CTBTO detects radioactivity consistent with 12 February announced North Korean nuclear test

Vienna, 23 April 2013

The CTBTO’s radionuclide network has made a significant detection of radioactive noble gases that could be attributed to the nuclear test announced by the Democratic People’s Republic of Korea (DPRK) on 12 February 2013. The detection was made at the radionuclide station in Takasaki, Japan, located at around 1,000 kilometres, or 620 miles, from the DPRK test site. Lower levels were picked up at another station in Ussuriysk, Russia. Two radioactive isotopes of the noble gas xenon were identified, xenon-131m and xenon-133, which provide reliable information on the nuclear nature of the source. The ratio of the detected xenon isotopes is consistent with a nuclear fission event occurring more than 50 days before the detection (nuclear fission can occur in both nuclear explosions and nuclear energy production). This coincides very well with announced nuclear test by the DPRK that occurred on 12 February 2013, 55 days before the measurement. Using Atmospheric Transport Modelling (ATM), which calculates the three-dimensional travel path of airborne radioactivity on the basis of weather data, the DPRK test site was identified as a possible source for the emission. Watch the video here. CTBTO radionuclide expert Mika Nikkinen said: “We are in the process of eliminating other possible sources that could explain the observations; the radionuclides could have come from a nuclear reactor or other nuclear activity under certain specific conditions, but so far we do not have information on such a release.” For further information on the radionuclide detection, see Q&A sheet [here]. On 12 February, the DPRK event was detected immediately, reliably and precisely by 94 seismic stations and two infrasound stations of the CTBTO’s International Monitoring System. The first data were made available to CTBTO Member States in little more than one hour, and before the DPRK announced that it had conducted a nuclear test. The event recorded at 02.57.51 (UTC) was found to have a magnitude of 4.9 using the CTBTO International Data Centre’s magnitude scale. The location was in the vicinity of the two previous nuclear tests (Lat.: 41.313 degrees north; long.: 129.101 degrees east). --- The radionuclide technology is the only one of the four monitoring technologies employed by the CTBTO that can provide clear evidence of the nuclear nature of an explosion. After an underground nuclear explosion, radioactive noble gases can seep through layers of rock and sediment until they escape into the air. Alternatively, the radioactivity may also be released by man-made activities at the test site.  Exposed to prevailing winds, the noble gases are dispersed in the atmosphere and may, after a certain period of time, be detected thousands of kilometres away from the explosion site. The CTBTO currently has 66 radionuclide stations in operation across the globe, of which 30 are able to detect noble gases. The CTBTO is the international organization responsible for ensuring that no nuclear explosion goes undetected. It uses four complementary verification technologies: seismic, hydroacoustic, infrasound and radionuclide monitoring. Traces of the radionuclide noble gas xenon 133 were registered after the 2006 DPRK nuclear test, but there were no detections following the 2009 DPRK test. In total, over 87 percent of the CTBTO’s 337 monitoring facilities are now up and running; see interactive map. The DPRK’s action had been strongly condemned by Tibor Tóth, the Executive Secretary of the CTBTO, and by Jan Petersen, Chairperson of the CTBTO’s executive body. Broadcasters – see CTBTO Newsroom forbroadcast quality video and audio available, free of rights, for broadcasters to download. The package includes animation, sound bites and b-roll including from the CTBTO’s Takasaki radionuclide and noble gas monitoring station in Japan.

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