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Nuclear weapon test in North Korea

FOI has determined, on the basis of seismic data, that on January 6th North Korea conducted a nuclear weapon test, the fourth since 2006.

North Korea continues to develop its nuclear weapons program, in defiance of several UN resolutions that prohibit the country from developing nuclear arms, warheads and delivery systems, especially missiles. But, in spite of international sanctions and long-standing attempts to delay North Korea’s efforts, little is known about the country’s actual nuclear weapons capacity. This makes the information that can be collected from its weapons tests an especially important contribution to the overall knowledge about its nuclear weapons program.

Based on readings from FOI’s seismic measuring station, in Hagfors, and on those from the international monitoring system, the blast’s resulting quake was approximately 5.0 on the Richter scale. That seismic signal is comparable to the one from North Korea’s previous test, in 2013, which had an estimated yield of between 10 and 20 kilotons.

“We’re still waiting to see if anything shows up on sensor systems in the region,” says Anders Ringbom, one of a group of FOI researchers whom the Ministry for Foreign Affairs has assigned the responsibility for Sweden’s assessment.

“We still don’t know whether we’re going to receive any more information about the explosion.”

Several international measuring stations for so-called radionuclides, such as isotopes of the noble gas, xenon, are located in the region. Among others, a station in Japan is equipped with the Swedish system, SAUNA (Swedish Automatic Unit for Noble Gas Acquisition), developed by FOI. Analysis of data from this kind of measuring system can provide additional information about the nature of the detonation.

International reactions to the weapon test have been strong and most countries, Sweden among them, have concluded that it was some type of nuclear weapon test. The test has already been condemned by the UN Security Council, noting that it is in defiance of the Non-Proliferation Treaty (NPT), the Comprehensive Test Ban Treaty (CTBT) and the UN’s resolutions. The Minister for Foreign Affairs, Margot Wallström, made this comment about the event on January 6th:

In English

“The sanctions that have been directed at North Korea so far have clearly not worked,” concludes John Rydqvist, security policy analyst in FOI’s Asia and the Middle East Security Programme. “What the global community needs to decide on is which objective the sanctions should have. Is it to create further obstacles for North Korea’s capability to develop nuclear weapons and their delivery systems? Or is it about finding a new approach for getting North Korea to sit down at the negotiating table? Will the rest of the world be able to agree more effectively on countermeasures, or will China and the USA disagree about what must be done?” comments John Rydqvist.

As a permanent member of the Security Council, and with a unique historical relation to North Korea, China has a decisive role with regard to the measures the UN will adopt.

“North Korea’s behaviour will certainly worsen its relations with China, at least for the moment. But China does not want to risk further isolation of North Korea. That’s why Beijing’s statement after the nuclear test is in principal identical with the one it made after North Korea’s test in 2013. Its reaction after the first test blast, in 2006, was for example harder,” said Jerker Hellström, also with FOI’s Asia and Middle East Security Programme.

“From China’s perspective, both carrot and stick are necessary; the UN sanctions must be combined with dialogue and incentives. But there’s no guarantee that Beijing will receive international support for such tactics,” he adds.



FOI has been assigned by the Ministry of Foreign Affairs to lead Sweden’s work in monitoring nuclear weapons testing, in accordance with the international nuclear test ban treaty, CTBT. FOI’s measuring station in Hagfors is part of a global network of seismic stations. FOI also has stations for measuring airborne radiation (including xenon) in Stockholm.

FOI, Swedish Defence Research Agency

Swedish Defence Research Agency
SE-164 90 Stockholm

Phone +46 8 555 030 00
Fax +46 8 555 031 00

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