The skeptic in me wonders if this is part of the reason for the possibly no more nuke test.
http://thehill.com/policy/national-security/384756-report-north-korea-nuclear-test-site-largely-unusable...“The occurrence of the collapse should deem the underground infrastructure beneath mountain Mantap not be used for any future nuclear tests,†reads an abstract for the study published by the University of Science and Technology of China, according to the Journal.
North Korea experts at Johns Hopkins University, however, told the Journal that parts of the facility could still be fully functional and that testing could resume....