North Korea’s nuclear test site has collapsed ... and that may be why Kim Jong-un suspended tests The mountain’s collapse after a fifth blast last fall has led to the creation of a massive ‘chimney’ that could leak radioactive fallout into the air, researchers have found North Korea’s mountain nuclear test site has collapsed, putting China and other nearby nations at unprecedented risk of radioactive exposure, two separate groups of Chinese scientists studying the issue have confirmed. The collapse after five nuclear blasts may be why North Korean leader Kim Jong-un declared on Friday that he would freeze the hermit...