Low-Yield Nuclear Testing by North Korea in May 2010: Assessing the Evidence with Atmospheric Transport Models and Xenon Activity Calculations

This article investigates the possibility presented by De Geer (2012) that radionuclides detected at stations in South Korea, Japan, and Russia in May 2010 were evidence that North Korea conducted at least one unannounced low yield nuclear test on 11 May. It provides HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory Model) atmospheric transport modeling of the observed radionuclides assuming candidate origins in North Korea, ROK, Japan, Russia, mainland China, and Taiwan. Xenon activity calculations for reactor- and explosion-produced isotopes are used to ascertain possible release ratios and source terms. The HYSPLIT modeling finds that the most likely origin of the radionuclides is close to the site of North Korea's declared nuclear tests in 2006 and 2009. The activity calculations show that the source term is consistent with a nuclear test up to a few hundred tons yield. These results are discussed in the context of a decoupled but uncontained nuclear test by North Korea on 11 May 2010. If the scenario suggested by De Geer and supported here is correct, it seems that there is a significant possibility of detecting even a small, decoupled nuclear test in North East Asia using components of the International Monitoring System of the Comprehensive Test Ban Treaty.