Update: 02/19 20:49 GMT by S : The story below has been retracted upon further examination of the research. There has been no detection of radioactivity.
gbrumfiel writes "A global network of sensors has picked up faint traces of radioactive gas that probably seeped from last week's underground nuclear test by North Korea. The detection of xenon-133 in Japan and Russia provides further evidence of the nuclear nature of the test, but offers no hint as to the type of weapon used. Atmospheric modelling by the Central Institute for Meteorology and Geodynamics in Vienna shows that the gas likely seeped from North Korea's test site on 15 February, three days after the original test. That indicates that the test was well sealed deep underground."