This morning North Korea announced that it had conducted a third underground nuclear weapons test. The test was detected by US Geologic Survey (USGS) seismic-monitoring stations and those of the Comprehensive Test Ban Treaty Organization in Vienna, which reported “explosion-like characteristics”. The yield of the test is believed to be roughly 3–10 kilotonnes, according to James Acton, a physicist at the Carnegie Endowment for International Peace in Washington DC.
In a statement from the Korean Central News Agency, North Korea claimed that the test was of a “smaller and lighter A-bomb”. The bomb performed as expected, “demonstrating the good performance of [the country’s] nuclear deterrence that has become diversified”, according to the statement.
North Korea did similar tests in 2006 and 2009, but this one seems to have been more successful than either of the previous attempts. The 2006 test was widely believed to be a “fissile” ‘fizzle’, in which the nuclear material failed to ignite completely, and the 2009 test appeared to be at least partially successful. The USGS put the magnitude of the seismic event associated with the latest explosion at 5.1, several times as powerful as the 2009 test.
A crucial question is what kind of bomb was tested. To date, North Korea has worked only with plutonium, but some believe that the country might be close to testing a uranium weapon. Other arms-control analysts have speculated that the bomb might contain a fusion component to boost its power.
The test comes just two months after North Korea successfully launched its first satellite into orbit.