North Korea won't give up  its nuclear weapons, for the communist dictatorship sees the nukes as the only way to retain their control of North Korea, and protect themselves from attack by America or South Korea. Moreover, South Korea doesn't really want reunification of the north and south any time soon, because they have done the math, and realize that reunification would cause a severe drop in living standards in the south. Allowing that would be political suicide for southern politicians. Better to do all that is possible to help the economy in the north get back on its feet, and limp along. A side effect of all this is declining military power in the north. South Korea is rapidly building up its own defenses, and expects to be clearly superior to the north in a decade. Already, southern generals are confident they could stop any invasion from the north.