Reinforced evidence of a low-yield nuclear test in North Korea on 11 May 2010

In May 2010 unique aerosol-bound and noble gas (xenon) radionuclide signatures were observed at four East Asian surveillance stations designed to detect evidence of nuclear testing. An article published in early 2012 provided an analysis that suggested the findings were due to a low-yield underground nuclear test in North Korea on 11 May 2010. As the aerosol and noble gas datings, however, only agreed on the fringes of their uncertainties an official North Korean telegram that on 12 May 2010 reported about a nuclear fusion experiment 1 month earlier inspired a solution. Assuming that included a low-yield nuclear explosion and that it had left xenon isotopes in the same cavity, the xenon dating could be “moved” to overlap with the aerosol dating. The article stirred a serious controversy where representatives of the U.S. government and the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) refused to comment on it. In this paper the xenon dating agrees with the aerosol one without resorting to a previous explosion. It shows instead that fractionation during lava cooling is the explanation and how that plays a paramount role in how xenon signatures from underground nuclear explosions should be interpreted. It also presents new observations that effectively imply that no nuclear reactor or any other nuclear installation could have caused the May 2010 signals. All in all these are the most interesting and rich ones ever encountered by the Organization and they truly demonstrate that the verification system can deliver much better sensitivity than it was originally designed for.