So... now we know his reason.
‘ENVIRONMENTAL CATASROPHE’
North Korea’s Nuclear Test Site Has ‘Collapsed’
North Korea’s underground nuclear test site has become unusable after a large part of it collapsed, Chinese scientists say.
Their evidence comes just one week after a surprise announcement from leader Kim Jong Un that North Korea would stop nuclear tests, with one researcher suggesting to the South China Morning Post that the collapse was the real reason for the unexpected suspension.
The experts, led by researchers at the University of Science and Technology of China, have warned that another blast in the same spot and with similar yield to one in September, which is believed to have caused the collapse, could lead to “environmental catastrophe.” “The occurrence of the collapse should deem the underground infrastructure beneath mountain Mantap not be used for any future nuclear tests,” said an abstract for the study.
Read it at The Wall Street Journal