Pyongyang conducted its third nuclear bomb test this past Tuesday, February 12. As usual, the United Nations Security Council denounced North Korea’s behaviour. It goes without saying that world opinion is cold towards North Korea at the best of times. Being the only country to test nuclear weapons since Pakistan and India has not burnished Pyongyang’s reputation.
However, the Security Council’s reaction was quite predictable. More interesting is the question of whether this actually changes anything in northeast Asia and the rest of the Pacific?
The technical details of the test matter in this case. Seismic evidence suggests the explosive yield was considerably larger than the 2006 and 2009 tests. This is important for North Korea, since nuclear tests are not purely political acts. They are important technical exercises, and for North Korea’s weapon engineers, whose 2006 and 2009 tests may have yielded “fizzles” (explosions that missed their yield targets), Tuesday’s explosion (which may have been as half as powerful as the Nagasaki bomb) was an important achievement.
More important to the rest of the world was the size of the device and whether it was made from plutonium or highly enriched uranium.
North Korea’s official news agency (KCNA) claims the test was “of a smaller and light A-bomb unlike the previous ones, yet with great explosive power.” While Pyongyang was remarkably open about the failure of its April 2012 Unha-3 space launch vehicle/ballistic missile test, getting the truth out of KCNA news reports is generally akin to reading tea leaves. However, last December Pyongyang did successfully launch an Unha-3 rocket. This means that Korean miniaturization claims should be taken seriously. Building a nuclear explosive is one challenge. Building one small enough to fit atop a ballistic missile is another thing, and a fairly serious engineering challenge. So far, there is little (if any) public evidence that North Korean engineers have managed that task. But if and when they do, it will mean that North Korea has something approaching a fully militarized nuclear capability. This will certainly raise anxieties in Japan and South Korea, and will probably prompt calls within the US to take a harder line with Pyongyang. At this point North Korea’s claims that they’ve miniaturized their nuclear weapon designs is a serious signal that they are trying to do so, but isn’t evidence that they’ve been successful.
The second technical issue is: what was the bomb made of? North Korea has a limited supply of weapon-usable plutonium, as the 5 MW reactor and plutonium separation facilities at Yongbyon have not been operating for years. North Korea probably had no more than 40 kg of separated plutonium before the February 12 test, and, if the weapon that was exploded on Tuesday was made of plutonium, they now have at least two kilograms less. That would be welcome news, since every gram of fissile material they blow up in tests gives them one less (albeit tiny) bargaining chip at the negotiation table.
If the weapon was made of uranium this is more concerning. It will give us some idea about how well developed North Korea’s centrifuge program is, and it could suggest plans to build a larger arsenal. Given the lack of international monitoring of North Korea’s uranium enrichment program, it is difficult to precisely assess how much uranium Pyongyang is enriching. While North Korea’s uranium enrichment program has been public knowledge for a while now, Pyongyang has claimed that it is meant to fuel civilian light water nuclear reactors. If the weapon proves to be a miniaturized bomb, then we can tentatively conclude that North Korea is well on the way to having a deliverable nuclear weapon. Continue reading