North Korea preparing new nuclear test

Pyongyang could be in the final stages of preparations for
a sixth nuclear test, according to intelligence reports

PUNGGYE-RI TEST SITE

Tests conducted in horizontal tunnels stretching about 1km into Mount Mantap – 2,205m granite peak 80km from nearest city

TUNNEL LAYOUT: Based on tunnel featured in propaganda film
of 2009 test. Shaped like fish-hook, similar to design
used by Pakistan

Sharp corners, and several dead ends used as debris
traps, help deflect and absorb blast

Blast doors

Debris trap

RUSSIA

NORTH KOREA

CHINA

Hamgyong Mts.

Punggye-ri

P’yongyang

Demilitarized Zone (DMZ)

SOUTH KOREA

100km 60 miles

Tunnel: 3m wide x 3m high

Tunnel entrance

Blast intended to be absorbed within area defined by
first four bulkheads

NUCLEAR TESTS
Estimated yields (1 kilotonne equivalent to 1,000 tonnes of TNT) Quake magnitude

Oct 2006 1kt 4.3

May 2009 2-5kt 4.7

Feb 2013

Jan 2016 7-10kt 5.1

Sep 2016 20-30kt 5.3

5.1 kt 5.1

Test estimated to be conducted 700 metres
underground

Nuclear device: Placed at farthest end of tunnel

Sand, gravel or other materials can be mixed
with concrete to plug segments of tunnel to further contain explosion and prevent ejecta from escaping
into atmosphere

Sources: Federal Institute for Geosciences and Natural Resources, Bulletin of Atomic Scientists, USGS, AP