I refuse to believe that there isn't a secret containment plan that all nuclear powers are coerced into agreeing to that basically gives every other nuclear power the right to intervene and secure the nukes from paramilitaries and terrorists in the event of state collapse.
The only reason I would presume NK isn't in on it is because everyone's agreed by now that if they fall it's gonna be a race between China and South Korea for who can press a legitimate claim first.