Geoff FordenDPRK: Practicalities of Interdicting WMD

UNSC Resolution 1874:

12. Calls upon all Member States to inspect vessels, with the consent of the flag State, on the high seas, if they have information that provides reasonable grounds to believe that the cargo of such vessels contains items the supply, sale, transfer, or export of which is prohibited by paragraph 8 (a), 8 (b), or 8 ( c ) of resolution 1718 (2006) or by paragraph 9 or 10 of this resolution, for the purpose of ensuring strict implementation of those provisions;

With the passage of UNSC resolution 1874 last Saturday, a young techno-wonk’s thoughts immediately turn to the question of how do you have reasonable grounds to stop a ship on the high seas. (I hope to look at the legal questions in a future post, after I finish with these practical details.) We will only consider some of the issues related to nuclear proliferation here. Some rough numbers immediately jump to mind. These include things like: how many centrifuges can you ship in a single cargo container? How many centrifuges fit on a single ship? What is the “background” to detecting such a ship? (Background in the physicist’s sense: is there a lot of shipping going into and leaving North Korea that could “mask” the WMD ship?) Could you detect the loading of a ship using photoreconnaissance satellites? UAV’s? How could you track it? So here goes:

1) How many centrifuges fit in a cargo container? Libya’s centrifuges were packaged in boxes roughly 2m by 0.6 m by 0.3 m. (All these numbers are rough. We just don’t need better accuracy, as you will see.) We know from images released by the US government that two outer casings were shipped in each box. Since you cannot ship the rotors already in the centrifuge (it damages the ball bearing the rotor rests on; P-1 designs are assembled on site), there is probably another box with two rotors in it that was not shown for nonproliferation reasons. If we assume roughly the same size of box, that means that a standard shipping container (which is roughly 14.6 m by 2.5 m by 2.5 m) could carry, on average, 96 complete centrifuges.

2) How many centrifuges onboard a cargo ship? If you look at the port of Rajin, there is a bulk cargo ship at the only Port in North Korea that I have seen (see North Korea Economy Watch ) with port-based cranes whose below-decks storage area measures roughly 112 × 25 × 21 meters so it could fit 630 such cargo containers below decks. That means a grand total of 60,480 centrifuges could be carried onboard a single ship. Since, as Alex Glaser has shown in his wonderful paper Characteristics of the Gas Centrifuge for Uranium Enrichment and their Relevance for Nuclear Weapon Proliferation, Libya’s design for a “cascade interconnect” bomb factory needed only 5800 centrifuges to enrich over three bombs worth of weapons grade uranium from natural in a year. That would fit in about 61 cargo containers. Clearly, a single ship can pose a significant proliferation risk!

Tomorrow, we will consider some of these other questions.

Update (6 pm): The New York Times reports that the US will not board by force any ships sailing out of North Korea. That was clear from the wording of the resolution: “with the consent of the flag State.” I wonder how many, if any, ocean-going carrier vessels North Korea has. Does anyone know of a publicly available list of ship flagging? My guess would be nearly zero ships owned by the DPRK.


  1. Lisa Simpson (History)

    Not that it changes your calculation, but…

    The 4000 Libyan “centrifuges” were just outer casings. Getting the rotors formed was one of the obstacles they were running into.

  2. Sharon Squassoni (History)

    Thank you for that public service, Jeffrey! I’m guessing that a recipient wouldn’t risk its whole program in a single shipment, nor could the North Koreans crank out that many centrifuges at once. So we’d probably be looking at multiple, smaller shipments over time, perhaps using different kinds of transportation and routes. If the IC is lucky, they’d get wind of some test centrifuge shipments (even if they couldn’t stop them) and be on the lookout for more. Another practical consideration is how to get such a ship into port where it could be completely unloaded. My guess is that the good stuff would not be easily accessible. So you need reasonable grounds to inspect a ship that is flagged by a country that complies with the UNSC resolution provision that it will direct the ship to a port that has the appropriate capacity and will to comply.

  3. Pavel

    The main practicality is that no inspection can happen without NK consent.

  4. V.S. (History)

    Dear Geoffrey,

    you picked up an interesting issue. Could you repeat the same calculations for airoplanes, particularly airliners, that are also covered by PSI. (cough-Air cough-Koryo)

    Thank you.

  5. Geoff Forden (History)

    Pavel, Not necessarily with the North’s consent. It certainly has to have the consent of the nation whose flag the carrier vessel is flying but my guess is that is not North Korea. (Please see the update that I’ve just entered.)

  6. V.S. (History)


    Actually under paragraph 11 of the 1874 Resolution even North Korean vessels (sea-faring or air-faring), in theory cannot escape inspection as long as they are in the territory of a state that intends to honor its obligations under Resolution 1874.

    Of course, in order to avoid interception in a “play it safe way”, a vessel loaded with “goodies” would only have to go from the national waters of the sender, through high seas, to the national waters of the recipient. But then at least the trail is more obvious. In the case of the Khan network and the shipment to Libya, they tried to cover their trails by using a hub (Dubai). With a binding Resolution like that, its more risky for them to do the same. And its more risky to trust a vessel under foreign flag also.

    So now with the Resolution in place at least they would have to expose their dealings, because it would be prudent:

    1) To use a ship of their own (or of the recipient state, if the recipient is indeed a state and not a non-state actor)

    2) To “set sail” directly from the sender (DPRK) to the recipient.

    Even if North Koreans don’t give a dime for the Resolution, I cannot think of many potential recipients that would do the same.

    So, I think that given the circumstances, the Resolution contains the DPRK pretty well.

  7. blowback (History)

    The North Koreans can just go out, buy a ship (there are a lot going spare at the moment and some won’t cost a lot) and reflag it as North Korean. Who can touch it then?

    BTW, we should not forget the infamous ‘cement ship’ that was ‘used’ to transport reactor parts from North Korea to Syrian. It was still shuttling between Egypt and Syria transporting ‘cement’ and it was still flagged as South Korean the last time I checked so why haven’t the USN, ROKN or ISC stopped it and inspected its cargo?

  8. Geoff Forden (History)

    V.S., If they used a 727-200F (and I have no idea if they have access to such an aircraft) I think it could carry 275 complete centrifuges.

    There is a certain amount of uncertainty here. It is possible that this is the lift capacity of a 727-200 cargo bay below the passenger deck. I can’t verify that it is the “f” variant.

  9. Rwendland (History)

    On practical details, if you did stop a mid-sized container ship at sea, is there a reasonable way to get to a particular container boxed in the middle of a hold or stack to inspect it? Wouldn’t you need to re-arrange the containers, which does not sound practical at sea?

  10. V.S. (History)

    Thank you for taking the time to calculate Geoff.

    I insisted in airplanes, because I remembered an article in Reuters making reference to a recent study by Hazel Smith, a DPRK expert, coming to the coclusion that it was more likely that NorKs use airplanes.

    Well, Air Koryo, the state-owned airline company of North Korea, and of course the only airline company of our beloved DPRK, has Russian airliners, (Illiushins, Tupolevs, Antonovs etc.) My source is wikipedia that in this case I think must be accurate.

    And I guess that the number of centrifuges that potentially could be carried wouldn’t be much bigger than the number you mention (475).

    I also remember another incident, that took place on August 7th, 2008, reported a couple of months later though, that received little attention back then.

    According to Aswakumaran Vinod Kumar, an Associate Fellow at the Institute for Defence Studies and Analyses, New Delhi:
    (the following excerpt is taken from

    “On November 1, The Wall Street Journal confirmed that India might have blocked a North Korean Air Koryo aircraft from delivering cargo to Iran on August 7 following a request by Washington, which feared it might be carrying materials related to weapons of mass destruction (WMD).
    The Journal, quoting US administration officials, said the North Korean jet stationed in Mandalay in Myanmar was initially given permission for overflying Indian air space by the Kolkata Air Traffic Control (ATC), but was subsequently denied over-flight after instructions from the [Indian] Directorate General of Civil Aviation (DGCA).”

  11. spaceman africa

    This old article covers some other angles:

  12. Andy (History)


    There are a few subscription-based ship information services available. One with a lot of “free” info is here but I doubt these public lists are complete. Proliferators often change ship names and take other measures to making tracking difficult.

  13. Geoff Forden (History)

    Thanks Spaceman! Interestingly enough, the legal aspect means that the country under which the ship sails is the one who, at least according to the UNSC resolution, is the country that gives permission to stop and search. On the political side, I wonder what North Korea would say if a country that flagged a North Korean ship gave its permission to board a ship owned by the DPRK.

    Andy, Thanks very much for this website! Here is the displacement weights for those flagged under North Korea:

  14. chris green (History)

    The Hazel Smith report mentioned by V.S., “North Korean Shipping,” can be found at;

    It shows a surprisingly diverse shipping sector, a broadly, inadvertantly, but opaquely privatized industry, and a sum total of 242 ships owned by North Korea, of which a modest but not insignificant number are multi-purpose ocean going cargo vessels. It also pretty much discounts and to an extent scorns the notion that North Korea would use its shipping fleet to transport WMD materials at this point, given how often its ships are stopped and checked simply because they are a) North Korean, and b) in fairly poor condition.

  15. Lab Lemming (History)

    Australia seized, and then eventually released a DPRK cargo ship last decade when it was caught making drug shipments in Australia waters. So they have cargo ships and a history of using them for illicit activities.

  16. Josh (History)


    Wouldn’t the devices be going to NK, not from NK, at least at this stage?


    Legalities aside, I’d suggest that “reasonable grounds” for an interdiction would bear some relationship to confidence that the item(s) of interest are actually onboard. Otherwise, it gets embarrassing. This is an iffy business: the Yinhe incident reportedly involved a copy of a shipping manifest, but the precursor chemicals believed to be onboard turned out not to be, after all.

    For this reason, denying airspace to a plane is a comparatively low-risk action. Here’s the original WSJ article referenced by V.S.

  17. Geoff Forden (History)

    Josh, Today I am going to start considering how to tell whether or not there are proscribed items on board. This post was meant to set the stage by getting a feel for the magnitude of how much could be on a ship. (And thanks for giving me an opportunity to explain that!)

  18. Allen Thomson (History)

    With regard to that NK ship putting into Tartus on 3 Sep 2007, David Sanger made a slightly curious statement in a NYT article yesterday:

    U.S. to Confront, Not Board, North Korean Ships
    Published: June 16, 2009

    American officials believe that previous North Korean shipments of nuclear technology and missiles have gone undetected. The North Koreans were deeply involved in the construction of a reactor in Syria until September 2007, when the reactor was destroyed in an Israeli air raid. But no ships or aircraft carrying parts for that reactor were ever found.

  19. Matthew Hoey (History)

    Nice piece as always Geoff.

    I found these numbers:

    total: 167
    country comparison to the world: 39
    by type: bulk carrier 11, cargo 121, carrier 1, chemical tanker 4, container 3, passenger/cargo 3, petroleum tanker 19, refrigerated cargo 4, roll on/roll off 1
    foreign-owned: 19 (Egypt 1, Greece 1, Lebanon 1, Lithuania 1, Romania 4, Syria 1, UAE 8, Yemen 2)
    registered in other countries: 2 (Mongolia 1, Panama 1) (2008)

  20. Allen Thomson (History)

    > But no ships or aircraft carrying parts for that reactor were ever found.

    The meme seems to be going around:,8599,1905098,00.html

    Will Offshore Searches Slow North Korean Nukes?
    By Mark Thompson / Washington
    Wednesday, Jun. 17, 2009

    But Pentagon officials also acknowledge their track record on monitoring North Korea shipping leaves something to be desired. Pyongyang played a major role in the development of a nuclear reactor that Syria was building until the Israeli air force bombed it into rubble in 2007. U.S. intelligence never has been able to identify what North Korean ships, if any, were involved in its construction. Which raises a troubling notion: North Korea’s nuclear know-how may be able to elude even the tightest naval noose.

  21. Miles Pomper (History)

    Interesting piece, as always.
    Two things:
    1)The key part of the resolution is that states are not supposed to allow NK vessels to refuel if they are suspected of having proscribed items on board. Presumably this limits the range of any shipping, particularly if it not intended to be direct.

    2) Do you really think NK is going to ship whole centrifuges or centrifuge parts? It would make more sense to just ship HEU, no? At this point they should be importing/not exporting centrifuges or manufacturing them for domestic use.

  22. Geoff Forden (History)

    Hi Miles,

    Thanks for your comments! As to your points, let me just say a couple of things. First, they still need “reasonable grounds” before they refuse to refuel ships either flagged to North Korea or shipping North Korean cargo. These posts are intended to explore how that “reasonable grounds” are determined. As to simply shipping Pu or HEU, that is not what they apparently did with Syria. If anything, they shipped a complete reactor to that country. (And, of course, we can reasonably expect the DPRK to want its own enrichment facility. All these considerations apply to both importing and exporting.)

    I picked a complete centrifuge plant to illustrate the magnitude of cargo problem as well as a convenient yardstick to compare various scenarios with. This way we have a nice, well defined task that can quickly and easily be broken down in your head to multiple shipping. Thus for instance, in the next posting we see it takes five hours (or less, depending on the North’s loading efficiency) to load a complete bomb factory onboard. We will compare that to how often a spy satellite flies overhead.

    Of course, if they were asking me for advice on the best way of acquiring and assimilating enrichment technology, I would tell them to start with a handful of centrifuges imported from a foreign source as well as their manufacturing line. They could then play around with ten or twenty centrifuges (a lot less than one shipping container and even much less than a 727-200 load) in either one or two stages. This is what Iran has done and they have been very successful in assimilating the technology. But sometimes proliferators do not want go this systematic route. Iraq, for instance, torpedoed its own attempt to import a complete VX plant from Pfaudler Corporation of Rochester, New York by insisting on an industrial scale plant rather than the pilot plant (for production of Amiton, which bears a striking similarity to VX).

  23. SW (History)

    A successful non-consensual boarding of a NK cargo ship Pong Su (registered under a Tuvalu flag) on the high seas by Australian Special Forces in April 2003 is quite instructive, even though it was not done in the proliferation context. Google ‘Pong Su’ or ‘Operation Sorbet’.

    The Pong Su was eventually used for bombing practice, and spectacularly sunk in deep water 140km off Jervis Bay NSW on 23 March 2006, by two 2000lb. laser guided bombs from a RAAF F-111. Note that Pong Su was found to have been modified, with additional fuel and water tanks fitted to enable very long range voyages without refuelling or reprovisioning at foreign ports.

  24. LAC (History)

    I’ve enjoyed your series of pieces on these related issues. With reports today that the Kang Nam is heading toward Burma, what’s the likelihood it can make it all the way there without having to refuel in Singapore or elsewhere? Is it possible if we assume refitting as with the Pong Su?

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