South Korea will conduct a full-scale study this year on the possibility of radiation leaks from North Korea’s underground nuclear test site and test hundreds of defectors for signs of medical issues from radiation exposure, the unification ministry has announced. 

A ministry spokesperson said the study aims to provide a comprehensive update to a 2017-2018 survey that did not find any evidence of significant radiation exposure among 40 defectors from around the Punggye-ri nuclear test site, where the DPRK has conducted six nuclear tests since Oct. 2006.