Reports that North Korea has launched a fourth nuclear weapons test—backed by convincing seismic data—have caused widespread alarm. North Korean officials announced in advance that the test would involve “a totally different type of nuclear bomb“ from those trialed in previous years. Following the test, North Korean state television lauded the first detonation of a ”hydrogen bomb“ as a ”national epoch-making event.”
Moving to a new form of nuclear weapons technology will likely have significant implications for North Korea, although some experts have expressed skepticism about these claims and there are clear benefits for Pyongyang to exaggerate its nuclear capabilities. While details of the test will remain unclear for some time, the term “hydrogen bomb” is also somewhat ambiguous, leaving further room for speculation about the true nature of North Korea’s nuclear technology.
Fission Devices
There are two basic types of nuclear weapons: fission weapons and fusion weapons. First developed during World War II through the U.S.-led Manhattan Project, fission devices (commonly known as atom bombs) create an explosion by splitting the nuclei of heavy atoms. These types of weapons were dropped on Hiroshima and Nagasaki in Japan, killing hundreds of thousands of people.
The core of a fission weapon is composed of weapons-grade fissile material such as highly enriched uranium or plutonium, which on its own is not explosive. When detonated, this core is compressed using conventional high explosives into a critical mass capable of sustaining a nuclear chain reaction.
Firing neutrons at the atomic nuclei in the core causes them to split (or fission) into several lighter nuclei, releasing energy and, crucially, more neutrons. These extra neutrons create further fissions in the core that, in turn, release even more neutrons giving rise to a self-sustaining chain reaction. This releases huge quantities of energy, many orders of magnitude greater than that of conventional explosives.
