I would also apply at other plants, and when you get some experience if you can get in at another plant, you will be more able to go to the plant you really want to work at. This is assuming you can't get into Cook or Pali.
It really is about who you know, how bad they need to hire, and how much experience/education you have. If you can make a good impression (because the last thing a hiring manager wants is another guy that causes problems or won't do his job) once you get into the interview room, then you also have a chance.
By the way, many nuclear jobs are boring (not challenging) too and hiring managers know this, so have some good answers about why you want to come back to nuke aside from the challenging thing.