CORRECTION: The research this blog is based on has been questioned and Nature (our source) has retracted its article pending further study.

From Nature:

After the story was published, the Comprehensive Nuclear Test-Ban Treaty Organization (CTBTO) in Vienna contacted Nature to say that the radioisotope station primarily responsible for the measurement, located in Takasaki, Japan, regularly detects xenon-133 from surrounding nuclear facilities. Following discussion with the ZAMG scientists, both bodies concluded that the xenon-133 seen in Japan cannot be directly linked to the North Korean test. The ZAMG has taken down its analysis of the xenon release from its website.

The original report detailed the detection of a radioactive isotope in the region surrounding North Korea on Feb. 15 days after the nation claimed to have tested its third and most powerful nuclear weapon. The radioactive signature — that normally poses no health risk — was reported to have been measured in Japan and Russia. This wouldn’t have been without precedent — the 2006 N. Korea test yielded a radioactive signature, whereas the 2009 test did not.

The North Korean regime claimed it had carried out a nuclear test on Feb. 12 and global seismometers confirmed this to be the case. From those measurements, scientists were able to deduce that the weapon detonated was in the several kiloton range — a similar yield to the bomb dropped on Hiroshima in 1945 by the U.S.

The original radiation study, carried out by scientists of the Central Institute for Meteorology and Geodynamics (ZAMG) in Vienna, claimed the detection of radioactive isotope xenon-133 indicated it came from North Korea. This, in turn, suggested that the bomb was buried well underground — the xenon-133 took some time to escape to the surface.

Recent Discovery News article on the N. Korea nuclear test: Nuke Test Sensors Double as Scientific Tools

Image credit: Corbis