No country can hide a nuclear detonation from the US. It has a very reliably detectable signature which is detectable from anywhere on the planet. The US has been in the detection game since Stalin blew off his first nuke in the 1940's, and they are very, very good at it.
According to reports, the last nuke test by the DPRK had the effective yield of about 6 KTons. Recent reports claim that it might have been a uranium bomb. (DPRK's previous tests were supposedly plutonium.)
The difference between the two is important. Also, the previous tests were highly questionable whether they succeeded. But a uranium bomb -- one made from U235 -- is a very simple device. It's like the one which blew up at Hiroshima. It was never tested because of its simplicity. The Nagasaki bomb (Pu239) was tested at Alamagordo before it was dropped on Japan.
I think that the facts will bear out that the DPRK does not have a functional nuclear weapon. Why abandon the Pu bomb for a simpler, and less efficient U bomb? Why did the last test only yield a relatively tiny 6 KTons, about a third of the Hiroshima bomb which was a small nuke by today's standards? Why does the physics community not agree on whether the DPRK actually has a nuke, especially since such a detonation is so easily detectable?
It's simple. They don't have one. It's like everything else about North Korea. They are all bloviating talk and saber rattling; but no substance.
Concerning their nuke tests, it seems like they all seem to predetonate. That's the simplest explanation for the lack of a nuke signature and simultaneously the small yields (on the order of a conventional explosion). I don't think they know how to do it yet. An atomic bomb isn't just slamming a super-critical mass together. There's much more to it. You actually have to trigger the damned thing at the precise point that the super-critical mass assembles. Without a proper trigger -- no trivial task -- the damn thing blows itself apart before it can get the chain reaction going.
I don't think the DPRK knows how to do that yet. Thank goodness.
However, they may have a dirty bomb. Very worrisome if they use it, but not a city buster.
= new reply since forum marked as read