How Many Bombs Can North Korea Make?

Earlier this week, a small earthquake was noted in North Korea, and Twitter speculation turned to another North Korean nuclear test. It turned out not to be, but Robert Farley (@drfarls) made an interesting point.

North Korea has a limited amount of fissile material, the enriched uranium or plutonium that is necessary for nuclear bombs. How significant is the amount used in a test? Are they depleting this limited supply?

Marcy Wheeler (@emptywheel) asked what that supply was and how many bombs they might make from it.

I went to a talk today by Siegfried Hecker, former director of Los Alamos, who has visited North Korea several times and seen parts of their nuclear program. He knows those numbers better than anyone, although North Korea is so secretive that even his numbers are estimates verging on guesses.

Hecker’s estimates for North Korea’s current inventory is 30-40 kilograms of plutonium and a “couple hundred” kilograms of highly enriched uranium. The Nagasaki bomb contained 6.2 kilograms of plutonium; the Hiroshima bomb, sixty-some kilograms of highly enriched uranium. Hecker said that modern designs use less, so let’s say 4 kilograms of plutonium or 40 of enriched uranium.

That is enough material for maybe 10 plutonium bombs and maybe 5 uranium bombs. Probably enough, depending on how the North Koreans judge such things, to spare for an occasional test. That material also has to be formed properly and fitted with conventional explosives, detonators, and electronics. North Korea’s capacity, in personnel and facilities, to build such things would also limit their numbers of nuclear weapons.



  1. Alex W. · March 18, 2016

    One small thing — if they had the knowledge to do so, they can presumably economize fissile material by mixing HEU and Pu into composite bombs. It would be a smarter way to use their HEU than as pure-HEU bombs, in any case — composite bombs with Pu pits surrounded by a little HEU give better bang for the buck than pure HEU (taking advantage of the Pu’s spontaneous fission rate, or something like that), or so I have been led to understand by various declassified documents. I don’t have any quantitative understanding of how many more bombs that might stretch it out to. I don’t think it changes the basic quantity much.

    I wonder how the government analysts rate the pros and cons of each test. Pro, destroys a possible bomb that could be used in the future, perhaps buys some more time until they have a larger arsenal. Con, might give knowledge/experience that could increase the effectiveness of any future bombs…


  2. Mark Gorwitz · March 28, 2016

    North Korea has the capability to perform core or tamper boosting using either solid or gas systems. They have had the ability to produce Li6 for a number of years.


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