I understand but my point is that when NK decides to use nukes everything else will not matter. whether radiation reaches China or not, whether NK wins or not.
Using nukes is equivalent to suicide bombing. The country will die. not literally, I really doubt anyone will launch nukes at NK even if Seul gets nuked.
NK ruling party members will be found and sentenced to death, rest of the government and remaining military which survived onslaught from chinese, south korean and marican troops disbanded.
Whether China is pleased or not will matter not. That is not the factor deciding whether one should or should not nuke another country.
Kim J. is capable of doing that, but I believe he has still enough reason to not do this. But the time will come when he is dieing and in his delusional mind he might decide to attack.
The question is whether people in his surroundings are as brainless as we think and whether they will listen to him. Hopefully not.

I think anyone who is crazy enough to brazenly test nukes and a few days later threaten to attack an adjacent territory, should not be under-estimated. Clearly nobody knows what he is capable of or what is going through his crazy head. We can hope that his advisors are not just as crazy as he is but if his people are united in thinking that he can do no wrong....shudder.
I know that the WP reports that SK is doubful of NK's threats of aggressive action but that, to me, sounds like they are trying to reassure the public. It wouldn't do any good to have the entire populace of Seoul thinking that their end may be days or weeks away.
And as far as the rest of the world is concerned, how badly do they want nukes sent their way. Does anyone know how many nukes NK may actually have? Would they risk some devestation in order to eradicate the North Korean threat?

The latest estimate I heard:
"It is estimated that North Korea has about 30 to 50 kilograms of plutonium ― enough to make six to 10 nuclear bombs." ( From The Korea Times website 26/05/2009, http://www.koreatimes.co.kr/www/news/nation/2009/05/116_45716.html)
I think this whole situation is a case of North Korea rattling the sabre because they are getting close to having an effective nuclear deterrent. They are simply letting the west know that the rules of the game are changing. At the moment just because they may be able to produce 10 nuclear bombs doesn't mean they have the ability to deliver that payload even to South Korea, however recent missile tests suggests they are getting close.
If and when that occurs, the traditional attitudes and foreign policies of my country and others will need to be reviewed as we will no longer be in a position where we can theoretically act with impunity.

I heard they may have as many as seven warheads already, although 3-5 seems to be the general estimate.
I think if they get backed into a corner, and the panic, they may do something catastrophic.
They only really have the capacity to attack S.Korea though, which means the South are feeling very nervous right now.
Mind you, some hawkish parts of the Japanese government are apparently trying to push for the possibility of a pre-emtive strike if the North look able and willing to attack Japan. Thats a very big deal given the structure of the Japanese military (defence only).
And finally, I feel its always worth posting a link to the pictures of North Korea at night, to show the contrast with the rest of the region.
http://news.cnet.com/2300-11392_3-6128466-1.html