Japanese Sensors have detected a trace amount of radiation off the central coast of the main Island of Honshu.  The lack of detectable radiation from North Korea’s 12 February nuclear weapon test has so far confounded scientists wondering what North Korea is up to.

The Japanese planes detected Xenon-133 at 30,000 feet up in the atmosphere, off the coast at Nagoya.  But this Xenon isotope has a relatively short half-life, usually less than the time that has commenced since the North Korea test.  And it is often the by-product of a standard nuclear reactor or even medical science.

Experts in South Korea have said they have yet to detect any radiation from the North.