38North has important analysis of very recent satellite imagery (March 25) from the North Korean nuclear weapons test site at Punggye-ri
New commercial satellite imagery of the Punggye-ri Nuclear Test Site from March 25 shows the continued presence of three to four vehicles or equipment trailers at the entrance to the North Portal. The texture of the ground from the portal entrance past the vehicles or equipment trailers suggests that communications cables may have been laid on the ground. This equipment would likely be used to initiate the test, collect data from the explosion and process the data. Also notable, water is being pumped out of the portal and draining downhill to the east and west, presumably to keep the tunnel dry for monitoring or communications equipment
This suggests, indeed strongly suggests, that North Korea is putting the final touches to preparations for a sixth nuclear weapons test.
It has taken North Korea, over five laboratory condition tests, to reach a nominal yield of 20 kilotons associated with a first generation nuclear device. North Korea itself has stated that it has the ability to miniaturise a nuclear warhead for delivery by ballistic missile.
Another report at 38North, based on the latest satellite imagery of the Yongbyon nuclear facility, shows continued activity at the complex especially activity associated with the Radiochemical Labroatory where North Korea reprocesses plutonium from spent fuel from its 5MWe nuclear reactor.
As the report suggests North Korea may be set upon another reprocessing campaign at Yongbyon in order to increase its stock of plutonium. This allows North Korea to conduct more nuclear tests without depleting its plutonium stockpile.
But another suggestion, of four, was made by the report. Namely, that this activity might be related to tritium separation.
Now that is suggestive. A recent report, again at 38North, showed that, under the North portal, North Korea has been building deeper tunnels possibly to contain larger nuclear explosions. A capacity of containment with an upper bound of 282 kilotons was suggested.
Tritium is used to “boost” the yield of a nuclear explosion by increasing the efficiency of the fission process through the production of neutrons by way of fusion reactions.
Whilst we have been focusing on a possible ICBM test, MRBM tests and launches, and static rocket engine tests North Korea might well have been gearing up for the most significant nuclear test to date, one with ambitions to go beyond the 20 kiloton nominal yield.
This all of course is speculative.
I fear we may soon find out what the deal is here.