NK {we. think.} is working only with Pu, not U235. No 'separation' efforts (that anyone knows about -- but then, why would they know? -- ain't none of the spooks gots even a peek inside that Ideal-Cheney/Republican State.)
A simple {ie. "gun type"} device cannot be made with Pu, for inescapable physics reasons of pre-ignition cf. The Curve of Binding Energy. Now, it's just barely conceivable that Kim-Il-Egosan might force an expensive Proof of that principle: and this was it == Yup, gun-type, it be no workie.
{Hey, Shrub ain't the Only ideologue that flips coins for all decisions beyond the workings of his sparse supply of little-grey-cells.}
Implosion devices need that aberration-free ~perfectly uniform array of HE of varying er, brissance - to maintain the compression field for many 'shakes' of neutron multiplication. In that direction lies Efficiency (sorta the same simplest goal as Econ, eh?)
Same outcome as any silly gun try re this explosion: implosion lens perfection not achieved, ergo dud-level yield.
Note that Iran groks to fullness, the problem of undertaking Perfection in explosives, via stone knives and bearskins -
Moral?
WATCH the centrifuge folks. Almost anyone could get a gun device to work; insurance there consists of ... simply possessing enough excess material beyond calc. critical mass to ensure ignition, even if a Microsoft-grade design.
Corollary -
IF the NKers do manage world-death-class implosion techno to a fare-thee-Well.. guess how many .pdfs of that design shall escape the Invincible Bush Mouth-Quarantine and all subsequent threats to draft prepubescent Brownies and Boy Scouts, to surround the borders, tie banzai scarfs about pretty little heas and -- then invade.
Tragicomedy.. Love. It.
PS: remember.. we tested the scary/improbable implosion device at Alamogordo.
But dropped the gun-type Uranium bomb first: on Hiroshima
(that one wasted Lots of -235, but then we had built Oak Ridge for the Ages and had tons coming.)