A new analysis suggests North Korea likely achieved significant advancements in miniaturizing nuclear warheads and enhancing designs during its six previous nuclear tests. Consequently, experts speculate that a seventh nuclear test may not be necessary for further technological improvements.
38 North, a North Korea-focused media outlet operated by the U.S. think tank Stimson Center, reassessed the country’s previous nuclear tests. Their analysis concluded that North Korea may have secured a considerable level of warhead miniaturization and design enhancement after conducting three to four tests. Notably, they believe the sixth nuclear test in 2017 likely involved testing a completed boosted fission bomb, a key technology for missile deployment.
38 North characterized the first and second nuclear tests conducted in 2006 and 2009 as experiments with limited explosive power, but still valuable. The report suggests that advanced design concepts, such as the levitated core developed through the Manhattan Project to increase explosive power, might have been applied to North Korea’s nuclear tests. This indicates that North Korea may have sought to enhance efficiency and reduce warhead size from the outset.
The analysis noted that starting with the third nuclear test in 2013, North Korea officially began mentioning miniaturization and lightweight design. The fourth and fifth nuclear tests conducted in 2016 likely involved experiments related to boosted fission bombs or improved fission warheads aimed at increasing explosive power.
38 North interpreted this process not merely as a technological upgrade for explosive power but as a design enhancement process aimed at missile deployment. This analysis suggests that the miniaturization and standardization of nuclear weapons, based on strategic operational considerations, may have progressed incrementally through the six nuclear tests.
Notably, the explosive power of the sixth nuclear test conducted in September 2017 is estimated to be in the range of tens to hundreds of kilotons (kt), which aligns with North Korea’s claim of a thermonuclear weapon designed for intercontinental ballistic missiles (ICBMs).
38 North emphasized that the sixth test likely involved experiments related to a completed boosted fission bomb, suggesting that North Korea may have developed the capability to control warhead output. This implies that Pyongyang has accumulated significant design capability for warheads applicable to various missiles.
Consequently, even if North Korea is preparing for a seventh nuclear test, 38 North predicts it will serve more to verify performance and evaluate new operational concepts rather than to enhance warhead-related technology. It may involve practical verification of the tactical nuclear cartridge Hwasan-31, which has already been declared complete, or testing a multiple independently targetable reentry vehicle (MIRV) system capable of attacking multiple Targets with a single missile.