The temporary damage will actualy be technicaly perminate, because nuke damage rebuilds very slowly, in addition to lowering the upper limit of the reactor without any rebuilds allowed. Or something like that. Needless to say, nuking a reactor is worse then having it taken in ground combat and lost. The wiki says so.
Anywho, about war in Asia. I really don't see a clear war goal. Before war started, I would have been content to hand over Shanghi in exchange for peace. Now, it would almost be an insult to Japan to peace out right away, but seriously, the war is not only unwinnable, but there are no goals involved either!