The theory that the NKers merely set off 500 tonnes of conventional explosive is looking better and better ...
Do you have a programme to convert tonnes to metres?
One problem with that theory is the volume. We would have seen all that material being moved to the test site with our eyes in the sky.
That's my thinking too. Without sniffing the radiation evidence, Kim must be thinking he can use a large conventional blast dubbed "nuclear" as a bargaining chip to get the US to concede to negotiations and folk like Richardson are eating it up.
Without an explosion going "critical", all they can develop is the equivalent of a dirty bomb. A strong blast? Yes. Thermo-nuclear? Not today.
The fact they're so naive thinking the international community can't tell if it's nuclear or conventional is a sure sign of NK's isolation and ignorance of the matter.