Conveniently, North Korea’s latest nuclear test came just as my Nuclear Weapons and Power class was coming to the section on proliferation, so of course it has me thinking. But I don’t have a fully coherent set of thoughts that would support one of my typical overly-long and involved posts. So here’s some undigested, or perhaps half-digested, thoughts.
- The biggest obstacle to countries trying to develop nuclear weapons is access to highly enriched uranium. North Korea has access to uranimum–their mines are estimated to contain over 1/4 million tons (up to 4 million tons of uranimum ore with about .08 extractable uranium). They also have the means to enrich that uranium
- Once a country has highly enriched uranium (HEU), building a basic bomb is shockingly simple. Simply dropping one piece onto another or holding one in each hand and clapping will create a substantial nuclear explosion. A gun-type bomb (the Manhattan Project’s “Little Boy” design) is simply a gun barrel in which conventional explosives slam one piece of HEU into another at high speed. Its simplicity is so great that no testing is necessary. The Manhattan Project did not bother to test this design, and South Africa’s nuclear program focused solely on the gun-type bomb so that they would not have to bother with testing. And all their equipment for the program was essentially off-the-shelf, available for commercial purchase. They never had more than 150 people involved at any time, and spent a total of around $25 million. In the 1960s Lawrence Livermore Labs conducted the “Nth Country Experiment, recruiting 3 recent Ph.D. in recipients who had no previous nuclear weapons design knowledge, to see if they could design a workable atomic bomb. The young physicists did, but notably they focused on developing a plutonium (implosion, or “Fat Man,” style) bomb, because they decided that designing a gun-type bomb was too easy, did not give them enough of a challenge. But while gun-type bombs are distressingly simple, they are at least less destructive than plutonium (although still shockingly devastating, as the bomb dropped on Hiroshima demonstrated).
- With some superficial searching I can’t find much in the media about what type of bomb the DPRK is trying to develop, but it appears to me to be an implosion, plutonium, bomb. Gun-type bombs don’t work with plutonium, because as the pieces are accelerated toward each other they will begin reacting too soon and bleed off too much potential energy to achieve the desired explosive level, so an implosion design is necessary. The technological trick here is to shape the explosive charges so that the plutonium sphere compresses equally. Imagine compressing a water balloon with simultaneous and equal pressure across its whole surface. Failure to do this well will result in a “fizzle,” an incomplete explosion. North Korea’s first test in 2006 seems to have been a fizzle, which they surely wouldn’t have resulted if they were using a uranium gun-type bomb. The fact that they are bothering to test may also indicate they’re building plutonium bomb, although it’s also possible they’re using the tests for political purposes as much as, or conceivably even instead of, technological ones.
- North Korea’s second test in 2009 was estimated at 2-6 kilotons, and the latest test was estimated at 6-7 kilotons. For comparison, Fat Man’s estimated yield was 18-23 kilotons (and our first hydrogen bomb was 10-12 megatons). Consequently, I’ve seen some media claims that we shouldn’t worry much because DPNK’s bombs aren’t very big. But here’s another comparison–America’s battlefield tactical nukes are low yield devices, running as low as .72 kilotons, only 1/10th the size of DPNK’s latest effort. If North Korea doesn’t yet have a true strategic nuclear weapon, it at least has some really kick-ass tactical nukes.
- Do we really need to fear DPNK using their bombs? I don’t think so. Even assuming their rocketry was sufficient to enable a strike on the U.S., there would be no hiding the action, and our retaliatory capacity would be left wholly intact. They can reach Japan, for whom they have no love, but the same logic applies. Nor will they strike China, which is their grudging patron (primarily because DPNK acts as a buffer against South Korean based U.S. aggression). The only possibly logical target is Seoul, and perhaps they hate the South Korean government enough to try that, but again that leaves U.S. retaliation a possibility, and not only do we have a long-standing commitment to South Korea’s security, but we have a military garrison there–an attack on Seoul would be an attack on the U.S. military. It seems to me that DPNK’s purpose is defense against potential U.S. aggression. And it beggars imagination to hypothesize that they haven’t internalized the lesson of the U.S. response to Pakistani and Indian nukes, which is, shall we say, not entirely in compliance with the Nuclear Non-Proliferation Treaty.
- The real purpose for trying to stop DPNK’s nuclear weapons program is not the direct threat they pose but to keep moving the world toward total nuclear disarmament. Under no circumstances could North Korea’s nuclear weapons program pose an existential threat to the U.S. Even if we abandoned all our nuclear weapons, and North Korea struck us with all of theirs, we would retain such massive convention capacity that we could overwhelm and destroy their military and government; and our allies would not hesitate to help us. DPNK nuclear action could only stimulate the creation a coalition of the really goddammed eager. Nevertheless, getting rid of all nuclear weapons is the only way to ensure that no other countries continue to seek them. The Canberra Commission on Nuclear Weapons termed this the “axiom of proliferation:” “The possession of nuclear weapons by any state is a constant stimulus to other states to acquire them.”
- The U.S. has limited political capital for arguing against nuclear weapons development and testing. We are signatories to, but have never formally ratified, the indefinite extension of the Nuclear Non-Proliferation Treaty and the Comprehensive Test Ban Treaty. On the plus side, although we are not formally bound to the Test Ban Treaty we have not conducted any nuclear tests since before it was negotiated.