 1998. Fissile material losses due to the next round of testing have probably been factored into the modest Pakistani increases in Pu stockpile.

    • Jeffrey (History)

      I wasn’t terribly impressed by the Karpin book, but perhaps I need to give it another try.

      I seem to remember that Ted Taylor, having viewed the Vanunu photographs, concluded that Israel had alarm-clock like weapons with a maximum yield on the order of 100 KT, but not classic Teller-Ulam devices with MT yields.

      I’ll have to look that up tomorrow.

      The caveat is that the Vanunu revelations are a complete look at Israel’s weapons designs as of the mid-1980s.

  2. John Schilling (History)

    I am skeptical of the claim that uranium warheads are generally and substantially heavier than plutonium ones. In particular, I note that the W-33 8″ nuclear artillery shell was pretty clearly a uranium warhead, delivering ~10 kt from a ~100 kg package, and I don’t see Pakistan having any urgent need or desire to field weapons in the <<100 kg class.

    Of greater relevance to Pakistan is the need to economize on fissile materials. That means A: implosion devices and B: a substantial reflector/tamper surrounding the fissile core. Even in a relatively lightweight (500-1000 kg) missile warhead with an HEU core, the tamper will likely outweigh the fissile material by a substantial margin, and the implosion assembly has to compress them both. Back of the envelope, I get an HEU-based equivalent of the Trinity Gadget weighing in at all of 8% heavier than the historic plutonium version.

    And, also historically, we know that the United States shifted fairly early to composite cores, and to interchangeable cores, to make the most complete and efficient use of whatever mix of fissile materials became available. With the possible exception of the Mk. 12, there were no particularly lightweight, plutonium-only bombs in the early US arsenal, and no shortage of moderately lightweight bombs that would have been quite suitable as warheads for Pakistan's present missiles.

    If Pakistan is breeding plutonium, that is most likely because the Pakistanis believe that this is now the cheapest way to give them a combined inventory of deliverable Pu and HEU weapons sufficient for whatever they consider a reasonable deterrent. Or because of bureaucratic infighting between the Khans. Not because they consider their Uranium bombs to be too heavy and plan to retire them.

    • Ben (History)

      Pakistan has a limited supply of domestic uranium, so it makes sense to produce plutonium, it’s more efficient as a fissile material. The mass discrepancy is a minor bonus.

      In terms of Pakistan’s weapons designs versus its urgent minimum need, who knows? Confessional States have a tendency towards over-militarization due an inability to project themselves as viable nations. Few would have thought before Vanunu that Israel would pursue a single stage thermonuclear design (by producing lithium-6 deuteride) for a weapon yield in the ~400 kt range. That was in the mid 1980’s, by now it certainly has two stage and neutron designs.

    • John Schilling (History)

      Israel’s desire for thermonuclear weapons is not at all surprising. Their worst-case scenario calls for imposing MAD on an enemy with a population of several hundred million and an unusually high tolerance for casualties. A hundred or so basic fission bombs might plausibly fail to deter an Arab world that has united under the banner of militant anti-Zionism.

      Israel’s present posession of two-stage thermonuclear weapons would be somewhat surprising. That really is a quite advanced technology, difficult to develop without at least some testing. If the Vela incident were an Israeli test of a fully-instrumented primary, yes, otherwise I am skeptical.

      Alarm-Clock devices are probably good enough for Israel’s real and percieved needs, they are a technology that can credibly be made to work without testing, and thanks to Vanunu everyone is aware that Israel probably has them. A technically superior but still secret weapon would not be a superior deterrent, and I’d want more evidence before I would consider it at all certain that Israel has either two-stage or neutron bombs.

      Pakistan, might have something approaching Israel’s percieved need for thermonuclear weapons, but not the capability. They will go for all the fission weapons they can get at this point, possibly with composite cores as the most efficient use of all available resources. There may come a day when they look upon their arsenal and say, “OK, this is enough”, but I doubt that day will come soon.

    • Ben (History)

      On Israel’s possesion of a two stage design I can really only refer to Michael Karpin’s book, ‘The Bomb in the Basement’ and the support and succor given to the nascent Israeli program by Edward Teller and others within the US nuclear establishment. It would be naive to assume they haven’t got the Teller-Ulam design.

    • John Schilling (History)

      It’s not clear what you mean by “got the Teller-Ulam design, but if you mean that Israel has complete design details for a working two-stage hydrogen bomb, that’s far from clear. In particular, that’s something that never would have fit inside Edward Teller’s head, and the missing parts are not mere trivial details to be reconstituted by the engineering staff.

      If you know everything that Teller ever did, you’re still a very substantial R&D program (and probably a mushroom cloud or two) away from a working Teller-Ulam bomb. And if you come by a working hydrogen bomb via technology transfer from an existing thermonuclear power, that’s either a matter of deliberate policy or a truly remarkable feat of espionage, not a couple of scientists deciding to help you in their spare time. Probably the best advice Teller could have given the Israelis is, “I couldn’t do this without Los Alamos backing me up, you can’t either, but here’s a simpler concept that might fit your needs…”

    • Ben (History)

      I don’t believe the espionage or ‘concerted help’ would be all that remarkable.

      It’s actually unsuprising how driven some people were given the proximity to Jewish genocide in Europe. It’s the reason why someone like Michael Michaels of the UKAEA lobbies vociferously to give Israel 10 mg of plutonium in the 1960’s against UK government stated policy.

      It’s the reason why 200 kg of uranium goes ‘missing’ at NUMEC. It’s the reason why after the 1971 Indo-Pak war and the 1974 Indian test, A Q Khan was always going to be a proliferation risk.

      It would be strange then in this context, for someone like Jefferey Goldberg, no stranger to being briefed by (and not to mention acting on the behest of) the Israeli defence establishment to write, specifically in the context of the Israeli arsenal,

      ‘…acknowledging the existence of the country’s nuclear arsenal, which consists of more than 100 weapons, mainly two-stage thermonuclear devices, capable of being delivered by missile, fighter-bomber, or submarine…’

      Obviously I have no proof. But I just think it’s naive to believe that an undeniably talented pool of nuclear scientists has been sitting on their hands for the past 25 years. One of the main intelligence goals after the near defeat of the Yom Kippur war would have been to aquire a two stage design that would have been able to fit a missile warhead. By hook or by crook.

  3. FSB (History)

    From what I can see it is “Cold Start” and the Indian BMD programme as well as India’s own prodigious Pu production (outside IAEA) that is motivating Pakistani military planners to up the nukes.

    Maybe sit the Pakistanis down withe Indians to talk about all this, and Kashmir.

    And, in the future, let’s not help the Pakistanis or others get nuclear weapons:

    “Working as a Central Intelligence Agency (CIA) counter-proliferation intelligence officer in the 1980s, Richard Barlow learned that top U.S. officials were allowing Pakistan to manufacture and possess nuclear weapons, and that the A.Q. Khan nuclear network was violating U.S. laws. He also discovered that top officials were hiding these activities from Congress, since telling the truth would have legally obligated the U.S. government to cut off its overt military aid to Pakistan at a time when covert military aid was being funneled through Pakistan to Afghan jihadists in the war against the Soviets….”

    • sanman (History)

      Like a broken record, the Pakistani line is to keep harping on Kashmir – basically, it’s irredentism. Here’s what Dick Clarke has to say about that:

      I’d say Pakistan has deeper issues which force it to maintain conflict with outsiders. Those deeper issues originate in the year 1839, which was over a century before Pakistan was even born.

      Nuclear weapons can’t make Pakistan safe, just as they didn’t keep the USSR from collapsing. If terrorists ever steal a nuke from someone, it won’t be from India, but from Pakistan.

    • Anon (History)

      Yes, but they can keep India safe, right?

      I think FSB has it about right.

    • sanman (History)

      Dear Anon, straw man much?

      India’s attentions aren’t Pak-centric — India developed nuclear weapons to deter China, which threatened to invade India’s northeast at the end of the 1971 Indo-Pakistani war. Furthermore, the Sino-Indian territorial dispute is easily far larger than the Indo-Pakistani territorial dispute. Why would India want nuclear weapons to deter a smaller Pakistan it already had conventional superiority over?

      Certainly, it’s quite rational for India to have developed nuclear weapons in response to nuclear-armed China. India is not responsible for creating the hardline type of regime in charge of Beijing since 1949 – you can blame Imperial Japan and the Soviet Union for that.

    • kme (History)

      The geopolitical reality is that India is an existential threat to Pakistan – and this is true independent of the current or future disposition of the regimes governing those states.

      Thus Pakistan’s acquisition of nuclear weapons is entirely rational, at least as much as India’s (in the latter case, it appears extremely unlikely that China could project significant power over the Himalayas).

      The game of “their nukes are bad, but ours are lily-white due to our special circumstances” is tiresome.

    • Anon (History)

      kme and FSB are right.

      btw, why is India pouring $$$ into a BMD system? Looks like they want ASATs too….very smart people indeed.

    • sanman (History)


      Who developed nuclear capability first – India or Pakistan? I think it’s pretty obvious that India did. So were Pakistani cities glowing in the dark, as a result of this? No – so that’s an indication that India is not an existential threat to Pakistan.

      Let’s contrast this to nuclear-armed China and the US threatening to invade Northeastern India in 1971. When nuclear-armed powers threaten to invade a non-nuclear one, then naturally they’re spurring the non-nuclear one to acquire nuclear capability.

      You write:
      “The game of “their nukes are bad, but ours are lily-white due to our special circumstances” is tiresome.”

      Heh – what do you think the NPT does? The NPT does exactly this – so by your logic, the double-standard asserted by the NPT should be no less tiresome. That tiresome game is exactly why some have chosen to reject the NPT. Crippling its Article 6 by eliminating NPT renewal clause doesn’t ameliorate the situation, either.

    • sanman (History)

      India’s investing in BMD probably because of Pakistan’s missile threat. As far as ASAT capability, India appears to be developing it not just as a deterrent to China’s already-demonstrated ASAT capability, but also because India doesn’t want to get shafted the way it did when the NPT was created to freeze India out of the exclusive club. If India develops this capability, then it gets a seat at that table, since there’s no pretext for locking it out of these negotiations.

      As NPT proved to India, when you show restraint in avoiding development of nuclear arms, then you get shoved to the underside of the apartheid system. Even after China weaponized, I’d say India’s nuclear program was still more advanced than China’s overall. But India’s lack of weaponization didn’t seem to impress the apartheid bloc, and indeed was seen as weakness to be exploited.

    • Anon (History)

      Very nice arguments sanman, but let’s not pretend surprise that there will be regional consequences.


      The world in interlinked.

      Plus, the Indians should learn from the US that BMD does not work — no matter how good it gets there will be a reasonable chance that 1 nuclear tipped missile gets thru so India will be deterred as well with it, as with out it.

      And India’s ASAT ambitions will not “deter” anything in China.

      Both BMD and ASAT only encourage more missiles and ASATs. They incite proliferation, while being ineffective at defense.

    • sanman (History)


      So why shouldn’t the world urge China more than India, to restrain its nuclear activities? China is the greater industrial power, with far greater economic and military might, as well as being a tightly locked-down police state. Please note that year after year, the Chinese military have sneakily shifted the boundary demarcation posts along the disputed Line of Actual Control between the 2 countries, to make incremental territorial gains clandestinely. China has even done this with Russia. This is something India doesn’t do, and it doesn’t appear to the hallmark of a pacifist power.

      So what I get from you is that regardless of whatever one side does, let’s always try to assert moral equivalency, regardless of asymmetries in behavior, because you feel there is no way to gauge what asymmetry is or whether it has occurred.

      What I also get from the wider debate is that democratic states should be subjected to greater pressure, because democracy should be seen as a vulnerability – an opportunity through which national will can be deflected or derailed.

      As for whether BMD works or not, take a look at this:

      Certainly we can conclude from this that proliferation works, and pays very handsome dividends. We can see what results when international control regimes are tailored to favor specific powers – powers which are neither constrained by having to obtain broader domestic consensus, nor by a sense of shared responsibility for international stability or peace.

      What I’m constantly reminded of is that cheaters do prosper – China certainly has. This is more than just an academic Prisoner Problem – it’s a reality that states which take shortcuts like dictatorship and authoritarianism can more expediently move to triumph over states less inclined towards such shortcuts. Nice guys really do finish last – but because we find it hard to acknowledge such ugly facts of life, we demur by telling ourselves that they probably weren’t so nice anyway. (“Those grapes were probably sour”)

    • sanman (History)

      Furthermore, Anon, allow me to correct your poor-quality chart into the following:

      USA >> China <> India

      I feel that Pakistani and NorthKorean arsenals should be regarded merely as extensions of the Chinese arsenal, since neither Pakistan nor NorthKorea possess the intrinsic capabilities to build their own nuclear arsenals by themselves. It’s helpful to see China+Pakistan+NorthKorea as a single entity, since the decision to nuclearize Pakistan and NorthKorea was mainly a Chinese one.

    • kme (History)

      sanman, India as an existential threat to Pakistan is not a matter of history or of politics, but a simple geopolitical fact – that is, one defined by the geography of the situation.

      And yes – it is equally tiresome when, for example, the UK government declares their nuclear deterrent to be “the ultimate guarantee of national security”. This obviously begs the question “if for you, then why not for us?”.

      The double-standard of the NPT is only defensible in the context of Article VI, and moving towards disarmament.

  4. Anon (History)

    The ISIS analysis refers to their own past analysis — which was exaggerated.

    There are limits to what Pakistan can do:

    As Ben wrote in a previous thread:

    “This myth really grew up because of yet another cack-handed analysis by ISIS and David Albright et al who seemed, at the time, determined to tell anyone who’d listen that a 40 MW reactor should actually be rated at 1000 MW, and that the Khushab complex was Savannah River Mark II. It just isn’t true.”

    • pkr (History)

      op. cit:
      “by 2020, Pakistan could have accumulated approximately 450 kg of plutonium from the Khushab reactors and 2500–6000 kg of highly enriched uranium (HEU) (90 percent enriched) for enrichment capacities ranging from 15,000–75,000 SWU. These stocks would be sufficient for perhaps 100–240 simple fission weapons based on HEU and for 90 plutonium weapons.”

      I would assume, that Pakistan is looking somewhat beyond simple fission weapons..

      Additionally the authors make very clear, that their analysis is based on a very limited data:

      “There is also little official information regarding other details of Pakistan’s fuel cycle activities, such as uranium mining and milling, fuel fabrication, and reprocessing, all of which are unsafeguarded. In the absence of such information, one is required to rely on a combination of judgments by a handful of independent analysts and media reports, augmented by occasional statements from officials.”

      “Since Pakistan does not publish uranium production data, the paper relies on estimates of Pakistan’s domestic uranium production reported in the biennial worldwide assessment of uranium resources and production, Uranium Resources, Production and Demand,
      published by the Organisation for Economic Co-operation and DevelopmentFissile Material Production in Pakistan 79
      (OECD) and the International Atomic Energy Agency (IAEA), commonly
      known as the “Red Book.”

      and they admit that

      “There are important uncertainties regarding what the status of Pakistan’s fissile material production program could be even a decade from now.”

      They explore reasons why Pakistan might limit the production of HEU/Pu, but we should also consider the possibility that Pakistan could be able to develop new U deposits domestically or succeed in obtaining additional U from abroad….

    • Ben (History)

      The report has the usual caveats that all academic essays do, but it’s basically sound. Pakistan’s uranium deposits are scarce and of a poor quality, you don’t use in-situ leeching if you’re sitting on high grade ores.

      Pakistan is unlikely to obtain uranium from abroad due to NSG rules (the reason why India cut a nuclear deal in the first place). It’s interesting to speculate that Pakistan may have moved to Pu production recently due to uranium scarcity and to difficulties in obtaining critical components for it’s centrifuges.

      Besides that, Pakistans nuclear program is well attested. It’s not difficult to make a reasonable estimate of a program consisting of ~

      4 x 40 MW D20/H20 reactors – (I’d like to see evidence the first reactor is even operational though)
      ~140 ton/yr reprocessing capacity
      ~10000 swu enrichment

      Is the fact that a single Indian 220 MW safeguard free reactor being able to produce 150 – 200 kg per year of WGPu, of no consequence to Albright? Why didn’t India agree to a moratorium of fissile material production in the US-India deal?

      Where’s the analysis on why Israel requires a two-stage thermonuclear capability as well Jericho-III ICBMs?
      We know (thanks to wikileaks) it imports Ammonium Pechlorate, so where are the fancy diagrams of the front companies/smuggling networks?

  5. FSB (History)

    A single Khushab reactor could make ~11 kg of Pu per yr. (at 70% efficiency).

    What is ISIS assuming for the Pu per bomb?

    Their numbers do not compute.

    It would be good if Mr. Albright published ref. 1 in his article so we can check his math. (Or maths, if you live in the UK.)

    Interesting M.O.: press releases galore with no supporting documentation.

    • ZeeKay (History)

      Referring to Ben and FSB’s observations about the ‘anamolies’ Mr Albright’s assessments that are taken as gospel – I’d like to share a recent opinion piece in Defence News. It quotes Mansoor Ahmed:
      “…the three reactors at Khushab can produce 50 megawatts apiece, and can produce 9 to 12 kilograms of plutonium annually, while India is working on a second 100-megawatt thermal plutonium production reactor and has 950 kilograms of weapons-grade plutonium and 11.5 tons of weapon-usable, reactor-grade plutonium. Assuming five kilograms of weapon-grade and 10 kilograms of reactor-grade plutonium per weapon, these stocks are sufficient for India to develop 190 and 1,150 nuclear warheads, respectively.India can potentially add 1,250 kilograms of weapon-usable, reactor-grade plutonium from its eight unsafeguarded heavy water power reactors, 130 kilograms of weapon-grade plutonium from each of its five existing and planned unsafeguarded fast-breeder reactors to its existing stocks of fissile material each year.”
      What is the eminent gents opinion on above assertion?

  6. pkr (History)

    Maybe Pakistan has some use for small warheads, at least they seem to be looking into systems, that by most standards (and claims of Pakistani analysts) would go as substrategic (aka tactical) nukes. As the Inter Services Puclic Relations office proudly announced recently:

    No PR94/2011-ISPR Dated: April 19, 2011
    Rawalpindi – April 19, 2011:
    Pakistan today successfully conducted the 1st flight test of the newly developed Short Range Surface to Surface Multi Tube Ballistic Missile Hatf IX (NASR). The missile has been developed to add deterrence value to Pakistan’s Strategic Weapons Development programme at shorter ranges. NASR, with a range of 60 km, carries nuclear warheads of appropriate yield with high accuracy, shoot and scoot attributes. This quick response system addresses the need to deter evolving threats.

    The test was witnessed by Director General Strategic Plans Division, Lieutenant General (Retired) Khalid Ahmed Kidwai, Chairman NESCOM Mr Irfan Burney, senior officers from the strategic forces, scientists and engineers of strategic organizations.

    On this occasion, the Director General Strategic Plans Division, Lieutenant General (Retired) Khalid Ahmed Kidwai said that the test was a very important milestone in consolidating Pakistan’s strategic deterrence capability at all levels of the threat spectrum. He said in that hierarchy of military operations, the NASR Weapon System now provides Pakistan with short range missile capability in addition to the already available medium and long range ballistic missiles and cruise missiles in its inventory.

    I leave the analysis of the few available pictures of the missile to the experts, but it seems that the diameter of this missile would require pretty small warheads…

    At least this is what some Pakistani analysts are claiming

    Haris Khan, of the Pakistan Military Consortium think tank, said Nasr answers India’s Cold Start doctrine.

    “Hatf-IX is a perfect answer to the Indian concept of Cold Start,” Khan said. “It establishes that tactical nuclear weapons will be deployed very close to its border with minimum reaction time to counter any armor or mechanized thrust by an enemy into its Pakistani territory.”

    The Nasr test shows Pakistan can build small nuclear warheads for all kinds of delivery platforms, said Mansoor Ahmed, a lecturer at Quaid-e-Azam University here who specializes in nonconventional weapons and missiles.

    “Theoretically, 1 kilogram of weapons-grade plutonium boosted with 4-5 grams of tritium gives a 10-20KT yield, provided the trigger is sophisticated,” Ahmed said. “However, the diameter size of Nasr suggests that the warhead would be less than 1 kilogram, and would be of sub-kiloton range, suitable for battlefield use and could be a fission boosted sub-kiloton fission device.”Pakistan will now “not accept any cap in plutonium production in the foreseeable future,” he said.

  7. Gregory Matteson (History)

    A question for the experts here: Everyone in the linked papers seems to pretty explicitly assume that a “basic” fission bomb is 20Kt.. When I read early histories, and the public record on early Atomic tests, it looks like one or two instrumented tests prompted immediate upgrade of their basic fission bombs to 40+Kt, in all cases. Have I misunderstood the record, or is a refined basic bomb substantially increased in power over a first permutation design?

    • John Schilling (History)

      There are a number of fairly basic enhancements that were understood from the outset but didn’t quite make the cut for the Manhattan project due to extreme schedule pressure. Pit levitation being the most obvious, but also beryllium tampers, alternate lens geometries (2- or 92-point), and so forth. Any emerging nuclear power is going to pick these up fairly quickly, and quite likely have them in place for their first tests and/or weapons.

      However, basic pure-fission weapon design operates in a three-dimensional trade space: weapon yield, weapon size, and fissile content. To boost the yield you have to either add more fissile material, or add more high explosives to the implosion device, or add cleverness substantially beyond the first-generation techniques just described. And if you’ve got that cleverness, you can just as easily use it to generate the same yield with reduced mass and/or fissile content.

      Historically, early nuclear weapons development was carried out by people who were planning to use heavy bombers to deliver the things, which took weapon mass out of the equation (at least for the strategic-weapons people). The really huge fission devices were probably not a cost-effective use of limited HEU/WGPU inventories, but ~50 kilotons or so might be the sweet spot when you don’t care that your bomb will weigh a ton or more.

      If the weapon has to fit in the nose of a typical short- or medium-range ballistic missile, and if your enrichment cascade has to fit in a cave somewhere, then 10-20 kilotons is probably about right. Big enough that there’s no risk of a complete fizzle, big enough that nobody will dismiss it as “not really a proper nuclear weapon”, but limited use of scarce fissile materials and still fits the delivery system.

      The North Korean 4-kiloton test, and the uncertain but low yield of the 1998 Pakistani tests, are somewhat interesting. Either an attempt to push “small but not too small” to the very limit, or an underperforming attempt at a 10-20 kt design, or both.

    • Alex W. (History)

      The 20-to-40 kt jump was accomplished after Operation Sandstone, in 1948. Sandstone tested a number of new features for bomb design, some of which had been developed during World War II but not adopted into the first bombs because of their design freezes and their emphasis on getting them out the door as soon as possible.

      According to Hansen and Sublette, the features tested at Sandstone were, more or less: 1. levitated cores (an air gap between core and tamper which allows the imploding tamper to increase in velocity before beginning compression); 2. U-235 implosion pits (which were apparently a little harder to pull off than Pu-239 pits); 3. composite pits (pits that were Pu-239 and U-235 mixes); and 4. new tamper arrangements.

      The overall effect of #1 and probably #4 were that the efficiency went up — you could either get more blast out of a given amount of fissile material, or use less fissile material for the same blast.

      The overall effect of #2 and #3 was allowing you to use U-235 in the implosion arsenal, which allows easy increase of the stockpile, as well as much better use of U-235. It also gave them more flexibility in their production — if Hanford had to shut down because of pile problems (a major issue in the late 1940s), it wouldn’t mean the whole atomic assembly line had to stop.

      (The Little Boy bomb used 64 kg of U-235, compared to the 9 kg of Pu-239 used in Fat Man. Oppenheimer had suggested, after Trinity, that maybe they should take LB apart and make seven U-235 implosion bombs out of it, but Groves nixed the idea because of the time constraints, among other things.)

      The Soviets similarly first made a Fat Man clone, but their scientists had already come up with clever modifications that seemed to have improved things in the same way Sandstone did. They only detonated the FM clone because Beria insisted that the first one be guaranteed to work.

      I’m not sure though that the Manhattan Project program should be used as a model for anything these days. The technology has changed a lot, the amount in the public domain has changed a lot, and the fact that many things can be made to work is well-known, which takes a huge amount of uncertainty out of the equation (it ceases to be a matter of “can this work?” and instead one of “how do we make this work?”).

  8. Mansoor Ahmed (History)

    There is much that has yet to be made public on the various milestones of Pakistan’s nuclear program and the roles played by Munir Ahmad Khan and A Q Khan. Except for the centrifuge project at Kahuta, uranium exploration, processing, conversion and metallurgy projects,comprising the HEU route, were planned and built by PAEC.

    The plutonium route was entirely PAEC’s work- so was the nuclear weapons design, development and testing. A Q Khan only claims to have carried out one cold test, and no one witnessed it. PAEC carried out the first cold test of a working nuclear device on March 11, 1983. The results were reported to President Zia the same evening by Munir Ahmad Khan. A second cold test was carried out afew weeks later and was witnessed by Ghulam Ishaq Khan, Gen. Arif and Munir Ahmad Khan and the photograph of at least one such test with all three together is now public.

    From that point on, PAEC carried out 24 more cold tests of different weapon designs. As for Khushab- it was on the table since 1973- but was temporarily shelved soon after India’s 1974 test as other fuel cycle projects got the first priority- which were originally conceived under a comprehensive nuclear prepared by the Chairman of PAEC and approved by Mr. Bhutto in May 1972.

    The idea of the Khushab Nuclear Complex, however, was re-activated in 1984,as soon as other projects, like Kahuta, New Labs, CPC, KNFC and those related to nuclear weapons development were completed and made operational.


  9. Anon (History)

    Is there any evidence that the putative fissile material is being made into weapons? Or are they storing it up for possible future use?

    Potential weapons are different from fissile stocks.

  10. Gregory Matteson (History)

    Thanks. I thought this before; the 1 ton size range for a refined full strength fission bomb makes an uncomfortable convergence with the similar 1 ton per bomb proven capability of the fighter-bombers that first tier manufacturing nations provide to everyone else. I recall reading both Pakistani and Indian claims of aerial delivery capability.
    Perhaps it is plausible that they would produce a mix of small weapons for their missiles and yield-optimized weapons to be air delivered? Though I recall that at least early schemes for fighter-bomber delivery of full strength bombs involved lobbing the weapon on a parabolic path to avoid self-immolation; not super accurate.

  11. archjr (History)

    Jeffrey: it seems to me there is no inherent conflict between being “Mr. Minimum Deterrence” and “Mr. Nuclear Supermarket.”

    While AQ’s work carried an indubitable influence on the development of Pakistan’s nuclear forces, it is unclear whether he had any influence on the development of nuclear strategy. This despite the clear impact of technology on choice of delivery systems, and hence on one’s concept of deterrence. In other words, it may be that AQ’s primary influence on Pakistani policy depended on what material he could reliably produce.

    From everything I read, the (less-mysterious-by-the-day) deterrent posture Pakistan has adopted probably had nothing to do with AQ’s views beyond his place in internal councils and friendship with Presidents beginning with Bhutto the elder. Kudos to Krepon and others for shedding light on Pakistani (and Indian) thinking.

    Random thoughts: I always found it interesting that AQ was an engineer (focused on the enrichment plans he stole from URENCO), Munir a chemist (whose charge was the plutonium route), which I think partly explains the differences, that were legendary, between them. Munir became the face of Pakistan’s nuclear program, at least at the IAEA, NEA, etc. Khan’s reputation, before the revelations about enrichment and other weapons-technology transfers outside Pakistan, was that of a competent engineer and a history-making thief.

    Still and all, I selfishly think AQ’s op-ed is important because it lends credence to the view I have held for decades, that Pakistan’s fixation on India, its relationship with China, and its limited resources, have dictated a sufficient and small, if not minimal, role for its nuclear weapons.

    A more personal note: I had coffee with Munir at the IAEA GC every year in the 80’s and 90’s. He was unfailingly polite and very funny. He always spoke fondly of his time in Indiana. Soon after our first talk in Vienna, it became routine for our conversation to begin with my asking where Pakistan’s nuclear weapons were. He would laugh and shift the conversation to the right of Pakistan to pursue, peacefully, all nuclear options. Initially the subtext, later the unspoken context, of our conversations was that Pakistan really had no choice but to go nuclear. I think I first met him in 1981, at which time the Paks’ decision to go nuclear was at least a decade old.

    • archjr (History)

      Forgot to mention that Munir was a staff member at the IAEA almost from the beginning, one of the first from a developing country.

    • Mansoor Ahmed (History)

      Munir was a nuclear engineer trained under the Atoms for Peace Program at Argonne National Laboratory. He served as a reactor design engineer at ANL and AMF-Atomics before moving on to the Reactor Engineering Section of the Nuclear Power and Reactors Division of IAEA in 1958. Urenco was the not the only source of information for PAEC for its centrifuge program. Other sources were successfully tapped and a fair amount of indigenous R&D went in before the stolen designs were anywhere useful for making a prototype centrifuge.

    • archjr (History)

      Thanks, Mansoor. I clearly misremembered.

  12. Anon (History)

    Dear ISIS,
    your exhortations would be more convincing if you also shed some light on the Indian Pu production:

    But alas balance is not your strong suit.