FOI has assessed that today, as previously announced, North Korea conducted its second nuclear weapons test.

"Based on seismic measurements taken at the FOI seismic station in Hagfors, together with measurements from the international monitoring system, the magnitude was approximately 4.5 on the Richter scale,"  says FOI research leader, Anders Ringbom, who is one of those responsible for monitoring nuclear weapons tests. The test was conducted at 02.54 local Swedish time in the same area as the first test in October 2006, i.e. approximately 40 km northwest of the city of Kilchu. The blast had a yield of approximately 2-5 kilotons, which is several times greater than the test in 2006.

"It is reasonable to assume that this test was also conducted in a tunnel under Mant'ap-san Mountain and that at least some radioactive inert gases, such as xenon, have leaked out. These gases are not dangerous to the surrounding area, but with sensitive measuring devices, they can be detected very far away. Unlike in 2006, today, there are two FOI-developed systems in the region that can detect and measure xenon gases and FOI participates actively in such efforts," concludes Anders Ringbom.

Background
FOI leads an assignment from Sweden's Ministry of Foreign Affairs to monitor nuclear weapons tests, in accordance with CTBT, the Comprehensive Nuclear-Test-Ban Treaty. The FOI seismic station in Hagfors is part of a worldwide network of seismic stations. FOI also has a measuring station for xenon located in Stockholm.

Following North Korea's first nuclear test in 2006, FOI's experts provided South Korea with assistance in the form of equipment and analyses in order to confirm that a nuclear test had actually taken place.