Aaron SteinNorth Korea Tested an H-Bomb?

North Korea tested a nuclear weapon, claiming it was an H-bomb. Was it? Aaron Stein returns to talk with Jeffrey about North Korea’s nuclear weapons program.


  1. bob (History)

    H-bombs per se won’t be affected by this development


    however a cheap and unconrollable source of heavy water may have other effects.

  2. Ben D (History)

    Who is to say…. I find this a realistic opinion though…”Why North Korea’s Claim That It Has a Hydrogen Bomb Is Worrisome” by Bruce Klingner, a senior research fellow for Northeast Asia at The Heritage Foundation’s Asian Studies Center, spent 20 years in the intelligence community working at the CIA and Defense Intelligence …http://dailysignal.com/2015/12/10/why-north-koreas-claim-that-it-has-a-hydrogen-bomb-is-worrisome/

    • Jeffrey Lewis (History)

      Bruce is great. One of my favorite people.

  3. tobiaspiechowiak (History)

    Does anybody has a magnitude – yield regression function for this type of soil, or anybody knows where to find it?
    I recall there was a similar discussion regarding anyother test?

  4. Tobias Piechowiak (History)

    So I read sonething about 9 kT yield…the magnitude responses look like those from the 2013 test..
    Can anybody confirm that?

    • Jeffrey Lewis (History)

      There are number of equations used for calibrated test sites that can applied by analogy. For those who have tried to model the DPRK test site, a popular equation is:

      mb = 1.0125 log (Yield in kt) − 0.7875 log (overburden in m)  + 5.887

      The equation includes a parameter for depth of burial because the DPRK tests may be heavily overburied. This can have a significant effect on yield.

      So, for example, using Mb=4.9-5.1, one gets a yield range of 7-18 kt with 200-400 meters of overburden.

  5. J_kies (History)

    I rolled numbers and if you believe that the 4.7 Magnitude event in 2009 was likely 4-6kT as reported then both the 2013 and 2016 events at 5.1 (USGS) magnitude then the similar uncertainty gives most likely yields between 10kT and 15kT. The ‘miniaturized atomic bomb’ and the ‘H-bomb’ were effectively indistinguishable.

  6. cthippoCthippo (History)

    Between North Korea and Iran, It’s been a good week to be a wonk!

    Couple of thoughts on this…

    While they may build test devices, they’re not going to build a production warhead that they can’t deliver which puts a hard upper limit on the physical dimensions and weight of the warhead. To some extent this means that North Korea is going to have to work harder than other countries which have developed nuclear weapons, but had bombers with big bomb bays to deliver them. Even the US with it’s essentially unlimited production and testing ability took over a decade to build a warhead that would reliably work in a missile. On the one hand, the NKs have an advantage because it’s been done before and so they have some hints as to how to do it, but it still means they have a lot of work to get to a deliverable weapon .

    The other thought is that tritium production for boosted weapons really eats into your plutonium production. I can’t remember the exact numbers off hand, but for every gram of tritium you produce, you give up 4 or 8 grams of plutonium production. Given that North Korea only has one operating reactor, this is a big argument for them using uranium in their weapons. Tritium also has a relatively short half life of 12.7 years and the isotope it decays into (He3) is a nuclear poison, so while plutonium will last forever, you have to keep making tritium because it goes bad fairly quickly. Not an issue for test devices, but a real headache for maintaining a stockpile.

  7. Ben D (History)

    Jeffrey….the news from media outlets around the world after the first day put the earthquake/detonation at Punggye-ri, at a depth at10 Km, based on official USGS measurements. USGS are now saying it was at 0 Km.. If it were to have taken place at 10 Km depth, what would be the approximate yield?

  8. Cthippo (History)

    Further thoughts, now with added caffeine!

    Assuming that this is indeed a program with a goal of a missile deliverable three stage thermonuclear weapon then they’re going about it differently than how other nations proceeded, but still in a logical manor. I think that a lot of people are subconsiously assuming that because the history of the North Korean tests doesn’t look like the history of everyone else’s tests then their program is going badly. I think this is a flawed assumption based on a misunderstanding of the circumstances surrounding historical nuclear programs.

    First off, as I mentioned above, nobody builds a weapon they can’t deliver. The Fat Man and Little Boy and RDS1 were the size they were because the nations that built them could (barely) deliver 5 foot diameter, 10,000 lbs bombs. North Korea can’t deliver such a device and so was now going to build one. The physical constraints of their warheads dictates the size and characteristics of their bombs.

    Secondly, the US, USSR, Great Briton, France, etc set out to build deliverable atomic bombs. North Korea set out (I’m postulating) to build a fission primary for a thermonuclear weapon, which is not the same as fission weapon. Primaries typically have a yield in the 5-10kt range because that’s all the bigger they need to be to do their job and you get a lot more yield out of an extra kilogram of secondary than you do out of an extra kilo of primary. When you’re building giant bombs to drop out of airplanes, who cares, but when every kilo counts, as in missile warheads, you don’t over-engineer more than you need to.

    It’s for exactly this reason that modern primaries are normally boosted, despite the extra complexity and maintenance to keep replacing the tritium. The boosting isn’t so much about extra yield, but about achieving the same yield in a smaller and lighter package.

    If this were the case then North Korean claims of a thermonuclear weapon test that looks exactly like their previous fission weapons tests would make sense. If their goal is a deliverable three stage weapons, then successful test of a boosted primary with the same yield would be a necessary technological milestone along the way. Their milestones look different that our historical milestones because they are pursuing a different goal now then we were then.

    So if this is the case, where does their program go from here? Bang, mostly. The next technological step towards a staged weapon is to demonstrate that their primary design can successfully ignite the secondary. The theory of radiation implosion has been around for 65 years now, but I’ve heard that staging, especially close to the minimum energy threshold, can be tricky You can bet they won’t mess with cryogenic fuels, but will jump straight to small quantities of solid fuel. These tests will necessarily have higher yields, but perhaps not so much higher that they will stand out. I think North Korea can confidently develop a multi-stage weapon without testing it full scale, but it will probably take a number of further tests similar to the ones we’ve seen so far to develop that confidence.

    In addition to development tests, they will also have to do a certain amount of reliability testing. At some point they will want to know if their weapon is one-point safe and just how roughly you can handle it before something important breaks. This process will require probably at least one or two more detonations before they are ready to field their warheads.

    So, if all goes well for the North’s program, expect to start seeing bigger, but not necessarily huge, tests followed by an announcement of operational capability in the next 5 years or so. A full scale, possibility atmospheric, test could happen, but is probably not a necessity to developing a reliable, deliverable warhead. Whether they test at full scale is going to depend on the political calculus of how much they feel they have to prove it to us versus how much they are willing to irritate (and irradiate) China and potentially Russia.

  9. Arun Vishwanathan (History)

    A technical analysis of the North Korean nuclear test can be read at the link below